Migration from 2.5.x to OpenVpn 2.6.3 error (tcp)

[AndreL]

Hi,

After migration no connection from Windows Openvpn client:

Nb: change in the config from [cipher aes-256-cbc] to [data-ciphers-fallback aes-256-cbc]

2023-05-06 22:45:28 OpenVPN 2.6.3 [git:v2.6.3/94aad8c51043a805] Windows-MSVC [SSL (OpenSSL)] [LZO] [LZ4] [PKCS11] [AEAD] [DCO] built on Apr 26 2023
2023-05-06 22:45:28 Windows version 10.0 (Windows 10 or greater), amd64 executable
2023-05-06 22:45:28 library versions: OpenSSL 3.1.0 14 Mar 2023, LZO 2.10
2023-05-06 22:45:28 DCO version: v0
2023-05-06 22:45:29 WARNING: No server certificate verification method has been enabled. See http://openvpn.net/howto.html#mitm for more info.
2023-05-06 22:45:29 TCP/UDP: Preserving recently used remote address: [AF_INET]xx:1394
2023-05-06 22:45:29 Attempting to establish TCP connection with [AF_INET]xx.4:1394
2023-05-06 22:45:29 TCP connection established with [AF_INET]xx:1394
2023-05-06 22:45:29 TCPv4_CLIENT link local: (not bound)
2023-05-06 22:45:29 TCPv4_CLIENT link remote: [AF_INET]xx:1394
2023-05-06 22:45:29 WARNING: this configuration may cache passwords in memory -- use the auth-nocache option to prevent this
2023-05-06 22:45:29 TLS ERROR: Unknown key_method/flags=95 received from remote host
2023-05-06 22:45:29 TLS Error: TLS handshake failed
2023-05-06 22:45:29 Fatal TLS error (check_tls_errors_co), restarting
2023-05-06 22:45:29 SIGUSR1[soft,tls-error] received, process restarting
2023-05-06 22:45:30 WARNING: No server certificate verification method has been enabled. See http://openvpn.net/howto.html#mitm for more info.
2023-05-06 22:45:30 TCP/UDP: Preserving recently used remote address: [AF_INET]xx:1394
2023-05-06 22:45:30 Attempting to establish TCP connection with [AF_INET]xx:1394
2023-05-06 22:45:30 TCP connection established with [AF_INET]xx:1394
2023-05-06 22:45:30 TCPv4_CLIENT link local: (not bound)
2023-05-06 22:45:30 TCPv4_CLIENT link remote: [AF_INET]xx:1394
2023-05-06 22:45:30 TLS ERROR: Unknown key_method/flags=95 received from remote host
2023-05-06 22:45:30 TLS Error: TLS handshake failed
2023-05-06 22:45:30 Fatal TLS error (check_tls_errors_co), restarting
2023-05-06 22:45:30 SIGUSR1[soft,tls-error] received, process restarting
2023-05-06 22:45:31 WARNING: No server certificate verification method has been enabled. See http://openvpn.net/howto.html#mitm for more info.
2023-05-06 22:45:31 TCP/UDP: Preserving recently used remote address: [AF_INET]xx:1394
2023-05-06 22:45:31 Attempting to establish TCP connection with [AF_INET]xx:1394
2023-05-06 22:45:31 TCP connection established with [AF_INET]xx:1394
2023-05-06 22:45:31 TCPv4_CLIENT link local: (not bound)
2023-05-06 22:45:31 TCPv4_CLIENT link remote: [AF_INET]x:1394
2023-05-06 22:45:32 TLS ERROR: Unknown key_method/flags=95 received from remote host
2023-05-06 22:45:32 TLS Error: TLS handshake failed
2023-05-06 22:45:32 Fatal TLS error (check_tls_errors_co), restarting
2023-05-06 22:45:32 SIGUSR1[soft,tls-error] received, process restarting
2023-05-06 22:45:33 WARNING: No server certificate verification method has been enabled. See http://openvpn.net/howto.html#mitm for more info.
2023-05-06 22:45:33 TCP/UDP: Preserving recently used remote address: [AF_INET]xx:1394
2023-05-06 22:45:33 Attempting to establish TCP connection with [AF_INET]xx:1394
2023-05-06 22:45:33 TCP connection established with [AF_INET]xx:1394
2023-05-06 22:45:33 TCPv4_CLIENT link local: (not bound)
2023-05-06 22:45:33 TCPv4_CLIENT link remote: [AF_INET]xx:1394
2023-05-06 22:45:33 TLS ERROR: Unknown key_method/flags=95 received from remote host
2023-05-06 22:45:33 TLS Error: TLS handshake failed
2023-05-06 22:45:33 Fatal TLS error (check_tls_errors_co), restarting
2023-05-06 22:45:33 SIGUSR1[soft,tls-error] received, process restarting
2023-05-06 22:45:34 WARNING: No server certificate verification method has been enabled. See http://openvpn.net/howto.html#mitm for more info.
2023-05-06 22:45:34 TCP/UDP: Preserving recently used remote address: [AF_INET]xx:1394
2023-05-06 22:45:34 Attempting to establish TCP connection with [AF_INET]xx:1394
2023-05-06 22:45:34 TCP connection established with [AF_INET]xx:1394
2023-05-06 22:45:34 TCPv4_CLIENT link local: (not bound)
2023-05-06 22:45:34 TCPv4_CLIENT link remote: [AF_INET]xx:1394
2023-05-06 22:45:34 TLS ERROR: Unknown key_method/flags=95 received from remote host
2023-05-06 22:45:34 TLS Error: TLS handshake failed
2023-05-06 22:45:34 Fatal TLS error (check_tls_errors_co), restarting
2023-05-06 22:45:34 SIGUSR1[soft,tls-error] received, process restarting
2023-05-06 22:45:36 WARNING: No server certificate verification method has been enabled. See http://openvpn.net/howto.html#mitm for more info.
2023-05-06 22:45:36 TCP/UDP: Preserving recently used remote address: [AF_INET]xx:1394
2023-05-06 22:45:36 Attempting to establish TCP connection with [AF_INET]xx:1394
2023-05-06 22:45:36 TCP connection established with [AF_INET]xx:1394
2023-05-06 22:45:36 TCPv4_CLIENT link local: (not bound)
2023-05-06 22:45:36 TCPv4_CLIENT link remote: [AF_INET]xx:1394
2023-05-06 22:45:36 TLS ERROR: Unknown key_method/flags=95 received from remote host
2023-05-06 22:45:36 TLS Error: TLS handshake failed
2023-05-06 22:45:36 Fatal TLS error (check_tls_errors_co), restarting
2023-05-06 22:45:36 SIGUSR1[soft,tls-error] received, process restarting

Any help is welcome...