netdev - [RFC] Zero-length write() does not generate a datagram on connected socket

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Message-ID: <20070924153435.14249225@freepuppy.rosehill>
Date:	Mon, 24 Sep 2007 15:34:35 -0700
From:	Stephen Hemminger <shemminger@...ux-foundation.org>
To:	netdev@...r.kernel.org
Subject: [RFC] Zero-length write() does not generate a datagram on connected
 socket

The bug http://bugzilla.kernel.org/show_bug.cgi?id=5731
describes an issue where write() can't be used to generate a zero-length
datagram (but send, and sendto do work).

I think the following is needed:

--- a/net/socket.c	2007-08-20 09:54:28.000000000 -0700
+++ b/net/socket.c	2007-09-24 15:31:25.000000000 -0700
@@ -777,8 +777,11 @@ static ssize_t sock_aio_write(struct kio
 	if (pos != 0)
 		return -ESPIPE;
 
-	if (iocb->ki_left == 0)	/* Match SYS5 behaviour */
-		return 0;
+	if (unlikely(iocb->ki_left == 0)) {
+		struct socket *sock = iocb->ki_filp->private_data;
+		if (sock->type == SOCK_STREAM)
+			return 0;
+	}
 
 	x = alloc_sock_iocb(iocb, &siocb);
 	if (!x)
-
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