MTU issues

[dorian]

Hi All,
Sorry for disturbing you if the issues has been discussed earlier but I
cannot find clear explanation of my problem.

Tracing the tinc logs (a debug level) I have found that the MTU value of
the connection is determined and chosen at the beginning of the tunnel
setup.

My question is following: is the MTU value renegotiated / rechecked
after the tunnel is established?

The question concerns the following observation.
After successful connection everything is working correctly.
Unfortunately since I am using tunnelling over GPRS media -for some time
the quality of the connection is degraded.

When it happens I am observing icmp "fragmentation needed" packets sent
from clients to some http server.
It looks like the servers ignore this kind of icmp messages (maybe
because of improper firewall?) and the packets sent to clients are never
fragmented.
As the result - for the clients some part of the web becomes inaccessible.

Manual tunnel down/up fixes the problem immediately since (probably - I
didn't compare them) new lower MTU is chosen.


I am wondering if it is possible to make MTU renegotiation to be automatic?

Please advice,
Dorian