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ipv6: Limit mtu to 65575 bytes

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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 <f.wellenreiter@gmail.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2014-04-10 21:23:36 -07:00 committed by David S. Miller
parent 05ab8f2647
commit 30f78d8ebf
2 changed files with 8 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
include/net/ip6_route.h
View File

@ -32,6 +32,11 @@ 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

5
net/ipv6/route.c
View File

@ -1338,7 +1338,7 @@ 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;
@ -1348,7 +1348,8 @@ 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;