Date: Fri, 24 Aug 2001 14:39:52 -0700 From: Kris Kennaway <kris@obsecurity.org> To: Steven Holmes <steg@pc1-east2-0-cust144.ren.cable.ntl.com> Cc: freebsd-stable@FreeBSD.ORG Subject: Re: Weird networking problem Message-ID: <20010824143952.A83415@xor.obsecurity.org> In-Reply-To: <E15aOe2-0000Bd-00@pc1-east2-0-cust144.ren.cable.ntl.com>; from steg@pc1-east2-0-cust144.ren.cable.ntl.com on Fri, Aug 24, 2001 at 10:37:38PM %2B0100 References: <E15aOe2-0000Bd-00@pc1-east2-0-cust144.ren.cable.ntl.com>
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--BXVAT5kNtrzKuDFl Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Aug 24, 2001 at 10:37:38PM +0100, Steven Holmes wrote: >=20 > While trying to access some websites, I discovered a strange > networking problem that I am unable to solve. >=20 > Some IPs I am unable to connect to using TCP. tcpdump shows the SYN > packets that I send to have a bad checksum (I have included a sample > tcpdump output below). However, these are the only packets that > tcpdump shows a problem for, and all my other packets seem to have > correct checksums. >=20 > I can access everything from my internal windows box, which I am > performing NAT for. I am running ipf and ipnat, and have tried > disabling both, but without any result. I have tried with > tcp_extensions both enabled and disabled, have tried a different > network card and have tried with numerous different clients (including > telnet), but the problem remains. >=20 > I get no response to my initial packet (The checksum is always bad), > and this is the only packet that is sent. I am on a cable modem. >=20 >=20 > Sample tcpdump output for accessing www.slashdot.org (a problem IP): >=20 > 22:15:24.687044 pc1-east2-0-cust144.ren.cable.ntl.com.1034 > > 64.28.67.150.http: S [bad tcp cksum fffe!] 1158842795:1158842795(0) > win 16384 <mss 1460> (DF) (ttl 64, id 2222, len 44) How new is your kernel? Kris --BXVAT5kNtrzKuDFl Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.0.6 (FreeBSD) Comment: For info see http://www.gnupg.org iD8DBQE7hsmoWry0BWjoQKURAlOqAKDtNriD5CbdIJikeBzp1ow6PvHcKQCg/o+U gD0RnSmvLJIvXVATqtzAoT0= =BPhL -----END PGP SIGNATURE----- --BXVAT5kNtrzKuDFl-- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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