Tunnel disconnects with "peer ignored channel window"

[Damien Miller]

On Sun, 19 Oct 2025, valt aran wrote:

> Tried it with the patch and version 10.2
> Error messages are something like
> "channel 0: datagram length 1444 too big for window 1206 or maximum packet 32768"
> Length or window can have different values.
> Connection still breaks after a while.
> Then I disabled the automatic disconnecting in the source code (which says the connection could deadlock in this case.)
> However, no disconnects up to now. Though I seem to get lots of
> 
> "debug1: rekeying in progress
> debug1: enqueue packet: ...
> "
> 
> messages which I did not get before. Not sure if this is relevant or happens because the connection is now running longer.

Did you try removing the section of code I suggested?

> I'm suspicious of this section of code in channel_input_data():
> 
>   3498          if (c->datagram)
>   3499                  win_len += 4;  /* string length header */
> 
> might be double-counting the header and permanently shrinking the
> channel window for each tunneled packet received. You could try
> removing or commenting it out and seeing if it solves the problem.