[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>

4 files changed, 130 insertions, 33 deletions

diff --git a/net/sctp/associola.c b/net/sctp/associola.c
index 61bebb9b96e6..a016e78061f4 100644
--- a/net/sctp/associola.c
+++ b/net/sctp/associola.c
@@ -61,6 +61,7 @@
 
 /* Forward declarations for internal functions. */
 static void sctp_assoc_bh_rcv(struct work_struct *work);
+static void sctp_assoc_free_asconf_acks(struct sctp_association *asoc);
 
 
 /* 1st Level Abstractions. */
@@ -242,6 +243,7 @@ static struct sctp_association *sctp_association_init(struct sctp_association *a
         asoc->addip_serial = asoc->c.initial_tsn;
 
         INIT_LIST_HEAD(&asoc->addip_chunk_list);
+        INIT_LIST_HEAD(&asoc->asconf_ack_list);
 
         /* Make an empty list of remote transport addresses.  */
         INIT_LIST_HEAD(&asoc->peer.transport_addr_list);
@@ -431,8 +433,7 @@ void sctp_association_free(struct sctp_association *asoc)
         asoc->peer.transport_count = 0;
 
         /* Free any cached ASCONF_ACK chunk. */
-        if (asoc->addip_last_asconf_ack)
-                sctp_chunk_free(asoc->addip_last_asconf_ack);
+        sctp_assoc_free_asconf_acks(asoc);
 
         /* Free any cached ASCONF chunk. */
         if (asoc->addip_last_asconf)
@@ -1485,3 +1486,56 @@ retry:
         asoc->assoc_id = (sctp_assoc_t) assoc_id;
         return error;
 }
+
+/* Free asconf_ack cache */
+static void sctp_assoc_free_asconf_acks(struct sctp_association *asoc)
+{
+        struct sctp_chunk *ack;
+        struct sctp_chunk *tmp;
+
+        list_for_each_entry_safe(ack, tmp, &asoc->asconf_ack_list,
+                                transmitted_list) {
+                list_del_init(&ack->transmitted_list);
+                sctp_chunk_free(ack);
+        }
+}
+
+/* Clean up the ASCONF_ACK queue */
+void sctp_assoc_clean_asconf_ack_cache(const struct sctp_association *asoc)
+{
+        struct sctp_chunk *ack;
+        struct sctp_chunk *tmp;
+
+        /* We can remove all the entries from the queue upto
+         * the "Peer-Sequence-Number".
+         */
+        list_for_each_entry_safe(ack, tmp, &asoc->asconf_ack_list,
+                                transmitted_list) {
+                if (ack->subh.addip_hdr->serial ==
+                                htonl(asoc->peer.addip_serial))
+                        break;
+
+                list_del_init(&ack->transmitted_list);
+                sctp_chunk_free(ack);
+        }
+}
+
+/* Find the ASCONF_ACK whose serial number matches ASCONF */
+struct sctp_chunk *sctp_assoc_lookup_asconf_ack(
+                                        const struct sctp_association *asoc,
+                                        __be32 serial)
+{
+        struct sctp_chunk *ack = NULL;
+
+        /* Walk through the list of cached ASCONF-ACKs and find the
+         * ack chunk whose serial number matches that of the request.
+         */
+        list_for_each_entry(ack, &asoc->asconf_ack_list, transmitted_list) {
+                if (ack->subh.addip_hdr->serial == serial) {
+                        sctp_chunk_hold(ack);
+                        break;
+                }
+        }
+
+        return ack;
+}
diff --git a/net/sctp/outqueue.c b/net/sctp/outqueue.c
index fa76f235169b..a42af865c2ef 100644
--- a/net/sctp/outqueue.c
+++ b/net/sctp/outqueue.c
@@ -716,7 +716,29 @@ int sctp_outq_flush(struct sctp_outq *q, int rtx_timeout)
                 new_transport = chunk->transport;
 
                 if (!new_transport) {
-                        new_transport = asoc->peer.active_path;
+                        /*
+                         * If we have a prior transport pointer, see if
+                         * the destination address of the chunk
+                         * matches the destination address of the
+                         * current transport.  If not a match, then
+                         * try to look up the transport with a given
+                         * destination address.  We do this because
+                         * after processing ASCONFs, we may have new
+                         * transports created.
+                         */
+                        if (transport &&
+                            sctp_cmp_addr_exact(&chunk->dest,
+                                                &transport->ipaddr))
+                                        new_transport = transport;
+                        else
+                                new_transport = sctp_assoc_lookup_paddr(asoc,
+                                                                &chunk->dest);
+
+                        /* if we still don't have a new transport, then
+                         * use the current active path.
+                         */
+                        if (!new_transport)
+                                new_transport = asoc->peer.active_path;
                 } else if ((new_transport->state == SCTP_INACTIVE) ||
                            (new_transport->state == SCTP_UNCONFIRMED)) {
                         /* If the chunk is Heartbeat or Heartbeat Ack,
@@ -729,9 +751,12 @@ int sctp_outq_flush(struct sctp_outq *q, int rtx_timeout)
                          * address of the IP datagram containing the
                          * HEARTBEAT chunk to which this ack is responding.
                          * ...
+                         *
+                         * ASCONF_ACKs also must be sent to the source.
                          */
                         if (chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT &&
-                            chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT_ACK)
+                            chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT_ACK &&
+                            chunk->chunk_hdr->type != SCTP_CID_ASCONF_ACK)
                                 new_transport = asoc->peer.active_path;
                 }
 
diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
index 8138bbd93210..7fd6a6b68614 100644
--- a/net/sctp/sm_make_chunk.c
+++ b/net/sctp/sm_make_chunk.c
@@ -1275,6 +1275,9 @@ nodata:
 /* Release the memory occupied by a chunk.  */
 static void sctp_chunk_destroy(struct sctp_chunk *chunk)
 {
+        BUG_ON(!list_empty(&chunk->list));
+        list_del_init(&chunk->transmitted_list);
+
         /* Free the chunk skb data and the SCTP_chunk stub itself. */
         dev_kfree_skb(chunk->skb);
 
@@ -1285,9 +1288,6 @@ static void sctp_chunk_destroy(struct sctp_chunk *chunk)
 /* Possibly, free the chunk.  */
 void sctp_chunk_free(struct sctp_chunk *chunk)
 {
-        BUG_ON(!list_empty(&chunk->list));
-        list_del_init(&chunk->transmitted_list);
-
         /* Release our reference on the message tracker. */
         if (chunk->msg)
                 sctp_datamsg_put(chunk->msg);
@@ -2980,11 +2980,9 @@ done:
          * after freeing the reference to old asconf ack if any.
          */
         if (asconf_ack) {
-                if (asoc->addip_last_asconf_ack)
-                        sctp_chunk_free(asoc->addip_last_asconf_ack);
-
                 sctp_chunk_hold(asconf_ack);
-                asoc->addip_last_asconf_ack = asconf_ack;
+                list_add_tail(&asconf_ack->transmitted_list,
+                              &asoc->asconf_ack_list);
         }
 
         return asconf_ack;
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;