Re: short reads on unix stream on netbsd-10

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Wed, Sep 06, 2023 at 09:28:31AM -0400, Mouse wrote:
> > serv_input: read@3 need 468 got 396 (and disconnects).
> 
> > The code is:
> >                 if (i != (nchars = read(fd, T.c, i))) {
> > 			fprintf(stderr, "serv_input: read@%d need %d got %d\n",
> > 				fd, i, nchars);
> > 			server_died();
> > 		}
> 
> > fd 3 is a unix stream socket
> > I didn't find any place where this file descriptor could have been
> > put to nonblocking.
> 
> > I could wrap the read in a loop to work around this, but I wonder if
> > it's expected behavior to get short reads in this case ?
> 
> That's a good question.  In general, SOCK_STREAM socket connections
> never promise atomicity of anything larger than one byte.  It's
> possible AF_LOCAL provides a stronger promise, but, if so, I'm not sure
> where that promise is documented, or how widespread it is.
> 
> As for it being _expected_ behaviour...I wouldn't call it "expected",
> exactly, but I would call it "not particularly surprising".
> 
> So, I'd say the code you quote is at fault here.

thanks. I remplaced the read with a poll()/read() loop; this fixes the issue.

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--