Assertion failed at socket.c: 2719 (buf_defined(&sb->next)) caused by duplicate CN

[tct]

Ref: ​https://forums.openvpn.net/viewtopic.php?f=4&t=31444

Using duplicate CNs on a server which does not define --duplicate-cn causes ASSERT on the client.

[Gert Döring]

The log is not verbose enough to see what is going on (this seems to be "default verb", not "verb 4").

From what I could see, this is the *client* crashing, if someone else connects to the same *server* with a duplicate CN. Which does not make any sense at all, as the client wouldn't even see "the other" client.

Now, if the server sends a client exit message, *and* this is sort of being misparsed, or triggering something that is new on 2.5.0, this would start to make sense - but lots of guesswork.

It would be really really good to have a) the full client and server config (without secret material, of course) and b) a client log with verb 4.

I *guess* this is related to TCP, and the server cuts the TCP connection in an unfriendly way, so when the client tries to get the next message out of the stream buffer, there is none. But the code really should handle that, otherwise we'd have many more reports about "my TCP session was broken, and then openvpn died".

Since I do not have much time, I'm not going to chase this unless I have more logs.

[tct]

I'll see if I can replicate this.

[tct]

Corrected Forum URL