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Date:	Mon, 10 Feb 2014 09:41:54 +0100
From:	Ortwin Gl├╝ck <>
Subject: xfrm: is pmtu broken with ESP tunneling?


I am using Openswan to configure an IPSec VPN (using the xfrm/netkey 
backend). Large HTTP POST requests from the client seem to get stuck, 
because the outgoing packets are 1530 bytes (before being wrapped into 
ESP packets). The problem goes away by setting sysctl 

May have something to do with it:
The tunneled network is and I am SNAT'ing some destinations 
to that IP, so they get routed through the tunnel. Any other networks 
are not to go through the tunnel.

iptables -t nat -A POSTROUTING -d "${R}" -j SNAT --to-source

It seems quite clear to me that xfrm is doing something wrong here.

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