Author: tuexen
Date: Mon Nov 30 10:58:06 2020
New Revision: 368183
URL: https://svnweb.freebsd.org/changeset/base/368183

Log:
   MFC r367530:
   RFC 7323 specifies that:
   * TCP segments without timestamps should be dropped when support for
     the timestamp option has been negotiated.
   * TCP segments with timestamps should be processed normally if support
     for the timestamp option has not been negotiated.
   This patch enforces the above.
   Manually resolved merge conflicts.
  
   MFC 367891:
   Fix an issue I introuced in r367530: tcp_twcheck() can be called
   with to == NULL for SYN segments. So don't assume tp != NULL.
   Thanks to jhb@ for reporting and suggesting a fix.
  
   MFC r367946:
   Fix two occurences of a typo in a comment introduced in r367530.
   Thanks to lstewart@ for reporting them.
  
  PR:                   250499
  Reviewed by:          gnn, rrs
  Sponsored by:         Netflix, Inc.
  Differential Revision:        https://reviews.freebsd.org/D27148

Modified:
  stable/11/sys/netinet/tcp_input.c
  stable/11/sys/netinet/tcp_syncache.c
  stable/11/sys/netinet/tcp_timewait.c
Directory Properties:
  stable/11/   (props changed)

Modified: stable/11/sys/netinet/tcp_input.c
==============================================================================
--- stable/11/sys/netinet/tcp_input.c   Mon Nov 30 09:47:53 2020        
(r368182)
+++ stable/11/sys/netinet/tcp_input.c   Mon Nov 30 10:58:06 2020        
(r368183)
@@ -992,8 +992,8 @@ relocked:
                }
                INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
 
-               if (thflags & TH_SYN)
-                       tcp_dooptions(&to, optp, optlen, TO_SYN);
+               tcp_dooptions(&to, optp, optlen,
+                   (thflags & TH_SYN) ? TO_SYN : 0);
                /*
                 * NB: tcp_twcheck unlocks the INP and frees the mbuf.
                 */
@@ -1729,20 +1729,29 @@ tcp_do_segment(struct mbuf *m, struct tcphdr *th, stru
        }
 
        /*
-        * If timestamps were negotiated during SYN/ACK they should
-        * appear on every segment during this session and vice versa.
+        * If timestamps were negotiated during SYN/ACK and a
+        * segment without a timestamp is received, silently drop
+        * the segment.
+        * See section 3.2 of RFC 7323.
         */
        if ((tp->t_flags & TF_RCVD_TSTMP) && !(to.to_flags & TOF_TS)) {
                if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
                        log(LOG_DEBUG, "%s; %s: Timestamp missing, "
-                           "no action\n", s, __func__);
+                           "segment silently dropped\n", s, __func__);
                        free(s, M_TCPLOG);
                }
+               goto drop;
        }
+       /*
+        * If timestamps were not negotiated during SYN/ACK and a
+        * segment with a timestamp is received, ignore the
+        * timestamp and process the packet normally.
+        * See section 3.2 of RFC 7323.
+        */
        if (!(tp->t_flags & TF_RCVD_TSTMP) && (to.to_flags & TOF_TS)) {
                if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
                        log(LOG_DEBUG, "%s; %s: Timestamp not expected, "
-                           "no action\n", s, __func__);
+                           "segment processed normally\n", s, __func__);
                        free(s, M_TCPLOG);
                }
        }

Modified: stable/11/sys/netinet/tcp_syncache.c
==============================================================================
--- stable/11/sys/netinet/tcp_syncache.c        Mon Nov 30 09:47:53 2020        
(r368182)
+++ stable/11/sys/netinet/tcp_syncache.c        Mon Nov 30 10:58:06 2020        
(r368183)
@@ -1111,6 +1111,40 @@ syncache_expand(struct in_conninfo *inc, struct tcpopt
                }
 
