Investigating an OpenVPN connection problem in Gentoo Linux and Lubuntu 22.04 but not in Android 13

Back in 2020 I successfully used OpenVPN to access a remote server from my laptop and from my smartphone. Fast forward to 2023 and I needed to use OpenVPN again to access the same remote server. I could again access the remote server when connecting from my smartphone, now running Android 13, using the OpenVPN client app. However, when I tried to use OpenVPN from my laptop running Gentoo Linux, and from my desktop machine running Lubuntu 22.04, VPN connection attempts always timed out. The OpenVPN client configuration file (referred to generically as ‘client.ovpn‘ in some articles, named ‘bsf1.ovpn‘ in my case) and the OpenVPN password were both correct, so I did not understand why a connection could not be established from the laptop and desktop machine to the remote server, especially as there was not a problem connecting from my smartphone running Android 13.

I use KDE in Gentoo Linux, and Lubuntu 22.04 uses LXQt. In both those Desktop Environments I used the relevant GUI front-end to NetworkManager to import the client.ovpn file and to try to connect to the VPN server. As these connection attempts had failed, I launched the OpenVPN client from the command line in Gentoo Linux to see if there were any error messages, and the output is shown below. (For privacy reasons I have annonimised my public IP address, domain, e-mail address, country, location and organisation in all the command line output shown in this post.)

root # openvpn --config bsf1.ovpn
2023-09-30 01:07:02 WARNING: Compression for receiving enabled. Compression has been used in the past to break encryption. Sent packets are not compressed unless "allow-compression yes" is also set.
2023-09-30 01:07:02 DEPRECATED OPTION: --cipher set to 'AES-128-CBC' but missing in --data-ciphers (AES-256-GCM:AES-128-GCM:CHACHA20-POLY1305). OpenVPN ignores --cipher for cipher negotiations. 
2023-09-30 01:07:02 OpenVPN 2.6.4 x86_64-pc-linux-gnu [SSL (OpenSSL)] [LZO] [LZ4] [EPOLL] [MH/PKTINFO] [AEAD]
2023-09-30 01:07:02 library versions: OpenSSL 3.0.10 1 Aug 2023, LZO 2.10
2023-09-30 01:07:02 WARNING: No server certificate verification method has been enabled.  See http://openvpn.net/howto.html#mitm for more info.
Enter Private Key Password:
2023-09-30 01:08:57 WARNING: this configuration may cache passwords in memory -- use the auth-nocache option to prevent this
2023-09-30 01:08:58 TCP/UDP: Preserving recently used remote address: [AF_INET]111.222.333.444:1194
2023-09-30 01:08:58 Socket Buffers: R=[131072->131072] S=[16384->16384]
2023-09-30 01:08:58 Attempting to establish TCP connection with [AF_INET]111.222.333.444:1194
2023-09-30 01:08:58 TCP connection established with [AF_INET]111.222.333.444:1194
2023-09-30 01:08:58 TCPv4_CLIENT link local: (not bound)
2023-09-30 01:08:58 TCPv4_CLIENT link remote: [AF_INET]111.222.333.444:1194
2023-09-30 01:08:58 NOTE: UID/GID downgrade will be delayed because of --client, --pull, or --up-delay
2023-09-30 01:08:58 TLS: Initial packet from [AF_INET]111.222.333.444:1194, sid=fc150984 3a9d3b4f
2023-09-30 01:08:58 TLS error: Unsupported protocol. This typically indicates that client and server have no common TLS version enabled. This can be caused by mismatched tls-version-min and tls-version-max options on client and server. If your OpenVPN client is between v2.3.6 and v2.3.2 try adding tls-version-min 1.0 to the client configuration to use TLS 1.0+ instead of TLS 1.0 only
2023-09-30 01:08:58 OpenSSL: error:0A000102:SSL routines::unsupported protocol
2023-09-30 01:08:58 TLS_ERROR: BIO read tls_read_plaintext error
2023-09-30 01:08:58 TLS Error: TLS object -> incoming plaintext read error
2023-09-30 01:08:58 TLS Error: TLS handshake failed
2023-09-30 01:08:58 Fatal TLS error (check_tls_errors_co), restarting
2023-09-30 01:08:58 SIGUSR1[soft,tls-error] received, process restarting
2023-09-30 01:08:58 Restart pause, 1 second(s)
2023-09-30 01:08:59 WARNING: No server certificate verification method has been enabled.  See http://openvpn.net/howto.html#mitm for more info.
2023-09-30 01:08:59 TCP/UDP: Preserving recently used remote address: [AF_INET]111.222.333.444:1194
2023-09-30 01:08:59 Socket Buffers: R=[131072->131072] S=[16384->16384]
2023-09-30 01:08:59 Attempting to establish TCP connection with [AF_INET]111.222.333.444:1194
2023-09-30 01:08:59 TCP connection established with [AF_INET]111.222.333.444:1194
2023-09-30 01:08:59 TCPv4_CLIENT link local: (not bound)
2023-09-30 01:08:59 TCPv4_CLIENT link remote: [AF_INET]111.222.333.444:1194
2023-09-30 01:08:59 TLS: Initial packet from [AF_INET]111.222.333.444:1194, sid=00c193e4 f375c3df
2023-09-30 01:08:59 TLS error: Unsupported protocol. This typically indicates that client and server have no common TLS version enabled. This can be caused by mismatched tls-version-min and tls-version-max options on client and server. If your OpenVPN client is between v2.3.6 and v2.3.2 try adding tls-version-min 1.0 to the client configuration to use TLS 1.0+ instead of TLS 1.0 only
2023-09-30 01:08:59 OpenSSL: error:0A000102:SSL routines::unsupported protocol
2023-09-30 01:08:59 TLS_ERROR: BIO read tls_read_plaintext error
2023-09-30 01:08:59 TLS Error: TLS object -> incoming plaintext read error
2023-09-30 01:08:59 TLS Error: TLS handshake failed
2023-09-30 01:08:59 Fatal TLS error (check_tls_errors_co), restarting
2023-09-30 01:08:59 SIGUSR1[soft,tls-error] received, process restarting
2023-09-30 01:08:59 Restart pause, 1 second(s)
2023-09-30 01:09:00 WARNING: No server certificate verification method has been enabled.  See http://openvpn.net/howto.html#mitm for more info.
2023-09-30 01:09:00 TCP/UDP: Preserving recently used remote address: [AF_INET]111.222.333.444:1194
2023-09-30 01:09:00 Socket Buffers: R=[131072->131072] S=[16384->16384]
2023-09-30 01:09:00 Attempting to establish TCP connection with [AF_INET]111.222.333.444:1194
2023-09-30 01:09:00 TCP connection established with [AF_INET]111.222.333.444:1194
2023-09-30 01:09:00 TCPv4_CLIENT link local: (not bound)
2023-09-30 01:09:00 TCPv4_CLIENT link remote: [AF_INET]111.222.333.444:1194
2023-09-30 01:09:00 TLS: Initial packet from [AF_INET]111.222.333.444:1194, sid=415fddcd dc5faf65
2023-09-30 01:09:01 TLS error: Unsupported protocol. This typically indicates that client and server have no common TLS version enabled. This can be caused by mismatched tls-version-min and tls-version-max options on client and server. If your OpenVPN client is between v2.3.6 and v2.3.2 try adding tls-version-min 1.0 to the client configuration to use TLS 1.0+ instead of TLS 1.0 only
2023-09-30 01:09:01 OpenSSL: error:0A000102:SSL routines::unsupported protocol
2023-09-30 01:09:01 TLS_ERROR: BIO read tls_read_plaintext error
2023-09-30 01:09:01 TLS Error: TLS object -> incoming plaintext read error
2023-09-30 01:09:01 TLS Error: TLS handshake failed
2023-09-30 01:09:01 Fatal TLS error (check_tls_errors_co), restarting
2023-09-30 01:09:01 SIGUSR1[soft,tls-error] received, process restarting
2023-09-30 01:09:01 Restart pause, 1 second(s)
2023-09-30 01:09:02 WARNING: No server certificate verification method has been enabled.  See http://openvpn.net/howto.html#mitm for more info.
2023-09-30 01:09:02 TCP/UDP: Preserving recently used remote address: [AF_INET]111.222.333.444:1194
2023-09-30 01:09:02 Socket Buffers: R=[131072->131072] S=[16384->16384]
2023-09-30 01:09:02 Attempting to establish TCP connection with [AF_INET]111.222.333.444:1194
2023-09-30 01:09:02 TCP connection established with [AF_INET]111.222.333.444:1194
2023-09-30 01:09:02 TCPv4_CLIENT link local: (not bound)
2023-09-30 01:09:02 TCPv4_CLIENT link remote: [AF_INET]111.222.333.444:1194
2023-09-30 01:09:02 TLS: Initial packet from [AF_INET]111.222.333.444:1194, sid=1458e510 821d0c37
2023-09-30 01:09:02 TLS error: Unsupported protocol. This typically indicates that client and server have no common TLS version enabled. This can be caused by mismatched tls-version-min and tls-version-max options on client and server. If your OpenVPN client is between v2.3.6 and v2.3.2 try adding tls-version-min 1.0 to the client configuration to use TLS 1.0+ instead of TLS 1.0 only
2023-09-30 01:09:02 OpenSSL: error:0A000102:SSL routines::unsupported protocol
2023-09-30 01:09:02 TLS_ERROR: BIO read tls_read_plaintext error
2023-09-30 01:09:02 TLS Error: TLS object -> incoming plaintext read error
2023-09-30 01:09:02 TLS Error: TLS handshake failed
2023-09-30 01:09:02 Fatal TLS error (check_tls_errors_co), restarting
2023-09-30 01:09:02 SIGUSR1[soft,tls-error] received, process restarting
2023-09-30 01:09:02 Restart pause, 1 second(s)
2023-09-30 01:09:03 WARNING: No server certificate verification method has been enabled.  See http://openvpn.net/howto.html#mitm for more info.
2023-09-30 01:09:03 TCP/UDP: Preserving recently used remote address: [AF_INET]111.222.333.444:1194
2023-09-30 01:09:03 Socket Buffers: R=[131072->131072] S=[16384->16384]
2023-09-30 01:09:03 Attempting to establish TCP connection with [AF_INET]111.222.333.444:1194
2023-09-30 01:09:03 TCP connection established with [AF_INET]111.222.333.444:1194
2023-09-30 01:09:03 TCPv4_CLIENT link local: (not bound)
2023-09-30 01:09:03 TCPv4_CLIENT link remote: [AF_INET]111.222.333.444:1194
2023-09-30 01:09:03 TLS: Initial packet from [AF_INET]111.222.333.444:1194, sid=9ab3df76 86d3e81d
2023-09-30 01:09:03 TLS error: Unsupported protocol. This typically indicates that client and server have no common TLS version enabled. This can be caused by mismatched tls-version-min and tls-version-max options on client and server. If your OpenVPN client is between v2.3.6 and v2.3.2 try adding tls-version-min 1.0 to the client configuration to use TLS 1.0+ instead of TLS 1.0 only
2023-09-30 01:09:03 OpenSSL: error:0A000102:SSL routines::unsupported protocol
2023-09-30 01:09:03 TLS_ERROR: BIO read tls_read_plaintext error
2023-09-30 01:09:03 TLS Error: TLS object -> incoming plaintext read error
2023-09-30 01:09:03 TLS Error: TLS handshake failed
2023-09-30 01:09:03 Fatal TLS error (check_tls_errors_co), restarting
2023-09-30 01:09:03 SIGUSR1[soft,tls-error] received, process restarting
2023-09-30 01:09:03 Restart pause, 2 second(s)
2023-09-30 01:09:05 WARNING: No server certificate verification method has been enabled.  See http://openvpn.net/howto.html#mitm for more info.
2023-09-30 01:09:05 TCP/UDP: Preserving recently used remote address: [AF_INET]111.222.333.444:1194
2023-09-30 01:09:05 Socket Buffers: R=[131072->131072] S=[16384->16384]
2023-09-30 01:09:05 Attempting to establish TCP connection with [AF_INET]111.222.333.444:1194
2023-09-30 01:09:05 TCP connection established with [AF_INET]111.222.333.444:1194
2023-09-30 01:09:05 TCPv4_CLIENT link local: (not bound)
2023-09-30 01:09:05 TCPv4_CLIENT link remote: [AF_INET]111.222.333.444:1194
2023-09-30 01:09:05 TLS: Initial packet from [AF_INET]111.222.333.444:1194, sid=9f21e4f5 a4d9fecb
2023-09-30 01:09:05 TLS error: Unsupported protocol. This typically indicates that client and server have no common TLS version enabled. This can be caused by mismatched tls-version-min and tls-version-max options on client and server. If your OpenVPN client is between v2.3.6 and v2.3.2 try adding tls-version-min 1.0 to the client configuration to use TLS 1.0+ instead of TLS 1.0 only
2023-09-30 01:09:05 OpenSSL: error:0A000102:SSL routines::unsupported protocol
2023-09-30 01:09:05 TLS_ERROR: BIO read tls_read_plaintext error
2023-09-30 01:09:05 TLS Error: TLS object -> incoming plaintext read error
2023-09-30 01:09:05 TLS Error: TLS handshake failed
2023-09-30 01:09:05 Fatal TLS error (check_tls_errors_co), restarting
2023-09-30 01:09:05 SIGUSR1[soft,tls-error] received, process restarting
2023-09-30 01:09:05 Restart pause, 4 second(s)
2023-09-30 01:09:09 WARNING: No server certificate verification method has been enabled.  See http://openvpn.net/howto.html#mitm for more info.
2023-09-30 01:09:10 TCP/UDP: Preserving recently used remote address: [AF_INET]111.222.333.444:1194
2023-09-30 01:09:10 Socket Buffers: R=[131072->131072] S=[16384->16384]
2023-09-30 01:09:10 Attempting to establish TCP connection with [AF_INET]111.222.333.444:1194
2023-09-30 01:09:10 TCP connection established with [AF_INET]111.222.333.444:1194
2023-09-30 01:09:10 TCPv4_CLIENT link local: (not bound)
2023-09-30 01:09:10 TCPv4_CLIENT link remote: [AF_INET]111.222.333.444:1194
2023-09-30 01:09:10 TLS: Initial packet from [AF_INET]111.222.333.444:1194, sid=bb6d7166 52844953
2023-09-30 01:09:10 TLS error: Unsupported protocol. This typically indicates that client and server have no common TLS version enabled. This can be caused by mismatched tls-version-min and tls-version-max options on client and server. If your OpenVPN client is between v2.3.6 and v2.3.2 try adding tls-version-min 1.0 to the client configuration to use TLS 1.0+ instead of TLS 1.0 only
2023-09-30 01:09:10 OpenSSL: error:0A000102:SSL routines::unsupported protocol
2023-09-30 01:09:10 TLS_ERROR: BIO read tls_read_plaintext error
2023-09-30 01:09:10 TLS Error: TLS object -> incoming plaintext read error
2023-09-30 01:09:10 TLS Error: TLS handshake failed
2023-09-30 01:09:10 Fatal TLS error (check_tls_errors_co), restarting
2023-09-30 01:09:10 SIGUSR1[soft,tls-error] received, process restarting
2023-09-30 01:09:10 Restart pause, 8 second(s)
2023-09-30 01:09:18 WARNING: No server certificate verification method has been enabled.  See http://openvpn.net/howto.html#mitm for more info.
2023-09-30 01:09:18 TCP/UDP: Preserving recently used remote address: [AF_INET]111.222.333.444:1194
2023-09-30 01:09:18 Socket Buffers: R=[131072->131072] S=[16384->16384]
2023-09-30 01:09:18 Attempting to establish TCP connection with [AF_INET]111.222.333.444:1194
2023-09-30 01:09:19 TCP connection established with [AF_INET]111.222.333.444:1194
2023-09-30 01:09:19 TCPv4_CLIENT link local: (not bound)
2023-09-30 01:09:19 TCPv4_CLIENT link remote: [AF_INET]111.222.333.444:1194
2023-09-30 01:09:19 TLS: Initial packet from [AF_INET]111.222.333.444:1194, sid=099e3b11 8ddc87c1
2023-09-30 01:09:19 TLS error: Unsupported protocol. This typically indicates that client and server have no common TLS version enabled. This can be caused by mismatched tls-version-min and tls-version-max options on client and server. If your OpenVPN client is between v2.3.6 and v2.3.2 try adding tls-version-min 1.0 to the client configuration to use TLS 1.0+ instead of TLS 1.0 only
2023-09-30 01:09:19 OpenSSL: error:0A000102:SSL routines::unsupported protocol
2023-09-30 01:09:19 TLS_ERROR: BIO read tls_read_plaintext error
2023-09-30 01:09:19 TLS Error: TLS object -> incoming plaintext read error
2023-09-30 01:09:19 TLS Error: TLS handshake failed
2023-09-30 01:09:19 Fatal TLS error (check_tls_errors_co), restarting
2023-09-30 01:09:19 SIGUSR1[soft,tls-error] received, process restarting
2023-09-30 01:09:19 Restart pause, 16 second(s)
2023-09-30 01:09:35 WARNING: No server certificate verification method has been enabled.  See http://openvpn.net/howto.html#mitm for more info.
2023-09-30 01:09:35 TCP/UDP: Preserving recently used remote address: [AF_INET]111.222.333.444:1194
2023-09-30 01:09:35 Socket Buffers: R=[131072->131072] S=[16384->16384]
2023-09-30 01:09:35 Attempting to establish TCP connection with [AF_INET]111.222.333.444:1194
2023-09-30 01:09:35 TCP connection established with [AF_INET]111.222.333.444:1194
2023-09-30 01:09:35 TCPv4_CLIENT link local: (not bound)
2023-09-30 01:09:35 TCPv4_CLIENT link remote: [AF_INET]111.222.333.444:1194
2023-09-30 01:09:35 TLS: Initial packet from [AF_INET]111.222.333.444:1194, sid=38ffac21 50e59cc4
2023-09-30 01:09:35 TLS error: Unsupported protocol. This typically indicates that client and server have no common TLS version enabled. This can be caused by mismatched tls-version-min and tls-version-max options on client and server. If your OpenVPN client is between v2.3.6 and v2.3.2 try adding tls-version-min 1.0 to the client configuration to use TLS 1.0+ instead of TLS 1.0 only
2023-09-30 01:09:35 OpenSSL: error:0A000102:SSL routines::unsupported protocol
2023-09-30 01:09:35 TLS_ERROR: BIO read tls_read_plaintext error
2023-09-30 01:09:35 TLS Error: TLS object -> incoming plaintext read error
2023-09-30 01:09:35 TLS Error: TLS handshake failed
2023-09-30 01:09:35 Fatal TLS error (check_tls_errors_co), restarting
2023-09-30 01:09:35 SIGUSR1[soft,tls-error] received, process restarting
2023-09-30 01:09:35 Restart pause, 32 second(s)
^C

The error message ‘TLS error: Unsupported protocol. This typically indicates that client and server have no common TLS version enabled.‘ made me suspect that the version of the OpenSSL package (which also provides TLS) in Gentoo Linux on my laptop is incompatible with the version of the OpenSSL package on the remote server.

