[34-longterm 196/260] net: Fix IPv6 PMTU disc. w/ asymmetric routes

Paul Gortmaker
2011-01-02T07:40:18Z

From: Maciej Żenczykowski <maze@google.com>

commit ae878ae280bea286ff2b1e1cb6e609dd8cb4501d upstream.

Signed-off-by: Maciej Żenczykowski <maze@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
---
net/ipv6/route.c | 28 ++++++++++++++++++++++++----
1 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 40f6f13..4f4b21d 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -1561,14 +1561,13 @@ out:
* i.e. Path MTU discovery
*/

-void rt6_pmtu_discovery(struct in6_addr *daddr, struct in6_addr *saddr,
- struct net_device *dev, u32 pmtu)
+static void rt6_do_pmtu_disc(struct in6_addr *daddr, struct in6_addr *saddr,
+ struct net *net, u32 pmtu, int ifindex)
{
struct rt6_info *rt, *nrt;
- struct net *net = dev_net(dev);
int allfrag = 0;

- rt = rt6_lookup(net, daddr, saddr, dev->ifindex, 0);
+ rt = rt6_lookup(net, daddr, saddr, ifindex, 0);
if (rt == NULL)
return;

@@ -1636,6 +1635,27 @@ out:
dst_release(&rt->u.dst);
}

+void rt6_pmtu_discovery(struct in6_addr *daddr, struct in6_addr *saddr,
+ struct net_device *dev, u32 pmtu)
+{
+ struct net *net = dev_net(dev);
+
+ /*
+ * RFC 1981 states that a node "MUST reduce the size of the packets it
+ * is sending along the path" that caused the Packet Too Big message.
+ * Since it's not possible in the general case to determine which
+ * interface was used to send the original packet, we update the MTU
+ * on the interface that will be used to send future packets. We also
+ * update the MTU on the interface that received the Packet Too Big in
+ * case the original packet was forced out that interface with
+ * SO_BINDTODEVICE or similar. This is the next best thing to the
+ * correct behaviour, which would be to update the MTU on all
+ * interfaces.
+ */
+ rt6_do_pmtu_disc(daddr, saddr, net, pmtu, 0);
+ rt6_do_pmtu_disc(daddr, saddr, net, pmtu, dev->ifindex);
+}
+
/*
* Misc support functions
*/
--
1.7.3.3