sctp: refactor sctp_packet_append_chunk and clenup some memory leaks

While doing some recent work on sctp sack bundling I noted that
sctp_packet_append_chunk was pretty inefficient.  Specifially, it was called
recursively while trying to bundle auth and sack chunks.  Because of that we
call sctp_packet_bundle_sack and sctp_packet_bundle_auth a total of 4 times for
every call to sctp_packet_append_chunk, knowing that at least 3 of those calls
will do nothing.

So lets refactor sctp_packet_bundle_auth to have an outer part that does the
attempted bundling, and an inner part that just does the chunk appends.  This
saves us several calls per iteration that we just don't need.

Also, noticed that the auth and sack bundling fail to free the chunks they
allocate if the append fails, so make sure we add that in
Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
CC: Vlad Yasevich <vyasevich@gmail.com>
CC: "David S. Miller" <davem@davemloft.net>
CC: linux-sctp@vger.kernel.org
Acked-by: Vlad Yasevich <vyasevich@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sctp/output.c

@@ -64,6 +64,8 @@
 #include <net/sctp/checksum.h>
 
 /* Forward declarations for private helpers. */
+static sctp_xmit_t __sctp_packet_append_chunk(struct sctp_packet *packet,
+					      struct sctp_chunk *chunk);
 static sctp_xmit_t sctp_packet_can_append_data(struct sctp_packet *packet,
 					   struct sctp_chunk *chunk);
 static void sctp_packet_append_data(struct sctp_packet *packet,
@@ -224,7 +226,10 @@ static sctp_xmit_t sctp_packet_bundle_auth(struct sctp_packet *pkt,
 	if (!auth)
 		return retval;
 
-	retval = sctp_packet_append_chunk(pkt, auth);
+	retval = __sctp_packet_append_chunk(pkt, auth);
+
+	if (retval != SCTP_XMIT_OK)
+		sctp_chunk_free(auth);
 
 	return retval;
 }
@@ -256,48 +261,31 @@ static sctp_xmit_t sctp_packet_bundle_sack(struct sctp_packet *pkt,
 			asoc->a_rwnd = asoc->rwnd;
 			sack = sctp_make_sack(asoc);
 			if (sack) {
-				retval = sctp_packet_append_chunk(pkt, sack);
+				retval = __sctp_packet_append_chunk(pkt, sack);
+				if (retval != SCTP_XMIT_OK) {
+					sctp_chunk_free(sack);
+					goto out;
+				}
 				asoc->peer.sack_needed = 0;
 				if (del_timer(timer))
 					sctp_association_put(asoc);
 			}
 		}
 	}
+out:
 	return retval;
 }
 
+
 /* Append a chunk to the offered packet reporting back any inability to do
  * so.
  */
-sctp_xmit_t sctp_packet_append_chunk(struct sctp_packet *packet,
-				     struct sctp_chunk *chunk)
+static sctp_xmit_t __sctp_packet_append_chunk(struct sctp_packet *packet,
+					      struct sctp_chunk *chunk)
 {
 	sctp_xmit_t retval = SCTP_XMIT_OK;
 	__u16 chunk_len = WORD_ROUND(ntohs(chunk->chunk_hdr->length));
 
-	SCTP_DEBUG_PRINTK("%s: packet:%p chunk:%p\n", __func__, packet,
-			  chunk);
-
-	/* Data chunks are special.  Before seeing what else we can
-	 * bundle into this packet, check to see if we are allowed to
-	 * send this DATA.
-	 */
-	if (sctp_chunk_is_data(chunk)) {
-		retval = sctp_packet_can_append_data(packet, chunk);
-		if (retval != SCTP_XMIT_OK)
-			goto finish;
-	}
-
-	/* Try to bundle AUTH chunk */
-	retval = sctp_packet_bundle_auth(packet, chunk);
-	if (retval != SCTP_XMIT_OK)
-		goto finish;
-
-	/* Try to bundle SACK chunk */
-	retval = sctp_packet_bundle_sack(packet, chunk);
-	if (retval != SCTP_XMIT_OK)
-		goto finish;
-
 	/* Check to see if this chunk will fit into the packet */
 	retval = sctp_packet_will_fit(packet, chunk, chunk_len);
 	if (retval != SCTP_XMIT_OK)
@@ -339,6 +327,43 @@ sctp_xmit_t sctp_packet_append_chunk(struct sctp_packet *packet,
 	return retval;
 }
 
+/* Append a chunk to the offered packet reporting back any inability to do
+ * so.
+ */
+sctp_xmit_t sctp_packet_append_chunk(struct sctp_packet *packet,
+				     struct sctp_chunk *chunk)
+{
+	sctp_xmit_t retval = SCTP_XMIT_OK;
+
+	SCTP_DEBUG_PRINTK("%s: packet:%p chunk:%p\n", __func__, packet,
+			  chunk);
+
+	/* Data chunks are special.  Before seeing what else we can
+	 * bundle into this packet, check to see if we are allowed to
+	 * send this DATA.
+	 */
+	if (sctp_chunk_is_data(chunk)) {
+		retval = sctp_packet_can_append_data(packet, chunk);
+		if (retval != SCTP_XMIT_OK)
+			goto finish;
+	}
+
+	/* Try to bundle AUTH chunk */
+	retval = sctp_packet_bundle_auth(packet, chunk);
+	if (retval != SCTP_XMIT_OK)
+		goto finish;
+
+	/* Try to bundle SACK chunk */
+	retval = sctp_packet_bundle_sack(packet, chunk);
+	if (retval != SCTP_XMIT_OK)
+		goto finish;
+
+	retval = __sctp_packet_append_chunk(packet, chunk);
+
+finish:
+	return retval;
+}
+
 /* All packets are sent to the network through this function from
  * sctp_outq_tail().
  *