[SCTP] Update pmtu handling to be similar to tcp

Introduce new function sctp_transport_update_pmtu that updates
the transports and destination caches view of the path mtu.

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

2 files changed, 43 insertions, 14 deletions

diff --git a/net/sctp/input.c b/net/sctp/input.c
index 885109fb3dda..45d6a644cf06 100644
--- a/net/sctp/input.c
+++ b/net/sctp/input.c
@@ -371,20 +371,8 @@ void sctp_icmp_frag_needed(struct sock *sk, struct sctp_association *asoc,
                 return;
 
         if (t->param_flags & SPP_PMTUD_ENABLE) {
-                if (unlikely(pmtu < SCTP_DEFAULT_MINSEGMENT)) {
-                        printk(KERN_WARNING "%s: Reported pmtu %d too low, "
-                               "using default minimum of %d\n",
-                               __FUNCTION__, pmtu,
-                               SCTP_DEFAULT_MINSEGMENT);
-                        /* Use default minimum segment size and disable
-                         * pmtu discovery on this transport.
-                         */
-                        t->pathmtu = SCTP_DEFAULT_MINSEGMENT;
-                        t->param_flags = (t->param_flags & ~SPP_PMTUD) |
-                                SPP_PMTUD_DISABLE;
-                } else {
-                        t->pathmtu = pmtu;
-                }
+                /* Update transports view of the MTU */
+                sctp_transport_update_pmtu(t, pmtu);
 
                 /* Update association pmtu. */
                 sctp_assoc_sync_pmtu(asoc);
diff --git a/net/sctp/transport.c b/net/sctp/transport.c
index 961df275d5b9..e14c271cf28b 100644
--- a/net/sctp/transport.c
+++ b/net/sctp/transport.c
@@ -241,6 +241,47 @@ void sctp_transport_pmtu(struct sctp_transport *transport)
                 transport->pathmtu = SCTP_DEFAULT_MAXSEGMENT;
 }
 
+/* this is a complete rip-off from __sk_dst_check
+ * the cookie is always 0 since this is how it's used in the
+ * pmtu code
+ */
+static struct dst_entry *sctp_transport_dst_check(struct sctp_transport *t)
+{
+        struct dst_entry *dst = t->dst;
+
+        if (dst && dst->obsolete && dst->ops->check(dst, 0) == NULL) {
+                dst_release(t->dst);
+                t->dst = NULL;
+                return NULL;
+        }
+
+        return dst;
+}
+
+void sctp_transport_update_pmtu(struct sctp_transport *t, u32 pmtu)
+{
+        struct dst_entry *dst;
+
+        if (unlikely(pmtu < SCTP_DEFAULT_MINSEGMENT)) {
+                printk(KERN_WARNING "%s: Reported pmtu %d too low, "
+                       "using default minimum of %d\n",
+                       __FUNCTION__, pmtu,
+                       SCTP_DEFAULT_MINSEGMENT);
+                /* Use default minimum segment size and disable
+                 * pmtu discovery on this transport.
+                 */
+                t->pathmtu = SCTP_DEFAULT_MINSEGMENT;
+                t->param_flags = (t->param_flags & ~SPP_PMTUD) |
+                        SPP_PMTUD_DISABLE;
+        } else {
+                t->pathmtu = pmtu;
+        }
+
+        dst = sctp_transport_dst_check(t);
+        if (dst)
+                dst->ops->update_pmtu(dst, pmtu);
+}
+
 /* Caches the dst entry and source address for a transport's destination
  * address.
  */