                /*
+                * If timestamps were not negotiated during SYN/ACK and a
+                * segment with a timestamp is received, ignore the
+                * timestamp and process the packet normally.
+                * See section 3.2 of RFC 7323.
+                */
+               if (!(sc->sc_flags & SCF_TIMESTAMP) &&
+                   (to->to_flags & TOF_TS)) {
+                       if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
+                               log(LOG_DEBUG, "%s; %s: Timestamp not "
+                                   "expected, segment processed normally\n",
+                                   s, __func__);
+                               free(s, M_TCPLOG);
+                               s = NULL;
+                       }
+               }
+
+               /*
+                * If timestamps were negotiated during SYN/ACK and a
+                * segment without a timestamp is received, silently drop
+                * the segment.
+                * See section 3.2 of RFC 7323.
+                */
+               if ((sc->sc_flags & SCF_TIMESTAMP) &&
+                   !(to->to_flags & TOF_TS)) {
+                       SCH_UNLOCK(sch);
+                       if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
+                               log(LOG_DEBUG, "%s; %s: Timestamp missing, "
+                                   "segment silently dropped\n", s, __func__);
+                               free(s, M_TCPLOG);
+                       }
+                       return (-1);  /* Do not send RST */
+               }
+
+               /*
                 * Pull out the entry to unlock the bucket row.
                 * 
                 * NOTE: We must decrease TCPS_SYN_RECEIVED count here, not
@@ -1153,32 +1187,6 @@ syncache_expand(struct in_conninfo *inc, struct tcpopt
                        log(LOG_DEBUG, "%s; %s: SEQ %u != IRS+1 %u, segment "
                            "rejected\n", s, __func__, th->th_seq, sc->sc_irs);
                goto failed;
-       }
-
-       /*
-        * If timestamps were not negotiated during SYN/ACK they
-        * must not appear on any segment during this session.
-        */
-       if (!(sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) {
-               if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
-                       log(LOG_DEBUG, "%s; %s: Timestamp not expected, "
-                           "segment rejected\n", s, __func__);
-               goto failed;
-       }
-
-       /*
-        * If timestamps were negotiated during SYN/ACK they should
-        * appear on every segment during this session.
-        * XXXAO: This is only informal as there have been unverified
-        * reports of non-compliants stacks.
-        */
-       if ((sc->sc_flags & SCF_TIMESTAMP) && !(to->to_flags & TOF_TS)) {
-               if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
-                       log(LOG_DEBUG, "%s; %s: Timestamp missing, "
-                           "no action\n", s, __func__);
-                       free(s, M_TCPLOG);
-                       s = NULL;
-               }
        }
 
        *lsop = syncache_socket(sc, *lsop, m);

Modified: stable/11/sys/netinet/tcp_timewait.c
==============================================================================
--- stable/11/sys/netinet/tcp_timewait.c        Mon Nov 30 09:47:53 2020        
(r368182)
+++ stable/11/sys/netinet/tcp_timewait.c        Mon Nov 30 10:58:06 2020        
(r368183)
@@ -373,9 +373,10 @@ tcp_twstart(struct tcpcb *tp)
 /*
  * Returns 1 if the TIME_WAIT state was killed and we should start over,
  * looking for a pcb in the listen state.  Returns 0 otherwise.
+ * It be called with to == NULL only for pure SYN-segments.
  */
 int
-tcp_twcheck(struct inpcb *inp, struct tcpopt *to __unused, struct tcphdr *th,
+tcp_twcheck(struct inpcb *inp, struct tcpopt *to, struct tcphdr *th,
     struct mbuf *m, int tlen)
 {
        struct tcptw *tw;
@@ -396,6 +397,8 @@ tcp_twcheck(struct inpcb *inp, struct tcpopt *to __unu
                goto drop;
 
        thflags = th->th_flags;
+       KASSERT(to != NULL || (thflags & (TH_SYN | TH_ACK)) == TH_SYN,
+               ("tcp_twcheck: called without options on a non-SYN segment"));
 
        /*
         * NOTE: for FIN_WAIT_2 (to be added later),
@@ -443,6 +446,16 @@ tcp_twcheck(struct inpcb *inp, struct tcpopt *to __unu
         */
        if ((thflags & TH_ACK) == 0)
                goto drop;
+
+       /*
+        * If timestamps were negotiated during SYN/ACK and a
+        * segment without a timestamp is received, silently drop
+        * the segment.
+        * See section 3.2 of RFC 7323.
+        */
+       if (((to->to_flags & TOF_TS) == 0) && (tw->t_recent != 0)) {
+               goto drop;
+       }
 
        /*
         * Reset the 2MSL timer if this is a duplicate FIN.
_______________________________________________
svn-src-all@freebsd.org mailing list
https://lists.freebsd.org/mailman/listinfo/svn-src-all
To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"

Reply via email to