The command line output in Lubuntu 22.04 on the desktop machine also showed there was a problem with TLS when I tried to launch the VPN client:

user $ sudo openvpn --config bsf1.ovpn
[sudo] password for fitzcarraldo: 
2023-10-03 14:00:43 WARNING: Compression for receiving enabled. Compression has been used in the past to break encryption. Sent packets are not compressed unless "allow-compression yes" is also set.
2023-10-03 14:00:43 DEPRECATED OPTION: --cipher set to 'AES-128-CBC' but missing in --data-ciphers (AES-256-GCM:AES-128-GCM). Future OpenVPN version will ignore --cipher for cipher negotiations. Add 'AES-128-CBC' to --data-ciphers or change --cipher 'AES-128-CBC' to --data-ciphers-fallback 'AES-128-CBC' to silence this warning.
2023-10-03 14:00:43 OpenVPN 2.5.5 x86_64-pc-linux-gnu [SSL (OpenSSL)] [LZO] [LZ4] [EPOLL] [PKCS11] [MH/PKTINFO] [AEAD] built on Jul 14 2022
2023-10-03 14:00:43 library versions: OpenSSL 3.0.2 15 Mar 2022, LZO 2.10
2023-10-03 14:00:43 WARNING: No server certificate verification method has been enabled.  See http://openvpn.net/howto.html#mitm for more info.
🔐 Enter Private Key Password: ************            
2023-10-03 14:00:48 WARNING: this configuration may cache passwords in memory -- use the auth-nocache option to prevent this
2023-10-03 14:00:48 Outgoing Control Channel Authentication: Using 256 bit message hash 'SHA256' for HMAC authentication
2023-10-03 14:00:48 Incoming Control Channel Authentication: Using 256 bit message hash 'SHA256' for HMAC authentication
2023-10-03 14:00:48 RESOLVE: Cannot resolve host address: bsfitzgerald.ddns.net:1194 (Temporary failure in name resolution)
2023-10-03 14:00:48 RESOLVE: Cannot resolve host address: bsfitzgerald.ddns.net:1194 (Temporary failure in name resolution)
2023-10-03 14:00:48 Could not determine IPv4/IPv6 protocol
2023-10-03 14:00:48 NOTE: UID/GID downgrade will be delayed because of --client, --pull, or --up-delay
2023-10-03 14:00:48 SIGUSR1[soft,init_instance] received, process restarting
2023-10-03 14:00:48 Restart pause, 5 second(s)
2023-10-03 14:00:53 WARNING: No server certificate verification method has been enabled.  See http://openvpn.net/howto.html#mitm for more info.
2023-10-03 14:00:53 Outgoing Control Channel Authentication: Using 256 bit message hash 'SHA256' for HMAC authentication
2023-10-03 14:00:53 Incoming Control Channel Authentication: Using 256 bit message hash 'SHA256' for HMAC authentication
2023-10-03 14:00:55 TCP/UDP: Preserving recently used remote address: [AF_INET]111.222.333.444:1194
2023-10-03 14:00:55 Socket Buffers: R=[131072->131072] S=[16384->16384]
2023-10-03 14:00:55 Attempting to establish TCP connection with [AF_INET]111.222.333.444:1194 [nonblock]
2023-10-03 14:00:55 TCP connection established with [AF_INET]111.222.333.444:1194
2023-10-03 14:00:55 TCP_CLIENT link local: (not bound)
2023-10-03 14:00:55 TCP_CLIENT link remote: [AF_INET]111.222.333.444:1194
2023-10-03 14:00:56 TLS: Initial packet from [AF_INET]111.222.333.444:1194, sid=c3ec9433 c4139af0
2023-10-03 14:00:57 VERIFY OK: depth=1, C=PE, ST=Loreto, L=Iquitos, O=Work, OU=vpn, CN=server, name=server, emailAddress=brian@bsfitzgerald.com
2023-10-03 14:00:57 VERIFY OK: depth=0, C=PE, ST=Loreto, L=Iquitos, O=Work, OU=vpn, CN=server, name=server, emailAddress=brian@bsfitzgerald.com
2023-10-03 14:00:58 OpenSSL: error:0A0C0103:SSL routines::internal error
2023-10-03 14:00:58 TLS_ERROR: BIO read tls_read_plaintext error
2023-10-03 14:00:58 TLS Error: TLS object -> incoming plaintext read error
2023-10-03 14:00:58 TLS Error: TLS handshake failed
2023-10-03 14:00:58 Fatal TLS error (check_tls_errors_co), restarting
2023-10-03 14:00:58 SIGUSR1[soft,tls-error] received, process restarting
2023-10-03 14:00:58 Restart pause, 5 second(s)
2023-10-03 14:01:03 WARNING: No server certificate verification method has been enabled.  See http://openvpn.net/howto.html#mitm for more info.
2023-10-03 14:01:03 Outgoing Control Channel Authentication: Using 256 bit message hash 'SHA256' for HMAC authentication
2023-10-03 14:01:03 Incoming Control Channel Authentication: Using 256 bit message hash 'SHA256' for HMAC authentication
2023-10-03 14:01:03 TCP/UDP: Preserving recently used remote address: [AF_INET]111.222.333.444:1194
2023-10-03 14:01:03 Socket Buffers: R=[131072->131072] S=[16384->16384]
2023-10-03 14:01:03 Attempting to establish TCP connection with [AF_INET]111.222.333.444:1194 [nonblock]
2023-10-03 14:01:03 TCP connection established with [AF_INET]111.222.333.444:1194
2023-10-03 14:01:03 TCP_CLIENT link local: (not bound)
2023-10-03 14:01:03 TCP_CLIENT link remote: [AF_INET]111.222.333.444:1194
2023-10-03 14:01:03 TLS: Initial packet from [AF_INET]111.222.333.444:1194, sid=486e45aa bbf5d0b0
2023-10-03 14:01:05 VERIFY OK: depth=1, C=GB, ST=Loreto, L=Iquitos, O=Work, OU=vpn, CN=server, name=server, emailAddress=brian@bsfitzgerald.com
2023-10-03 14:01:05 VERIFY OK: depth=0, C=GB, ST=Loreto, L=Iquitos, O=Work, OU=vpn, CN=server, name=server, emailAddress=brian@bsfitzgerald.com
2023-10-03 14:01:05 OpenSSL: error:0A0C0103:SSL routines::internal error
2023-10-03 14:01:05 TLS_ERROR: BIO read tls_read_plaintext error
2023-10-03 14:01:05 TLS Error: TLS object -> incoming plaintext read error
2023-10-03 14:01:05 TLS Error: TLS handshake failed
2023-10-03 14:01:05 Fatal TLS error (check_tls_errors_co), restarting
2023-10-03 14:01:05 SIGUSR1[soft,tls-error] received, process restarting
2023-10-03 14:01:05 Restart pause, 5 second(s)
2023-10-03 14:01:10 WARNING: No server certificate verification method has been enabled.  See http://openvpn.net/howto.html#mitm for more info.
2023-10-03 14:01:10 Outgoing Control Channel Authentication: Using 256 bit message hash 'SHA256' for HMAC authentication
2023-10-03 14:01:10 Incoming Control Channel Authentication: Using 256 bit message hash 'SHA256' for HMAC authentication
2023-10-03 14:01:10 TCP/UDP: Preserving recently used remote address: [AF_INET]111.222.333.444:1194
2023-10-03 14:01:10 Socket Buffers: R=[131072->131072] S=[16384->16384]
2023-10-03 14:01:10 Attempting to establish TCP connection with [AF_INET]111.222.333.444:1194 [nonblock]
2023-10-03 14:01:10 TCP connection established with [AF_INET]111.222.333.444:1194
2023-10-03 14:01:10 TCP_CLIENT link local: (not bound)
2023-10-03 14:01:10 TCP_CLIENT link remote: [AF_INET]111.222.333.444:1194
2023-10-03 14:01:11 TLS: Initial packet from [AF_INET]111.222.333.444:1194, sid=2523066e a7169e23
2023-10-03 14:01:12 VERIFY OK: depth=1, C=GB, ST=Loreto, L=Iquitos, O=Work, OU=vpn, CN=server, name=server, emailAddress=brian@bsfitzgerald.com
2023-10-03 14:01:12 VERIFY OK: depth=0, C=GB, ST=Loreto, L=Iquitos, O=Work, OU=vpn, CN=server, name=server, emailAddress=brian@bsfitzgerald.com
2023-10-03 14:01:13 OpenSSL: error:0A0C0103:SSL routines::internal error
2023-10-03 14:01:13 TLS_ERROR: BIO read tls_read_plaintext error
2023-10-03 14:01:13 TLS Error: TLS object -> incoming plaintext read error
2023-10-03 14:01:13 TLS Error: TLS handshake failed
2023-10-03 14:01:13 Fatal TLS error (check_tls_errors_co), restarting
2023-10-03 14:01:13 SIGUSR1[soft,tls-error] received, process restarting
2023-10-03 14:01:13 Restart pause, 5 second(s)
^C

The version of OpenSSL currently running on the remote server is as follows:

user $ openssl version
OpenSSL 1.0.2l  25 May 2017

whereas the version of OpenSSL currently running in Gentoo Linux on the laptop is:

user $ openssl version
OpenSSL 3.0.10 1 Aug 2023 (Library: OpenSSL 3.0.10 1 Aug 2023)

and the version of OpenSSL currently running in Lubuntu 22.04 on the desktop machine is:

user $ openssl version
OpenSSL 3.0.2 15 Mar 2022 (Library: OpenSSL 3.0.2 15 Mar 2022)

The last time I successfully used the OpenVPN client on the laptop was in 2020, when the version of OpenSSL on the laptop was 1.1.1g, so my suspicion grew that the root cause of the problem is a version difference in OpenSSL between the client machine and the remote server.

I searched the Web and found OpenVPN bug report #348: ‘2.6 client cannot connect to old 2.2 and 2.1 server‘. Therefore I tried adding the following three lines to the client.ovpn file (bsf1.ovpn) in Gentoo Linux:

tls-cert-profile insecure
providers legacy default
compat-mode 1.1.1

Now the laptop can connect to the remote VPN server via the command line in a terminal window, as shown in the output below:

root # openvpn --config bsf1.ovpn
2023-09-30 03:13:26 WARNING: Compression for receiving enabled. Compression has been used in the past to break encryption. Sent packets are not compressed unless "allow-compression yes" is also set.
2023-09-30 03:13:26 OpenVPN 2.6.4 x86_64-pc-linux-gnu [SSL (OpenSSL)] [LZO] [LZ4] [EPOLL] [MH/PKTINFO] [AEAD]
2023-09-30 03:13:26 library versions: OpenSSL 3.0.10 1 Aug 2023, LZO 2.10
2023-09-30 03:13:26 WARNING: No server certificate verification method has been enabled.  See http://openvpn.net/howto.html#mitm for more info.
Enter Private Key Password:
2023-09-30 03:13:33 WARNING: this configuration may cache passwords in memory -- use the auth-nocache option to prevent this
2023-09-30 03:13:33 TCP/UDP: Preserving recently used remote address: [AF_INET]111.222.333.444:1194
2023-09-30 03:13:33 Socket Buffers: R=[131072->131072] S=[16384->16384]
2023-09-30 03:13:33 Attempting to establish TCP connection with [AF_INET]111.222.333.444:1194
2023-09-30 03:13:33 TCP connection established with [AF_INET]111.222.333.444:1194
2023-09-30 03:13:33 TCPv4_CLIENT link local: (not bound)
2023-09-30 03:13:33 TCPv4_CLIENT link remote: [AF_INET]111.222.333.444:1194
2023-09-30 03:13:33 NOTE: UID/GID downgrade will be delayed because of --client, --pull, or --up-delay
2023-09-30 03:13:33 TLS: Initial packet from [AF_INET]111.222.333.444:1194, sid=4103e161 8493e221
2023-09-30 03:13:34 VERIFY OK: depth=1, C=PE, ST=Loreto, L=Iquitos, O=Work, OU=vpn, CN=server, name=server, emailAddress=brian@bsfitzgerald.com
2023-09-30 03:13:34 VERIFY OK: depth=0, C=PE, ST=Loreto, L=Iquitos, O=Work, OU=vpn, CN=server, name=server, emailAddress=brian@bsfitzgerald.com
2023-09-30 03:13:35 Control Channel: TLSv1, cipher SSLv3 DHE-RSA-AES256-SHA, peer certificate: 2048 bit RSA, signature: RSA-SHA256
2023-09-30 03:13:35 [server] Peer Connection Initiated with [AF_INET]111.222.333.444:1194
2023-09-30 03:13:35 TLS: move_session: dest=TM_ACTIVE src=TM_INITIAL reinit_src=1
2023-09-30 03:13:35 TLS: tls_multi_process: initial untrusted session promoted to trusted
2023-09-30 03:13:36 SENT CONTROL [server]: 'PUSH_REQUEST' (status=1)
2023-09-30 03:13:36 PUSH: Received control message: 'PUSH_REPLY,redirect-gateway def1,dhcp-options DNS 8.8.8.8,route-gateway 10.10.1.1,topology subnet,ping 10,ping-restart 120,ifconfig 10.10.1.4 255.255.255.0'
2023-09-30 03:13:36 Options error: Unrecognized option or missing or extra parameter(s) in [PUSH-OPTIONS]:2: dhcp-options (2.6.4)
2023-09-30 03:13:36 OPTIONS IMPORT: --ifconfig/up options modified
2023-09-30 03:13:36 OPTIONS IMPORT: route options modified
2023-09-30 03:13:36 OPTIONS IMPORT: route-related options modified
2023-09-30 03:13:36 Using peer cipher 'AES-128-CBC'
2023-09-30 03:13:36 net_route_v4_best_gw query: dst 0.0.0.0
2023-09-30 03:13:36 net_route_v4_best_gw result: via 192.168.96.245 dev wlp3s0
2023-09-30 03:13:36 ROUTE_GATEWAY 192.168.96.245/255.255.255.0 IFACE=wlp3s0 HWADDR=d8:fc:93:c5:f4:6d
2023-09-30 03:13:36 TUN/TAP device tun0 opened
2023-09-30 03:13:36 net_iface_mtu_set: mtu 1500 for tun0
2023-09-30 03:13:36 net_iface_up: set tun0 up
2023-09-30 03:13:36 net_addr_v4_add: 10.10.1.4/24 dev tun0
2023-09-30 03:13:36 net_route_v4_add: 111.222.333.444/32 via 192.168.96.245 dev [NULL] table 0 metric -1
2023-09-30 03:13:36 net_route_v4_add: 0.0.0.0/1 via 10.10.1.1 dev [NULL] table 0 metric -1
2023-09-30 03:13:36 net_route_v4_add: 128.0.0.0/1 via 10.10.1.1 dev [NULL] table 0 metric -1
2023-09-30 03:13:36 UID set to nobody
2023-09-30 03:13:36 GID set to nogroup
2023-09-30 03:13:36 Capabilities retained: CAP_NET_ADMIN
2023-09-30 03:13:36 Initialization Sequence Completed
2023-09-30 03:13:36 Data Channel: cipher 'AES-128-CBC', auth 'SHA256', compression: 'lzo'
2023-09-30 03:13:36 Timers: ping 10, ping-restart 12
[...]

and I can access the SMB shares on the remote server by entering ‘smb://192.168.0.10‘ in the Dolphin file manager’s window in KDE on the laptop.

However, if I terminate the openvpn client on the command line and then import the modified bsf1.ovpn file into NetworkManager using plasma-nm (the KDE GUI front-end to NetworkManager), connection attempts to the VPN still time out. The created NetworkManager connection file /etc/NetworkManager/system-connections/bsf1.nmconnection does not contain the settings in the additional three lines that I added to the client.ovpn file, as apparently they are meaningless to NetworkManager. When I use the plasma-nm GUI to import the client.ovpn file I assume plasma-nm or NetworkManager simply ignore the additional three lines when they parse the configuration file.

In Lubuntu 22.04 I edited bsf1.ovpn to add the three lines:

tls-cert-profile insecure
providers legacy default
compat-mode 1.1.1

and launched the openvpn client from the command line, but OpenVPN objected to the compat-mode line:

user $ sudo openvpn --config wjh1.ovpn
Options error: Unrecognized option or missing or extra parameter(s) in bsf1.ovpn:93: compat-mode (2.5.5)
Use --help for more information.

For the openvpn client command to execute successfully in Lubuntu 22.04 I had to omit the line ‘compat-mode 1.1.1‘, i.e. the two manually-added lines to bsf1.ovpn in Lubuntu 22.04 are:

tls-cert-profile insecure
providers legacy default

In my situation (i.e. the client is using OpenSSL 3.x.x in Lubuntu 22.04 and the remote server is using OpenSSL 1.x.x) the VPN connection still times out when attempting to connect using the GUI front-end (nm-tray or nm-applet) to NetworkManager in LXQt, so the work-around is still to launch the OpenVPN client from the command line as already explained:

user $ openvpn --conf bsf1.ovpn

and I can access the SMB shares on the remote server by entering ‘smb://192.168.0.10‘ in the PCManFM-Qt file manager’s window in LXQt on the desktop machine.

