Subject: Re: dhcpd(8) & Sockets API
To: None <firstname.lastname@example.org>
From: Todd Vierling <email@example.com>
Date: 01/07/2002 13:15:11
: >Dennis's analysis seems dead-on to me. The fix would be to have some
: >kind of BSD Sockets API extension that could be used to identify the
: >arriving interface for DHCP REQUEST packets. Ideally, such an
: >extension would be coordinated with the other *BSD kernel folks,
: >so it could be more widely implemented than just NetBSD.
Getting back to the original part of this:
bpf requires that it be bound to a specific interface. From bpf(4):
BIOCSETIF (struct ifreq)
Sets the hardware interface associate with the file. This
command must be performed before any packets can be read.
There isn't a bpf "listen on all interfaces at once" mode, or at least, the
manpage and API seem to say this. And the code in dhcp seems to agree with
this assessment; see src/dist/dhcp/common/bpf.c:if_register_bpf() (the only
function that opens the bpf device). From line 128 of this file, after
opening the bpf device:
/* Set the BPF device to point at this interface. */
if (ioctl (sock, BIOCSETIF, info -> ifp) < 0)
log_fatal ("Can't attach interface %s to bpf device %s: %m",
info -> name, filename);
Note that dhcpd *does* open a socket on port 68, bound to all interfaces,
for the purpose of direct communication and fallback. So it's possible that
either (1) we have a bug in packet processing somewhere, or (2) the original
poster didn't have ipf set Correctly for testing (maybe just a simple
This "bug" needs much more analysis before coming to conclusions about how
to "fix" it.
-- Todd Vierling <firstname.lastname@example.org> * Wasabi & NetBSD: Run with it.
-- CDs, Integration, Embedding, Support -- http://www.wasabisystems.com/