Date: Mon, 5 Sep 2005 15:51:51 +0200 From: Folkert Saathoff <folkert@feedface.com> To: snap-users@kame.net Cc: freebsd-mobile@freebsd.org Subject: Re: DUPlicate icmpv6 echo replies over wi0 Message-ID: <E9D3E995-B93A-4CE5-8137-656793576B42@feedface.com> In-Reply-To: <rmi64tfpsbt.fsf@fnord.ir.bbn.com> References: <49D89F36-BEDB-4FAE-80BE-3F73FA74D773@feedface.com> <rmi64tfpsbt.fsf@fnord.ir.bbn.com>
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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 5 Sep 2005, at 15:17 PM, Greg Troxel wrote: > The 802.11 mac layer can cause duplicates. If the receiver hears the > packet and sends an ack, but the ack is lost, the sender will > retransmit, leading to two copies of the packet. In theory a receiver > could filter dups, but I haven't noticed code to do this. So I would > suggest trying with other traffic and seeing if it is really a > ICMPv6-specific problem. Your description makes it sound to me like > something other than 802.11 MAC-layer dups are happening, though. I > would also suggest tcpdumping on the host behind the router and the > hostap machine. when pinging a host behind the access point/ router, the DUPs still happen, but tcpdump on the pinged host reports only one reply for each request. i should have mentioned that there is no problem whatsoever with the client and another hostap (which is same hardware, same setup). also, the antennas are about 5 cm away from each other, and i changed the frequency to the one which worked with the other hostap, which did not help at all. i dont think that a 802.11b retransmit would occur with such predictablility and regularity, especially in my test environment. (there are a _LOT_ of echo replies on the ether ;) i have noticed that the machine which i suspect is causing the trouble has a different station firmware version. dmesg on the two good machines tells me: wi0: using RF:PRISM2 MAC:HFA3841 CARD:HWB3163 rev.A wi0: Intersil Firmware: Primary (0.3.0), Station (1.7.1) while on the bad machine its wi0: using RF:PRISM2 MAC:HFA3841 CARD:HWB3163 rev.A wi0: Intersil Firmware: Primary (0.3.0), Station (0.8.3) i dont even know what a station firmware does, but i can imagine this being the guilty party. so my next question would be: how do i dump the firmware of a prism2 card in freebsd and subsequently flash it on another host? :) thnx, /folkert /* _ _ * _|| _ * || folkert@feedface.com * */ -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.1 (Darwin) iD8DBQFDHE18IA10xPlRIZURArI6AJ46sukIUCpEffjb7AWH80ZQ/szFFwCgkpwS /V77KiVXyv/z8tvEiBh7qNw= =sFRW -----END PGP SIGNATURE-----
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