The remaining question I had was why my Samsung Galaxy Note 20 Ultra 5G running Android 13 can connect to the remote server via OpenVPN. I suspected that Android 13 uses an earlier version of OpenSSL that is compatible with the version on the remote server. A little research online showed me that Android 13 (and a couple of previous versions of Android) uses a Google fork of OpenSSL called BoringSSL. So, to find the version of OpenSSL/BoringSSL in Android 13, I cloned the BoringSSL repository on my laptop:

user $ git clone https://android.googlesource.com/platform/external/boringssl

and then I searched for the environment variable OPENSSL_VERSION_TEXT:

user $ grep -r OPENSSL_VERSION_TEXT boringssl/*
boringssl/include/openssl/crypto.h:// OPENSSL_VERSION_TEXT contains a string the identifies the version of
boringssl/include/openssl/crypto.h:#define OPENSSL_VERSION_TEXT "OpenSSL 1.1.1 (compatible; BoringSSL)"
boringssl/src/include/openssl/crypto.h:// OPENSSL_VERSION_TEXT contains a string the identifies the version of
boringssl/src/include/openssl/crypto.h:#define OPENSSL_VERSION_TEXT "OpenSSL 1.1.1 (compatible; BoringSSL)"
boringssl/src/crypto/crypto_test.cc:// Test that OPENSSL_VERSION_NUMBER and OPENSSL_VERSION_TEXT are consistent.
boringssl/src/crypto/crypto_test.cc:// Node.js parses the version out of OPENSSL_VERSION_TEXT instead of using
boringssl/src/crypto/crypto_test.cc:            std::string(OPENSSL_VERSION_TEXT).substr(0, strlen(expected)));

As I had surmised, OpenSSL (well, the fork BoringSSL) in Android 13 is Version 1.1.1. That is why the original bsf1.ovpn still works with the OpenVPN client on my phone to access the OpenVPN server running on the remote server.

By the way, in order to use OpenVPN in Lubuntu 22.04, you need to install the following three Ubuntu packages:

openvpn
network-manager-openvpn
network-manager-openvpn-gnome (despite Lubuntu using LXQt rather than GNOME)

The NetworkManager GUI front-end nm-tray does not support password asking, so you need to use the NetworkManager GUI front-end nm-applet to connect to the VPN (assuming both client and server have compatible versions of OpenSSL, that is). You can either type ‘nm-applet‘ on the command line or you can switch to using nm-applet instead of nm-tray by deselecting nm-tray in LXQt ‘Application Menu’ > ‘Preferences’ > ‘LXQt Settings’ > ‘Session Settings’ > ‘Autostart’ and adding nm-applet to the Autostart list. See Lubuntu Manual Appendix G Advanced Networking for further details. As already mentioned, in my situation the client is using OpenSSL 3.x.x and the server is using OpenSSL 1.x.x so the VPN connection still times out, therefore the work-around is still to launch openvpn from the command line:

user $ openvpn --conf bsf1.ovpn

To summarise my situation:

On my smartphone running Android 13 I simply use the OpenVPN client app for Android with the original client.ovpn configuration file (named ‘bsf1.ovpn‘ in my case) in order to connect to the VPN server on the remote server running OpenSSL 1.0.2l.

In Gentoo Linux currently running OpenSSL 3.0.10, I have to edit the original client.ovpn configuration file and add three lines, then launch the openvpn client from the command line in a terminal window in order to connect to the VPN server on the remote server running OpenSSL 1.0.2l.

In Lubuntu 22.04 currently running OpenSSL 3.0.2, I have to edit the original client.ovpn configuration file and add two lines, then launch the openvpn client from the command line in a terminal window in order to connect to the VPN server on the remote server running OpenSSL 1.0.2l.

The bottom line is: To avoid problems, check you have the same version of OpenSSL installed in the client and server devices when using OpenVPN.

Continuing my familiarisation with GeckoLinux/openSUSE

In an earlier post I described how I installed and configured GeckoLinux on an old nettop. GeckoLinux is actually pre-configured openSUSE:

GeckoLinux is a set of Linux spins built from the openSUSE distribution, with a focus on polish and out-of-the-box usability on the desktop. It is available in Static (based on openSUSE Leap) and Rolling (based on openSUSE Tumbleweed) editions.

As my old nettop only has an Intel dual-core Atom 330 CPU I wanted to install a spin with a lightweight desktop environment. I opted for the LXQt spin based on openSUSE Tumbleweed (see the aforementioned earlier post for details), and am pleased with its functionality and performance.

Upgrading

Since installing GeckoLinux/openSUSE I have periodically upgraded the installation, which is easy to do using two commands as root user in a terminal window:

ion330ht:/home/fitzcarraldo # zypper refresh
ion330ht:/home/fitzcarraldo # zypper dist-upgrade

(The command ‘zypper dist-upgrade‘ can be shortened to ‘zypper dup‘.)

Rolling back to an earlier snapshot

On one occasion the above-mentioned upgrade process did not work as expected. When I rebooted the nettop, the Display Manager’s login page appeared even though I had previously configured the system to login automatically. Furthermore, nothing happened when I entered my password. Although unwelcome, this meant I could try the openSUSE rollback feature for the first time. I rebooted the nettop and, when the GRUB menu screen appeared, instead of allowing openSUSE to boot normally I selected ‘Start bootloader from a read-only snapshot’. The next screen to appear displayed a list of snapshots; I selected one that appeared to be a snapshot taken before the upgrade. The system then continued booting, logged in automatically and displayed the LXQt Desktop. Great! However, snapshots are read-only so I needed to rollback to it to make it the current installation. After doing that I could then try again to upgrade the installation. A day had passed since the problematic upgrade, so I hoped that whatever package(s) had caused the problem would have already been revised. Anyway, to rollback to the snapshot I entered the following commands as root user:

ion330ht:/home/fitzcarraldo # snapper --ambit classic rollback
ion330ht:/home/fitzcarraldo # reboot

(The simpler command ‘snapper rollback‘ was not accepted in my case; I had to enter the command shown above.)

I then entered the aforementioned two zypper commands in order to refresh the repositories’ metadata and upgrade the installation to latest. This time the upgrade was successful and the nettop rebooted to the LXQt Desktop as expected. Phew! I think the ability to rollback to an earlier snapshot is an excellent feature of openSUSE.

Adding a network management applet to the LXQt Panel

After the steps in my earlier post I did not end up with an icon on the LXQt Panel for a NetworkManager applet, so I decided to add one to the Panel. In the other distributions I have used, the GTK+ package is called ‘nm-applet‘. However in GeckoLinux/openSUSE it is called ‘NetworkManager-applet‘. The package had been installed automatically when I installed GeckoLinux but, when I right-clicked on the LXQt Panel and selected ‘Manage Widgets’, I could not see the widget in the list of available widgets (click on the ‘+’ button). It turns out that I needed to add the ‘Status Notifier’ widget. The steps I followed are listed below.

1. Right-click on the Panel, select ‘Manage Widgets’ then click on the ‘+’ button and add the ‘Status Notifier’ widget. Click on the ‘Up’ or ‘Down’ arrow buttons to move the widget icon to where you want it to be on the Panel.

2. There should now be a network icon on the Panel for NetworkManager-applet. If you right-click on it the pop-up menu should enable you to enable/disable wired and wireless networking, select individual network connections, edit connections etc.

3. On the LXQt applications menu, select ‘Preferences’ > ‘LXQt Settings’ > ‘Session Settings’. Click on ‘Autostart’. Ensure ‘Network’ is ticked in the list under ‘Global Autostart’, as shown in the screenshot below.

NetworkManager-applet selected in the Autostart section of LXQt Session Settings.

The applet’s icon on the Panel is visible in the screenshot below.

NetworkManager-applet on the LXQt Panel.

If the NetworkManager-applet package has not been installed you can use Yast2 (GUI) or zypper (command line) to install it.

If you cannot get the above to work or you would like to try a Qt-based NetworkManager applet instead of the GTK+ based NetworkManager-applet (a.k.a. nm-applet), you can install the package nm-tray using Yast2 (GUI) or zypper (command line). In my case installing the package nm-tray resulted in two new entries in the LXQt ‘Application Autostart’ list of ‘LXQt Settings’ > ‘Session Settings’: ‘nm-tray’ in the ‘Global Autostart’ section, and ‘LXQt Network Applet’ in the ‘LXQt Autostart’ section. I had to untick ‘Network’ and ‘nm-tray’, and tick ‘LXQt Network Applet’, as shown in the screenshot below.

nm-tray applet selected in the Autostart section of LXQt Session Settings.

The applet’s icon on the Panel is visible in the screenshot below.

nm-tray applet on the LXQt Panel.

Either applet works fine in my installation, but you might decide to use nm-tray in LXQt rather than NetworkManager-applet, given that the former uses Qt whereas the latter uses GTK+. I notice that LXQt-based Lubuntu has switched from nm-applet to nm-tray, for example.

‘IP configuration was unavailable’: a laptop cannot connect wirelessly to a router

I recently switched my ISP from BT to Virgin Media because the speed and reliability of the broadband connection were low. A Virgin Media Hub 3 was supplied as part of the package, and the TV, laptops (Gentoo Linux, Windows 10 and macOS), desktops (Lubuntu and Windows 10), tablets and phones (Android and iOS) could connect to the Hub 3 without any trouble. A few weeks later Virgin Media offered to upgrade the hub to a Hub 4. I don’t look a gift horse in the mouth, so I accepted the offer. The Hub 4 does indeed improve on the already excellent broadband speeds I was getting with the Hub 3. On the downside the Hub 4’s configuration software has a couple of bugs, but I was able to live with them.

In addition to the above-mentioned hub configuration bugs, one of my laptops (a Compal NBLB2 with Intel Wireless WiFi Link 5300 AGN adapter) running Linux could not connect to the hub via Wi-Fi, even though it had no trouble connecting to the Hub 3. All other devices so far can connect to the Hub 4, so I was scratching my head. The laptop has no trouble connecting to the Hub 4 via Ethernet cable.

The hub’s 5G and 2.4G Wi-Fi bands originally had the same SSID (I’ll call it ‘VM1234567‘ here). I decided to rename the two bands ‘VM1234567_5G‘ and ‘VM1234567_2.4G‘ respectively, via the hub’s Settings in a Web browser. Very occasionally the laptop could connect to either SSID, but usually it could not connect and the following notification would pop up:

Wireless interface (wlan0)
IP configuration was unavailable

I did various things to try to get the laptop to connect, such as:

• changing Wi-Fi channel selection in the hub from Auto to Manual and specifying different channels myself;
• specifying the BSSID in the Desktop Environment’s GUI front-end to NetworkManager;
• explicitly restricting the connection to the specific (and only) Wi-Fi interface (‘wlan0‘, in my case) in the DE’s GUI front-end to NetworkManager;
• disabling IPv6 (Virgin Media does not use IPv6) in the DE’s GUI front-end to NetworkManager;
• disabling the UFW firewall.

None of the above enabled the laptop to connect to the hub via Wi-Fi.

I installed the GUI Wi-Fi scanner LinSSID on my other Linux machines so I could check which 2.4G and 5G Wi-Fi channels were being used by the hub and by my neighbours’ hubs/routers. Note that LinSSID requires the utility iw to be installed and CONFIG_CFG80211_WEXT to be set in the kernel. The NetworkManager command ‘nmcli dev wifi list‘ can also be used to check which channels are being used. The channels selected automatically by the hub looked reasonable to me, and the different channels I selected manually did not improve the situation.

Now, coincidentally that laptop can dual-boot Windows 7, so I booted Windows 7 to see if it could connect to the hub via Wi-Fi. However, Windows 7 had the same Wi-Fi connectivity problem as Linux. The Network and Sharing Centre displayed the error message ‘The default gateway is not available’ and allowed me to run the so-called Troubleshooter, which fixed the problem in Windows 7. The laptop could then connect to the hub and to the Internet via the 5G Wi-Fi band (the hub’s DHCP server allocated IP address 192.168.0.145 to the laptop). So it appeared the lack of a specified default gateway was the problem in both OSs. This surprised me because I had never had to specify a default gateway on my machines, and still do not have to on the other machines. Anyway, I booted back into Linux and did the following:

STEP 1 (on the Compal laptop)

Connected to the hub via an Ethernet cable.

Opened the Hub 4 Settings page (192.168.0.1) in a Web browser.

Selected ‘Advanced settings’ > ‘DHCP’

Added the MAC address of the laptop’s Wi-Fi adapter and the IP address 192.168.0.145 to the Reserved list.

STEP 2 (on the Compal laptop)

Selected ‘System Settings’ > ‘Network’ | ‘Connections’

Selected Wi-Fi connection VM1234567_5G

Entered the following on the ‘IPv4’ tab:

Method: Manual
DNS Servers: 194.168.4.100,194.168.8.100
Search Domains: cable.virginm.net (The laptop connects without this entry, so I’m not sure if it makes any difference.)

Clicked ‘+ Add’ and added the gateway details as follows:

Address
192.168.0.145

Netmask
255.255.255.0

Gateway
192.168.0.1

Ticked ‘IPv4 is required for this connection’.

Set the following on the ‘Wi-Fi’ tab (this is optional):

BSSID: <hub’s MAC address corresponding to the SSID>
Restrict to device: wlan0 (<MAC address of the laptop’s Wi-Fi adapter>)

The BSSID can be found either by using LinSSID on a machine that can access the Wi-Fi network or by using the command ‘nmcli dev wifi list‘ in a terminal window. The MAC address of the laptop’s Wi-Fi adapter can be found using the commands ‘ip link‘ or ‘ifconfig‘.

Clicked on the down arrow in the ‘Restrict to device:’ box and selected the device (wlan0, in my case).

STEP 3 (on the Compal laptop)

Selected ‘System Settings’ > ‘Network’ | ‘Connections’

Selected Wi-Fi connection VM1234567_2.4G

Performed the same configuration steps as for VM1234567_5G except that the SSID V1234567_2.4G has a different BSSID (found using LinSSID or nmcli) to the SSID V1234567_5G.

The laptop’s 5G W-Fi connection now works very well with the Hub 4. The 2.4G connection can be slow (even when the signal is at 100%) and sometimes stalls, so I’m not sure I have fixed that connection completely, or even if it is fixable in this case. I still do not know why the problem occurs with the Hub 4 but not the Hub 3, and why it only happens with one specific machine. Anyway, the 5G connection now works fine, so I’m happy.

croc – another file transfer method

I have lost count of the number of times I have had to send a large file to someone at work, usually in a hurry. I’ve used Dropbox, ownCloud, Firefox Send (no longer available) etc. Transferring large files became a bit easier when e-mail service providers increased the size limit for attachments, but that is still not a solution for very large files. The xkcd cartoon FILE TRANSFER sums up the situation nicely.

I recently discovered the command line utility croc, which the author claims is a way to ‘easily and securely transfer stuff from one computer to another.’ I thought I’d give it a try, if only to have another tool to fall back on in an emergency. It does rely on both ends having croc installed, but hopefully that should not be a show-stopper as croc is available for Linux, Windows, macOS and BSD. To quote the author:

croc differs from a utility like scp because it doesn’t require any two computers to have enabled port-forwarding. Instead, croc will uses a relay – a temporary server setup locally (if both computers are on lan) or publicly (default is at croc4.schollz.com). Any two computers can connect to the relay, and after securing their channel with PAKE [password authenticated key exchange], they can transfer encrypted metadata and data through the relay. The relay works by first having the computers communicate the PAKE protocol via websockets, and then exchanging encrypted metadata, and then stapling the TCP connections directly so that they can transfer directly.

So, to use croc you will be dependent on the public relay provided by the author unless you set up your own relay (instructions are provided in the author’s original 2018 blog post introducing croc – see link above – and in various third-party articles about croc, such as ‘Securely Transfer Files and Folders Between Computers Using Croc‘ and ‘Transfer Files And Folders Between Computers With Croc‘).

Anyway, I installed croc in Lubuntu and Gentoo Linux from the author’s GitHub repository and indeed it is easy to use and works fine. The binary releases for the various OSs and Linux distributions can be found on the Releases page of the GitHub repository or via the OS package manager.

Lubuntu 20.10:

user $ wget https://github.com/schollz/croc/releases/download/v9.1.6/croc_9.1.6_Linux-64bit.deb
user $ sudo dpkg -i croc_9.1.6_Linux-64bit.deb

Gentoo Linux:

root # emerge net-misc/croc

(Note that croc ebuilds are not currently marked as Stable in the Gentoo Linux Portage tree, so you’ll have to unmask them by keyword if you are using the Stable branch.)

Termux:

I even installed croc in Termux on my Samsung Galaxy Note 20 Ultra 5G, and it works in Android too:

$ pkg install croc

Other OSs and other Linux distributions:

See the instructions in the README file online.

Using croc

Using croc is as simple as entering a command on one computer, informing (via e-mail, telephone, SMS, Signal or other social media) the person using the other computer of the command to use, and entering that command on the other computer. For example:

Sender

user $ croc send Documents/flight-times.ods
Sending 'flight-times.ods' (16.6 kB)
Code is: 8878-salary-courage-roger
On the other computer run

croc 8878-salary-courage-roger

Receiver

user $ croc 8878-salary-courage-roger
Accept 'flight-times.ods' (16.6 kB)? (Y/n) 

If the receiving user then enters ‘Y’, the sending user sees something similar to this:

user $ croc send Documents/flight-times.ods
Sending 'flight-times.ods' (16.6 kB)
Code is: 8878-salary-courage-roger
On the other computer run

croc 8878-salary-courage-roger

Sending (->192.168.1.74:60740)
 100% |████████████████████| (17/17 kB, 10.918 MB/s)
user $ 

and the receiving user sees something similar to this:

user $ croc 8878-salary-courage-roger
Accept 'flight-times.ods' (16.6 kB)? (Y/n) Y

Receiving (<-[::1]:39442)
 100% |████████████████████| (17/17 kB, 3.989 MB/s)
user $ 

The observant reader will notice that the above example shows a file being transferred on the same computer. When transferred between different computers the IP addresses of each computer will be displayed instead. I have used croc to transfer files between different computers on my home network (I would normally just use my NAS for this, though), between remote computers on the Internet, and between my computers and my phone via mobile broadband, and croc works in all cases.

I have not mentioned all croc’s features. I’ll leave you to read up on croc in more detail in the links I’ve given above. It looks like it might be a useful tool to have installed.

Using NetworkManager in Gentoo Linux

My current two laptops running Gentoo Linux (both with OpenRC, elogind, eudev and wpa_supplicant) use NetworkManager rather than Netifrc. (Actually, my desktop machines also use NetworkManager even though they are always connected to the same network.) NetworkManager has worked with wired and wireless networking on these laptops without any issues for over five years now. This post summarises how it is installed and configured.

