From 5976aed862c07c698554edb89955f3f554a0921e 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: Ben Hutchings --- include/net/ip6_route.h | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'include') diff --git a/include/net/ip6_route.h b/include/net/ip6_route.h index 5e91b72..4913dac 100644 --- a/include/net/ip6_route.h +++ b/include/net/ip6_route.h @@ -34,6 +34,11 @@ struct route_info { #define RT6_LOOKUP_F_SRCPREF_PUBLIC 0x00000010 #define RT6_LOOKUP_F_SRCPREF_COA 0x00000020 +/* We do not (yet ?) support IPv6 jumbograms (RFC 2675) + * Unlike IPv4, hdr->seg_len doesn't include the IPv6 header + */ +#define IP6_MAX_MTU (0xFFFF + sizeof(struct ipv6hdr)) + /* * rt6_srcprefs2flags() and rt6_flags2srcprefs() translate * between IPV6_ADDR_PREFERENCES socket option values -- cgit v1.1