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[UNIX]: EOF on non-blocking SOCK_SEQPACKET 

I am not absolutely sure whether this actually is a bug (as in: I've got
no clue what the standards say or what other implementations do), but at
least I was pretty surprised when I noticed that a recv() on a
non-blocking unix domain socket of type SOCK_SEQPACKET (which is connection
oriented, after all) where the remote end has closed the connection
returned -1 (EAGAIN) rather than 0 to indicate end of file.

This is a test case:

| #include <sys/types.h>
| #include <unistd.h>
| #include <sys/socket.h>
| #include <sys/un.h>
| #include <fcntl.h>
| #include <string.h>
| #include <stdlib.h>
| 
| int main(){
| 	int sock;
| 	struct sockaddr_un addr;
| 	char buf[4096];
| 	int pfds[2];
| 
| 	pipe(pfds);
| 	sock=socket(PF_UNIX,SOCK_SEQPACKET,0);
| 	addr.sun_family=AF_UNIX;
| 	strcpy(addr.sun_path,"/tmp/foobar_testsock");
| 	bind(sock,(struct sockaddr *)&addr,sizeof(addr));
| 	listen(sock,1);
| 	if(fork()){
| 		close(sock);
| 		sock=socket(PF_UNIX,SOCK_SEQPACKET,0);
| 		connect(sock,(struct sockaddr *)&addr,sizeof(addr));
| 		fcntl(sock,F_SETFL,fcntl(sock,F_GETFL)|O_NONBLOCK);
| 		close(pfds[1]);
| 		read(pfds[0],buf,sizeof(buf));
| 		recv(sock,buf,sizeof(buf),0); // <-- this one
| 	}else accept(sock,NULL,NULL);
| 	exit(0);
| }

If you try it, make sure /tmp/foobar_testsock doesn't exist.

The marked recv() returns -1 (EAGAIN) on 2.6.23.9. Below you find a
patch that fixes that.

Signed-off-by: Florian Zumbiehl <florz@florz.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Florian Zumbiehl 2007-11-29 23:19:23 +11:00 committed by Herbert Xu
parent 6ab3b487db
commit 0a11225887
1 changed files with 8 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
net/unix/af_unix.c
View File

@ -1637,8 +1637,15 @@ static int unix_dgram_recvmsg(struct kiocb *iocb, struct socket *sock,
mutex_lock(&u->readlock);
skb = skb_recv_datagram(sk, flags, noblock, &err);
if (!skb)
if (!skb) {
unix_state_lock(sk);
/* Signal EOF on disconnected non-blocking SEQPACKET socket. */
if (sk->sk_type == SOCK_SEQPACKET && err == -EAGAIN &&
(sk->sk_shutdown & RCV_SHUTDOWN))
err = 0;
unix_state_unlock(sk);
goto out_unlock;
}
wake_up_interruptible_sync(&u->peer_wait);