I have an OpenVPN server running on a Windows 10 machine at home. The server is behind a CISCO router with static routing set up. It works flawlessly, redirects internet traffic, handles multiple clients, and torrenting works from a Windows client.
HOWEVER, I just tried downloading a torrent from a Linux client (Elementary OS), and the moment the torrent client tries to connect, the VPN stops working. I tried both qBitTorrent and Transmission, which work flawlessly on a Windows client. After this happens, no new clients can connect, and all existing clients lose connectivity. The only way to resolve this is to restart the OpenVPN server.
I thought it was a firewall/SPI issue, so I disabled both in the router, but that changed nothing. I also tried changing the MTU setting on the client. Here is my full server config:
dev tun
proto udp
port 1155
ca ca.crt
cert server.crt
key server.key
dh dh4096.pem
duplicate-cn
topology subnet
server 10.8.0.0 255.255.255.0
push "dhcp-option DNS 8.8.8.8"
push "dhcp-option DNS 8.8.4.4"
push "redirect-gateway def1"
client-to-client
keepalive 10 120
remote-cert-tls client
tls-version-min 1.2
tls-auth ta.key 0
cipher AES-256-CBC
auth SHA256
auth-nocache
comp-lzo
persist-key
persist-tun
status openvpn-status.log
status-version 3
verb 3
Any ideas will be much appreciated!
EDIT1: Disconnecting the OpenVPN server (from the GUI) causes it to hang until force stopped.
EDIT2: Server log at verbosity level 6 when the connection stops:
Fri Feb 23 18:16:14 2018 {profile-name}/{client-ip} UDPv6 WRITE [38] to [AF_INET6]::ffff:{client-ip}:57317: P_DATA_V1 kid=0 DATA len=37
Fri Feb 23 18:16:24 2018 {profile-name}/{client-ip} UDPv6 WRITE [38] to [AF_INET6]::ffff:{client-ip}:57317: P_DATA_V1 kid=0 DATA len=37
Fri Feb 23 18:16:35 2018 {profile-name}/{client-ip} UDPv6 WRITE [38] to [AF_INET6]::ffff:{client-ip}:57317: P_DATA_V1 kid=0 DATA len=37
Fri Feb 23 18:16:45 2018 {profile-name}/{client-ip} UDPv6 WRITE [38] to [AF_INET6]::ffff:{client-ip}:57317: P_DATA_V1 kid=0 DATA len=37
Fri Feb 23 18:16:55 2018 {profile-name}/{client-ip} UDPv6 WRITE [38] to [AF_INET6]::ffff:{client-ip}:57317: P_DATA_V1 kid=0 DATA len=37
Fri Feb 23 18:17:05 2018 {profile-name}/{client-ip} UDPv6 WRITE [38] to [AF_INET6]::ffff:{client-ip}:57317: P_DATA_V1 kid=0 DATA len=37
Client log:
Fri Feb 23 18:20:01 2018 us=463024 TUN READ [76]
Fri Feb 23 18:20:01 2018 us=463061 UDP WRITE [101] to [AF_INET]{server-ip}:{port}: P_DATA_V2 kid=0 DATA len=100
Fri Feb 23 18:20:01 2018 us=535515 TUN READ [132]
Fri Feb 23 18:20:01 2018 us=535573 UDP WRITE [157] to [AF_INET]{server-ip}:{port}: P_DATA_V2 kid=0 DATA len=156
Fri Feb 23 18:20:06 2018 us=535976 TUN READ [93]
Fri Feb 23 18:20:06 2018 us=536044 UDP WRITE [118] to [AF_INET]{server-ip}:{port}: P_DATA_V2 kid=0 DATA len=117
Fri Feb 23 18:20:09 2018 us=925150 UDP READ [38] from [AF_INET]{server-ip}:{port}: P_DATA_V1 kid=0 DATA len=37
Fri Feb 23 18:20:11 2018 us=536196 TUN READ [132]
Fri Feb 23 18:20:11 2018 us=536258 UDP WRITE [157] to [AF_INET]{server-ip}:{port}: P_DATA_V2 kid=0 DATA len=156
Fri Feb 23 18:20:11 2018 us=712774 TUN READ [76]
Fri Feb 23 18:20:11 2018 us=712829 UDP WRITE [101] to [AF_INET]{server-ip}:{port}: P_DATA_V2 kid=0 DATA len=100
