3 files changed, 45 insertions, 34 deletions

diff --git a/net/sctp/input.c b/net/sctp/input.c
index 621b5ca..141c9c4 100644
--- a/net/sctp/input.c
+++ b/net/sctp/input.c
@@ -399,20 +399,24 @@ void sctp_icmp_frag_needed(struct sock *sk, struct sctp_association *asoc,
 		return;
 	}
 
-	if (t->param_flags & SPP_PMTUD_ENABLE) {
-		/* Update transports view of the MTU */
-		sctp_transport_update_pmtu(t, pmtu);
-
-		/* Update association pmtu. */
-		sctp_assoc_sync_pmtu(asoc);
-	}
+	if (!(t->param_flags & SPP_PMTUD_ENABLE))
+		/* We can't allow retransmitting in such case, as the
+		 * retransmission would be sized just as before, and thus we
+		 * would get another icmp, and retransmit again.
+		 */
+		return;
 
-	/* Retransmit with the new pmtu setting.
-	 * Normally, if PMTU discovery is disabled, an ICMP Fragmentation
-	 * Needed will never be sent, but if a message was sent before
-	 * PMTU discovery was disabled that was larger than the PMTU, it
-	 * would not be fragmented, so it must be re-transmitted fragmented.
+	/* Update transports view of the MTU. Return if no update was needed.
+	 * If an update wasn't needed/possible, it also doesn't make sense to
+	 * try to retransmit now.
 	 */
+	if (!sctp_transport_update_pmtu(t, pmtu))
+		return;
+
+	/* Update association pmtu. */
+	sctp_assoc_sync_pmtu(asoc);
+
+	/* Retransmit with the new pmtu setting. */
 	sctp_retransmit(&asoc->outqueue, t, SCTP_RTXR_PMTUD);
 }
 
diff --git a/net/sctp/stream.c b/net/sctp/stream.c
index 06b644d..cedf672 100644
--- a/net/sctp/stream.c
+++ b/net/sctp/stream.c
@@ -156,9 +156,9 @@ int sctp_stream_init(struct sctp_stream *stream, __u16 outcnt, __u16 incnt,
 	sctp_stream_outq_migrate(stream, NULL, outcnt);
 	sched->sched_all(stream);
 
-	i = sctp_stream_alloc_out(stream, outcnt, gfp);
-	if (i)
-		return i;
+	ret = sctp_stream_alloc_out(stream, outcnt, gfp);
+	if (ret)
+		goto out;
 
 	stream->outcnt = outcnt;
 	for (i = 0; i < stream->outcnt; i++)
@@ -171,19 +171,17 @@ in:
 	if (!incnt)
 		goto out;
 
-	i = sctp_stream_alloc_in(stream, incnt, gfp);
-	if (i) {
-		ret = -ENOMEM;
-		goto free;
+	ret = sctp_stream_alloc_in(stream, incnt, gfp);
+	if (ret) {
+		sched->free(stream);
+		kfree(stream->out);
+		stream->out = NULL;
+		stream->outcnt = 0;
+		goto out;
 	}
 
 	stream->incnt = incnt;
-	goto out;
 
-free:
-	sched->free(stream);
-	kfree(stream->out);
-	stream->out = NULL;
 out:
 	return ret;
 }
diff --git a/net/sctp/transport.c b/net/sctp/transport.c
index 1e5a224..47f82bd 100644
--- a/net/sctp/transport.c
+++ b/net/sctp/transport.c
@@ -248,28 +248,37 @@ void sctp_transport_pmtu(struct sctp_transport *transport, struct sock *sk)
 		transport->pathmtu = SCTP_DEFAULT_MAXSEGMENT;
 }
 
-void sctp_transport_update_pmtu(struct sctp_transport *t, u32 pmtu)
+bool sctp_transport_update_pmtu(struct sctp_transport *t, u32 pmtu)
 {
 	struct dst_entry *dst = sctp_transport_dst_check(t);
+	bool change = true;
 
 	if (unlikely(pmtu < SCTP_DEFAULT_MINSEGMENT)) {
-		pr_warn("%s: Reported pmtu %d too low, using default minimum of %d\n",
-			__func__, pmtu, SCTP_DEFAULT_MINSEGMENT);
-		/* Use default minimum segment size and disable
-		 * pmtu discovery on this transport.
-		 */
-		t->pathmtu = SCTP_DEFAULT_MINSEGMENT;
-	} else {
-		t->pathmtu = pmtu;
+		pr_warn_ratelimited("%s: Reported pmtu %d too low, using default minimum of %d\n",
+				    __func__, pmtu, SCTP_DEFAULT_MINSEGMENT);
+		/* Use default minimum segment instead */
+		pmtu = SCTP_DEFAULT_MINSEGMENT;
 	}
+	pmtu = SCTP_TRUNC4(pmtu);
 
 	if (dst) {
 		dst->ops->update_pmtu(dst, t->asoc->base.sk, NULL, pmtu);
 		dst = sctp_transport_dst_check(t);
 	}
 
-	if (!dst)
+	if (!dst) {
 		t->af_specific->get_dst(t, &t->saddr, &t->fl, t->asoc->base.sk);
+		dst = t->dst;
+	}
+
+	if (dst) {
+		/* Re-fetch, as under layers may have a higher minimum size */
+		pmtu = SCTP_TRUNC4(dst_mtu(dst));
+		change = t->pathmtu != pmtu;
+	}
+	t->pathmtu = pmtu;
+
+	return change;
 }
 
 /* Caches the dst entry and source address for a transport's destination