[SCTP]: Update ASCONF processing to conform to spec.

The processing of the ASCONF chunks has changed a lot in the
spec.  New items are:
    1. A list of ASCONF-ACK chunks is now cached
    2. The source of the packet is used in response.
    3. New handling for unexpect ASCONF chunks.

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 42 insertions, 22 deletions

diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
index b6aaa7e97d8..a1be9d93f1a 100644
--- a/net/sctp/sm_statefuns.c
+++ b/net/sctp/sm_statefuns.c
@@ -3402,48 +3402,68 @@ sctp_disposition_t sctp_sf_do_asconf(const struct sctp_endpoint *ep,
 
 	/* Verify the ASCONF chunk before processing it. */
 	if (!sctp_verify_asconf(asoc,
-	    (sctp_paramhdr_t *)((void *)addr_param + length),
-	    (void *)chunk->chunk_end,
-	    &err_param))
+			    (sctp_paramhdr_t *)((void *)addr_param + length),
+			    (void *)chunk->chunk_end,
+			    &err_param))
 		return sctp_sf_violation_paramlen(ep, asoc, type,
-			   (void *)&err_param, commands);
+						  (void *)&err_param, commands);
 
-	/* ADDIP 4.2 C1) Compare the value of the serial number to the value
+	/* ADDIP 5.2 E1) Compare the value of the serial number to the value
 	 * the endpoint stored in a new association variable
 	 * 'Peer-Serial-Number'.
 	 */
 	if (serial == asoc->peer.addip_serial + 1) {
-		/* ADDIP 4.2 C2) If the value found in the serial number is
-		 * equal to the ('Peer-Serial-Number' + 1), the endpoint MUST
-		 * do V1-V5.
+		/* If this is the first instance of ASCONF in the packet,
+		 * we can clean our old ASCONF-ACKs.
+		 */
+		if (!chunk->has_asconf)
+			sctp_assoc_clean_asconf_ack_cache(asoc);
+
+		/* ADDIP 5.2 E4) When the Sequence Number matches the next one
+		 * expected, process the ASCONF as described below and after
+		 * processing the ASCONF Chunk, append an ASCONF-ACK Chunk to
+		 * the response packet and cache a copy of it (in the event it
+		 * later needs to be retransmitted).
+		 *
+		 * Essentially, do V1-V5.
 		 */
 		asconf_ack = sctp_process_asconf((struct sctp_association *)
 						 asoc, chunk);
 		if (!asconf_ack)
 			return SCTP_DISPOSITION_NOMEM;
-	} else if (serial == asoc->peer.addip_serial) {
-		/* ADDIP 4.2 C3) If the value found in the serial number is
-		 * equal to the value stored in the 'Peer-Serial-Number'
-		 * IMPLEMENTATION NOTE: As an optimization a receiver may wish
-		 * to save the last ASCONF-ACK for some predetermined period of
-		 * time and instead of re-processing the ASCONF (with the same
-		 * serial number) it may just re-transmit the ASCONF-ACK.
+	} else if (serial < asoc->peer.addip_serial + 1) {
+		/* ADDIP 5.2 E2)
+		 * If the value found in the Sequence Number is less than the
+		 * ('Peer- Sequence-Number' + 1), simply skip to the next
+		 * ASCONF, and include in the outbound response packet
+		 * any previously cached ASCONF-ACK response that was
+		 * sent and saved that matches the Sequence Number of the
+		 * ASCONF.  Note: It is possible that no cached ASCONF-ACK
+		 * Chunk exists.  This will occur when an older ASCONF
+		 * arrives out of order.  In such a case, the receiver
+		 * should skip the ASCONF Chunk and not include ASCONF-ACK
+		 * Chunk for that chunk.
 		 */
-		if (asoc->addip_last_asconf_ack)
-			asconf_ack = asoc->addip_last_asconf_ack;
-		else
+		asconf_ack = sctp_assoc_lookup_asconf_ack(asoc, hdr->serial);
+		if (!asconf_ack)
 			return SCTP_DISPOSITION_DISCARD;
 	} else {
-		/* ADDIP 4.2 C4) Otherwise, the ASCONF Chunk is discarded since
+		/* ADDIP 5.2 E5) Otherwise, the ASCONF Chunk is discarded since
 		 * it must be either a stale packet or from an attacker.
 		 */
 		return SCTP_DISPOSITION_DISCARD;
 	}
 
-	/* ADDIP 4.2 C5) In both cases C2 and C3 the ASCONF-ACK MUST be sent
-	 * back to the source address contained in the IP header of the ASCONF
-	 * being responded to.
+	/* ADDIP 5.2 E6)  The destination address of the SCTP packet
+	 * containing the ASCONF-ACK Chunks MUST be the source address of
+	 * the SCTP packet that held the ASCONF Chunks.
+	 *
+	 * To do this properly, we'll set the destination address of the chunk
+	 * and at the transmit time, will try look up the transport to use.
+	 * Since ASCONFs may be bundled, the correct transport may not be
+	 * created untill we process the entire packet, thus this workaround.
 	 */
+	asconf_ack->dest = chunk->source;
 	sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(asconf_ack));
 
 	return SCTP_DISPOSITION_CONSUME;