[PATCH v4] sctp: fix the sendmsg() flag SCTP_EOF to comply to spec

[Wei Yongjun <yjwei@xxxxxxxxxxxxxx>]

It should be possible to send a message and set the SCTP_EOF flag
at the same time, but we don't support it yet. This patch fix the
sendmsg() flag SCTP_EOF to comply to spec.

Signed-off-by: Wei Yongjun <yjwei@xxxxxxxxxxxxxx>
---
 include/net/sctp/structs.h |    3 ++-
 net/sctp/socket.c          |   40 ++++++++++++++++++++++++++++++++--------
 2 files changed, 34 insertions(+), 9 deletions(-)

diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
index 828185c..dc894e0 100644
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h
@@ -1924,7 +1924,8 @@ struct sctp_association {
 	__u16 active_key_id;
 
 	__u8 need_ecne:1,	/* Need to send an ECNE Chunk? */
-	     temp:1;		/* Is it a temporary association? */
+	     temp:1,		/* Is it a temporary association? */
+	     eof_pending:1;	/* SCTP_EOF flag is indicated in send() */
 };
 
 
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 0af3a8c..44c1773 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -1555,13 +1555,11 @@ SCTP_STATIC int sctp_sendmsg(struct kiocb *iocb, struct sock *sk,
 		goto out_nounlock;
 	}
 
-	/* If SCTP_EOF is set, no data can be sent. Disallow sending zero
-	 * length messages when SCTP_EOF|SCTP_ABORT is not set.
-	 * If SCTP_ABORT is set, the message length could be non zero with
-	 * the msg_iov set to the user abort reason.
+	/* Disallow sending zero length messages when SCTP_EOF|SCTP_ABORT
+	 * is not set. If SCTP_ABORT is set, the message length could be
+	 * non zero with the msg_iov set to the user abort reason.
 	 */
-	if (((sinfo_flags & SCTP_EOF) && (msg_len > 0)) ||
-	    (!(sinfo_flags & (SCTP_EOF|SCTP_ABORT)) && (msg_len == 0))) {
+	if (!(sinfo_flags & (SCTP_EOF|SCTP_ABORT)) && (msg_len == 0)) {
 		err = -EINVAL;
 		goto out_nounlock;
 	}
@@ -1608,6 +1606,12 @@ SCTP_STATIC int sctp_sendmsg(struct kiocb *iocb, struct sock *sk,
 	if (asoc) {
 		SCTP_DEBUG_PRINTK("Just looked up association: %p.\n", asoc);
 
+		/* Previous send() is called with SCTP_EOF flag */
+		if (asoc->eof_pending) {
+			err = -ESHUTDOWN;
+			goto out_unlock;
+		}
+
 		/* 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
@@ -1618,13 +1622,24 @@ SCTP_STATIC int sctp_sendmsg(struct kiocb *iocb, struct sock *sk,
 			goto out_unlock;
 		}
 
-		if (sinfo_flags & SCTP_EOF) {
+		/* Forbid SCTP_EOF and send a message combination
+		 * on non-blocking sockets.
+		 */
+		if ((sinfo_flags & SCTP_EOF) && msg_len != 0 &&
+		    sk->sk_socket->file &&
+		    (sk->sk_socket->file->f_flags & O_NONBLOCK)) {
+			err = -EWOULDBLOCK;
+			goto out_nounlock;
+		}
+
+		if (sinfo_flags & SCTP_EOF && msg_len == 0) {
 			SCTP_DEBUG_PRINTK("Shutting down association: %p\n",
 					  asoc);
 			sctp_primitive_SHUTDOWN(asoc, NULL);
 			err = 0;
 			goto out_unlock;
 		}
+
 		if (sinfo_flags & SCTP_ABORT) {
 
 			chunk = sctp_make_abort_user(asoc, msg, msg_len);
@@ -1644,7 +1659,7 @@ SCTP_STATIC int sctp_sendmsg(struct kiocb *iocb, struct sock *sk,
 	if (!asoc) {
 		SCTP_DEBUG_PRINTK("There is no association yet.\n");
 
-		if (sinfo_flags & (SCTP_EOF | SCTP_ABORT)) {
+		if (sinfo_flags & SCTP_ABORT) {
 			err = -EINVAL;
 			goto out_unlock;
 		}
@@ -1850,6 +1865,15 @@ SCTP_STATIC int sctp_sendmsg(struct kiocb *iocb, struct sock *sk,
 	else
 		err = msg_len;
 
+	if (sinfo_flags & SCTP_EOF) {
+		SCTP_DEBUG_PRINTK("Shutting down association: %p\n",
+				  asoc);
+		if (sctp_state(asoc, ESTABLISHED))
+			sctp_primitive_SHUTDOWN(asoc, NULL);
+		else
+			asoc->eof_pending = 1;
+	}
+
 	/* If we are already past ASSOCIATE, the lower
 	 * layers are responsible for association cleanup.
 	 */
-- 
1.6.5.2


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