sctp: deal with multiple COOKIE_ECHO chunks

Attempt to reduce the number of IP packets emitted in response to single
SCTP packet (2e3216cd) introduced a complication - if a packet contains
two COOKIE_ECHO chunks and nothing else then SCTP state machine corks the
socket while processing first COOKIE_ECHO and then loses the association
and forgets to uncork the socket. To deal with the issue add new SCTP
command which can be used to set association explictly. Use this new
command when processing second COOKIE_ECHO chunk to restore the context
for SCTP state machine.

Signed-off-by: Max Matveev <makc@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 12 insertions, 0 deletions

diff --git a/include/net/sctp/command.h b/include/net/sctp/command.h
index 6506458ccd3..712b3bebeda 100644
--- a/include/net/sctp/command.h
+++ b/include/net/sctp/command.h
@@ -109,6 +109,7 @@ typedef enum {
         SCTP_CMD_SEND_MSG,       /* Send the whole use message */
         SCTP_CMD_SEND_NEXT_ASCONF, /* Send the next ASCONF after ACK */
         SCTP_CMD_PURGE_ASCONF_QUEUE, /* Purge all asconf queues.*/
+        SCTP_CMD_SET_ASOC,       /* Restore association context */
         SCTP_CMD_LAST
 } sctp_verb_t;
 
diff --git a/net/sctp/sm_sideeffect.c b/net/sctp/sm_sideeffect.c
index 167c880cf8d..76388b083f2 100644
--- a/net/sctp/sm_sideeffect.c
+++ b/net/sctp/sm_sideeffect.c
@@ -1689,6 +1689,11 @@ static int sctp_cmd_interpreter(sctp_event_t event_type,
                 case SCTP_CMD_PURGE_ASCONF_QUEUE:
                         sctp_asconf_queue_teardown(asoc);
                         break;
+
+                case SCTP_CMD_SET_ASOC:
+                        asoc = cmd->obj.asoc;
+                        break;
+
                 default:
                         pr_warn("Impossible command: %u, %p\n",
                                 cmd->verb, cmd->obj.ptr);
diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
index 49b847b00f9..a0f31e6c1c6 100644
--- a/net/sctp/sm_statefuns.c
+++ b/net/sctp/sm_statefuns.c
@@ -2047,6 +2047,12 @@ sctp_disposition_t sctp_sf_do_5_2_4_dupcook(const struct sctp_endpoint *ep,
         sctp_add_cmd_sf(commands, SCTP_CMD_NEW_ASOC, SCTP_ASOC(new_asoc));
         sctp_add_cmd_sf(commands, SCTP_CMD_DELETE_TCB, SCTP_NULL());
 
+        /* Restore association pointer to provide SCTP command interpeter
+         * with a valid context in case it needs to manipulate
+         * the queues */
+        sctp_add_cmd_sf(commands, SCTP_CMD_SET_ASOC,
+                         SCTP_ASOC((struct sctp_association *)asoc));
+
         return retval;
 
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