I installed the package with the following USE flags enabled:

bluetooth dhclient elogind introspection modemmanager ncurses nss policykit ppp wext wifi

and the following USE flags disabled:

audit connection-sharing dhcpcd gnutls iwd json ofono ovs resolvconf selinux systemd teamd test vala

The precise status can be seen in the output of the eix command on my main laptop that uses Gentoo Stable:

root # eix -I net-misc/networkmanager
[I] net-misc/networkmanager
     Available versions:  [M]~1.22.10-r12^t 1.26.4^t ~1.26.6^t ~1.28.0-r1^t {audit bluetooth +concheck connection-sharing debug (+)dhclient dhcpcd elogind examples (+)gnutls gtk-doc (+)introspection iwd json libpsl lto (+)modemmanager ncurses (+)nss ofono ovs (+)policykit (+)ppp resolvconf selinux syslog systemd teamd test +tools vala (+)wext +wifi ABI_MIPS="n32 n64 o32" ABI_S390="32 64" ABI_X86="32 64 x32" KERNEL="linux"}
     Installed versions:  1.26.4^t(00:33:18 02/01/21)(bluetooth dhclient elogind introspection modemmanager ncurses nss policykit ppp wext wifi -audit -connection-sharing -dhcpcd -gnutls -iwd -json -ofono -ovs -resolvconf -selinux -systemd -teamd -test -vala ABI_MIPS="-n32 -n64 -o32" ABI_S390="-32 -64" ABI_X86="64 -32 -x32" KERNEL="linux")
     Homepage:            https://wiki.gnome.org/Projects/NetworkManager
     Description:         A set of co-operative tools that make networking simple and straightforward

I use network file systems, so I also configured the netmount service to run, and specified that NetworkManager is the network manager:

root # grep -v "^#\|^$" /etc/conf.d/netmount
rc_need="NetworkManager"

The network-related services that I configured to be started at boot are as follows:

root # rc-update show -v | grep -i net
       NetworkManager |      default
                local |      default nonetwork
           net-online |
         net.enp4s0f1 |
               net.lo |
             netmount |      default

(It is correct that net-online, net.enp4s0f1 and net.lo are not in any runlevel.)

Neither dhcpd nor dhcpcd services must be started at boot, as they would interfere with NetworkManager:

root # rc-update show -v | grep -i dhcp
               dhcpcd |   
                dhcpd |

By the way, if the output of the command ‘rc-update show -v‘ incudes non-existent physical interfaces not shown in the output of the ‘ifconfig‘ or ‘ip a‘ commands, you can delete the corresponding symlinks. For example, the only physical interfaces listed by the ifconfig command on my older laptop running Gentoo Linux Testing (~amd64) are eth0 and wlan0, but the ‘rc-update show -v‘ command originally showed many other interfaces, so I deleted them as follows:

root # cd /etc/init.d/
root # rm net.aol
root # rm net.ra*
root # rm net.ath*
root # rm net.eth[1,2,3,4,5,6,7,8]
root # rm net.ppp*
root # rm net.wlan[1,2,3]

The installation on that laptop is left with the correct symlinks:

root # ls -la /etc/init.d/net.*
lrwxrwxrwx 1 root root     6 Mar 30  2010 /etc/init.d/net.eth0 -> net.lo
-rwxr-xr-x 1 root root 19861 Feb 15 01:05 /etc/init.d/net.lo
lrwxrwxrwx 1 root root     6 Mar 30  2010 /etc/init.d/net.wlan0 -> net.lo

Anyway, coming back to my main laptop, all the services running in Gentoo Linux on it are shown below, for information:

root # rc-status
Runlevel: default
 dbus                                                       [  started  ]
 NetworkManager                                             [  started  ]
 netmount                                                   [  started  ]
 syslog-ng                                                  [  started  ]
 cupsd                                                      [  started  ]
 samba                                                      [  started  ]
 cronie                                                     [  started  ]
 clamd                                                      [  started  ]
 bluetooth                                                  [  started  ]
 xdm                                                        [  started  ]
 wsdd                                                       [  started  ]
 cups-browsed                                               [  started  ]
 sshd                                                       [  started  ]
 local                                                      [  started  ]
Dynamic Runlevel: hotplugged
Dynamic Runlevel: needed/wanted
 xdm-setup                                                  [  started  ]
 avahi-daemon                                               [  started  ]
Dynamic Runlevel: manual

I specified the laptop’s hostname in /etc/hosts, /etc/conf.d/hostname, /etc/hostname and /etc/dhcp/dhclient.conf:

root # grep -v "^#\|^$" /etc/hosts
127.0.0.1       clevow230ss     localhost
::1             clevow230ss     localhost

root # cat /etc/conf.d/hostname
# Set to the hostname of this machine
hostname="clevow230ss"

root # cat /etc/hostname
clevow230ss

root # grep -v "^#\|^$" /etc/dhcp/dhclient.conf
send host-name "clevow230ss";
supersede host-name "clevow230ss";

The purpose of the ‘supersede‘ statement in dhclient.conf is explained in man dhclient.conf(5):

supersede [ option declaration ] ;

If for some option the client should always use a locally-configured value or values rather than whatever is supplied by the server, these values can be defined in the supersede statement.

In other words, I do not want the hostname to be specified by a dhcp server (as this has caused problems for me in the past when connected to some networks).

I edited the configuration file /etc/NetworkManager/NetworkManager.conf to contain the following:

[main]
plugins=keyfile
rc-manager=none
dhcp=dhclient
no-auto-default=*

[keyfile]
hostname=clevow230ss

In earlier days it was necessary to specify the hostname in /etc/NetworkManager/NetworkManager.conf but that is no longer required. According to NetworkManager.conf(5) man page: ‘This key is deprecated and has no effect since the hostname is now stored in /etc/hostname or other system configuration files according to build options.’ I just left it in the file because it does no harm.

NetworkManager’s configuration files for your wired and wireless connections are normally created and edited by using the GUI network configuration tool (a.k.a. ‘front end’) in the Desktop Environment, such as plasma-nm and nm-applet, but can also be created/edited manually. For example, the NetworkManager file for my home Wi-Fi connection contains the following:

root # cat /etc/NetworkManager/system-connections/BT-5DF82T.nmconnection
[connection]
id=BT-5DF82T
uuid=3190e9d6-961f-38ab-fb90-1d323e6f35d2
type=wifi
autoconnect=false
permissions=

[wifi]
mac-address-blacklist=
mode=infrastructure
ssid=BT-5DF82T

[wifi-security]
key-mgmt=wpa-psk
psk-flags=1

[ipv4]
dns-search=
method=auto

[ipv6]
addr-gen-mode=stable-privacy
dns-search=
method=auto

NetworkManager generates the UUID automatically, but it could be generated manually (I have never bothered to do that):

The UUID values in the config files must be unique. You can use uuidgen command line tool to generate such values. Alternatively, you can leave out UUID entirely. In that case NetworkManager will generate a UUID based on the file name.

iwd (iNet Wireless Daemon)

Note that NetworkManager can be used with iwd instead of wpa_supplicant, although I have never bothered to try iwd, as NetworkManager with wpa_supplicant works fine on my laptops. If you want to try iwd instead of wpa_supplicant, NetworkManager will have to be installed with the iwd and introspection USE flags enabled, and you may have to make sure iwd is running before NetworkManager — see the following for further details:

• Gentoo Linux Forums – [SOLVED]NetworkManager WiFi unavailable
• NetworkManager – iwd backend gets activated but NM considers the device unavailable
• iwd Mailing List – Start iwd only after dbus

A Linux command-line utility to discover and list WSD-enabled computers and printers on a home network

In an earlier post I covered the installation and use of wsdd, a WS-Discovery (WSD) daemon that can run on Linux machines and enable machines running Microsoft Windows 10 to discover Linux machines in File Explorer now that Windows 10 has dropped Computer Browser, NetBIOS and SMBv1. All my Linux machines in my home network have wsdd running alongside NetBIOS broadcast name resolution, SMBv2 (used by my Android phone) and SMBv3 (used by my Linux machines). If any visitors to my house happen to bring a laptop running Windows 10, they will be able to discover my SMB shares in File Explorer, which I have always been able to do in Linux and in earlier Windows releases that supported NetBIOS and Computer Browser.

As I pointed out in a comment to another of my earlier posts, a downside of not using the (insecure) SMBv1 protocol is that the Samba utility smbtree incorrectly returns nothing if you enter the command smbtree when using SMBv2 or SMBv3. As all the Linux machines in my home network are running the wsdd daemon in addition to NetBIOS, SMBv2 and SMBv3 — and any visitors’ laptops could be running Windows 10 — it would be nice to have a command-line utility that would discover all machines. Well, here is a stab at such a utility, written by a close relative of mine as a learning exercise in WSD and Python, and is provided here as-is without any warranty or support. It consists of the following five files:

wsd-discover.sh

#!/bin/bash

function del-tmp-files() {
   if ls /tmp/wsd-*.txt 1> /dev/null 2>&1; then
      rm /tmp/wsd-*
   fi
return 0
}

# Delete pre-existing temporary work files.

del-tmp-files

# Get the V5 UUID of this machine
UUID=$(python3 $HOME/discover/wsd-gen-uuid.py)

# Send a multicast probe to all WSD capable devices and store the XML output in wsd-probe1.txt
echo
echo "Please wait.....sending multicast discovery probe and waiting 2 seconds for responses"
echo
python3 $HOME/discover/wsd-mcast-probe.py > /tmp/wsd-probe1.txt

# Iterate through the XML until the UUID to IPv4 mappings are obtained in wsd-probe9.txt
more /tmp/wsd-probe1.txt | grep Computer | awk -F "<wsa:Address>" '{print $2}' > /tmp/wsd-probe2.txt

sort -u /tmp/wsd-probe2.txt > /tmp/wsd-probe3.txt

more /tmp/wsd-probe3.txt | awk -F "uuid:" '{print $2}' > /tmp/wsd-probe4.txt

more /tmp/wsd-probe4.txt | awk -F "</wsa:Address>" '{print $1,"******",$2}' > /tmp/wsd-probe5.txt

more /tmp/wsd-probe5.txt | awk -F "from" '{print $1,"******",$2}' > /tmp/wsd-probe6.txt

more /tmp/wsd-probe6.txt | awk -F "******" '{print $1 $3}' > /tmp/wsd-probe7.txt

more /tmp/wsd-probe7.txt | awk -F "\\\('" '{print $1 $2}' > /tmp/wsd-probe8.txt

more /tmp/wsd-probe8.txt | awk -F "'" '{print $1}' > /tmp/wsd-probe9.txt

# Read the UUID to IPv4 mappings until end of file and send XML requests to each WSD host

while read RECORD; do

	URN=$(echo $RECORD | cut -d" " -f1)
	IPA=$(echo $RECORD | cut -d" " -f2)

	# Generate the HTTP/XML request file from the template
	cat $HOME/discover/wsd-template.xml | sed 's/XXXXXXXXXX/'$URN'/g' > /tmp/wsd-request.txt
	cat /tmp/wsd-request.txt | sed -i 's/YYYYYYYYYY/'$UUID'/g' /tmp/wsd-request.txt

	# Send the XML/SOAP request to the target machine
	curl -s -A wsd --header "Accept-Encoding: identity" --header "Connection: Close" \
	--header "Content-Type: application/soap+xml" --header "User-Agent: wsd" \
	--data @/tmp/wsd-request.txt http://$IPA:5357/$URN > /tmp/wsd-response-$IPA.txt

	# Extract, format and display the information returned
	echo
	echo "Device IP : $IPA"
	echo "==========================="
	echo -n "Name         :";cat /tmp/wsd-response-$IPA.txt | awk -F "FriendlyName" '{print $2}' | awk -F "<" '{print $1}' | cut -d">" -f2
	echo -n "Manufacturer :";cat /tmp/wsd-response-$IPA.txt | awk -F "Manufacturer" '{print $2}' | awk -F "<" '{print $1}' | cut -d">" -f2
	echo -n "Model        :";cat /tmp/wsd-response-$IPA.txt | awk -F "ModelName" '{print $2}' | awk -F "<" '{print $1}' | cut -d">" -f2
	echo -n "Category     :";cat /tmp/wsd-response-$IPA.txt | awk -F "DeviceCategory" '{print $2}' | awk -F "<" '{print $1}' | cut -d">" -f2
	echo -n "URN          :";cat /tmp/wsd-response-$IPA.txt | awk -F "Address" '{print $2}' | awk -F "<" '{print $1}' | cut -d">" -f2
	echo -n "Type         :";cat /tmp/wsd-response-$IPA.txt | awk -F "Types" '{print $2}' | awk -F "<" '{print $1}' | cut -d">" -f2
	echo -n "Workgroup    :";cat /tmp/wsd-response-$IPA.txt | awk -F "<pub:Computer" '{print $2}' | awk -F "<" '{print $1}' | cut -d">" -f2
	echo

done < /tmp/wsd-probe9.txt

# This next bit is just a bit of fluff to display printers. The formatting is inconsistent because every printer
# has a different web page. Printer manufacturers are listed in the file $HOME/discover/printers.txt. If the printer
# is not in this file it won't be found in the HTTP information

# Check whether the original multicast response contains any printer information
cat /tmp/wsd-probe1.txt | grep -q -A2 Print

if [[ $? -eq 0 ]]; then # A printer of some sort has been found

   # Get the line that contains 'Print' and the two lines after it (one of which contains the printer IP and URL)
   more /tmp/wsd-probe1.txt | grep -A2 Print > /tmp/wsd-probe10.txt

   # Remove any duplicate entries
   sort -u /tmp/wsd-probe10.txt > /tmp/wsd-probe11.txt

   # Isolate the printer IP and URL information
   cat /tmp/wsd-probe11.txt | awk -F"XAddrs>" '{print $2}' | awk -F"/wsd" '{print $1}' > /tmp/wsd-probe12.txt

   # Remove blank lines to clean up the file
   sed '/^$/d' /tmp/wsd-probe12.txt > /tmp/wsd-probe13.txt

   # Read each line of the file containing the printer URLs and contact the printers in turn
   while read RECORD; do

	echo "Printers"
	echo "==========================="
	URL=$RECORD
	# Try to get the printer's HTML page
        curl -s $URL/index.html > /tmp/wsd-printer.txt
	if [[ $? -ne 0 ]]; then
           echo "Couldn't get HTML info from $URL"
	else
	   # Read each line of the printers.txt file and try to get the Make and Model from the HTML
           while read PRT; do
		 grep -q $PRT /tmp/wsd-printer.txt
		 if [[ $? -eq 0 ]]; then # Printer in the list is contained in the returned HTML
		    # Extract the Make and the following word hoping it's the Model
		    TYP=$(grep $PRT /tmp/wsd-printer.txt | awk -v a=$PRT '{for(i=1;i<=NF;i++) if ($i==a) print $i,$(i+1)}')
		    echo "URL   : $URL"
                    echo "Make  : $TYP"
		 fi
	   done < $HOME/discover/printers.txt
	fi

   done < /tmp/wsd-probe13.txt

fi

echo

#
# Delete the latest temporary work files.
#
del-tmp-files

wsd-gen-uuid.py

import uuid
import socket

hostName = (socket.gethostname())

# nameSpaces = [uuid.NAMESPACE_DNS, uuid.NAMESPACE_URL, uuid.NAMESPACE_OID, uuid.NAMESPACE_X500]
nameSpaces = [uuid.NAMESPACE_DNS]

for namespace in nameSpaces:

    print (uuid.uuid5(namespace, hostName))

wsd-mcast-probe.py

import socket
import struct
import sys
import uuid

# Create a V1 UUID for the MessageID based on the host address and current time
# The MessageID must be unique but it isn't necessary to have anything other than a V1 UUID
uuid1 = uuid.uuid1()
myuuid = str(uuid1)
print ("Generating UUID for MessageID")
print(myuuid)

# The string 'message' is a template WSD probe that is multicast to group 239.255.255.250 port 3702
# The template should not change unless there is a major change to the WSD specifications
# Escape double quotation marks within the message string (but not the outer double quotation marks)
message = "<?xml version=\"1.0\" encoding=\"utf-8\"?><soap:Envelope xmlns:pnpx=\"http://schemas.microsoft.com/windows/pnpx/2005/10\" xmlns:pub=\"http://schemas.microsoft.com/windows/pub/2005/07\" xmlns:soap=\"http://www.w3.org/2003/05/soap-envelope\" xmlns:wsa=\"http://schemas.xmlsoap.org/ws/2004/08/addressing\" xmlns:wsd=\"http://schemas.xmlsoap.org/ws/2005/04/discovery\" xmlns:wsdp=\"http://schemas.xmlsoap.org/ws/2006/02/devprof\" xmlns:wsx=\"http://schemas.xmlsoap.org/ws/2004/09/mex\"><soap:Header><wsa:To>urn:schemas-xmlsoap-org:ws:2005:04:discovery</wsa:To><wsa:Action>http://schemas.xmlsoap.org/ws/2005/04/discovery/Probe</wsa:Action><wsa:MessageID>urn:uuid:" + myuuid + "</wsa:MessageID></soap:Header><soap:Body><wsd:Probe><wsd:Types>wsdp:Device</wsd:Types></wsd:Probe></soap:Body></soap:Envelope>"

# Convert the message to a UTF-8 byte string
bytstr = message.encode('utf-8')

# Define a variable for the multicast group and multicast destination port
multicast_group = ('239.255.255.250', 3702)
multicast_address = '239.255.255.250'

# Cheeky way to get the Internet facing Ethernet IP address for use further down
# Create a socket, pretend to use it to connect to an Internet service. Nothing is actually sent
# but the IP address of the Internet facing interface is returned 
def get_ip_address():
    sock1 = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    sock1.connect(("8.8.8.8", 80))
    return sock1.getsockname()[0]

# Create datagram socket 1 for multicasts and allow the IP address and port to be reused in case something
# else is using them e.g. the WSD service
sock1 = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
sock1.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
sock1.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)

IPADDR = (get_ip_address())

# Set the multicasts TTL to 1 so they stay on the local segment
sock1.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_TTL, 1)

# Set a timeout so the socket stops listening if no data is received within the timeout
# This prevents it from locking up
sock1.settimeout(2.0)

# Bind the socket to the IP and port that we wish to use as the source IP and port of datagrams we transmit
# AND the destination IP and port of datagrams that we receive
sock1.bind ((IPADDR, 3702))

# Join the 239.255.255.250 multicast group. This isn't necessary if this script is being run on a machine
# that is also running the wsdd daemon. Joining the multicast group allows the script to be run on any
# machine regardless

mreq = struct.pack("4sl", socket.inet_aton(multicast_address), socket.INADDR_ANY)
sock1.setsockopt(socket.IPPROTO_IP, socket.IP_ADD_MEMBERSHIP, mreq)

try:

    # Send the WSD probe (bytstr) to the multicast group and port
    # print ('\nsending "%s"' % bytstr)
    sent = sock1.sendto(bytstr, multicast_group)

    # Listen for up to 4096 byte responses from all responders to the multicast message
    while True:
       print ('\nwaiting to receive responses')
       try:
           data, addr = sock1.recvfrom(4096)

           # We could use the format below to split 'addr' into its component IP and port fields but is isn't necessary
           # data, (ip, port) = sock1.recvfrom (4096)

       except:
           # This exception only occurs if no data is received on socket for the timeout period
           print ('\ntimed out, no more responses socket1')
           break
       else:
           # This is the response data that the bash script writes out to the wsd-probe1.txt file
           print ('\nreceived %s from %s' % (data.decode('utf-8'), addr))

finally:
    print ('\nsocket closed\n')

wsd-template.xml

<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope
      xmlns:pnpx="http://schemas.microsoft.com/windows/pnpx/2005/10"
      xmlns:pub="http://schemas.microsoft.com/windows/pub/2005/07"
      xmlns:soap="http://www.w3.org/2003/05/soap-envelope"
      xmlns:wsa="http://schemas.xmlsoap.org/ws/2004/08/addressing"
      xmlns:wsd="http://schemas.xmlsoap.org/ws/2005/04/discovery"
      xmlns:wsdp="http://schemas.xmlsoap.org/ws/2006/02/devprof"
      xmlns:wsx="http://schemas.xmlsoap.org/ws/2004/09/mex">
      <soap:Header>
            <wsa:To>urn:uuid:XXXXXXXXXX</wsa:To>
            <wsa:Action>http://schemas.xmlsoap.org/ws/2004/09/transfer/Get</wsa:Action>
            <wsa:MessageID>urn:uuid:fe11d044-bc13-11ea-b98c-2c56dc778d37</wsa:MessageID>
            <wsa:ReplyTo>
                 <wsa:Address>http://schemas.xmlsoap.org/ws/2004/08/addressing/role/anonymous</wsa:Address>
            </wsa:ReplyTo>
            <wsa:From>
                 <wsa:Address>urn:uuid:YYYYYYYYYY</wsa:Address>
            </wsa:From>
      </soap:Header>
      <soap:Body />
</soap:Envelope>

printers.txt

Brother
Canon
Epson
HP
Kodak
Lexmark

How to install

user $ mkdir $HOME/discover

Use a text editor to create the five files listed above in the directory $HOME/discover/.

