From owner-freebsd-transport@freebsd.org Fri May 13 17:36:40 2016 Return-Path: Delivered-To: freebsd-transport@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 727D6B392C3 for ; Fri, 13 May 2016 17:36:40 +0000 (UTC) (envelope-from hiren@strugglingcoder.info) Received: from mailman.ysv.freebsd.org (unknown [127.0.1.3]) by mx1.freebsd.org (Postfix) with ESMTP id 6269D13A8 for ; Fri, 13 May 2016 17:36:40 +0000 (UTC) (envelope-from hiren@strugglingcoder.info) Received: by mailman.ysv.freebsd.org (Postfix) id 5DC73B392C2; Fri, 13 May 2016 17:36:40 +0000 (UTC) Delivered-To: transport@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 5B0C7B392C1 for ; Fri, 13 May 2016 17:36:40 +0000 (UTC) (envelope-from hiren@strugglingcoder.info) Received: from mail.strugglingcoder.info (strugglingcoder.info [104.236.146.68]) by mx1.freebsd.org (Postfix) with ESMTP id 418BB13A6 for ; Fri, 13 May 2016 17:36:39 +0000 (UTC) (envelope-from hiren@strugglingcoder.info) Received: from localhost (unknown [10.1.1.3]) (Authenticated sender: hiren@strugglingcoder.info) by mail.strugglingcoder.info (Postfix) with ESMTPA id 723B9170C0 for ; Fri, 13 May 2016 10:36:33 -0700 (PDT) Date: Fri, 13 May 2016 10:36:33 -0700 From: hiren panchasara To: transport@FreeBSD.org Subject: Abrupt reset sent instead of retransmitting a lost packet Message-ID: <20160513173633.GG44085@strugglingcoder.info> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="64j1qyTOoGvYcHb1" Content-Disposition: inline User-Agent: Mutt/1.5.23 (2014-03-12) X-BeenThere: freebsd-transport@freebsd.org X-Mailman-Version: 2.1.22 Precedence: list List-Id: Discussions of transport level network protocols in FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 13 May 2016 17:36:40 -0000 --64j1qyTOoGvYcHb1 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable https://people.freebsd.org/~hiren/pcaps/tcp_weird_reset.txt Something we saw in the wild on 10.2ish systems (server and client both). The most interesting thing can be seen at the end of the file. 3298737767:3298739215 gets lost, client tells us about it via a bunch of dupacks with SACK info. It SACKs all the outstanding data but this one missing packet. We (server) never retransmits that missing packet but rather decide to send a Reset after 0.312582ms. Which somehow causes client to pause for 75secs. (which might be another issue and not particularly important for this discussion.) What could cause this behavior of sending a reset instead of retransmitting a lost packet?=20 Cheers, Hiren --64j1qyTOoGvYcHb1 Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQF8BAABCgBmBQJXNhCZXxSAAAAAAC4AKGlzc3Vlci1mcHJAbm90YXRpb25zLm9w ZW5wZ3AuZmlmdGhob3JzZW1hbi5uZXRBNEUyMEZBMUQ4Nzg4RjNGMTdFNjZGMDI4 QjkyNTBFMTU2M0VERkU1AAoJEIuSUOFWPt/ll9wH/jMku5AsfNer9G+owLpgIbIy +8z+A2csNJELmOd497IQfkkTvCtRO3xnzxFeV8uMer7ju+KiGX1xhVzEsEoQcyI1 y0qNel0zzhnnuUWisivBCnxA+rNhKRVd/tW7Vd3sX83Xjz9PaJZEvZqfwU8dTjsW fHN8ORU2b9eo5JL7SN/D5vknspFbkPdIOnDtKbQ0hODHuOW/Z1/D69R63h4aGikC Fm0eQRux41aQQ//eBQncm1BIQ4hJGb/1bzC8TgQxl7Xhd15WPv8WpMNGizUPVIj0 DI7JEuJnYYcs2bBvz+UFZ5tw+L7Zx+tOpvFg7dtJJEfkbx/P6aEdiTGj18cpZlQ= =lH+D -----END PGP SIGNATURE----- --64j1qyTOoGvYcHb1--