Date: Tue, 22 Apr 2003 15:13:02 -0700 (PDT) From: Don Lewis <truckman@FreeBSD.org> To: silby@silby.com Cc: freebsd-net@FreeBSD.org Subject: Re: IP fragmentation disagreement between current and stable Message-ID: <200304222213.h3MMD2XB027887@gw.catspoiler.org> In-Reply-To: <20030422004104.Q523@odysseus.silby.com>
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On 22 Apr, Mike Silbersack wrote: > > On Tue, 22 Apr 2003, Don Lewis wrote: > >> will contain 222 bytes of data. With a 14 byte Ethernet header and a 20 >> byte IP header, that just fits into one 256 byte mbuf. I wonder if >> there is a divide by 4 to calculate the number of words, and the >> >> Could this be a driver problem instead of a problem in the stack itself? >> Both ends are fxp cards. > > A similar problem was found with Via Rhine chips, where having multiple > packets exactly fill up the internal FIFO seemed to cause those packets to > be dropped. Naturally, this only cropped up with fragmented ping packets > of certain lengths. We never bothered patching it because, well, no clear > solution presented itself, and it wouldn't occur in normal usage. > (Actually, changing from store and forward back to smaller DMA sizes might > have fixed it, I'm not sure.) > > So, I would not rule out the possibility of a driver / chipset bug. That looks like the most likely problem. I swapped in an ancient de card on the -current box, and now it works. The fxp card that is is causing problems is a fairly recent Pro/100S desktop card that has an IBM OEM part number. I bought two of these cards from the same source over a period of several months, and both have another oddity. Neither one is probed by either the BIOS or the OS after a power-on cold boot. Not even the Intel diagnostic .exe program sees them. Hitting reset during the boot sequence or doing a reboot from the OS seems to reset something that allows the cards to work. I had to swap out the other card from the system that it was in and replace it with an older fxp that I had on hand because that system needed to be able to boot unattended after a power failure. I try the other card to see if it exhibits the same packet size problem. I'll also try a different flavor fxp, but that'll take some doing since the only remaining spare is on an older Asus motherboard that is on box running -stable.
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