[SCTP] Flag a pmtu change request

Currently, if the socket is owned by the user, we drop the ICMP
message.  As a result SCTP forgets that path MTU changed and
never adjusting it's estimate.  This causes all subsequent
packets to be fragmented.  With this patch, we'll flag the association
that it needs to udpate it's estimate based on the already updated
routing information.

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Acked-by: Sridhar Samudrala <sri@us.ibm.com>

3 files changed, 14 insertions, 1 deletions

diff --git a/net/sctp/associola.c b/net/sctp/associola.c
index df94e3cdfba3..498edb0cd4e5 100644
--- a/net/sctp/associola.c
+++ b/net/sctp/associola.c
@@ -1231,6 +1231,10 @@ void sctp_assoc_sync_pmtu(struct sctp_association *asoc)
         /* Get the lowest pmtu of all the transports. */
         list_for_each(pos, &asoc->peer.transport_addr_list) {
                 t = list_entry(pos, struct sctp_transport, transports);
+                if (t->pmtu_pending && t->dst) {
+                        sctp_transport_update_pmtu(t, dst_mtu(t->dst));
+                        t->pmtu_pending = 0;
+                }
                 if (!pmtu || (t->pathmtu < pmtu))
                         pmtu = t->pathmtu;
         }
diff --git a/net/sctp/input.c b/net/sctp/input.c
index 45d6a644cf06..d57ff7f3c576 100644
--- a/net/sctp/input.c
+++ b/net/sctp/input.c
@@ -367,9 +367,15 @@ static void sctp_add_backlog(struct sock *sk, struct sk_buff *skb)
 void sctp_icmp_frag_needed(struct sock *sk, struct sctp_association *asoc,
                            struct sctp_transport *t, __u32 pmtu)
 {
-        if (sock_owned_by_user(sk) || !t || (t->pathmtu == pmtu))
+        if (!t || (t->pathmtu == pmtu))
                 return;
 
+        if (sock_owned_by_user(sk)) {
+                asoc->pmtu_pending = 1;
+                t->pmtu_pending = 1;
+                return;
+        }
+
         if (t->param_flags & SPP_PMTUD_ENABLE) {
                 /* Update transports view of the MTU */
                 sctp_transport_update_pmtu(t, pmtu);
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 45510c46c223..6edaaa009d62 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -1662,6 +1662,9 @@ SCTP_STATIC int sctp_sendmsg(struct kiocb *iocb, struct sock *sk,
                 goto out_free;
         }
 
+        if (asoc->pmtu_pending)
+                sctp_assoc_pending_pmtu(asoc);
+
         /* If fragmentation is disabled and the message length exceeds the
          * association fragmentation point, return EMSGSIZE.  The I-D
          * does not specify what this error is, but this looks like