[SCTP] Handle accept() of a CLOSED association.

include/net/sctp/constants.h

@@ -216,7 +216,7 @@ typedef enum {
  * - A socket in SCTP_SS_LISTENING state indicates that it is willing to
  *   accept new associations, but cannot initiate the creation of new ones.
  * - A socket in SCTP_SS_ESTABLISHED state indicates that it has a single 
- *   association in ESTABLISHED state.
+ *   association.
  */
 typedef enum {
 	SCTP_SS_CLOSED         = TCP_CLOSE,

include/net/sctp/structs.h

@@ -1545,6 +1545,9 @@ struct sctp_association {
 	 * after reaching 4294967295.
 	 */
 	__u32 addip_serial;
+
+	/* Is it a temporary association? */ 
+	__u8 temp;
 };
 
 

net/sctp/sm_make_chunk.c

@@ -1308,6 +1308,7 @@ struct sctp_association *sctp_make_temp_asoc(const struct sctp_endpoint *ep,
 	asoc = sctp_association_new(ep, ep->base.sk, scope, gfp);
 	if (!asoc)
 		goto nodata;
+	asoc->temp = 1;
 	skb = chunk->skb;
 	/* Create an entry for the source address of the packet.  */
 	/* FIXME: Use the af specific helpers. */

net/sctp/sm_sideeffect.c

@@ -651,6 +651,24 @@ static void sctp_cmd_new_state(sctp_cmd_seq_t *cmds, struct sctp_association *as
 	}
 }
 
+/* Helper function to delete an association. */
+static void sctp_cmd_delete_tcb(sctp_cmd_seq_t *cmds,
+				struct sctp_association *asoc)
+{
+	struct sock *sk = asoc->base.sk;
+
+	/* If it is a non-temporary association belonging to a TCP-style
+	 * listening socket, do not free it so that accept() can pick it
+	 * up later.
+	 */ 
+	if ((SCTP_SOCKET_TCP == sctp_sk(sk)->type) &&
+	    (SCTP_SS_LISTENING == sk->state) && (!asoc->temp))
+		return;
+
+	sctp_unhash_established(asoc);
+	sctp_association_free(asoc);
+}
+
 /* These three macros allow us to pull the debugging code out of the
  * main flow of sctp_do_sm() to keep attention focused on the real
  * functionality there.
@@ -861,8 +879,7 @@ int sctp_cmd_interpreter(sctp_event_t event_type, sctp_subtype_t subtype,
 
 		case SCTP_CMD_DELETE_TCB:
 			/* Delete the current association.  */
-			sctp_unhash_established(asoc);
-			sctp_association_free(asoc);
+			sctp_cmd_delete_tcb(commands, asoc);
 			asoc = NULL;
 			break;
 

net/sctp/socket.c

@@ -688,6 +688,16 @@ SCTP_STATIC void sctp_close(struct sock *sk, long timeout)
 	/* Walk all associations on a socket, not on an endpoint.  */
 	list_for_each_safe(pos, temp, &ep->asocs) {
 		asoc = list_entry(pos, struct sctp_association, asocs);
+
+		/* A closed association can still be in the list if it
+		 * belongs to a TCP-style listening socket that is not
+		 * yet accepted.
+		 */
+		if ((SCTP_SOCKET_TCP == sctp_sk(sk)->type) &&
+		    (SCTP_STATE_CLOSED == asoc->state)) {
+			sctp_unhash_established(asoc);
+			sctp_association_free(asoc);
+		} else
 			sctp_primitive_SHUTDOWN(asoc, NULL);
 	}
 
@@ -718,6 +728,16 @@ SCTP_STATIC void sctp_close(struct sock *sk, long timeout)
 	SCTP_DBG_OBJCNT_DEC(sock);
 }
 
+/* Handle EPIPE error. */
+static int sctp_error(struct sock *sk, int flags, int err)
+{
+	if (err == -EPIPE)
+		err = sock_error(sk) ? : -EPIPE;
+	if (err == -EPIPE && !(flags & MSG_NOSIGNAL))
+		send_sig(SIGPIPE, current, 0);
+	return err;
+}
+
 /* API 3.1.3 sendmsg() - UDP Style Syntax
  *
  * An application uses sendmsg() and recvmsg() calls to transmit data to
@@ -763,6 +783,7 @@ SCTP_STATIC int sctp_sendmsg(struct kiocb *iocb, struct sock *sk,
 	long timeo;
 	__u16 sinfo_flags = 0;
 	struct sk_buff_head chunks;
+	int msg_flags = msg->msg_flags;
 
 	SCTP_DEBUG_PRINTK("sctp_sendmsg(sk: %p, msg: %p, msg_len: %d)\n",
 			  sk, msg, msg_len);
@@ -773,6 +794,12 @@ SCTP_STATIC int sctp_sendmsg(struct kiocb *iocb, struct sock *sk,
 
 	SCTP_DEBUG_PRINTK("Using endpoint: %s.\n", ep->debug_name);
 
+	if ((SCTP_SOCKET_TCP == sp->type) &&
+	    (SCTP_SS_ESTABLISHED != sk->state)) {
+		err = -EPIPE;
+		goto out_nounlock;
+	}
+
 	/* Parse out the SCTP CMSGs.  */
 	err = sctp_msghdr_parse(msg, &cmsgs);
 
@@ -859,6 +886,18 @@ SCTP_STATIC int sctp_sendmsg(struct kiocb *iocb, struct sock *sk,
 	if (asoc) {
 		SCTP_DEBUG_PRINTK("Just looked up association: "
 				  "%s. \n", asoc->debug_name);
+
+		/* We cannot send a message on a TCP-style SCTP_SS_ESTABLISHED 
+		 * socket that has an association in CLOSED state. This can
+		 * happen when an accepted socket has an association that is
+		 * already CLOSED. 
+		 */
+		if ((SCTP_STATE_CLOSED == asoc->state) &&
+		    (SCTP_SOCKET_TCP == sp->type)) {
+			err = -EPIPE;
+			goto out_unlock;
+		}
+
 		if (sinfo_flags & MSG_EOF) {
 			SCTP_DEBUG_PRINTK("Shutting down association: %p\n",
 					  asoc);
@@ -1067,7 +1106,7 @@ SCTP_STATIC int sctp_sendmsg(struct kiocb *iocb, struct sock *sk,
 	sctp_release_sock(sk);
 
 out_nounlock:
-	return err;
+	return sctp_error(sk, msg_flags, err);
 
 #if 0
 do_sock_err: