Date: Mon, 30 Nov 2020 10:58:07 +0000 (UTC) From: Michael Tuexen <tuexen@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: r368183 - stable/11/sys/netinet Message-ID: <202011301058.0AUAw7j2052448@repo.freebsd.org>
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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.
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