[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 b6aaa7e97d82..a1be9d93f1a8 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;