From: Alexander Sverdlin <alexander.sverdlin@xxxxxxx> Date: Mon, 02 Sep 2013 15:58:25 +0200 > From: Alexander Sverdlin <alexander.sverdlin@xxxxxxx> > > net: sctp: Fix data chunk fragmentation for MTU values which are not multiple of 4 > > Initially the problem was observed with ipsec, but later it became clear that > SCTP data chunk fragmentation algorithm has problems with MTU values which are > not multiple of 4. Test program was used which just transmits 2000 bytes long > packets to other host. tcpdump was used to observe re-fragmentation in IP layer > after SCTP already fragmented data chunks. ... > Here problem in data portion limit calculation leads to re-fragmentation in IP, > which is sub-optimal. The problem is max_data initial value, which doesn't take > into account the fact, that data chunk must be padded to 4-bytes boundary. > It's enough to correct max_data, because all later adjustments are correctly > aligned to 4-bytes boundary. > > After the fix is applied, everything is fragmented correctly for uneven MTUs: ... > The bug was there for years already, but > - is a performance issue, the packets are still transmitted > - doesn't show up with default MTU 1500, but possibly with ipsec (MTU 1438) > > Signed-off-by: Alexander Sverdlin <alexander.sverdlin@xxxxxxx> Applied, thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-sctp" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
