From owner-svn-src-head@FreeBSD.ORG Sun Oct 28 17:25:09 2012 Return-Path: Delivered-To: svn-src-head@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id B8350298; Sun, 28 Oct 2012 17:25:09 +0000 (UTC) (envelope-from andre@FreeBSD.org) Received: from svn.freebsd.org (svn.freebsd.org [IPv6:2001:4f8:fff6::2c]) by mx1.freebsd.org (Postfix) with ESMTP id 85BE58FC08; Sun, 28 Oct 2012 17:25:09 +0000 (UTC) Received: from svn.freebsd.org (localhost [127.0.0.1]) by svn.freebsd.org (8.14.4/8.14.4) with ESMTP id q9SHP9xI061869; Sun, 28 Oct 2012 17:25:09 GMT (envelope-from andre@svn.freebsd.org) Received: (from andre@localhost) by svn.freebsd.org (8.14.4/8.14.4/Submit) id q9SHP9Sw061865; Sun, 28 Oct 2012 17:25:09 GMT (envelope-from andre@svn.freebsd.org) Message-Id: <201210281725.q9SHP9Sw061865@svn.freebsd.org> From: Andre Oppermann Date: Sun, 28 Oct 2012 17:25:09 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r242250 - head/sys/netinet X-SVN-Group: head MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 28 Oct 2012 17:25:09 -0000 Author: andre Date: Sun Oct 28 17:25:08 2012 New Revision: 242250 URL: http://svn.freebsd.org/changeset/base/242250 Log: When SYN or SYN/ACK had to be retransmitted RFC5681 requires us to reduce the initial CWND to one segment. This reduction got lost some time ago due to a change in initialization ordering. Additionally in tcp_timer_rexmt() avoid entering fast recovery when we're still in TCPS_SYN_SENT state. MFC after: 2 weeks Modified: head/sys/netinet/tcp_input.c head/sys/netinet/tcp_syncache.c head/sys/netinet/tcp_timer.c Modified: head/sys/netinet/tcp_input.c ============================================================================== --- head/sys/netinet/tcp_input.c Sun Oct 28 17:16:09 2012 (r242249) +++ head/sys/netinet/tcp_input.c Sun Oct 28 17:25:08 2012 (r242250) @@ -345,10 +345,16 @@ cc_conn_init(struct tcpcb *tp) /* * Set the initial slow-start flight size. * - * RFC3390 says only do this if SYN or SYN/ACK didn't got lost. - * XXX: We currently check only in syncache_socket for that. - */ - if (V_tcp_do_rfc3390) + * RFC5681 Section 3.1 specifies the default conservative values. + * RFC3390 specifies slightly more aggressive values. + * + * If a SYN or SYN/ACK was lost and retransmitted, we have to + * reduce the initial CWND to one segment as congestion is likely + * requiring us to be cautious. + */ + if (tp->snd_cwnd == 1) + tp->snd_cwnd = tp->t_maxseg; /* SYN(-ACK) lost */ + else if (V_tcp_do_rfc3390) tp->snd_cwnd = min(4 * tp->t_maxseg, max(2 * tp->t_maxseg, 4380)); else { Modified: head/sys/netinet/tcp_syncache.c ============================================================================== --- head/sys/netinet/tcp_syncache.c Sun Oct 28 17:16:09 2012 (r242249) +++ head/sys/netinet/tcp_syncache.c Sun Oct 28 17:25:08 2012 (r242250) @@ -852,11 +852,12 @@ syncache_socket(struct syncache *sc, str tcp_mss(tp, sc->sc_peer_mss); /* - * If the SYN,ACK was retransmitted, reset cwnd to 1 segment. + * If the SYN,ACK was retransmitted, indicate that CWND to be + * limited to one segment in cc_conn_init(). * NB: sc_rxmits counts all SYN,ACK transmits, not just retransmits. */ if (sc->sc_rxmits > 1) - tp->snd_cwnd = tp->t_maxseg; + tp->snd_cwnd = 1; #ifdef TCP_OFFLOAD /* Modified: head/sys/netinet/tcp_timer.c ============================================================================== --- head/sys/netinet/tcp_timer.c Sun Oct 28 17:16:09 2012 (r242249) +++ head/sys/netinet/tcp_timer.c Sun Oct 28 17:25:08 2012 (r242250) @@ -539,7 +539,13 @@ tcp_timer_rexmt(void * xtp) } INP_INFO_RUNLOCK(&V_tcbinfo); headlocked = 0; - if (tp->t_rxtshift == 1) { + if (tp->t_state == TCPS_SYN_SENT) { + /* + * If the SYN was retransmitted, indicate CWND to be + * limited to 1 segment in cc_conn_init(). + */ + tp->snd_cwnd = 1; + } else if (tp->t_rxtshift == 1) { /* * first retransmit; record ssthresh and cwnd so they can * be recovered if this turns out to be a "bad" retransmit.