Include the timestamp TCP option in keep alive packets as well.

According to RFC 7323 "once TSopt has been successfully negotiated,
... [it] MUST be sent in every non-<RST> segment for the duration
of the connection."  Which means that keep alives which are just
ACK packets must include that too.

Pointed out and tested by Lauri Tirkkonen <lotheac at iki ! fi>, thanks!
ok mpi

diff --git a/sys/netinet/tcp_subr.c b/sys/netinet/tcp_subr.c
index c8c8e77..b98ecd2 100644 (file)
--- a/sys/netinet/tcp_subr.c
+++ b/sys/netinet/tcp_subr.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: tcp_subr.c,v 1.140 2015/03/14 03:38:52 jsg Exp $      */
+/*     $OpenBSD: tcp_subr.c,v 1.141 2015/05/07 09:19:31 mikeb Exp $    */
 /*     $NetBSD: tcp_subr.c,v 1.22 1996/02/13 23:44:00 christos Exp $   */
 
 /*
@@ -297,9 +297,6 @@ tcp_template(tp)
  * In any case the ack and sequence number of the transmitted
  * segment are as specified by the parameters.
  */
-#ifdef INET6
-/* This function looks hairy, because it was so IPv4-dependent. */
-#endif /* INET6 */
 void
 tcp_respond(struct tcpcb *tp, caddr_t template, struct tcphdr *th0,
     tcp_seq ack, tcp_seq seq, int flags, u_int rtableid)
@@ -372,10 +369,6 @@ tcp_respond(struct tcpcb *tp, caddr_t template, struct tcphdr *th0,
                flags = TH_ACK;
 #undef xchg
 
-       m->m_len = tlen;
-       m->m_pkthdr.len = tlen;
-       m->m_pkthdr.rcvif = (struct ifnet *) 0;
-       m->m_pkthdr.csum_flags |= M_TCP_CSUM_OUT;
        th->th_seq = htonl(seq);
        th->th_ack = htonl(ack);
        th->th_x2 = 0;
@@ -388,6 +381,22 @@ tcp_respond(struct tcpcb *tp, caddr_t template, struct tcphdr *th0,
        th->th_win = htons((u_int16_t)win);
        th->th_urp = 0;
 
+       if (tp && (tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&
+           (flags & TH_RST) == 0 && (tp->t_flags & TF_RCVD_TSTMP)) {
+               u_int32_t *lp = (u_int32_t *)(th + 1);
+               /* Form timestamp option as shown in appendix A of RFC 1323. */
+               *lp++ = htonl(TCPOPT_TSTAMP_HDR);
+               *lp++ = htonl(tcp_now + tp->ts_modulate);
+               *lp   = htonl(tp->ts_recent);
+               tlen += TCPOLEN_TSTAMP_APPA;
+               th->th_off = (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_APPA) >> 2;
+       }
+
+       m->m_len = tlen;
+       m->m_pkthdr.len = tlen;
+       m->m_pkthdr.rcvif = (struct ifnet *) 0;
+       m->m_pkthdr.csum_flags |= M_TCP_CSUM_OUT;
+
        /* force routing table */
        if (tp)
                m->m_pkthdr.ph_rtableid = tp->t_inpcb->inp_rtableid;