Make the Bash script and the Python scripts executable:

user $ chmod u+x $HOME/discover/*.sh $HOME/discover/*.py

How to use

user $ $HOME/discover/wsd-discover.sh

The script will list discovered devices (see the caveat in the Description section below). For example:

user $ $HOME/discover/wsd-discover.sh

Please wait.....sending multicast discovery probe and waiting 2 seconds for responses


Device IP : 192.168.1.121
===========================
Name         :WSD Device tutankhamun
Manufacturer :wsdd
Model        :wsdd
Category     :Computers
URN          :urn:uuid:ff03f853-8a45-5ad9-b75b-fe4f632c8c5b
Type         :pub:Computer
Workgroup    :TUTANKHAMUN/Workgroup:HOME


Device IP : 192.168.1.10
===========================
Name         :WSD Device akhanaten
Manufacturer :wsdd
Model        :wsdd
Category     :Computers
URN          :urn:uuid:ad8fedfb-a22c-5551-92b4-653aae69f379
Type         :pub:Computer
Workgroup    :AKHANATEN/Workgroup:HOME


Device IP : 192.168.1.74
===========================
Name         :WSD Device thutmoseiii
Manufacturer :wsdd
Model        :wsdd
Category     :Computers
URN          :urn:uuid:9bf49ac3-e58d-57a4-87ea-7c0d5ef02234
Type         :pub:Computer
Workgroup    :THUTMOSEIII/Workgroup:HOME

Printers
===========================
URL   : http://192.168.1.78:80
Make  : Canon MP560

The example output above was for a network of three Linux machines running the wsdd daemon, connected via Ethernet, plus a printer connected via Wi-Fi.

Description

The scripts are non-intrusive and discover WSD-enabled devices in multicast group 239.255.255.250 port 3702, namely a) Windows 10 and b) other Linux machines running the WSD daemon wsdd or other WSD software. It runs over Ethernet and Wi-Fi. The script joins the multicast group (with a reusable socket) and sends out a WSD Probe. The responses contain the UUID-to-IP address mappings of the devices it discovers. Each discovered device is then contacted individually on its IP address TCP port 5357 to retrieve basic information.

If you run the script on Linux with the WSD Daemon (wsdd) also running (see earlier post), the script discovers itself as well as other devices. If you run the script on a machine that is not running the WSD Daemon it still discovers other devices, but not itself.

The script also discovers any WSD-enabled printers that listen for multicasts on UPnP / SSDP group 239.255.255.250 but don’t care about what UDP port is being used. If a WSD-enabled printer is detected, the script attempts to retrieve the make and model of the printer using HTTP. To detect different printer makes, add the manufacturer e.g. Canon, Epson, Lexmark etc. to the file ‘printers.txt‘. The script reports on the printer make and tries to extract the model type. It may not always format the output 100% accurately.

The main thing to bear in mind is that the scripts do not maintain state i.e. a single discovery probe is transmitted. Multicast is fundamentally unreliable and only devices that respond are reported. If the probe is lost or an end device doesn’t respond, for whatever reason, it doesn’t get reported. You can run the script a few times to ensure that it picks up as many of the devices as it possibly can.

Firewall zones (profiles) in Linux, and how to switch them automatically if you use UFW

Firstly, a note on terminology: UFW (Uncomplicated Firewall) and its two GUI front-ends Gufw and UFW Frontends use the term ‘application profile’ to refer to a pre-configured set of rules specified in a file. Files containing UFW application profiles are placed in the directory /etc/ufw/applications.d/. An application profile for SMB, for example, enables the root user to use the UFW command ‘ufw allow Samba‘ (‘ufw allow CIFS‘ in Gentoo Linux) rather than having to enter UFW commands specifying the precise ports and network protocols that SMB uses. However, this blog post is not about UFW’s application profiles; it is about what Gufw calls ‘profiles’ and firewalld calls ‘zones’.

In essence a profile/zone is a collection of firewall policies and rules. Both Gufw and firewalld include the concept of a ‘zone’, although Gufw uses the term ‘profile’ rather than ‘zone’. UFW Frontends does not have the concept of a ‘zone’; rules entered via UFW Frontends apply to any network to which you connect your laptop. The ability to define different zones for different networks is handy. For example, you can have certain policies and rules when your laptop is connected to your home network, and different policies and rules when your laptop is connected to the network in a café, hotel, airport or other public place.

An attractive feature of firewalld when used in conjunction with NetworkManager and KDE Plasma is that it is possible to use the desktop environment’s network management module (‘System Settings’ > ‘Connections’) to specify a particular firewalld zone for a particular network connection. For example, let’s say you used firewalld to specify certain policies and rules for a zone you named ‘office’, and you then specified in the System Settings – Connections GUI that a connection named ‘ACM’ should use the zone ‘office’. Thereafter, whenever you connect your laptop to the network named ‘ACM’, firewalld will use the policies and rules you previously configured for the zone ‘office’.

Unlike firewalld, Gufw does not have the ability to switch profiles automatically according to which network the laptop is connected. You have to select manually the profile you wish to use. You would launch Gufw prior to connecting to, for example, your office’s network, select the profile ‘Office’ (or whatever you have named it), then connect your laptop to that network.

I think many people would be satisfied with the functionality currently provided by Gufw. I could use the Gufw GUI to create Gufw profiles with names such as ‘Home’, ‘HomeDave’, ‘Public’, ‘HQoffice’, ‘USoffice’, ‘PestanaRio’ and so on, and specify the different policies and rules I want for each profile. At home I would launch Gufw on my laptop and select the Home profile then connect to my home network; in the office at work I would launch Gufw on my laptop and select the HQoffice profile then connect to the office network; at my friend Dave’s house I would launch Gufw on my laptop and select the HomeDave profile then connect to the house network; and so on. Nevertheless I do see the attraction of automated zone switching, as provided by firewalld in conjunction with NetworkManager and KDE. It would be handy if my laptop could switch automatically to the Home profile when my laptop connected to the network at my home with the name ‘BTHub5-8EUQ’, automatically switch to the HQoffice profile when my laptop connected to the network named ‘HQ-Office2’ in the office, and so on.

I use UFW on my two laptops running Gentoo Linux. The package ufw-frontends is also installed but normally I use UFW directly via the command line. However I wanted to learn about zones/profiles while using UFW, and I also wanted to see if I could automate the switching of zones without resorting to installing firewalld. NetworkManager has the ability to launch ‘hook’ scripts when certain things happen — when a network connection changes, for example — and this seemed to me to be a way of switching profiles automatically.

I had not used Gufw before, so I decided to install it. A package is available in many Linux distributions but there is no ebuild for Gufw in Gentoo’s main Portage tree and I could not find an up-to-date ebuild for it in any Portage overlays. Therefore I created the ebuild for net-firewall/gufw-19.10.0 shown below. It probably needs improving, but it does install a working Gufw in Gentoo Linux.

# Copyright 1999-2019 Gentoo Foundation
# Distributed under the terms of the GNU General Public License v2
# $Header: $

EAPI=7
PYTHON_COMPAT=( python3_{5,6,7} )
DISTUTILS_IN_SOURCE_BUILD=1

inherit distutils-r1

MY_PN="gui-ufw"
MY_PV="$(ver_cut 1-2)"

DESCRIPTION="GUI frontend for managing ufw."
HOMEPAGE="https://gufw.org/"
SRC_URI="https://launchpad.net/${MY_PN}/trunk/${MY_PV}/+download/${MY_PN}-${PV}.tar.gz"

LICENSE="GPL-3"
SLOT="0"
KEYWORDS="~amd64"
IUSE=""

DEPEND="dev-python/python-distutils-extra"
RDEPEND="net-firewall/ufw
	dev-python/netifaces
	dev-python/pygobject:3
	net-libs/webkit-gtk[introspection]
	sys-auth/elogind
	sys-auth/polkit
	x11-libs/gtk+:3[introspection]
	x11-themes/gnome-icon-theme-symbolic
"
S=${WORKDIR}/${MY_PN}-${PV}

pkg_postinst() {
	sed '/dist-packages/d' -i /usr/bin/gufw-pkexec
	sed -E '/\/share\//d' -i /usr/bin/gufw-pkexec
	local PYTHONVERSION="$(python -c 'import sys; print("{}.{}".format(sys.version_info.major, sys.version_info.minor))')"
	sed -E "s|python3\.[0-9]|python${PYTHONVERSION}|g" -i /usr/bin/gufw-pkexec
	sed -E 's|\/lib\/|\/lib64\/|g' -i /usr/bin/gufw-pkexec
}

‘How To Set Up a Firewall with GUFW on Linux‘ is a good tutorial on Gufw.

As I had not used Gufw previously, I had to play around with it to understand better its functional design. I found that if I configure rules directly via UFW on the command line without using Gufw, Gufw does not allow me to edit those rules (but does allow me to delete them) and those rules exist whichever Gufw profile is selected in the Gufw GUI. Gufw profiles are stored in files named ‘/etc/gufw/*.profile‘ (e.g. /etc/gufw/Home.profile) and these files will not include UFW rules entered via the command line. On the other hand, UFW rules created via the Gufw GUI apply solely to the currently-selected Gufw profile, which is what I would have expected. In other words, I can create a different set of policies and rules in each Gufw profile. Therefore I believe Gufw profiles (as distinct from UFW application profiles) are basically analogous to firewalld’s zones. It also appears to me that Gufw maintains configuration files specifying policies and rules independently of UFW, which Gufw then applies to UFW. In other words, if you are a Gufw user you should not use UFW directly to configure policies and rules, otherwise Gufw’s configuration files will not include what you did directly using UFW. To reiterate, use only Gufw or only UFW, not both.

The current Gufw profile’s name is listed in the file /etc/gufw/gufw.cfg. For example, I currently have the Home profile selected in the Gufw GUI, and the file gufw.cfg contains the following:

[GufwConfiguration]
profile = Home
windowwidth = 542
windowheight = 530
confirmdetelerule = yes

If I examine the contents of the file /etc/gufw/Home.profle I see that it contains the UFW policies and rules I specified for the Gufw Home profile:

[fwBasic]
status = enabled
incoming = deny
outgoing = allow
routed = disabled

[Rule0]
ufw_rule = 137,138/udp ALLOW IN 192.168.1.0/24
description = Samba
command = /usr/sbin/ufw allow in proto udp from 192.168.1.0/24 to any port 137,138
policy = allow
direction = in
protocol = 
from_ip = 192.168.1.0/24
from_port = 
to_ip = 
to_port = 137,138/udp
iface = 
routed = 
logging = 

[Rule1]
ufw_rule = 139,445/tcp ALLOW IN 192.168.1.0/24
description = Samba
command = /usr/sbin/ufw allow in proto tcp from 192.168.1.0/24 to any port 139,445
policy = allow
direction = in
protocol = 
from_ip = 192.168.1.0/24
from_port = 
to_ip = 
to_port = 139,445/tcp
iface = 
routed = 
logging =

I also notice that the other Gufw profiles can differ. For example, my Office.profile file contains the following:

[fwBasic]
status = enabled
incoming = deny
outgoing = allow
routed = allow

The profile name listed in gufw.cfg gets changed when the user changes the profile using the Gufw GUI. It appears to me that only at the point in time when the user selects a certain Gufw profile in the Gufw GUI does Gufw parse the applicable *.profile file and issue commands to UFW to implement the policies and rules specified in the *.profile file.

Initially I tried to automate the process of changing the Gufw profile by doing the following:

1. I created a NetworkManager Dispatcher hook script to:
   1. detect when the laptop connects to a network;

   2. determine whether the network is at my home, at my workplace or in a public place (café, airport or wherever) by looking at the connection name;

   3. edit gufw.cfg to change the name of the Gufw profile according to the network connected.
2. I configured KDE to launch Gufw automatically at login, hoping that would implement the Gufw profile specified in gufw.cfg.

When I connected the laptop to various networks, Gufw did indeed show the name of the profile selected by the NetworkManager Dispatcher hook script, but the associated Gufw profile’s rules had not been applied. They were only applied if I clicked on the ‘Profile’ pull-down menu in Gufw, selected a different Gufw profile, then re-selected the desired Gufw profile. Therefore driving Gufw from a NetworkManager Dispatcher hook script is not possible. This is a pity, as Gufw is an easy way to manage UFW from a GUI; it allows the user to create, delete and edit zones (Gufw profiles) and to select them manually. What Gufw doesn’t do is enable the user to associate those zones with connection names, nor trigger specific zone automatically based on the selected network connection. firewalld, on the other hand, does enable the user to do both those things.

As my attempt at automating the switching of zones in Gufw had failed, I decided to create a NetworkManager Dispatcher hook script to switch zones automatically by using UFW commands. Initially I though about creating a bespoke UFW application profile for each zone and allowing/denying those in the script, but it is actually easier to use the fundamental UFW commands in the script, especially as UFW commands are relatively easy to understand. Also, this approach means everything is in a single file, which facilitates configuration. I can simply edit the script in order to: a) add or delete a zone; b) change a zone’s name; c) change policies and rules for a zone; d) add or delete a connection; e) change the name of a connection; f) change the zone a connection uses. Granted, editing a script is not as user-friendly as using the firewalld GUI to configure a zone and then using KDE Plasma’s system settings module Connections to specify that zone for a specific connection, but my script is not particularly difficult to understand and edit. And by using such a script I can continue to use UFW rather than installing firewalld and having to learn how to use it.

My NetworkManager Dispatcher hook script /etc/NetworkManager/dispatcher.d/20_ufw-zones is listed below. In the main body of the script I define the zone I wish to use for each connection, and in the function select_zone I define the policies and rules I want each zone to use.

#!/bin/bash
INTERFACE=$1
STATUS=$2
WIRED=enp4s0f1
WIFI=wlp3s0

CT_helper_rule() {
    echo "# The following is needed to enable Samba commands to" >> /etc/ufw/before.rules
    echo "# work properly for broadcast NetBIOS name resolution" >> /etc/ufw/before.rules
    echo "#"  >> /etc/ufw/before.rules
    echo "# raw table rules" >> /etc/ufw/before.rules
    echo "*raw" >> /etc/ufw/before.rules
    echo ":OUTPUT ACCEPT [0:0]" >> /etc/ufw/before.rules
    echo "-F OUTPUT" >> /etc/ufw/before.rules
    echo "-A OUTPUT -p udp -m udp --dport 137 -j CT --helper netbios-ns" >> /etc/ufw/before.rules
    echo "COMMIT" >> /etc/ufw/before.rules
}
 
select_zone() {
    ufw --force reset
    ufw --force enable
    ZONE=$1
    case "$ZONE" in
    'Home')
        ufw default deny incoming
        ufw default allow outgoing
        #
        # Rules for SMB
        ufw allow from 192.168.1.0/24 to any port 137,138 proto udp
        ufw allow from 192.168.1.0/24 to any port 139,445 proto tcp
        CT_helper_rule
        #
        # Rules for KDEConnect
        ufw allow from 192.168.1.0/24 to any port 1714:1764 proto udp
        ufw allow from 192.168.1.0/24 to any port 1714:1764 proto tcp
    ;;
    'Office')
        ufw default deny incoming
        ufw default allow outgoing
    ;;
    'Public')
        ufw default reject incoming
        ufw default allow outgoing
    ;;
    'JohnsHouse')
        ufw default deny incoming
        ufw default allow outgoing
        #
        # Rules for SMB
        ufw allow from 192.168.42.0/24 to any port 137,138 proto udp
        ufw allow from 192.168.42.0/24 to any port 139,445 proto tcp
        CT_helper_rule
        #
        # Rules for KDEConnect
        ufw allow from 192.168.42.0/24 to any port 1714:1764 proto udp
        ufw allow from 192.168.42.0/24 to any port 1714:1764 proto tcp
    ;;
    esac
    ufw --force reload
    rm /etc/ufw/*.rules.20* # Delete backups of *.rules files ufw makes every time it is reset
    echo -n `date +"[%F %T %Z]"` >> /var/log/ufw-zones.log
    echo " Zone $ZONE selected for connection $ACTIVE on interface $INTERFACE." >> /var/log/ufw-zones.log
}
 
# Check if either the wired or wireless interface is up
if [ "$INTERFACE" = "$WIRED" -o "$INTERFACE" = "$WIFI" ] && [ "$STATUS" = "up" ]; then
 
    # Check if a single connection is active
    if [ `nmcli c | grep -v "\-\-" | grep -v "NAME.*UUID.*TYPE.*DEVICE" | wc -l` -eq 1 ]; then
 
        # Ascertain the name of the active connection
        ACTIVE=`nmcli c | grep -v "\-\-" | grep -v "NAME.*UUID.*TYPE.*DEVICE" | awk -F' ' '{print $1}'`
 
        case "$ACTIVE" in
 
        'eth0')
            ZONE="Home"
        ;;
        'POR1-wired')
            ZONE="Office"
        ;;
        'BTHub5-8EUQ')
            ZONE="Home"
        ;;
        'BTHub5-8EUQ-5GHz')
            ZONE="Home"
        ;;
        'John1')
            ZONE="JohnsHouse"
        ;;
        'GRAND MERCURE')
            ZONE="Public"
        ;;
        *)
            # If connection name is not in above list
            ZONE="Public"
        ;;

        esac

        select_zone $ZONE
        exit $?

    fi
fi

The log file that the script uses contains a chronological record of the connections made and the zones selected:

$ cat /var/log/ufw-zones.log 
[2019-09-30 20:13:52 BST] Zone Home selected for connection eth0 on interface enp4s0f1.
[2019-10-01 22:59:18 BST] Zone Home selected for connection BTHub5-8EUQ-5GHz on interface wlp3s0.
[2019-10-02 17:59:23 EDT] Zone Public selected for connection loganwifi on interface wlp3s0.
[2019-10-03 10:12:46 EDT] Zone Office selected for connection POR1-wired on interface enp4s0f1.

