Date: Mon, 5 Dec 2016 06:20:27 +0000 (UTC) From: Hiren Panchasara <hiren@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-11@freebsd.org Subject: svn commit: r309548 - stable/11/sys/netinet Message-ID: <201612050620.uB56KRuO025639@repo.freebsd.org>
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Author: hiren Date: Mon Dec 5 06:20:27 2016 New Revision: 309548 URL: https://svnweb.freebsd.org/changeset/base/309548 Log: MFC r308943 For RTT calculations mid-session, we explicitly ignore ACKs with tsecr of 0 as many borken middle-boxes tend to do that. But during 3whs, in syncache_expand(), we don't do that which causes us to send a RST to such a client. Relax this constraint by only using tsecr to compare against timestamp that we sent when it is not 0. As a result, we'd now accept the final ACK of 3whs with tsecr of 0. Sponsored by: Limelight Networks Modified: stable/11/sys/netinet/tcp_syncache.c Directory Properties: stable/11/ (props changed) Modified: stable/11/sys/netinet/tcp_syncache.c ============================================================================== --- stable/11/sys/netinet/tcp_syncache.c Mon Dec 5 03:11:52 2016 (r309547) +++ stable/11/sys/netinet/tcp_syncache.c Mon Dec 5 06:20:27 2016 (r309548) @@ -1069,10 +1069,17 @@ syncache_expand(struct in_conninfo *inc, } /* - * If timestamps were negotiated the reflected timestamp - * must be equal to what we actually sent in the SYN|ACK. + * If timestamps were negotiated, the reflected timestamp + * must be equal to what we actually sent in the SYN|ACK + * except in the case of 0. Some boxes are known for sending + * broken timestamp replies during the 3whs (and potentially + * during the connection also). + * + * Accept the final ACK of 3whs with reflected timestamp of 0 + * instead of sending a RST and deleting the syncache entry. */ - if ((to->to_flags & TOF_TS) && to->to_tsecr != sc->sc_ts) { + if ((to->to_flags & TOF_TS) && to->to_tsecr && + to->to_tsecr != sc->sc_ts) { if ((s = tcp_log_addrs(inc, th, NULL, NULL))) log(LOG_DEBUG, "%s; %s: TSECR %u != TS %u, " "segment rejected\n",
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