Re: bug report: select on unconnected sockets

Radu Greab (radu@netsoft.ro)
Sat, 31 Mar 2001 19:26:00 +0300 (EEST)


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
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