Tincd cannot flush and resets the connection

[Guus Sliepen]

On Mon, Sep 21, 2009 at 11:13:33AM +0200, Hans de Groot wrote:

> Sorry to bother you, but I have been searching but cannot find any
> reason why my mysql sessions get stuck. (over tinc en over normal
> connections). Tinc gets stuck and needs to reconnect,, over normal
> connections only that session gets stuck and a retry works.
> 
> I did find a difference using tcpdump between a working request en one
> that is failing. Notice the  {1532:2304} on the last line of the failing
> session. Could this have something to do with fragmentation? I am
> searching google to try and find what the numbers between {} mean.

I don't see any fragmentation going on in your tcpdump log. (The tcpdump
manpage contains a description of what all those things mean.)

> I don't think its because my provider is capping things. I tried tinc on
> port 110.
> 
> I know this is not a tinc problem (al though I things it's weird that
> tinc gets stuck too) But maybe you have any hints where to look next. 

It could also be caused by a firewall blocking ICMP Fragmentation Needed
packets, which would make TCP connections get stuck when you transfer lots of
data over it. Try using the tracepath tool (from the iputils package,
http://www.skbuff.net/iputils/) to determine the MTU to the other end (via the
real network, not via the VPN). If the tracepath tool fails, try using the
option "-l 1000" to see if that does work. If so, then check if you have a
firewall that is blocking ICMP packets.

-- 
Met vriendelijke groet / with kind regards,
     Guus Sliepen <guus at tinc-vpn.org>
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