Prevent Linux firewalls interfering with Samba commands in a home network that uses broadcast NetBIOS name resolution

Or “How come devices in a home network can browse SMB shares but Linux Samba commands and Windows nbtstat commands do not work properly?”

Introduction

In a previous post I explained how it is possible to browse SMB shares when using broadcast NetBIOS name resolution in a home network consisting of machines running Linux, Windows and other operating systems. Browsing SMB/Samba shares will work as expected, but Samba commands such as ‘smbtree‘, ‘smbclient‘ and ‘nmblookup‘ will not work properly if the Linux machines use a firewall that has not been configured for broadcast NetBIOS name resolution. This post is to explain how to do that.

If broadcast NetBIOS name resolution is being used and none of the Linux machines has a firewall enabled, or if their firewalls have been correctly configured, the output of e.g. the ‘smbtree‘ command on one of those machines would look something like the example below.

anne@akhanaten:~$ smbtree
Enter anne's password: 
HOME
        \\AKHANATEN                     Samba 4.3.11-Ubuntu
                \\AKHANATEN\IPC$                IPC Service (Samba 4.3.11-Ubuntu)
                \\AKHANATEN\guest               guest account
                \\AKHANATEN\matthew             matthew share
                \\AKHANATEN\marilla             marilla share
                \\AKHANATEN\anne                anne share
        \\TUTANKHAMUN                   Samba 4.5.10
                \\TUTANKHAMUN\Samsung_Xpress_C460FW     Samsung Xpress C460FW
                \\TUTANKHAMUN\Canon_MP560_Printer       Canon PIXMA MP560
                \\TUTANKHAMUN\Canon_MP510_Printer       Canon PIXMA MP510
                \\TUTANKHAMUN\Virtual_PDF_Printer       Virtual PDF Printer
                \\TUTANKHAMUN\IPC$              IPC Service (Samba 4.2.11)
                \\TUTANKHAMUN\Public
                \\TUTANKHAMUN\anne-share
                \\TUTANKHAMUN\print$
                \\TUTANKHAMUN\netlogon          Network Logon Service
        \\BTHUB5                        BT Home Hub 5.0A File Server
                \\BTHUB5\IPC$                   IPC Service (BT Home Hub 5.0A File Server)
        \\THUTMOSEIII                   Windows 10 computer

If Linux firewalls have not been correctly configured, the output would be missing some information about other machines in the network. For example, compare the output above with the output below from the same network, this time with the Linux firewalls configured using typical rules for Samba specified in Web articles, blog posts and forums.

anne@akhanaten:~$ smbtree
Enter anne's password: 
HOME
        \\AKHANATEN                     Samba 4.3.11-Ubuntu
                \\AKHANATEN\IPC$                IPC Service (Samba 4.3.11-Ubuntu)
                \\AKHANATEN\guest               guest account
                \\AKHANATEN\matthew             matthew share
                \\AKHANATEN\marilla             marilla share
                \\AKHANATEN\anne                anne share
        \\TUTANKHAMUN                   Samba 4.5.10
        \\BTHUB5                        BT Home Hub 5.0A File Server
        \\THUTMOSEIII                   Windows 10 computer

To avoid this problem you need to add a further Linux firewall rule to the set of rules usually used for Samba. Below I first list the usual firewall rules for Samba, then I give the additional rule necessary if using broadcast NetBIOS name resolution. In each case I give the applicable rules for a pure IPTABLES firewall and for UFW (Uncomplicated Firewall). The rules listed here assume the IP address range of the home network is 192.168.1.0/24, so change the range to suit the specific network.

Firewall rules typically specified for machines using Samba

IPTABLES

The rules listed below assume the machine uses interface eth0, so change the interface to suit the specific machine.

# NetBIOS Name Service (name resolution)
iptables -A INPUT -i eth0 -p udp --dport 137 -s 192.168.1.0/24 -j ACCEPT

# NetBIOS Datagram Service (BROWSER service)
iptables -A INPUT -i eth0 -p udp --dport 138 -s 192.168.1.0/24 -j ACCEPT

# NetBIOS Session Service (data transfer legacy SMB/NetBIOS/TCP)
iptables -A INPUT -i eth0 -p tcp --dport 139 -s 192.168.1.0/24 -j ACCEPT

# Microsoft Directory Service (data transfer SMB/TCP)
iptables -A INPUT -i eth0 -p tcp --dport 445 -s 192.168.1.0/24 -j ACCEPT

UFW

In some Linux distributions the ufw application allows a single command to add Samba support, such as:

user $ sudo ufw allow Samba

or

user $ sudo ufw allow CIFS

These ‘application profiles’ are specified in files in the directory /etc/ufw/applications.d/, so you could add application profiles or modify existing ones if you wish. In one of my installations the file /etc/ufw/applications.d/ufw-fileserver includes the following application profile for Samba, for example:

[CIFS]
title=SMB/CIFS server
description=SMB/CIFS server
ports=137,138/udp|139,445/tcp

If such an application profile does not exist in your installation, typical Samba rules can be added in UFW using the following two commands:

user $ sudo ufw allow from 192.168.1.0/24 to any port 137,138 proto udp
user $ sudo ufw allow from 192.168.1.0/24 to any port 139,445 proto tcp

The correct addition of the rules can be checked using the following command:

user $ sudo ufw status verbose
Password:
Status: active
Logging: on (low)
Default: deny (incoming), allow (outgoing), disabled (routed)
New profiles: skip

To                         Action      From
--                         ------      ----
137,138/udp (CIFS)         ALLOW IN    192.168.1.0/24
139,445/tcp (CIFS)         ALLOW IN    192.168.1.0/24

The extra rule required when using broadcast NetBIOS name resolution

The reason why an extra rule is required when using broadcast NetBIOS name resolution is because UFW (which is based on IPTABLES) is ‘stateful’, as is a purely IPTABLES firewall (unless explicitly configured not to be stateful). The firewall does not consider packets it receives in response to its broadcast to be ESTABLISHED or RELATED, and therefore drops those packets. So, despite the IPTABLES and UFW rules listed above including a rule to accept incoming UDP packets on Port 137, any UDP packets received on Port 137 that do not constitute a one-to-one, two-way communication flow are dropped by the firewall. The extra rule below overrules this and makes the firewall accept packets coming from other devices’ Port 137 in response to broadcast NetBIOS Name Service packets. To do this, the extra rule uses a CT (Connection Tracking) helper named ‘netbios-ns‘ (obviously meaning ‘NetBIOS Name Service’). In order to use this rule the kernel must have been configured to use the IPTABLES ‘raw‘ table and to use CT (see the section ‘Kernel configuration’ further on).

IPTABLES

# All NetBIOS clients must have the netbios-ns helper enabled for broadcast name resolution to work
iptables -t raw -A OUTPUT -p udp -m udp --dport 137 -j CT --helper netbios-ns

By the way, in addition to flushing the usual tables, flush the ‘raw‘ table too when you restart the firewall:

iptables -t raw -F OUTPUT

UFW

Add the following lines to the end of the file /etc/ufw/before.rules

# The following is needed to enable Samba commands to
# work properly for broadcast NetBIOS name resolution
#
# raw table rules
*raw
:OUTPUT ACCEPT [0:0]
-F OUTPUT
-A OUTPUT -p udp -m udp --dport 137 -j CT --helper netbios-ns
COMMIT

Note that the output of the command ‘ufw status verbose‘ will not include the above rule. This is not a bug.

Kernel configuration

If you are using a binary-based distribution such as Ubuntu Linux, the kernel will probably have been configured to include the needed modules (CONFIG_IP_NF_RAW=m, CONFIG_IP6_NF_RAW=m and CONFIG_NETFILTER_XT_TARGET_CT=m), and the installation configured to load the modules automatically. However, if you are using a source-based distribution such as Gentoo Linux make sure the kernel configuration includes these three options before you build the kernel, and also add the module names ‘iptable_raw‘ and ‘xt_CT‘ to the module list in the file /etc/conf.d/modules as shown in the example below, so that the modules are loaded at boot:

modules="r8169 nvidia agpgart fuse bnep rfcomm hidp uvcvideo cifs mmc_block rtsx_pci snd-seq-midi vboxdrv vboxnetadp vboxnetflt iptable_raw xt_CT"

You can use the following two commands to check if the two modules are loaded:

user $ sudo lsmod | grep iptable_raw
user $ sudo lsmod | grep xt_CT

How to check the additional rule is active

You can use the command below whether you are using pure IPTABLES or UFW.

user $ sudo iptables -nvL -t raw
Password: 
Chain PREROUTING (policy ACCEPT 2613 packets, 1115K bytes)
 pkts bytes target     prot opt in     out     source               destination         

Chain OUTPUT (policy ACCEPT 2773 packets, 475K bytes)
 pkts bytes target     prot opt in     out     source               destination         
   16  1248 CT         udp  --  *      *       0.0.0.0/0            0.0.0.0/0            udp dpt:137 CT helper netbios-ns

The packet and byte counts will increase whenever you use a Samba command.

Bibliography

1. The netfilter.org "iptables" project
2. Iptables Tutorial
3. Introduction to IPTables
4. Gentoo Wiki : iptables
5. Arch Linux Wiki : Samba : "Browsing" network fails with "Failed to retrieve share list from server"
6. Ubuntu : Manpage : ufw-framework
7. Gentoo Wiki : UFW

A correct method of configuring Samba for browsing SMB shares in a home network

SMB
SMB (Server Message Block) is the underlying protocol that Microsoft Windows computers use to connect to resources, such as file shares and printers, and to transfer information when the connections are established. Samba is the Linux implementation of SMB that allows file and printer information to be transferred between Windows and Linux computers. An early variant of the SMB protocol is known as ‘CIFS’ (Common Internet File System). CIFS is actually obsolete, so the correct term to use these days is ‘SMB’ (see the blog post Why You Should Never Again Utter The Word, "CIFS"), although ‘CIFS’ is still used sometimes when referring to SMB.

Terminology
You are likely to come across several terms when reading about Samba, such as NetBIOS, Active Directory (AD), Lightweight Directory Access Protocol (LDAP), Kerberos, Windows Internet Name Service (WINS) and Winbind, to name but a few. Most are used in larger corporate or enterprise networks but you can ignore most of them – only broadcast NetBIOS name resolution or WINS are necessary to configure Samba in small home networks. For example, my home network uses broadcast NetBIOS name resolution and sometimes has up to 15 devices connected (Linux, Windows 7/10, macOS, Android and iOS), all of which can browse file shares using SMB/Samba.

Note: You should not use Broadcast NetBIOS Name Resolution and WINS at the same time.

To explain the terminology – Active Directory is a central database of user accounts and passwords used primarily in Windows networks to authenticate users, and LDAP is the protocol that clients and servers use to access the Active Directory database. Kerberos is a separate encrypted authentication mechanism used for client-server applications, such as computers that access a specific file or web server, or SQL database. WINS is a mechanism for storing Windows computer name to IP address mappings on a central server – the WINS Server. Computers in a LAN interrogate the WINS server to obtain the IP addresses of other computers. It’s a bit like DNS except that the WINS Server stores Windows computer names rather than URLs or domain names. Winbind is a Unix/Linux mechanism that allows Windows NT accounts to look like a Unix service to Unix/Linux machines.

NetBIOS
How is NetBIOS relevant to Samba? Samba uses NetBIOS in three different ways:

1. NetBIOS over UDP Port 137 to advertise Windows computer names for name to IP address resolution;
   

2. NetBIOS over UDP Port 138 to advertise services that the computer offers and to elect a ‘Master Browser’ (explained below);
   

3. SMB over NetBIOS over TCP/IP Port 139 to connect to file shares or printers. Once connected, the computers may negotiate using SMB direct over TCP/IP Port 445 to improve efficiency of the connection.

NetBIOS over UDP (Port 137) is a connectionless broadcast protocol that Windows machines use to advertise over the LAN their names and corresponding IP addresses. Other computers receive the broadcasts and cache the names and IP addresses in a name to IP address mapping table.

NetBIOS over UDP (Port 138) is a connectionless broadcast protocol that Windows machines use to advertise their eligibility to become the Master Browser or Backup Browser for a Windows Workgroup in the LAN. An automatic election process elects only one machine in a Workgroup to become the Master Browser for that workgroup, and elects one or more ‘Backup Browsers’ in the Workgroup. The Master Browser and Backup Browser(s) collate a list of all the computers in the Workgroup and the services that they offer. It is more efficient for a single computer to assume the master role and to collate the information than it is for the information to remain distributed. When you click on ‘Network’† in File Explorer’s ‘Network Neighbourhood’‡ window, your computer interrogates the Master Browser(s) to obtain a list of the Windows Workgroups in the LAN, the members of the Workgroup(s) and the file and printer services that each Workgroup member offers. If the Master Browser fails or is disconnected, a re-election takes place and a new Master Browser is elected from the list of Backup Browsers in that Workgroup. The same process occurs if you are using a Linux file manager (Dolphin in KDE, Nautilus in GNOME, etc.) with Samba. You can configure the ‘priority’ of the Samba server in each machine in the Workgroup so that it is either more likely or less likely to be elected the Master Browser for the Workgroup. You could even configure Samba on a Linux machine so that it will never be a Master Browser. (It is also possible to configure a Windows machine so that it will never be a Master Browser.)

    † Renamed ‘Entire Network’ in some versions of Windows.
    ‡ Renamed ‘My Network Places’ or simply ‘Network’ in some versions of Windows.

SMB over NetBIOS over TCP/IP (Port 139) is a connection orientated protocol that Windows computers use to connect to file shares and printers, to retrieve directory listings and to transfer files. Having obtained a list of computers and file shares from the Master Browser, if you click on a particular file share to connect to it, your computer looks up the name of the target computer in the local name table, obtains the target computer’s IP address and initiates a SMB over NetBIOS over TCP/IP connection to it. The target computer then issues a username and password prompt for you to complete the connection. If authentication is successful, the SMB protocol is used to transfer a directory listing of the contents of the share. If you drag and drop a file from the share to your local machine, or vice-versa, SMB is used to transfer the file. Behind the scenes, during the initial connection set-up, your computer and the target carry out a negotiation. If both machines support SMB direct over TCP/IP, the directory listing and subsequent file transfer are transported using SMB over TCP/IP Port 445. This is much more efficient because it eliminates completely the NetBIOS overhead.

When you install and configure Samba on a Linux computer, the ‘smbd‘ and ‘nmbd‘ daemons enable all of the functionality above. In a small network you do not need to enable or use AD, LDAP, Kerberos, WINS, Winbind or anything else for that matter. Samba and its built-in NetBIOS mechanisms will allow you to participate in a Windows Workgroup environment to share and use folders, files and printers.

Workgroups
The majority of Windows computers running in home networks are configured, by default, in a single Workgroup. A Workgroup is a simple way for computers in small networks to advertise and share resources, such as folders and printers, with other members of the same group. You can configure multiple Workgroups in the same LAN but each computer can belong to only one Workgroup. The theory is that different computers can share different resources within their group.

Please Note: A Windows Workgroup is not the same thing as a Windows HomeGroup. The latter concept was introduced in Windows 7 and is an ‘evolution’ of the Workgroup concept, in which you share folders and files but specify a pre-determined group password. All computers wishing to join the HomeGroup specify the same password to connect to the resources in that group. Samba does not participate in Windows HomeGroups because the latter is a Windows-only feature.

Configuring Samba
Firstly, install Samba on the Linux computer. Use Samba 4 and avoid Samba 3, which is obsolete. I have several laptops and a Network Addressable Storage (NAS) server, all running Linux with various releases of Samba 4. I also have a desktop computer running Windows 10 for family use. In addition, family and friends connect various laptops running Windows 7 and Windows 10 to my home network, as well as tablets and smartphones (see How to Access Shared Windows Folders on Android, iPad, and iPhone). This NAS runs 24/7 so I could have configured Samba to always make it the Master Browser but this is not necessary as the remaining computers in the network will elect a new Master Browser should the NAS fail.

Below is a summary of the steps to configure Samba in a Windows Workgroup:

1. Configure the same Workgroup name on all of the Windows computers (for example, How to Change Workgroup in Windows 10). The default Windows 10 Workgroup is called ‘WORKGROUP‘. In the example further down I used the Windows GUI to change the Workgroup name to ‘GREENGABLES‘. There is plenty of information on the Internet about how to configure Windows file sharing so I won’t repeat any of it here (for example, How to Enable Network Discovery and Configure Sharing Options in Windows 10 and How to set up file sharing on Windows 10 (Share files using File Explorer)).
   

2. Configure Samba on the Linux machines by editing the file ‘/etc/samba/smb.conf‘ on each. The contents of the file ‘smb.conf‘ are shown below for a Linux NAS and two Linux laptops. The NetBIOS name of the NAS is ‘akhanaten‘ and the laptops are ‘tutankhamun‘ and ‘smenkhkare‘. You can use either of the smb.conf files of the two laptops as a template for the smb.conf file of any Linux computer in your own home network. You can ignore the smb.conf file of the NAS if you simply want to be able to browse SMB/Samba shares on other computers in your home network.
   

