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authorMaciej Żenczykowski <maze@google.com>2016-11-04 14:51:54 -0700
committerDavid S. Miller <davem@davemloft.net>2016-11-09 13:19:32 -0500
commitfb56be83e43d0bb0cc9e8c35a6a9cac853231ba2 (patch)
tree2df54004541ac2397e6035d9301804b36c3b8ea3 /net/ipv6
parent3023898b7d4aac65987bd2f485cc22390aae6f78 (diff)
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net-ipv6: on device mtu change do not add mtu to mtu-less routes
Routes can specify an mtu explicitly or inherit the mtu from the underlying device - this inheritance is implemented in dst->ops->mtu handlers ip6_mtu() and ip6_blackhole_mtu(). Currently changing the mtu of a device adds mtu explicitly to routes using that device. ie. # ip link set dev lo mtu 65536 # ip -6 route add local 2000::1 dev lo # ip -6 route get 2000::1 local 2000::1 dev lo table local src ... metric 1024 pref medium # ip link set dev lo mtu 65535 # ip -6 route get 2000::1 local 2000::1 dev lo table local src ... metric 1024 mtu 65535 pref medium # ip link set dev lo mtu 65536 # ip -6 route get 2000::1 local 2000::1 dev lo table local src ... metric 1024 mtu 65536 pref medium # ip -6 route del local 2000::1 After this patch the route entry no longer changes unless it already has an mtu. There is no need: this inheritance is already done in ip6_mtu() # ip link set dev lo mtu 65536 # ip -6 route add local 2000::1 dev lo # ip -6 route add local 2000::2 dev lo mtu 2000 # ip -6 route get 2000::1; ip -6 route get 2000::2 local 2000::1 dev lo table local src ... metric 1024 pref medium local 2000::2 dev lo table local src ... metric 1024 mtu 2000 pref medium # ip link set dev lo mtu 65535 # ip -6 route get 2000::1; ip -6 route get 2000::2 local 2000::1 dev lo table local src ... metric 1024 pref medium local 2000::2 dev lo table local src ... metric 1024 mtu 2000 pref medium # ip link set dev lo mtu 1501 # ip -6 route get 2000::1; ip -6 route get 2000::2 local 2000::1 dev lo table local src ... metric 1024 pref medium local 2000::2 dev lo table local src ... metric 1024 mtu 1501 pref medium # ip link set dev lo mtu 65536 # ip -6 route get 2000::1; ip -6 route get 2000::2 local 2000::1 dev lo table local src ... metric 1024 pref medium local 2000::2 dev lo table local src ... metric 1024 mtu 65536 pref medium # ip -6 route del local 2000::1 # ip -6 route del local 2000::2 This is desirable because changing device mtu and then resetting it to the previous value shouldn't change the user visible routing table. Signed-off-by: Maciej Żenczykowski <maze@google.com> CC: Eric Dumazet <edumazet@google.com> Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv6')
-rw-r--r--net/ipv6/route.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 7403d90dcb38..1b57e11e6e0d 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -2761,6 +2761,7 @@ static int rt6_mtu_change_route(struct rt6_info *rt, void *p_arg)
PMTU discouvery.
*/
if (rt->dst.dev == arg->dev &&
+ dst_metric_raw(&rt->dst, RTAX_MTU) &&
!dst_metric_locked(&rt->dst, RTAX_MTU)) {
if (rt->rt6i_flags & RTF_CACHE) {
/* For RTF_CACHE with rt6i_pmtu == 0