From 132da31a0b0143cac11799dafa961c1969ee122c Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 10 Apr 2014 21:23:36 -0700 Subject: ipv6: Limit mtu to 65575 bytes [ Upstream commit 30f78d8ebf7f514801e71b88a10c948275168518 ] Francois reported that setting big mtu on loopback device could prevent tcp sessions making progress. We do not support (yet ?) IPv6 Jumbograms and cook corrupted packets. We must limit the IPv6 MTU to (65535 + 40) bytes in theory. Tested: ifconfig lo mtu 70000 netperf -H ::1 Before patch : Throughput : 0.05 Mbits After patch : Throughput : 35484 Mbits Reported-by: Francois WELLENREITER Signed-off-by: Eric Dumazet Acked-by: YOSHIFUJI Hideaki Acked-by: Hannes Frederic Sowa Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/ipv6/route.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'net') diff --git a/net/ipv6/route.c b/net/ipv6/route.c index 3fde3e97786..b2614b22622 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -1236,7 +1236,7 @@ static unsigned int ip6_mtu(const struct dst_entry *dst) unsigned int mtu = dst_metric_raw(dst, RTAX_MTU); if (mtu) - return mtu; + goto out; mtu = IPV6_MIN_MTU; @@ -1246,7 +1246,8 @@ static unsigned int ip6_mtu(const struct dst_entry *dst) mtu = idev->cnf.mtu6; rcu_read_unlock(); - return mtu; +out: + return min_t(unsigned int, mtu, IP6_MAX_MTU); } static struct dst_entry *icmp6_dst_gc_list; -- cgit v1.2.3-18-g5258