bug when using mptcp kernel

[KaleiRo]

Hi,

We have strange bug when using dco on 6.1 kernel and mptcp, reported by a bad socket or socket operation on non-socket :

dco_new_peer: netlink reports error (-3): Bad socket
dco_new_peer: failed to send netlink message: Socket operation on non-socket (-88)
Cannot add peer to DCO for xxxx/123.123.123.123:12345: Socket operation on non-socket (-88)

i am on debian 12 with openvpn 2.6.9 and dco-dkms 0.2.20231117

[ordex]

this is the netlink socket that was maybe closed or messed up.
is it easy to reproduce?

[schwabe]

@Kalimeiro while mptcp is mostly transparent to user space application, the transparency might not be there for a kernel module like ovpn-dco. So this has been probably not really tested/implementend yet.

[KaleiRo]

Thanks all for your response.

yes it's easy to reproduced, you need to use 6.1 kernel, configure multiple wan with mptcp, install openvpn/openvpn dco module from official repo, create an vpn with tcp protocol.

In UDP it's working fine, but it's normal.

[ordex]

@Kalimeiro does it mean that the issue shows up always in that configuration?

[KaleiRo]

yes, you can use OpenMPTCProuter easily to test, but i have abandonned this project.

[matttbe]

Hello,

FYI, I closed the same ticket that was opened on MPTCP side (multipath-tcp/mptcp_net-next#479), because there is not much we can do on our side.

Do not hesitate to ping us if you have are looking at supporting MPTCP and have questions ;)

[ordex]

Thanks @matttbe I'm keeping this ticket open because I will come back to this later for sure.