[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>

1 files changed, 41 insertions, 0 deletions

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.
  */