Date: Wed, 3 Feb 1999 13:10:11 -0500 (EST) From: Garrett Wollman <wollman@khavrinen.lcs.mit.edu> To: Robert Watson <robert+freebsd@cyrus.watson.org> Cc: security@FreeBSD.ORG Subject: Re: tcpdump Message-ID: <199902031810.NAA25118@khavrinen.lcs.mit.edu> In-Reply-To: <Pine.BSF.3.96.990203121931.28547B-100000@fledge.watson.org> References: <199902031549.KAA24669@khavrinen.lcs.mit.edu> <Pine.BSF.3.96.990203121931.28547B-100000@fledge.watson.org>
next in thread | previous in thread | raw e-mail | index | archive | help
<<On Wed, 3 Feb 1999 12:39:43 -0500 (EST), Robert Watson <robert@cyrus.watson.org> said:
> So the phase currently requiring BPF is presumably the bit where the
> client picks up the broadcast response as it doesn't have an IP address
> yet. The DHCP client also requires that it can set the source IP address
> for the outgoing requests. What changes to the protocol stack do you
> recommend to allow the reception of messages for the 0.0.0.0 (or whatever)
> address, and sending of appropriate packets?
There are several places in the code where it currently checks if
there are addresses configured, which need to be set up accept
broadcasts and multicasts; e.g., from netinet/ip_input.c:
/*
* If no IP addresses have been set yet but the interfaces
* are receiving, can't do anything with incoming packets yet.
* XXX This is broken! We should be able to receive broadcasts
* and multicasts even without any local addresses configured.
*/
if (TAILQ_EMPTY(&in_ifaddrhead))
goto bad;
(I wrote that comment about four years ago.) There are similar tests
in the top half, which also need to be fixed so a normal socket can be
bound by the DHCP client, and so that IP packets can be sent with a
source of 0.0.0.0 (which is fairly easy but needs to be done in
multiple places since we don't yet have ILP and some of the checks are
repeated at the IP layer). This may be easier to fix by simply
rewriting the UDP code (which I did most of several years ago).
-GAWollman
--
Garrett A. Wollman | O Siem / We are all family / O Siem / We're all the same
wollman@lcs.mit.edu | O Siem / The fires of freedom
Opinions not those of| Dance in the burning flame
MIT, LCS, CRS, or NSA| - Susan Aglukark and Chad Irschick
To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-security" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199902031810.NAA25118>