}
/* Update the retran path for sending a retransmitted packet.
- * Round-robin through the active transports, else round-robin
- * through the inactive transports as this is the next best thing
- * we can try.
+ * See also RFC4960, 6.4. Multi-Homed SCTP Endpoints:
+ *
+ * When there is outbound data to send and the primary path
+ * becomes inactive (e.g., due to failures), or where the
+ * SCTP user explicitly requests to send data to an
+ * inactive destination transport address, before reporting
+ * an error to its ULP, the SCTP endpoint should try to send
+ * the data to an alternate active destination transport
+ * address if one exists.
+ *
+ * When retransmitting data that timed out, if the endpoint
+ * is multihomed, it should consider each source-destination
+ * address pair in its retransmission selection policy.
+ * When retransmitting timed-out data, the endpoint should
+ * attempt to pick the most divergent source-destination
+ * pair from the original source-destination pair to which
+ * the packet was transmitted.
+ *
+ * Note: Rules for picking the most divergent source-destination
+ * pair are an implementation decision and are not specified
+ * within this document.
+ *
+ * Our basic strategy is to round-robin transports in priorities
+ * according to sctp_state_prio_map[] e.g., if no such
+ * transport with state SCTP_ACTIVE exists, round-robin through
+ * SCTP_UNKNOWN, etc. You get the picture.
*/
-void sctp_assoc_update_retran_path(struct sctp_association *asoc)
+static const u8 sctp_trans_state_to_prio_map[] = {
+ [SCTP_ACTIVE] = 3, /* best case */
+ [SCTP_UNKNOWN] = 2,
+ [SCTP_PF] = 1,
+ [SCTP_INACTIVE] = 0, /* worst case */
+};
+
+static u8 sctp_trans_score(const struct sctp_transport *trans)
{
- struct sctp_transport *t, *next;
- struct list_head *head = &asoc->peer.transport_addr_list;
- struct list_head *pos;
+ return sctp_trans_state_to_prio_map[trans->state];
+}
- if (asoc->peer.transport_count == 1)
- return;
+static struct sctp_transport *sctp_trans_elect_best(struct sctp_transport *curr,
+ struct sctp_transport *best)
+{
+ if (best == NULL)
+ return curr;
- /* Find the next transport in a round-robin fashion. */
- t = asoc->peer.retran_path;
- pos = &t->transports;
- next = NULL;
+ return sctp_trans_score(curr) > sctp_trans_score(best) ? curr : best;
+}
- while (1) {
- /* Skip the head. */
- if (pos->next == head)
- pos = head->next;
- else
- pos = pos->next;
+void sctp_assoc_update_retran_path(struct sctp_association *asoc)
+{
+ struct sctp_transport *trans = asoc->peer.retran_path;
+ struct sctp_transport *trans_next = NULL;
- t = list_entry(pos, struct sctp_transport, transports);
+ /* We're done as we only have the one and only path. */
+ if (asoc->peer.transport_count == 1)
+ return;
+ /* If active_path and retran_path are the same and active,
+ * then this is the only active path. Use it.
+ */
+ if (asoc->peer.active_path == asoc->peer.retran_path &&
+ asoc->peer.active_path->state == SCTP_ACTIVE)
+ return;
- /* We have exhausted the list, but didn't find any
- * other active transports. If so, use the next
- * transport.
- */
- if (t == asoc->peer.retran_path) {
- t = next;
+ /* Iterate from retran_path's successor back to retran_path. */
+ for (trans = list_next_entry(trans, transports); 1;
+ trans = list_next_entry(trans, transports)) {
+ /* Manually skip the head element. */
+ if (&trans->transports == &asoc->peer.transport_addr_list)
+ continue;
+ if (trans->state == SCTP_UNCONFIRMED)
+ continue;
+ trans_next = sctp_trans_elect_best(trans, trans_next);
+ /* Active is good enough for immediate return. */
+ if (trans_next->state == SCTP_ACTIVE)
break;
- }
-
- /* Try to find an active transport. */
-
- if ((t->state == SCTP_ACTIVE) ||
- (t->state == SCTP_UNKNOWN)) {
+ /* We've reached the end, time to update path. */
+ if (trans == asoc->peer.retran_path)
break;
- } else {
- /* Keep track of the next transport in case
- * we don't find any active transport.
- */
- if (t->state != SCTP_UNCONFIRMED && !next)
- next = t;
- }
}
- if (t)
- asoc->peer.retran_path = t;
- else
- t = asoc->peer.retran_path;
+ if (trans_next != NULL)
+ asoc->peer.retran_path = trans_next;
SCTP_DEBUG_PRINTK_IPADDR("sctp_assoc_update_retran_path:association"
- " %p addr: ",
+ " %p updated new path to addr: ",
" port: %d\n",
asoc,
- (&t->ipaddr),
- ntohs(t->ipaddr.v4.sin_port));
+ (&asoc->peer.retran_path->ipaddr),
+ ntohs(asoc->peer.retran_path->ipaddr.v4.sin_port));
}
-/* Choose the transport for sending retransmit packet. */
-struct sctp_transport *sctp_assoc_choose_alter_transport(
- struct sctp_association *asoc, struct sctp_transport *last_sent_to)
+struct sctp_transport *
+sctp_assoc_choose_alter_transport(struct sctp_association *asoc,
+ struct sctp_transport *last_sent_to)
{
/* If this is the first time packet is sent, use the active path,
* else use the retran path. If the last packet was sent over the
* retran path, update the retran path and use it.
*/
- if (!last_sent_to)
+ if (last_sent_to == NULL) {
return asoc->peer.active_path;
- else {
+ } else {
if (last_sent_to == asoc->peer.retran_path)
sctp_assoc_update_retran_path(asoc);
+
return asoc->peer.retran_path;
}
}
projects / GitHub / mt8127 / android_kernel_alcatel_ttab.git / blobdiff