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Date:      Fri, 15 Jun 2018 12:28:44 +0000 (UTC)
From:      Michael Tuexen <tuexen@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r335194 - head/sys/netinet
Message-ID:  <201806151228.w5FCSiBL086915@repo.freebsd.org>
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Author: tuexen
Date: Fri Jun 15 12:28:43 2018
New Revision: 335194
URL: https://svnweb.freebsd.org/changeset/base/335194

Log:
  When retransmitting TCP SYN-ACK segments with the TCP timestamp option
  enabled use an updated timestamp instead of reusing the one used in
  the initial TCP SYN-ACK segment.
  
  This patch ensures that an updated timestamp is used when sending the
  SYN-ACK from the syncache code. It was already done if the
  SYN-ACK was retransmitted from the generic code.
  
  This makes the behaviour consistent and also conformant with
  the TCP specification.
  
  Reviewed by:		jtl@, Jason Eggleston
  MFC after:		1 month
  Sponsored by:		Neflix, Inc.
  Differential Revision:	https://reviews.freebsd.org/D15634

Modified:
  head/sys/netinet/tcp_syncache.c
  head/sys/netinet/tcp_syncache.h

Modified: head/sys/netinet/tcp_syncache.c
==============================================================================
--- head/sys/netinet/tcp_syncache.c	Fri Jun 15 11:54:55 2018	(r335193)
+++ head/sys/netinet/tcp_syncache.c	Fri Jun 15 12:28:43 2018	(r335194)
@@ -1168,25 +1168,6 @@ syncache_expand(struct in_conninfo *inc, struct tcpopt
 		}
 	}
 
-	/*
-	 * 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 &&
-	    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",
-			    s, __func__, to->to_tsecr, sc->sc_ts);
-		goto failed;
-	}
-
 	*lsop = syncache_socket(sc, *lsop, m);
 
 	if (*lsop == NULL)
@@ -1513,7 +1494,6 @@ skip_alloc:
 		 */
 		if (to->to_flags & TOF_TS) {
 			sc->sc_tsreflect = to->to_tsval;
-			sc->sc_ts = tcp_ts_getticks();
 			sc->sc_flags |= SCF_TIMESTAMP;
 		}
 		if (to->to_flags & TOF_SCALE) {
@@ -1742,8 +1722,7 @@ syncache_respond(struct syncache *sc, struct syncache_
 			to.to_flags |= TOF_SCALE;
 		}
 		if (sc->sc_flags & SCF_TIMESTAMP) {
-			/* Virgin timestamp or TCP cookie enhanced one. */
-			to.to_tsval = sc->sc_ts;
+			to.to_tsval = sc->sc_tsoff + tcp_ts_getticks();
 			to.to_tsecr = sc->sc_tsreflect;
 			to.to_flags |= TOF_TS;
 		}
@@ -2050,8 +2029,7 @@ syncookie_generate(struct syncache_head *sch, struct s
 
 	/* Randomize the timestamp. */
 	if (sc->sc_flags & SCF_TIMESTAMP) {
-		sc->sc_ts = arc4random();
-		sc->sc_tsoff = sc->sc_ts - tcp_ts_getticks();
+		sc->sc_tsoff = arc4random() - tcp_ts_getticks();
 	}
 
 	TCPSTAT_INC(tcps_sc_sendcookie);
@@ -2140,7 +2118,6 @@ syncookie_lookup(struct in_conninfo *inc, struct synca
 	if (to->to_flags & TOF_TS) {
 		sc->sc_flags |= SCF_TIMESTAMP;
 		sc->sc_tsreflect = to->to_tsval;
-		sc->sc_ts = to->to_tsecr;
 		sc->sc_tsoff = to->to_tsecr - tcp_ts_getticks();
 	}
 

Modified: head/sys/netinet/tcp_syncache.h
==============================================================================
--- head/sys/netinet/tcp_syncache.h	Fri Jun 15 11:54:55 2018	(r335193)
+++ head/sys/netinet/tcp_syncache.h	Fri Jun 15 12:28:43 2018	(r335194)
@@ -56,7 +56,6 @@ struct syncache {
 	int		sc_rxttime;		/* retransmit time */
 	u_int16_t	sc_rxmits;		/* retransmit counter */
 	u_int32_t	sc_tsreflect;		/* timestamp to reflect */
-	u_int32_t	sc_ts;			/* our timestamp to send */
 	u_int32_t	sc_tsoff;		/* ts offset w/ syncookies */
 	u_int32_t	sc_flowlabel;		/* IPv6 flowlabel */
 	tcp_seq		sc_irs;			/* seq from peer */

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