3. Use the command ‘pdbedit‘ on each Linux machine to define and configure the Samba users on that machine. The command ‘smbpasswd‘ is an alternative to ‘pdbedit‘ but I recommend you use the latter, as ‘smbpasswd‘ is deprecated. Each Samba user must exist as a Linux user because it is the Linux users who own the shares and are used for authentication.
   

4. The NAS has Linux users ‘anne‘, ‘marilla‘, ‘matthew‘ and ‘guest‘, whereas each of the laptops has a Linux user ‘anne‘. The user name does not have to be the same on different computers.
   

5. The purpose of each variable in ‘smb.conf‘ is explained on the applicable Samba manual page (enter the command ‘man smb.conf‘ in a terminal window) and the Samba documentation page for smb.conf on the Web.

Furthermore, make sure the Winbind daemon is not running. If Winbind is installed, make sure the service is not running and is disabled.

smb.conf of NAS running Ubuntu Server Edition:

[global]
# SMB uses ports 139 & 445, as explained in this blog post
smb ports = 139 445
netbios name = akhanaten
workgroup = greengables

# Use either NetBIOS broadcast for name resolution or entries in the /etc/hosts file
name resolve order = bcast host

# Don't care if the workgroup name is upper or lower case
case sensitive = no

# User authentication is used to access the shares
security = user
map to guest = bad user
guest account = guest

# Don't allow the use of root for network shares
invalid users = root

# Domain master only applies to LANs that are inter-connected across a WAN
domain master = no

# This machine is eligible to be a Master Browser and its priority is 4
# (the higher the os level, the more preferred to be Master Browser)
# (the maximum allowable value for os level is 255)
preferred master = yes
os level = 4
dns proxy = no

# Always advertise the shares automatically
auto services = global

# Interfaces on which to listen for NetBIOS broadcasts and to allow SMB connections
# Include "lo" because it is the internal interface
# em1 is the name of the Ethernet interface, found using the ifconfig command
interfaces = lo em1
bind interfaces only = yes
log file = /var/log/samba/log.%m
max log size = 1000
syslog = 0

panic action = /usr/share/samba/panic-action %d
server role = standalone server
passdb backend = tdbsam
obey pam restrictions = yes

# Don't synchronise the Linux and Samba user passwords - they can be different
unix password sync = no
passwd program = /usr/bin/passwd %u
passwd chat = *Enter\snew\s*\spassword:* %n\n *Retype\snew\s*\spassword:* %n\n *password\supdated\ssuccessfully* .
pam password change = yes

# This Samba configuration does not advertise any printers
load printers = no

# File to map long usernames to shorter Unix usernames, if necessary
username map = /etc/samba/smbusers

# Allow guest user access if specified in the shares
guest ok = yes

# First user share is called "anne" - only user "anne" specified below can connect to the share
[anne]
comment = "anne share"
path = /nas/shares/anne
writeable = yes
valid users = anne

# Second user share is called "marilla" - only user "marilla" specified below can connect to the share
[marilla]
comment = "marilla share"
path = /nas/shares/marilla
writeable = yes
valid users = marilla

# Third user share is called "matthew" - only user "matthew" specified below can connect to the share
[matthew]
comment = "matthew share"
path = /nas/shares/matthew
writeable = yes
valid users = matthew

# Fourth user share is called "guest" - any user can connect to the share
[guest]
comment = "guest account"
path = /nas/shares/guest
writeable = yes
guest ok = yes
valid users = guest anne marilla matthew

smb.conf of laptop #1 running Gentoo Linux:

[global]
;no need to specify 'smb ports' as ports 139 & 445 used by default
workgroup = GREENGABLES
netbios name = tutankhamun
case sensitive = no
browseable = yes

;If this machine becomes a Master Browser, the following parameter allows it to hold the browse list
browse list = yes

printcap name = cups
printing = cups

log file = /var/log/samba/log.%m
max log size = 50

security = user
map to guest = bad user

encrypt passwords = yes
passdb backend = tdbsam

domain master = no
local master = yes
preferred master = yes
; os level = 6 on the other laptop, so I have made it 5 on this laptop.
os level = 5
name resolve order = bcast
wins support = no
dns proxy = no

;Listen for NetBIOS on Ethernet and Wireless interfaces
;Names of the interfaces found using ifconfig command
interfaces = enp4s0f1 wlp3s0

[netlogon]
comment = Network Logon Service
path = /var/lib/samba/netlogon
guest ok = yes

[printers]
comment = All Printers
path = /var/spool/samba
guest ok = yes
printable = yes
create mask = 0700

[print$]
path = /var/lib/samba/printers
write list = @adm root
guest ok = yes

[anne-share]
path = /home/anne/anne-share/
guest ok = yes
;read only = no
writeable = yes
browseable = yes
valid users = anne

[Public]
path = /home/anne/Public/
guest ok = yes
;read only = no
writeable = yes
browseable = yes

smb.conf of laptop #2 running Gentoo Linux:

[global]
;no need to specify 'smb ports' as ports 139 & 445 used by default
workgroup = GREENGABLES
netbios name = smenkhkare
case sensitive = no
browseable = yes

;If this machine becomes a Master Browser, the following parameter allows it to hold the browse list
browse list = yes

printcap name = cups
printing = cups

log file = /var/log/samba/log.%m
max log size = 50

security = user
map to guest = bad user

encrypt passwords = yes
passdb backend = tdbsam

domain master = no
local master = yes
preferred master = yes
; os level = 5 on the other laptop so I have made it 6 on this laptop
os level = 6
name resolve order = bcast
wins support = no
dns proxy = no

;Listen for NetBIOS on Ethernet and Wireless interfaces
;Names of the interfaces found using ifconfig command
interfaces = eth0 wlan0

[netlogon]
comment = Network Logon Service
path = /var/lib/samba/netlogon
guest ok = yes

[printers]
comment = All Printers
path = /var/spool/samba
guest ok = yes
printable = yes
create mask = 0700

[print$]
path = /var/lib/samba/printers
write list = @adm root
guest ok = yes

[anne-share]
path = /home/anne/share-share/
guest ok = yes
;read only = no
writeable = yes
browseable = yes
valid users = anne

[Public]
path = /home/anne/Public/
guest ok = yes
;read only = no
writeable = yes
browseable = yes

Samba Commands
The following are Samba commands you can use on any of the Linux computers to find information on the Samba shares.

The ‘smbtree‘ command lists the computers currently using SMB in the local network:

user $ smbtree
GREENGABLES
        \\AKHANATEN                     Samba 4.3.11-Ubuntu
                \\AKHANATEN\IPC$                IPC Service (Samba 4.3.11-Ubuntu)
                \\AKHANATEN\guest               guest account
                \\AKHANATEN\matthew             matthew share
                \\AKHANATEN\marilla             marilla share
                \\AKHANATEN\anne                anne share
        \\SMENKHKARE                    Samba 4.2.14
                \\SMENKHKARE\Samsung_CLX-8385ND Samsung CLX-8385ND
                \\SMENKHKARE\Canon_MP510_Printer        Canon MP510 Printer
                \\SMENKHKARE\Virtual_PDF_Printer        Virtual PDF Printer
                \\SMENKHKARE\Canon_MP560_WiFi   Canon MP560 WiFi
                \\SMENKHKARE\IPC$               IPC Service (Samba 4.2.14)
                \\SMENKHKARE\Public         
                \\SMENKHKARE\anne-share     
                \\SMENKHKARE\print$         
                \\SMENKHKARE\netlogon           Network Logon Service
        \\TUTANKHAMUN                   Samba 4.2.11
                \\TUTANKHAMUN\Samsung_Xpress_C460FW     Samsung Xpress C460FW
                \\TUTANKHAMUN\Canon_MP560_Printer       Canon PIXMA MP560
                \\TUTANKHAMUN\Canon_MP510_Printer       Canon PIXMA MP510
                \\TUTANKHAMUN\Virtual_PDF_Printer       Virtual PDF Printer
                \\TUTANKHAMUN\IPC$              IPC Service (Samba 4.2.11)
                \\TUTANKHAMUN\Public
                \\TUTANKHAMUN\anne-share
                \\TUTANKHAMUN\print$
                \\TUTANKHAMUN\netlogon          Network Logon Service
HOME
        \\BTHUB5                        BT Home Hub 5.0A File Server
                \\BTHUB5\IPC$                   IPC Service (BT Home Hub 5.0A File Server)

‘BTHUB5‘ is a BT Home Hub 5 (a network router and broadband modem). Notice that it is configured by default to be in a Windows Workgroup named ‘HOME‘. The BT Home Hub 5 has a USB port to which an external USB HDD could be attached, so I assume computers in the home network could have been configured to use the HOME Workgroup instead of GREENGABLES and hence access that USB HDD, i.e. use it as a NAS. However, no HDD is attached to the BT Home Hub 5, so just ignore the BTHUB5 device and the HOME Workgroup.

The ‘nmblookup‘ command is used to see which services each computer offers. The strings ‘..__MSBROWSE__.‘ and ‘<1d>‘ in the output indicate that the computer is currently the Master Browser (see the Microsoft TechNet article NetBIOS Over TCP/IP for details):

user $ nmblookup akhanaten
192.168.1.70 akhanaten<00>

user $ nmblookup -A 192.168.1.70
Looking up status of 192.168.1.70
        AKHANATEN       <00> -         B <ACTIVE>
        AKHANATEN       <03> -         B <ACTIVE>
        AKHANATEN       <20> -         B <ACTIVE>
        GREENGABLES     <00> - <GROUP> B <ACTIVE>
        GREENGABLES     <1e> - <GROUP> B <ACTIVE>

        MAC Address = 00-00-00-00-00-00

user $ nmblookup tutankhamun
192.168.1.79 tutankhamun<00>

user $ nmblookup -A 192.168.1.79
Looking up status of 192.168.1.79
        TUTANKHAMUN     <00> -         B <ACTIVE>
        TUTANKHAMUN     <03> -         B <ACTIVE>
        TUTANKHAMUN     <20> -         B <ACTIVE>
        GREENGABLES     <00> - <GROUP> B <ACTIVE>
        GREENGABLES     <1e> - <GROUP> B <ACTIVE>

        MAC Address = 00-00-00-00-00-00

user $ nmblookup smenkhkare
192.168.1.90 smenkhkare<00>

user $ nmblookup -A 192.168.1.90
Looking up status of 192.168.1.90
        SMENKHKARE      <00> -         B <ACTIVE>
        SMENKHKARE      <03> -         B <ACTIVE>
        SMENKHKARE      <20> -         B <ACTIVE>
        ..__MSBROWSE__. <01> - <GROUP> B <ACTIVE> 
        GREENGABLES     <00> - <GROUP> B <ACTIVE>
        GREENGABLES     <1d> -         B <ACTIVE>
        GREENGABLES     <1e> - <GROUP> B <ACTIVE>

        MAC Address = 00-00-00-00-00-00

‘..__MSBROWSE__.‘ and ‘<1d>‘ in the above output indicates that the laptop named smenkhkare is currently the Master Browser of the Workgroup named GREENGABLES. See the Microsoft TechNet article NetBIOS Over TCP/IP to interpret the output.

Now let’s look at what happens when thutmoseiii, the Windows 10 desktop connected to this home network, is powered up:

user $ smbtree
GREENGABLES
        \\AKHANATEN                     Samba 4.3.11-Ubuntu
                \\AKHANATEN\IPC$                IPC Service (Samba 4.3.11-Ubuntu)
                \\AKHANATEN\guest               guest account
                \\AKHANATEN\matthew             matthew share
                \\AKHANATEN\marilla             marilla share
                \\AKHANATEN\anne                anne share
        \\SMENKHKARE                    Samba 4.2.14
                \\SMENKHKARE\Samsung_CLX-8385ND Samsung CLX-8385ND
                \\SMENKHKARE\Canon_MP510_Printer        Canon MP510 Printer
                \\SMENKHKARE\Virtual_PDF_Printer        Virtual PDF Printer
                \\SMENKHKARE\Canon_MP560_WiFi   Canon MP560 WiFi
                \\SMENKHKARE\IPC$               IPC Service (Samba 4.2.14)
                \\SMENKHKARE\Public
                \\SMENKHKARE\anne-share
                \\SMENKHKARE\print$
                \\SMENKHKARE\netlogon           Network Logon Service
        \\TUTANKHAMUN                   Samba 4.2.11
                \\TUTANKHAMUN\Samsung_Xpress_C460FW     Samsung Xpress C460FW
                \\TUTANKHAMUN\Canon_MP560_Printer       Canon PIXMA MP560
                \\TUTANKHAMUN\Canon_MP510_Printer       Canon PIXMA MP510
                \\TUTANKHAMUN\Virtual_PDF_Printer       Virtual PDF Printer
                \\TUTANKHAMUN\IPC$              IPC Service (Samba 4.2.11)
                \\TUTANKHAMUN\Public
                \\TUTANKHAMUN\anne-share
                \\TUTANKHAMUN\print$
                \\TUTANKHAMUN\netlogon          Network Logon Service
        \\THUTMOSEIII                   Lounge Computer
HOME
        \\BTHUB5                        BT Home Hub 5.0A File Server
                \\BTHUB5\IPC$                   IPC Service (BT Home Hub 5.0A File Server)

user $ nmblookup thutmoseiii
192.168.1.74 thutmoseiii<00>
192.168.56.1 thutmoseiii<00>

user $ nmblookup -A 192.168.1.74
Looking up status of 192.168.1.74
        THUTMOSEIII     <20> -         B <ACTIVE> 
        THUTMOSEIII     <00> -         B <ACTIVE> 
        GREENGABLES     <00> - <GROUP> B <ACTIVE> 
        GREENGABLES     <1e> - <GROUP> B <ACTIVE> 

        MAC Address = AA-BB-CC-DD-EE-FF (anonymised by me)

So Linux computer smenkhkare remained the Master Browser. This is because the Windows 10 computer has its Registry subkey HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Browser\Parameters\MaintainServerList set to ‘Auto‘, and also there is no subkey \HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Browser\Parameters\IsDomainMaster so implicitly its value is False (i.e. the computer is not a Preferred Master Browser). See Microsoft TechNet article Specifying Browser Computers for details.

By the way, notice that two IP addresses are listed for thutmoseiii. This is because thutmoseiii is connected to two network adapters: 192.168.1.74 is the IP address of thutmoseiii in the home network, and 192.168.56.1 is the IP address of the virtual network interface for the virtual computers in VirtualBox installed on thutmoseiii.

If the Samba service on smenkhkare is now stopped from the command line, Windows 10 computer thutmoseiii is elected Master Browser after more than a minute has elapsed:

user $ nmblookup -A 192.168.1.74
Looking up status of 192.168.1.74
        THUTMOSEIII     <20> -         B <ACTIVE> 
        THUTMOSEIII     <00> -         B <ACTIVE> 
        GREENGABLES     <00> - <GROUP> B <ACTIVE> 
        GREENGABLES     <1e> - <GROUP> B <ACTIVE> 
        GREENGABLES     <1d> -         B <ACTIVE> 
        ..__MSBROWSE__. <01> - <GROUP> B <ACTIVE>

        MAC Address = AA-BB-CC-DD-EE-FF (anonymised by me)

If the Samba service on smenkhkare is then restarted from the command line and the Windows 10 computer is allowed to go to sleep, the laptop named smenkhkare becomes the Master Brower again as expected.

NetBIOS Commands in Windows
Now let’s look at some NetBIOS equivalent commands on the Windows 10 computer (Windows computer name: thutmoseiii).

First let’s see which remote computers thutmoseiii detects:

C:\WINDOWS\system32>nbtstat -c

VirtualBox Host-Only Network 2:
Node IpAddress: [192.168.56.1] Scope Id: []

    No names in cache

Ethernet:
Node IpAddress: [192.168.1.74] Scope Id: []

                  NetBIOS Remote Cache Name Table

        Name              Type       Host Address    Life [sec]
    ------------------------------------------------------------
    AKHANATEN      <20>  UNIQUE          192.168.1.70        381
    TUTANKHAMUN    <20>  UNIQUE          192.168.1.79        407
    SMENKHKARE     <20>  UNIQUE          192.168.1.90        416

WiFi:
Node IpAddress: [0.0.0.0] Scope Id: []

    No names in cache

Local Area Connection* 11:
Node IpAddress: [0.0.0.0] Scope Id: []

    No names in cache

Four adapters are listed in the above output: ‘VirtualBox Host-Only Network 2‘, ‘Ethernet‘, ‘WiFi‘ and ‘Local Area Connection* 11‘. Let’s look at why they are listed:

• The first adapter listed exists because VirtualBox is installed on thutmoseiii and has a virtual network adapter to enable virtual computers to be networked together (see What Is A Oracle VM VirtualBox Host-Only Network Adapter? if you don’t know what is a VirtualBox Host-Only Network Adapter).
  

• The second adapter listed is the computer’s Ethernet adapter. thutmoseiii is connected to the home network via this interface, and the above output shows that thutmoseiii has correctly detected the three other computers connected to the home network.
  

• The third adapter listed is the computer’s wireless adapter. thutmoseiii also has a Wi-Fi interface, currently disabled in Windows, hence no active wireless connection is listed.
  

• The fourth adapter is a ‘Microsoft Wi-Fi Direct Virtual Adapter’ according to the output of the ipconfig/all command. As the Wi-Fi interface is currently disabled in Windows, no active connection is listed here either.

Now let’s see what thutmoseiii reports about itself:

C:\WINDOWS\system32>nbtstat -n

VirtualBox Host-Only Network 2:
Node IpAddress: [192.168.56.1] Scope Id: []

                NetBIOS Local Name Table

       Name               Type         Status
    ---------------------------------------------
    THUTMOSEIII    <20>  UNIQUE      Registered
    THUTMOSEIII    <00>  UNIQUE      Registered
    GREENGABLES    <00>  GROUP       Registered
    GREENGABLES    <1E>  GROUP       Registered
    GREENGABLES    <1D>  UNIQUE      Registered
    ☺☻__MSBROWSE__☻<01>  GROUP       Registered

Ethernet:
Node IpAddress: [192.168.1.74] Scope Id: []

                NetBIOS Local Name Table

       Name               Type         Status
    ---------------------------------------------
    THUTMOSEIII    <20>  UNIQUE      Registered
    THUTMOSEIII    <00>  UNIQUE      Registered
    GREENGABLES    <00>  GROUP       Registered
    GREENGABLES    <1E>  GROUP       Registered

WiFi:
Node IpAddress: [0.0.0.0] Scope Id: []

    No names in cache

Local Area Connection* 11:
Node IpAddress: [0.0.0.0] Scope Id: []

    No names in cache

The above is correct: thutmoseiii is the Master Browser in the Windows Workgroup of VirtualBox Host-Only Network 2, but not a Master Browser in the GREENGABLES Workgroup to which thutmoseiii is connected by Ethernet cable. As the Wi-Fi interface in thutmoseiii is currently disabled, no active wireless connection is listed.

