Date: Wed, 4 Jul 2001 01:16:23 -0700 From: "Crist J. Clark" <cristjc@earthlink.net> To: cjclark@alum.mit.edu Cc: Ralph Huntington <rjh@mohawk.net>, freebsd-security@FreeBSD.ORG Subject: Re: firewall question Message-ID: <20010704011623.G1476@blossom.cjclark.org> In-Reply-To: <20010704002534.D1476@blossom.cjclark.org>; from cristjc@earthlink.net on Wed, Jul 04, 2001 at 12:25:34AM -0700 References: <20010702192720.P17514@speedy.gsinet> <Pine.BSF.4.21.0107031039010.18482-100000@mohegan.mohawk.net> <20010704002534.D1476@blossom.cjclark.org>
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On Wed, Jul 04, 2001 at 12:25:34AM -0700, Crist J. Clark wrote: > On Tue, Jul 03, 2001 at 10:45:27AM -0400, Ralph Huntington wrote: > > The dmesg command shows a lot of these: > > > > ipfw: -1 Refuse TCP W.X.Y.Z:0 A.B.C.D:0 in via fxp0 > > ipfw: -1 Refuse TCP S.T.U.V:0 A.B.C.D:0 in via fxp0 > > > > (The uppercase letters represent the ip addresses) > > > > There are no rules in ipfw blocking packets from addresses W.X.Y.Z or > > S.T.U.V to host A.B.C.D. Can someone tell me what is going on here? > > FINE POINTS > o There is one kind of packet that the firewall will always discard, > that is a TCP packet's fragment with a fragment offset of one. This > is a valid packet, but it only has one use, to try to circumvent > firewalls. When logging is enabled, these packets are reported as > being dropped by rule -1. Yuck, following up my own post. Anyway, I just wanted to note that I committed a fix to CURRENT that actually logs first fragments as fragments (PR 23446). It should make logs of -1 rules a little more clear. I plan to MFC it in a few days. -- Crist J. Clark cjclark@alum.mit.edu To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-security" in the body of the message
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