#include <stdio.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <unistd.h>
int main(int argc, char **argv) {
fd_set rfds, wfds, efds;
int s, rc;
struct timeval timeout;
char buf[1025];
s = socket(PF_INET, SOCK_STREAM, 0);
if (s == -1) {
perror("couldn't create socket");
return -1;
}
FD_ZERO(&rfds);
FD_SET(s, &rfds);
FD_ZERO(&wfds);
FD_SET(s, &wfds);
FD_ZERO(&efds);
FD_SET(s, &efds);
timeout.tv_sec = timeout.tv_usec = 0;
rc = select(s + 1, &rfds, &wfds, &efds, &timeout);
if (rc == -1) {
perror("select");
return -1;
}
printf("select result=%d\n", rc);
if (FD_ISSET(s, &rfds)) {
rc = read(s, buf, 1024);
if (rc == -1) {
perror("read");
return -1;
}
printf("read result=%d\n", rc);
}
return 0;
}
On Sat, Mar 31, 2001 at 06:44:20PM +0300, Radu Greab wrote:
> Sorry if this is already known: on a RH 7.0 system with kernel 2.4.2
> or 2.4.3, a select on an unconnected socket incorrectly says that the
> socket is ready for input and output. Of course, reading from the socket
> file descriptor returns -1 and errno is set to ENOTCONN as shown in
> the strace output:
>
> socket(PF_INET, SOCK_STREAM, IPPROTO_IP) = 3
> select(4, [3], [3], [3], {0, 0}) = 2 (in [3], out [3], left {0, 0})
> read(3, 0xbffff668, 1024) = -1 ENOTCONN (Transport endpoint is not connected)
>
> I attached a small example program to reproduce the bug.
bleah. which one is supposed to be right?
linux 2.4
---------
$ uname -a
Linux XXXXX 2.4.2-ac20 #8 Wed Mar 14 01:53:05 EST 2001 i686 unknown
$ ./t
select result=2
read: Transport endpoint is not connected
linux 2.2
---------
$ uname -a
Linux XXXXX 2.2.18 #1 Thu Dec 21 21:13:10 EST 2000 i586 unknown
$ ./t
select result=1
solaris
-------
$ uname -a
SunOS XXXXX 5.7 Generic_106541-07 sun4m sparc sun4m
$ ./t
select result=0
--
"Bobby, jiggle Grandpa's rat so it looks alive, please" -- gary larson
On Sun, 1 Apr 2001 02:15 +1000, john slee wrote:
> On Sat, Mar 31, 2001 at 06:44:20PM +0300, Radu Greab wrote:
> > Sorry if this is already known: on a RH 7.0 system with kernel 2.4.2
> > or 2.4.3, a select on an unconnected socket incorrectly says that the
> > socket is ready for input and output. Of course, reading from the socket
> > file descriptor returns -1 and errno is set to ENOTCONN as shown in
> > the strace output:
> >
> > socket(PF_INET, SOCK_STREAM, IPPROTO_IP) = 3
> > select(4, [3], [3], [3], {0, 0}) = 2 (in [3], out [3], left {0, 0})
> > read(3, 0xbffff668, 1024) = -1 ENOTCONN (Transport endpoint is not connected)
> >
> > I attached a small example program to reproduce the bug.
>
> bleah. which one is supposed to be right?
I think that the Solaris one is right.
>
> linux 2.4
> ---------
> $ uname -a
> Linux XXXXX 2.4.2-ac20 #8 Wed Mar 14 01:53:05 EST 2001 i686 unknown
> $ ./t
> select result=2
> read: Transport endpoint is not connected
Select says that the socket is ready for both input and output. A read
results in ENOTCONN, a write results in EPIPE.
> linux 2.2
> ---------
> $ uname -a
> Linux XXXXX 2.2.18 #1 Thu Dec 21 21:13:10 EST 2000 i586 unknown
> $ ./t
> select result=1
Select says that the socket is ready for output, but a write results
in EPIPE.
>
> solaris
> -------
> $ uname -a
> SunOS XXXXX 5.7 Generic_106541-07 sun4m sparc sun4m
> $ ./t
> select result=0
And Digital Unix is right too:
$ uname -a
OSF1 XXX V4.0 1229 alpha
$ ./a.out
select result=0
Thanks,
Radu Greab