Now let’s take a look at what thutmoseiii reports about akhanaten:

C:\WINDOWS\system32>nbtstat -a akhanaten

VirtualBox Host-Only Network 2:
Node IpAddress: [192.168.56.1] Scope Id: []

    Host not found.

Ethernet:
Node IpAddress: [192.168.1.74] Scope Id: []

           NetBIOS Remote Machine Name Table

       Name               Type         Status
    ---------------------------------------------
    AKHANATEN      <00>  UNIQUE      Registered
    AKHANATEN      <03>  UNIQUE      Registered
    AKHANATEN      <20>  UNIQUE      Registered
    GREENGABLES    <00>  GROUP       Registered
    GREENGABLES    <1E>  GROUP       Registered

    MAC Address = 00-00-00-00-00-00


WiFi:
Node IpAddress: [0.0.0.0] Scope Id: []

    Host not found.

Local Area Connection* 11:
Node IpAddress: [0.0.0.0] Scope Id: []

    Host not found.

The above is also correct, as akhanaten is indeed not a Master Browser.

Now let’s have a look at what thutmoseiii reports about tutankhamun:

C:\WINDOWS\system32>nbtstat -a tutankhamun

VirtualBox Host-Only Network 2:
Node IpAddress: [192.168.56.1] Scope Id: []

    Host not found.

Ethernet:
Node IpAddress: [192.168.1.74] Scope Id: []

           NetBIOS Remote Machine Name Table

       Name               Type         Status
    ---------------------------------------------
    TUTANKHAMUN    <00>  UNIQUE      Registered
    TUTANKHAMUN    <03>  UNIQUE      Registered
    TUTANKHAMUN    <20>  UNIQUE      Registered
    GREENGABLES    <00>  GROUP       Registered
    GREENGABLES    <1E>  GROUP       Registered

    MAC Address = 00-00-00-00-00-00


WiFi:
Node IpAddress: [0.0.0.0] Scope Id: []

    Host not found.

Local Area Connection* 11:
Node IpAddress: [0.0.0.0] Scope Id: []

    Host not found.

The above is also correct, as tutankhamun is indeed not a Master Browser.

Now let’s have a look at what thutmoseiii reports about smenkhkare:

C:\WINDOWS\system32>nbtstat -a smenkhkare

VirtualBox Host-Only Network 2:
Node IpAddress: [192.168.56.1] Scope Id: []

    Host not found.

Ethernet:
Node IpAddress: [192.168.1.74] Scope Id: []

           NetBIOS Remote Machine Name Table

       Name               Type         Status
    ---------------------------------------------
    SMENKHKARE     <00>  UNIQUE      Registered
    SMENKHKARE     <03>  UNIQUE      Registered
    SMENKHKARE     <20>  UNIQUE      Registered
    ☺☻__MSBROWSE__☻<01>  GROUP       Registered
    GREENGABLES    <00>  GROUP       Registered
    GREENGABLES    <1D>  UNIQUE      Registered
    GREENGABLES    <1E>  GROUP       Registered

    MAC Address = 00-00-00-00-00-00


WiFi:
Node IpAddress: [0.0.0.0] Scope Id: []

    Host not found.

Local Area Connection* 11:
Node IpAddress: [0.0.0.0] Scope Id: []

    Host not found.

The above is also correct, as smenkhkare is indeed the Master Browser (notice the ‘☺☻__MSBROWSE__☻‘ and ‘<1D>‘).

Q.E.D.
So there you have it; Browser Elections take place and the Master Browser is any one of the Linux or Windows computers in the home network, thus enabling SMB browsing to take place. No WINS, no LDAP, no AD, no Kerberos. All SMB communication is carried out using NetBIOS over TCP/IP and Broadcast NetBIOS Name Resolution, as shown by the output of the command ‘nbtstat -r‘ on thutmoseiii:

C:\WINDOWS\system32>nbtstat -r

    NetBIOS Names Resolution and Registration Statistics
    ----------------------------------------------------

    Resolved By Broadcast     = 65
    Resolved By Name Server   = 0

    Registered By Broadcast   = 233
    Registered By Name Server = 0

    NetBIOS Names Resolved By Broadcast
---------------------------------------------
           BTHUB5         <00>
           呂啈㕂†††††䱃噅坏㌲匰⁓†
           TUTANKHAMUN    <00>
           AKHANATEN      <00>
           SMENKHKARE     <00>

I assume the line of Chinese and other characters is because of some deficiency in NBTSTAT.EXE, CMD.EXE or Windows 10 generally — despite having entered ‘CHCP 65001‘ and chosen a Unicode TrueType font in CMD.EXE — but the important point is that the statistics listed by the ‘nbtstat -r‘ command clearly show that only broadcasts are used for NetBIOS Name resolution, as promised. NetBIOS name resolution works fine in the home network and all the sharing-enabled computers in the home network can browse SMB shares on other sharing-enabled computers, whether they are running Windows, Linux, macOS, Android or iOS. I reiterate that this is for a typical home network.

Command to find Master Browsers
In Linux you can use the ‘nmblookup‘ command as follows to find out which machine in the home network is currently the Master Browser in each Workgroup:

user $ nmblookup -M -- -
192.168.1.254 __MSBROWSE__
192.168.1.90 __MSBROWSE__
192.168.56.1 __MSBROWSE__

You can see above that there are currently three Master Browsers in this home network. Let’s check the details for these three Master Browsers:

user $ nmblookup -A 192.168.1.254
Looking up status of 192.168.1.254
        BTHUB5          <00> -         B <ACTIVE>
        BTHUB5          <03> -         B <ACTIVE>
        BTHUB5          <20> -         B <ACTIVE>
        ..__MSBROWSE__. <01> - <GROUP> B <ACTIVE>
        HOME            <1d> -         B <ACTIVE>
        HOME            <1e> - <GROUP> B <ACTIVE>
        HOME            <00> - <GROUP> B <ACTIVE>

        MAC Address = 00-00-00-00-00-00

You can see above that the machine BTHUB5 (which is actually the home network’s router) is the Master Browser in the Workgroup named HOME (see earlier).

user $ nmblookup -A 192.168.1.90
Looking up status of 192.168.1.90
        SMENKHKARE      <00> -         B <ACTIVE>
        SMENKHKARE      <03> -         B <ACTIVE>
        SMENKHKARE      <20> -         B <ACTIVE>
        ..__MSBROWSE__. <01> - <GROUP> B <ACTIVE>
        GREENGABLES     <00> - <GROUP> B <ACTIVE>
        GREENGABLES     <1d> -         B <ACTIVE>
        GREENGABLES     <1e> - <GROUP> B <ACTIVE>

        MAC Address = 00-00-00-00-00-00

You can see above that computer SMENKHKARE is currently the Master Browser in the Workgroup named GREENGABLES.

user $ nmblookup -A 192.168.56.1
Looking up status of 192.168.56.1
No reply from 192.168.56.1

You can see above that the network node 192.168.56.1 is inactive, which is not surprising considering that it is a node on a VirtualBox virtual subnet on the Windows 10 computer thutmoseiii (see earlier) and VirtualBox is not running at the moment on that computer.

On a Windows machine it is not quite so easy to find out which machines are currently Master Browsers. However, on the face of it the third-party utility lanscan.exe can do it (see How to Determine the Master Browser in a Windows Workgroup):

C:\WINDOWS\system32>lanscan

LANscanner v1.67 - ScottiesTech.Info

Scanning LAN...

Scanning workgroup: HOME...

Scanning workgroup: GREENGABLES...

BTHUB5            192.168.1.254    11-11-11-11-11-11  HOME         MASTER
THUTMOSEIII       192.168.56.1     22-22-22-22-22-22  GREENGABLES  MASTER
SMENKHKARE        192.168.1.90     aa-bb-cc-dd-ee-ff  GREENGABLES  MASTER
TUTANKHAMUN       192.168.1.79     33-33-33-33-33-33  GREENGABLES
AKHANATEN         192.168.1.70     55-55-55-55-55-55  GREENGABLES

Press any key to exit...

(MAC addresses anonymised by me.)

Notice above that lanscan.exe listed the VirtualBox virtual subnet node 192.168.56.1 in Windows 10 computer thutmoseiii (see earlier) but omitted to list the node 192.168.1.74 (also thutmoseiii) in the real network. Now, in this particular case thutmoseiii on 192.168.1.74 is not a Master Browser. Nevertheless, as lanscan.exe is supposed to list all nodes, its failure to list the node 192.168.1.74 is a shortcoming.

And what happens if thutmoseiii on node 192.168.1.74 becomes a Master Browser? In that case lanscan.exe still omits the node from the list and, in addition, wrongly shows tutankhamun as a Master Browser:

C:\WINDOWS\system32>nbtstat -n

VirtualBox Host-Only Network 2:
Node IpAddress: [192.168.56.1] Scope Id: []

                NetBIOS Local Name Table

       Name               Type         Status
    ---------------------------------------------
    THUTMOSEIII    <20>  UNIQUE      Registered
    THUTMOSEIII    <00>  UNIQUE      Registered
    GREENGABLES    <00>  GROUP       Registered
    GREENGABLES    <1E>  GROUP       Registered
    GREENGABLES    <1D>  UNIQUE      Registered
    ☺☻__MSBROWSE__☻<01>  GROUP       Registered

Ethernet:
Node IpAddress: [192.168.1.74] Scope Id: []

                NetBIOS Local Name Table

       Name               Type         Status
    ---------------------------------------------
    THUTMOSEIII    <20>  UNIQUE      Registered
    THUTMOSEIII    <00>  UNIQUE      Registered
    GREENGABLES    <00>  GROUP       Registered
    GREENGABLES    <1E>  GROUP       Registered
    GREENGABLES    <1D>  UNIQUE      Registered
    ☺☻__MSBROWSE__☻<01>  GROUP       Registered

WiFi:
Node IpAddress: [0.0.0.0] Scope Id: []

    No names in cache

Local Area Connection* 11:
Node IpAddress: [0.0.0.0] Scope Id: []

    No names in cache

C:\WINDOWS\system32>nbtstat -A 192.168.1.79

VirtualBox Host-Only Network 2:
Node IpAddress: [192.168.56.1] Scope Id: []

    Host not found.

Ethernet:
Node IpAddress: [192.168.1.74] Scope Id: []

           NetBIOS Remote Machine Name Table

       Name               Type         Status
    ---------------------------------------------
    TUTANKHAMUN    <00>  UNIQUE      Registered
    TUTANKHAMUN    <03>  UNIQUE      Registered
    TUTANKHAMUN    <20>  UNIQUE      Registered
    GREENGABLES    <00>  GROUP       Registered
    GREENGABLES    <1E>  GROUP       Registered

    MAC Address = 00-00-00-00-00-00


WiFi:
Node IpAddress: [0.0.0.0] Scope Id: []

    Host not found.

Local Area Connection* 11:
Node IpAddress: [0.0.0.0] Scope Id: []

    Host not found.

C:\WINDOWS\system32>lanscan

LANscanner v1.67 - ScottiesTech.Info

Scanning LAN...

Scanning workgroup: HOME...

Scanning workgroup: GREENGABLES...

BTHUB5            192.168.1.254    11-11-11-11-11-11  HOME         MASTER
THUTMOSEIII       192.168.56.1     22-22-22-22-22-22  GREENGABLES  MASTER
TUTANKHAMUN       192.168.1.79     33-33-33-33-33-33  GREENGABLES  MASTER
SMENKHKARE        192.168.1.90     aa-bb-cc-dd-ee-ff  GREENGABLES
AKHANATEN         192.168.1.70     55-55-55-55-55-55  GREENGABLES

Press any key to exit...

(MAC addresses anonymised by me.)

Linux appears to have the edge on Windows in this respect, as the Samba command ‘nmblookup -M -- -‘ detects all the Master Browsers correctly in the above situation:

user $ nmblookup -M -- -
192.168.1.254 __MSBROWSE__
192.168.1.74 __MSBROWSE__
192.168.56.1 __MSBROWSE__

So it appears that, from a Windows computer, the only sure way to find all Master Browsers is to use the command ‘nbtstat -a <computer name>‘ to check each remote machine in the home network, plus the command ‘nbtstat -n‘ to check the Windows computer you are using.

Footnote
The ebuild of the current Gentoo Stable Branch package net-fs/samba-4.2.11 (and probably the ebuild of the Testing Branch package net-fs/samba-4.2.14 as well) is not entirely correct, as it pulls in unnecessary dependencies (see Gentoo Bug Report No. 579088 – net-fs/samba-4.x has many hard dependencies, make some optional). For example, Kerberos is not required at all if you are not using LDAP, AD, etc. and are just using NETBIOS Name Resolution by Broadcast in a Windows Workgroup (like most home users). However, the Gentoo samba ebuild forces the user to install Kerberos (either the MIT implementation app-crypt/mit-krb5 or the Heimdal implementation app-crypt/heimdal) even if you specify that Samba should be built without support for LDAP, AD, etc. This does not cause any harm, but it is unnecessary.

user $ eix -I samba
[I] net-fs/samba
     Available versions:  3.6.25^t 4.2.11 ~4.2.14 [M]~4.3.11 [M]~4.4.5 [M]~4.4.6 [M]~4.5.0 {acl addc addns ads (+)aio avahi caps (+)client cluster cups debug dmapi doc examples fam gnutls iprint ldap ldb +netapi pam quota +readline selinux +server +smbclient smbsharemodes swat syslog +system-mitkrb5 systemd test (+)winbind zeroconf ABI_MIPS="n32 n64 o32" ABI_PPC="32 64" ABI_S390="32 64" ABI_X86="32 64 x32" PYTHON_TARGETS="python2_7"}
     Installed versions:  4.2.11(19:40:03 16/09/16)(avahi client cups fam gnutls pam -acl -addc -addns -ads -aio -cluster -dmapi -iprint -ldap -quota -selinux -syslog -system-mitkrb5 -systemd -test -winbind ABI_MIPS="-n32 -n64 -o32" ABI_PPC="-32 -64" ABI_S390="-32 -64" ABI_X86="64 -32 -x32" PYTHON_TARGETS="python2_7")
     Homepage:            http://www.samba.org/
     Description:         Samba Suite Version 4

If you are a Gentoo Linux user, you can merge the package net-fs/samba with the same USE flags shown above (obviously change “-systemd” to “systemd” if you use systemd instead of OpenRC), and use the laptops’ smb.conf files shown in this post as templates, and you will be able to share files and printers using Samba and NetBIOS name resolution. Don’t forget to use pdbedit to define the Samba users, and don’t forget to stop and disable winbindd if it is already installed.

Further reading

• How NetBIOS name resolution really works
• Name Resolution and Browsing (See the section Browser Elections)
• How Computer Browser Service Works
• NetBIOS Over TCP/IP
• Nbtstat
• Windows Networking

ADDENDUM (October 30, 2016): You probably already use the Public folder in Windows. If not, you can find a brief explanation in the article Simple Questions: What is the Public Folder & How to Use it?. There are a number of default sub-folders in C:\Users\Public\ on a Windows machine. There are some differences depending on the version of Windows, but in Windows 10 (Anniversary Update) these sub-folders are named:

C:\Public\Libraries
C:\Public\Public Account Pictures
C:\Public\Public Desktop
C:\Public\Public Documents
C:\Public\Public Downloads
C:\Public\Public Music
C:\Public\Public Pictures
C:\Public\Public Videos

These predefined sub-folders are not ordinary folders, and I have noticed a surmountable minor limitation when accessing them from a Linux machine using Samba, as explained below.

If I enable Public Folder Sharing on a Windows machine (‘Turn on sharing so that anyone with network access can read and write files in the Public folders’) and configure the security permissions of the Public folder for Everyone, from another Windows machine in the Workgroup I can copy files to the first machine’s Public folder and default sub-folders. From a Linux machine in the Workgroup I can copy files to the Public folder on Windows machines in the Workgroup but I cannot copy files to the default sub-folders (the Dolphin file manager displays the error message ‘Access denied. Could not write to .‘). However, this is not a big deal because I can copy files into the Public folder itself and into manually created sub-folders in the Public folder.

ADDENDUM (February 13, 2018): Windows 10 Version 1709 and later have the SMBv1/CIFS protocol disabled by default, so the Lanscan utility will no longer work in Windows 10 Version 1709. That is not a big deal if you also have Linux machines on your home network; just use the Samba commands from one of those Linux machines instead. If you have devices on your home network that only support SMBv1/CIFS protocol and they cannot be configured to use the SMBv3 protocol, your only option is to configure Windows 10 Version 1709 to use the SMBv1 protocol, which is less secure than the later SMB protocols. See e.g. the article Cannot browse network neighborhood under Windows 10 Fall Creators update 1709 and newer for how to configure Windows 10 Version 1709 to use the SMBv1 protocol. In my case, all my Linux machines using Samba can be configured via the smb.conf file to use a newer version of the SMB protocol (see ‘server min protocol’ and ‘server max protocol’ in the Samba documentation for smb.conf).

KDE Connect on a hotel Wi-Fi network

I am a fan of KDE Connect (see my 2014 post about an earlier version), but had previously been unable to use it with a hotel network. However today I managed to do that, and here is how I did it …

I first connected my laptop and my Samsung Galaxy Note 4 to the hotel’s Wi-Fi network, then used the ifconfig command in Linux on my laptop to find the IP address of my laptop on the hotel’s network. Note that the IP address one sees if one uses a Web site such as WhatIsMyIPAddress will be the laptop’s outward-facing IP address, not the IP address of the laptop on the hotel network. For example, the ifconfig command has just shown me that my current DHCP-allocated IP address is 10.154.245.40 on this hotel’s network for this session whereas the Web site WhatIsMyIPAddress is showing my IP address as 78.100.57.102.

By the way, I can also use the excellent Android utility Fing on my Galaxy Note 4 to find the IP address of my laptop on the hotel’s network. It is quite interesting to use Fing to see what other devices (their hostname and IP address) are currently connected to the hotel’s network.

Anyway, then I launched KDE Connect on the Galaxy Note 4, tapped ⋮ and ‘Add devices by IP’, and entered the laptop’s IP address (10.154.245.40 in this specific case). I was able to pair with KDE Connect running on my laptop and send files from my phone to the laptop, and vice versa.