Date: Wed, 02 Oct 1996 02:07:59 -0700 From: David Greenman <dg@root.com> To: Rowan Crowe <rowan@ozramp.net.au> Cc: bugs@FreeBSD.org Subject: Re: Possible low level TCP bug Message-ID: <199610020907.CAA06730@root.com> In-Reply-To: Your message of "Wed, 02 Oct 1996 18:40:33 %2B1000." <Pine.LNX.3.91.961002183806.30318A-100000@ozramp>
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> >On Tue, 1 Oct 1996, David Greenman wrote: > >> >The behaviour is this: seemingly small amounts of complete data (ie: a >> >line on IRC) are split into two packets, and are sent about a second >> >apart. The trace from my current router (not a FreeBSD box) shows this >> >behaviour. Note the first packet has the PSH attribute. >> >> What kind of ethernet card are you using? ...or is this with PPP or SLIP? > >Hello David, > >Don't laugh: I use 3c501 ethernet cards. The capture I sent to you was >carried over the ethernet from my FreeBSD box. However, I doubt that's >the problem, as I've observed inbound data (via serial/PPP) with this >same quirk. Actually, it's quite likely that the 3c501 could be the problem. The card has a total of 2K bytes of buffering - not enough to both receive and transmit a packet. Of all of the cards supported in FreeBSD, I'd rate the 3c501 at the very bottom in all respects. This isn't the first complaint like this I've seen with the 3c501. You'd do well to find an 8bit 3c503 or WD8003. As for PPP, that could be caused by a different problem. More analysis is needed. >Being new to FreeBSD I'm going to ask what might be a stupid question, >but is it possible to trace IP packets coming in and out of my FreeBSD >box, on the box itself? Yes. You need to add BPF to your kernel with: pseudo-device bpfilter 4 ...and create the bpf devices in /dev: cd /dev; MAKEDEV bpf0 bpf1 bpf2 bpf3 You can then use tcpdump to analyze the traffic. -DG David Greenman Core-team/Principal Architect, The FreeBSD Project
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