Date: Sun, 18 Aug 1996 16:48:37 -0600 From: Warner Losh <imp@village.org> To: Poul-Henning Kamp <phk@critter.tfs.com> Cc: hackers@freebsd.org Subject: Which fragments to discard (was Re: ipfw vs ipfilter) Message-ID: <199608182248.QAA01272@rover.village.org> In-Reply-To: Your message of Sun, 18 Aug 1996 16:42:33 %2B0200
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Poul-Henning Kamp writes: : This is a common mistake, only offset==1 needs to be discarded. Hmmm, since there are no comments in ip_fw.c as to why only offset 1 is a problem, I'll have to ask here. Why is that? A quick look at Stephens[*] shows that offset 2 could be used to rewrite the TCP flags, or if you have IP options that you can pad things such that even the TCP ports get overwritten. What have I missed? Warner [*] Stephens isn't good at explaining exactly what the ip_off is, but glosses over this detail, so maybe some of my thick-headedness on this comes from that gloss.
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