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Date: Tue, 29 May 2007 13:57:21 +0900
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From: JINMEI Tatuya / =?ISO-2022-JP?B?GyRCP0BMQEMjOkgbKEI=?=
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Subject: how ipfw2 handles fragmented packets
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Hello,

I have a question about how the ipfw2 implementation performs stateful
operation for (IPv4/IPv6) fragmented packets.  Is it possible to make
a state for a flow and match that state against fragmented packets?
As far as I can see from the source code (sys/netinet/ip_fw2.c) it
seems impossible because a state matching done in
lookup_dyn_rule_locked() only compares src/dst address/ports.

I'm also not sure whether the routine that follows IPv6 extension headers
in ipfw_chk() is correct.  It continues the processing after seeing a
fragment header regardless of the offset value, but it should be
meaningless except the first fragment (which has 0 offset).

If I miss something, could anyone point it out?

Thanks,

					JINMEI, Tatuya
					Communication Platform Lab.
					Corporate R&D Center, Toshiba Corp.
					jinmei@isl.rdc.toshiba.co.jp