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authorEric Dumazet <edumazet@google.com>2014-04-10 21:23:36 -0700
committerDavid S. Miller <davem@davemloft.net>2014-04-14 12:39:59 -0400
commit30f78d8ebf7f514801e71b88a10c948275168518 (patch)
treef1e3fc6c694aa8a153901ceadf2106b2d43a0470
parent05ab8f2647e4221cbdb3856dd7d32bd5407316b3 (diff)
ipv6: Limit mtu to 65575 bytes
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>
-rw-r--r--include/net/ip6_route.h5
-rw-r--r--net/ipv6/route.c5
2 files changed, 8 insertions, 2 deletions
diff --git a/include/net/ip6_route.h b/include/net/ip6_route.h
index 3c3bb184eb8..6c4f5eac98e 100644
--- a/include/net/ip6_route.h
+++ b/include/net/ip6_route.h
@@ -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
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 5015c50a5ba..5ea462eacd9 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -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;