Subject: Re: bin/35479: /usr/sbin/timedc fails
To: None <gnats-admin@netbsd.org, netbsd-bugs@netbsd.org, djv@bedford.net>
From: Woodchuck <djv@bedford.net>
List: netbsd-bugs
Date: 01/25/2007 16:50:02
The following reply was made to PR bin/35479; it has been noted by GNATS.
From: Woodchuck <djv@bedford.net>
To: gnats-bugs@NetBSD.org
Cc: gnats-admin@NetBSD.org, netbsd-bugs@NetBSD.org, djv@bedford.net
Subject: Re: bin/35479: /usr/sbin/timedc fails
Date: Thu, 25 Jan 2007 11:48:12 -0500 (EST)
On Thu, 25 Jan 2007, Christian Biere wrote:
> The following reply was made to PR bin/35479; it has been noted by GNATS.
>
> From: Christian Biere <christianbiere@gmx.de>
> To: gnats-bugs@NetBSD.org
> Cc: netbsd-bugs@netbsd.org
> Subject: Re: bin/35479: /usr/sbin/timedc fails
> Date: Thu, 25 Jan 2007 17:13:13 +0100
>
> djv@bedford.net wrote:
> > --- cmds.c.orig 2007-01-24 22:33:51.000000000 -0500
> > +++ cmds.c 2007-01-24 22:34:30.000000000 -0500
> > @@ -483,10 +483,11 @@
> > return(-1);
> > }
> >
> > + memset(&sin, 0, sizeof sin);
> > sin.sin_family = AF_INET;
> > sin.sin_addr.s_addr = 0;
> > for (port = IPPORT_RESERVED - 1; port > IPPORT_RESERVED / 2; port--) {
> > - sin.sin_port = htons((u_short)port);
> > + sin.sin_port = port;
> > if (bind(sock, (struct sockaddr*)&sin, sizeof (sin)) >= 0)
> > break;
>
> Sorry, but I don't get this. In how far is htons() a bug here? It certainly
> never mattered for a big-endian machine but on a little endian machine it
> definitely does. Albeit I'm having trouble to find this in the documentation,
> sin_port has to be initialized using big-endian (network byte order). For
> raw sockets this might differ but this is an UDP socket.
>
> > Eliminating the htons call on little-endian machines results in a port
> > assignment in the 0-1023 range as demanded by some hosts, and as appears to
> > be the intent of the programmer.
>
> I don't see how unless I'm missing something.
I determined the fix empirically.
Print out sin.sin_port with and without the htons, observe
results of a "clockdiff" command with and without the htons.
On a little-endian (i386) machine, the original code results in a
sin.sin_port value in the 63K range, and subsequent code that probes
the target host for time/udp will fail if the target expects a privileged
port. perhaps htons belongs *here*, perhaps another one elsewhere is
spurious. I was unable to find any semantics of the bind(2) call
in the man pages, except for the (irrelevant) UNIX domain.
I no longer have a working big-endian machine for testing, alas.
The OpenBSD version moves all these calls to timedc.c, and makes
the bind call with sin.sin_port set to zero. The relevant block
of code there is :
memset(&sin, 0, sizeof sin);
sin.sin_family = AF_INET;
sin.sin_addr.s_addr = INADDR_ANY;
if (bind(sock, (struct sockaddr *)&sin, sizeof(sin)) < 0) {
fprintf(stderr, "all reserved ports in use\n");
(void)close(sock_raw);
exit(1);
}
Looks I'd better subscribe to bugs@ ;-)
Dave