[SCTP] listen() backlog support for TCP-style sockets.

net/sctp/associola.c

@@ -290,14 +290,18 @@ sctp_association_t *sctp_association_init(sctp_association_t *asoc,
  */
 void sctp_association_free(sctp_association_t *asoc)
 {
+	struct sock *sk = asoc->base.sk;
 	struct sctp_transport *transport;
-	sctp_endpoint_t *ep;
 	struct list_head *pos, *temp;
 	int i;
 
-	ep = asoc->ep;
 	list_del(&asoc->asocs);
 
+	/* Decrement the backlog value for a TCP-style listening socket. */
+	if ((SCTP_SOCKET_TCP == sctp_sk(sk)->type) &&
+	    (SCTP_SS_LISTENING == sk->state))
+		sk->ack_backlog--;
+
 	/* Mark as dead, so other users can know this structure is
 	 * going away.
 	 */
@@ -818,12 +822,17 @@ static void sctp_assoc_bh_rcv(sctp_association_t *asoc)
 void sctp_assoc_migrate(sctp_association_t *assoc, struct sock *newsk)
 {
 	struct sctp_opt *newsp = sctp_sk(newsk);
+	struct sock *oldsk = assoc->base.sk;
 
 	/* Delete the association from the old endpoint's list of
 	 * associations.
 	 */
 	list_del(&assoc->asocs);
 
+	/* Decrement the backlog value for a TCP-style socket. */
+	if (SCTP_SOCKET_TCP == sctp_sk(oldsk)->type)
+		oldsk->ack_backlog--;
+
 	/* Release references to the old endpoint and the sock.  */
 	sctp_endpoint_put(assoc->ep);
 	sock_put(assoc->base.sk);

net/sctp/endpointola.c

@@ -177,8 +177,15 @@ sctp_endpoint_t *sctp_endpoint_init(sctp_endpoint_t *ep,
 /* Add an association to an endpoint.  */
 void sctp_endpoint_add_asoc(sctp_endpoint_t *ep, sctp_association_t *asoc)
 {
+	struct sock *sk = ep->base.sk;
+
 	/* Now just add it to our list of asocs */
 	list_add_tail(&asoc->asocs, &ep->asocs);
+
+	/* Increment the backlog value for a TCP-style listening socket. */
+	if ((SCTP_SOCKET_TCP == sctp_sk(sk)->type) &&
+	    (SCTP_SS_LISTENING == sk->state))
+		sk->ack_backlog++;
 }
 
 /* Free the endpoint structure.  Delay cleanup until

net/sctp/sm_statefuns.c

@@ -191,14 +191,9 @@ sctp_disposition_t sctp_sf_do_5_1B_init(const sctp_endpoint_t *ep,
 	sctp_chunk_t *err_chunk;
 	struct sctp_packet *packet;
 	sctp_unrecognized_param_t *unk_param;
+	struct sock *sk;
 	int len;
 
-	/* If the packet is an OOTB packet which is temporarily on the
-	 * control endpoint, respond with an ABORT.
-	 */
-	if (ep == sctp_sk((sctp_get_ctl_sock()))->ep)
-		return sctp_sf_ootb(ep, asoc, type, arg, commands);
-
 	/* 6.10 Bundling
 	 * An endpoint MUST NOT bundle INIT, INIT ACK or
 	 * SHUTDOWN COMPLETE with any other chunks.
@@ -206,6 +201,22 @@ sctp_disposition_t sctp_sf_do_5_1B_init(const sctp_endpoint_t *ep,
 	if (!chunk->singleton)
 		return SCTP_DISPOSITION_VIOLATION;
 
+	/* If the packet is an OOTB packet which is temporarily on the
+	 * control endpoint, respond with an ABORT.
+	 */
+	if (ep == sctp_sk((sctp_get_ctl_sock()))->ep)
+		return sctp_sf_tabort_8_4_8(ep, asoc, type, arg, commands);
+
+	sk = ep->base.sk;
+	/* If the endpoint is not listening or if the number of associations
+	 * on the TCP-style socket exceed the max backlog, respond with an
+	 * ABORT.
+	 */
+	if ((SCTP_SS_LISTENING != sk->state) ||
+	    ((SCTP_SOCKET_TCP == sctp_sk(sk)->type) &&
+	     (sk->ack_backlog >= sk->max_ack_backlog)))
+		return sctp_sf_tabort_8_4_8(ep, asoc, type, arg, commands);
+
 	/* Verify the INIT chunk before processing it. */
 	err_chunk = NULL;
 	if (!sctp_verify_init(asoc, chunk->chunk_hdr->type,

net/sctp/socket.c

@@ -2746,6 +2746,9 @@ int sctp_inet_listen(struct socket *sock, int backlog)
 	err = -EINVAL;
 	if (sock->state != SS_UNCONNECTED)
 		goto out;
+	if (unlikely(backlog < 0))
+		goto out;
+
 	switch (sock->type) {
 	case SOCK_SEQPACKET:
 		err = sctp_seqpacket_listen(sk, backlog);