ipv6: Handle PMTU in ICMP error handlers.

One tricky issue on the ipv6 side vs. ipv4 is that the ICMP callouts
to handle the error pass the 32-bit info cookie in network byte order
whereas ipv4 passes it around in host byte order.

Like the ipv4 side, we have two helper functions.  One for when we
have a socket context and one for when we do not.

ip6ip6 tunnels are not handled here, because they handle PMTU events
by essentially relaying another ICMP packet-too-big message back to
the original sender.

This patch allows us to get rid of rt6_do_pmtu_disc().  It handles all
kinds of situations that simply cannot happen when we do the PMTU
update directly using a fully resolved route.

In fact, the "plen == 128" check in ip6_rt_update_pmtu() can very
likely be removed or changed into a BUG_ON() check.  We should never
have a prefixed ipv6 route when we get there.

Another piece of strange history here is that TCP and DCCP, unlike in
ipv4, never invoke the update_pmtu() method from their ICMP error
handlers.  This is incredibly astonishing since this is the context
where we have the most accurate context in which to make a PMTU
update, namely we have a fully connected socket and associated cached
socket route.

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 4 deletions

diff --git a/include/net/ip6_route.h b/include/net/ip6_route.h
index a2cda240ca95..58cb3fc34879 100644
--- a/include/net/ip6_route.h
+++ b/include/net/ip6_route.h
@@ -140,10 +140,10 @@ extern void			rt6_redirect(const struct in6_addr *dest,
                                              u8 *lladdr,
                                              int on_link);
 
-extern void                     rt6_pmtu_discovery(const struct in6_addr *daddr,
-                                                   const struct in6_addr *saddr,
-                                                   struct net_device *dev,
-                                                   u32 pmtu);
+extern void ip6_update_pmtu(struct sk_buff *skb, struct net *net, __be32 mtu,
+                            int oif, u32 mark);
+extern void ip6_sk_update_pmtu(struct sk_buff *skb, struct sock *sk,
+                               __be32 mtu);
 
 struct netlink_callback;