Re: unfilled path in getsockname() for unix sockets

[Pino Toscano]

Alle domenica 4 dicembre 2011, Samuel Thibault ha scritto:
> Pino Toscano, le Sun 04 Dec 2011 13:14:52 +0100, a écrit :
> > while debugging, I apparently stumbled upon a bug of getsockname()
> > for a bound unix socket, as also the attached test program shows:
> > sun_path is left unfilled, as also the comment of
> > S_socket_whatis_address() in hurd/pflocal/pf.c would suggest.
> 
> Which is a design choice, apparently: only glibc's bind.c knows about
> the socket path.

Hmm :-/ And there's really no way to get it later?

> > There's also another possibly weird behaviour in that:
> > S_socket_whatis_address() sets its sockaddr_len parameter in what
> > seems also what Linux does, ie
> > 
> >   offsetof(struct sockaddr, sa_data) + strlen(sun_path) + 1
> > 
> > instead of sizeof(struct sockaddr_un),
> 
> Yes, because the size of the sun_path member is rather indicative
> only (and relatively small: 108 only!). Everything should also be
> working with bigger paths, so it does not really make sense to
> return the arbitrary size of sockaddr_un.

Yes, I knew sun_path was rather short, my doubt was whether which was a 
"better" return value, as usually socket functions return values of the 
whole sockaddr_* structs.

> > [1] in perl's code, I've seen this snippet:
> > unpack_sockaddr_un(sun_sv)
> > [...]
> > #   ifndef __linux__
> > 
> >         /* On Linux sockaddrlen on sockets returned by accept,
> >         recvfrom,
> >         
> >            getpeername and getsockname is not equal to
> >            sizeof(addr). */
> >         
> >         if (sockaddrlen != sizeof(addr)) {
> >         
> >             croak("Bad arg length for %s, length is %d, should be
> >             %d",
> >             
> >                         "Socket::unpack_sockaddr_un",
> >                         sockaddrlen, sizeof(addr));
> >         
> >         }
> > 
> > #   endif
> 
> I'd say restrict to !__GNU__ too, then.

I guess so.

-- 
Pino Toscano

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