Date: Sat, 28 Dec 2002 13:03:01 -0800 From: Eli Dart <dart@nersc.gov> To: Rostislav Krasny <rosti_bsd@yahoo.com> Cc: freeBSD-net@freebsd.org Subject: Re: PPPoE and troubles with TCP Message-ID: <20021228210301.77EF13B1AE@gemini.nersc.gov> In-Reply-To: Message from Rostislav Krasny <rosti_bsd@yahoo.com> of "Sat, 28 Dec 2002 11:54:57 PST." <20021228195457.86366.qmail@web14807.mail.yahoo.com>
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--==_Exmh_1841889117P Content-Type: text/plain; charset=us-ascii Well, I noticed one thing from the tcpdump files -- in the 1492 case, your machine is sending a FIN to www.ssh.com. In the 1484 case, of course no FIN is sent. However, if you look at the 1492 tcpdump you'll see connection establishment, a packet sent to www.ssh.com (an http request I assume), a retransmit of that packet a second later (implying that the first did not arrive), an ack for that packet from www.ssh.com, and a fin from your box, which is then acknowledged. I don't know what's causing it, but it appears that the application you're using is seeing something it doesn't like, and is closing its socket. I don't know why the www.ssh.com side does not send its own FIN -- it should (it may also not be getting to you). I would look at a tcpdump of a successful connection to www.freebsd.org with the 1492 config (you said in an earlier post that this works). You could also run with a slightly smaller MTU and declare victory :) --eli In reply to Rostislav Krasny <rosti_bsd@yahoo.com> : > > --0-2081754345-1041105297=:86278 > Content-Type: text/plain; charset=us-ascii > Content-Disposition: inline > > --- Eli Dart <dart@nersc.gov> wrote: > > > > In reply to Rostislav Krasny <rosti_bsd@yahoo.com> : > > > > > Thank you for your trying to help me. Your version of ppp.conf is very > > > similar to mine. I don't have LAN here, but only one box with FreeBSD > > > connected to the outside world through my ADSL modem. So ' set nat' and > > > ' set proxy' options are not required in my case. I don't use > > > ' set ifaddr' option because default arguments of it are good for me. > > > > > > I think that the source of my problem isn't in ppp.conf probably, > > > but somewhere in TCP. Nobody answered me how MTU == MRU == 1484 solves > > > my problem. Maybe there is a bug in TCP when MTU and MRU have some > > > unstandard value. When I use Win98SE in the same box and the same ADSL > > > modem with RASPPPOE driver of PPPoE I have no troubles when the MTU is > > > 1492 there. This is why I think the source of the problem is in TCP > > > implementation of FreeBSD. ppp have some dial with TCP, so maybe the > > > source of the problem is there but most likely not in ppp.conf > > > > Are you blocking ICMP for "security reasons?" If so, you can't do > > path mtu discovery, and tcp will break if it needs a smaller mtu > > (which it appears that you do). > > No, I'm not blocking ICMP. I have recently installed FreeBSD 4.7-RELEASE > with custom kernel that is a little simplified version of GENERIC. There > is no firewall enabled, yet. Look at CUST01 file in the attachments, this > is the configuration of the kernel of my system. I also ran `tcpdump -n` > and saved its output when I ran `links www.ssh.com` in other terminal. > I did it two times, the first when MRU == MTU == 1492 and the second when > it was 1484. Look at 1492.log and 1484.log files in the attachments. > > P.S. If one blocks ICMP why he have troubles when MTU == MRU == 1492 but > don't have the troubles when MTU == MRU == 1484 ? --==_Exmh_1841889117P Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.0.6 (FreeBSD) Comment: This is a comment. iD8DBQE+DhGFLTFEeF+CsrMRAgJkAKCDkpZAEtFNBHGD57B3eseNmMIFhACeJv9U BT/ksUWqjvEhMUv9mf7Lwz4= =bT4V -----END PGP SIGNATURE----- --==_Exmh_1841889117P-- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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