From owner-svn-src-stable-10@freebsd.org Thu Jun 23 08:38:02 2016 Return-Path: Delivered-To: svn-src-stable-10@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 BD6DCAC692D; Thu, 23 Jun 2016 08:38:02 +0000 (UTC) (envelope-from sephe@FreeBSD.org) Received: from repo.freebsd.org (repo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:0]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 7FB2B2687; Thu, 23 Jun 2016 08:38:02 +0000 (UTC) (envelope-from sephe@FreeBSD.org) Received: from repo.freebsd.org ([127.0.1.37]) by repo.freebsd.org (8.15.2/8.15.2) with ESMTP id u5N8c1uM054459; Thu, 23 Jun 2016 08:38:01 GMT (envelope-from sephe@FreeBSD.org) Received: (from sephe@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id u5N8c1w8054458; Thu, 23 Jun 2016 08:38:01 GMT (envelope-from sephe@FreeBSD.org) Message-Id: <201606230838.u5N8c1w8054458@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: sephe set sender to sephe@FreeBSD.org using -f From: Sepherosa Ziehau Date: Thu, 23 Jun 2016 08:38:01 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-10@freebsd.org Subject: svn commit: r302132 - stable/10/sys/netinet X-SVN-Group: stable-10 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: svn-src-stable-10@freebsd.org X-Mailman-Version: 2.1.22 Precedence: list List-Id: SVN commit messages for only the 10-stable src tree List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 23 Jun 2016 08:38:02 -0000 Author: sephe Date: Thu Jun 23 08:38:01 2016 New Revision: 302132 URL: https://svnweb.freebsd.org/changeset/base/302132 Log: MFC 300981 tcp: Don't prematurely drop receiving-only connections If the connection was persistent and receiving-only, several (12) sporadic device insufficient buffers would cause the connection be dropped prematurely: Upon ENOBUFS in tcp_output() for an ACK, retransmission timer is started. No one will stop this retransmission timer for receiving- only connection, so the retransmission timer promises to expire and t_rxtshift is promised to be increased. And t_rxtshift will not be reset to 0, since no RTT measurement will be done for receiving-only connection. If this receiving-only connection lived long enough (e.g. >350sec, given the RTO starts from 200ms), and it suffered 12 sporadic device insufficient buffers, i.e. t_rxtshift >= 12, this receiving-only connection would be dropped prematurely by the retransmission timer. We now assert that for data segments, SYNs or FINs either rexmit or persist timer was wired upon ENOBUFS. And don't set rexmit timer for other cases, i.e. ENOBUFS upon ACKs. Discussed with: lstewart, hiren, jtl, Mike Karels MFC after: 3 weeks Sponsored by: Microsoft OSTC Differential Revision: https://reviews.freebsd.org/D5872 Modified: stable/10/sys/netinet/tcp_output.c Directory Properties: stable/10/ (props changed) Modified: stable/10/sys/netinet/tcp_output.c ============================================================================== --- stable/10/sys/netinet/tcp_output.c Thu Jun 23 08:28:13 2016 (r302131) +++ stable/10/sys/netinet/tcp_output.c Thu Jun 23 08:38:01 2016 (r302132) @@ -127,6 +127,16 @@ SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, &VNET_NAME(tcp_autosndbuf_max), 0, "Max size of automatic send buffer"); +/* + * Make sure that either retransmit or persist timer is set for SYN, FIN and + * non-ACK. + */ +#define TCP_XMIT_TIMER_ASSERT(tp, len, th_flags) \ + KASSERT(((len) == 0 && ((th_flags) & (TH_SYN | TH_FIN)) == 0) ||\ + tcp_timer_active((tp), TT_REXMT) || \ + tcp_timer_active((tp), TT_PERSIST), \ + ("neither rexmt nor persist timer is set")) + static void inline hhook_run_tcp_est_out(struct tcpcb *tp, struct tcphdr *th, struct tcpopt *to, long len, int tso); @@ -1531,9 +1541,7 @@ timer: tp->t_softerror = error; return (error); case ENOBUFS: - if (!tcp_timer_active(tp, TT_REXMT) && - !tcp_timer_active(tp, TT_PERSIST)) - tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); + TCP_XMIT_TIMER_ASSERT(tp, len, flags); tp->snd_cwnd = tp->t_maxseg; return (0); case EMSGSIZE: