Re: Kernel bug with UNIX sockets not detecting other end gone?

[Kurt Roeckx <Q@ping.be>]

On Thu, May 17, 2001 at 11:57:45PM +0100, Chris Evans wrote:
> 
> Hi,
> 
> I wonder if the following is a bug? It certainly differs from FreeBSD 4.2
> behaviour, which gives the behaviour I would expect.
> 
> The following program blocks indefinitely on Linux (2.2, 2.4 not tested).
> Since the other end is clearly gone, I would expect some sort of error
> condition. Indeed, FreeBSD gives ECONNRESET.

I'm having a simular problem, but somehow can't recreate it.

The difference is that I set the sockets to non-blocking, and
expect it to return some error.

read() returns 0, with errno set to 0, if the socket is still
open it returns -1 with errno set 11 (EAGAIN).  I can understand
those behaviours.

What I'm seeing however in an other program is that select says I
can read from the socket, and that read returns 0, with errno set
to EGAIN.  I call select() again, with returns and says I can read
from that socket ..., which keeps going on.  It stops from the
moment there is any i/o on an other socket.

Is there any way you can detect the other side is gone without
using write()?  write() shoud return an EPIPE.  Should I be able
to detect it with read(), or some oter system call?


Kurt