Remove RFC1644 T/TCP support from the TCP side of the network stack.

A complete rationale and discussion is given in this message
and the resulting discussion:

 http://docs.freebsd.org/cgi/mid.cgi?4177C8AD.6060706

Note that this commit removes only the functional part of T/TCP
from the tcp_* related functions in the kernel.  Other features
introduced with RFC1644 are left intact (socket layer changes,
sendmsg(2) on connection oriented protocols)  and are meant to
be reused by a simpler and less intrusive reimplemention of the
previous T/TCP functionality.

Discussed on:	-arch

13 files changed, 34 insertions, 841 deletions

diff --git a/sys/netinet/ip_fw2.c b/sys/netinet/ip_fw2.c
index f963b81..e0bc321 100644
--- a/sys/netinet/ip_fw2.c
+++ b/sys/netinet/ip_fw2.c
@@ -412,11 +412,6 @@ tcpopts_match(struct ip *ip, ipfw_insn *cmd)
 			bits |= IP_FW_TCPOPT_TS;
 			break;
 
-		case TCPOPT_CC:
-		case TCPOPT_CCNEW:
-		case TCPOPT_CCECHO:
-			bits |= IP_FW_TCPOPT_CC;
-			break;
 		}
 	}
 	return (flags_match(cmd, bits));
diff --git a/sys/netinet/tcp.h b/sys/netinet/tcp.h
index cda7257..443b9b2 100644
--- a/sys/netinet/tcp.h
+++ b/sys/netinet/tcp.h
@@ -38,7 +38,6 @@
 #if __BSD_VISIBLE
 
 typedef	u_int32_t tcp_seq;
-typedef u_int32_t tcp_cc;		/* connection count per rfc1644 */
 
 #define tcp6_seq	tcp_seq	/* for KAME src sync over BSD*'s */
 #define tcp6hdr		tcphdr	/* for KAME src sync over BSD*'s */
@@ -94,13 +93,6 @@ struct tcphdr {
 
 #define	MAX_TCPOPTLEN		40	/* Absolute maximum TCP options len */
 
-#define	TCPOPT_CC		11		/* CC options: RFC-1644 */
-#define TCPOPT_CCNEW		12
-#define TCPOPT_CCECHO		13
-#define	   TCPOLEN_CC			6
-#define	   TCPOLEN_CC_APPA		(TCPOLEN_CC+2)
-#define	   TCPOPT_CC_HDR(ccopt)		\
-    (TCPOPT_NOP<<24|TCPOPT_NOP<<16|(ccopt)<<8|TCPOLEN_CC)
 #define	TCPOPT_SIGNATURE		19	/* Keyed MD5: RFC 2385 */
 #define	   TCPOLEN_SIGNATURE		18
 
diff --git a/sys/netinet/tcp_hostcache.c b/sys/netinet/tcp_hostcache.c
index bebd51f..e8fa357 100644
--- a/sys/netinet/tcp_hostcache.c
+++ b/sys/netinet/tcp_hostcache.c
@@ -121,7 +121,6 @@ struct hc_metrics {
 	u_long	rmx_cwnd;	/* congestion window */
 	u_long	rmx_sendpipe;	/* outbound delay-bandwidth product */
 	u_long	rmx_recvpipe;	/* inbound delay-bandwidth product */
-	struct	rmxp_tao rmx_tao; /* TAO cache for T/TCP */
 	/* tcp hostcache internal data */
 	int	rmx_expire;	/* lifetime for object */
 	u_long	rmx_hits;	/* number of hits */
@@ -457,28 +456,6 @@ tcp_hc_getmtu(struct in_conninfo *inc)
 }
 
 /*
- * External function: lookup an entry in the hostcache and fill out the
- * supplied t/tcp tao structure.  Fills in null when no entry was found
- * or a value is not set.
- */
-void
-tcp_hc_gettao(struct in_conninfo *inc, struct rmxp_tao *tao)
-{
-	struct hc_metrics *hc_entry;
-
-	hc_entry = tcp_hc_lookup(inc);
-	if (hc_entry == NULL) {
-		bzero(tao, sizeof(*tao));
-		return;
-	}
-	hc_entry->rmx_hits++;
-	hc_entry->rmx_expire = tcp_hostcache.expire; /* start over again */
-
-	bcopy(&hc_entry->rmx_tao, tao, sizeof(*tao));
-	THC_UNLOCK(&hc_entry->rmx_head->hch_mtx);
-}
-
-/*
  * External function: update the mtu value of an entry in the hostcache.
  * Creates a new entry if none was found.
  */
@@ -598,43 +575,6 @@ tcp_hc_update(struct in_conninfo *inc, struct hc_metrics_lite *hcml)
 }
 
 /*
- * External function: update the t/tcp tao of an entry in the hostcache.
- * Creates a new entry if none was found.
- */
-void
-tcp_hc_updatetao(struct in_conninfo *inc, int field, tcp_cc ccount, u_short mss)
-{
-	struct hc_metrics *hc_entry;
-
-	hc_entry = tcp_hc_lookup(inc);
-	if (hc_entry == NULL) {
-		hc_entry = tcp_hc_insert(inc);
-		if (hc_entry == NULL)
-			return;
-	}
-	hc_entry->rmx_updates++;
-	hc_entry->rmx_expire = tcp_hostcache.expire; /* start over again */
-
-	switch(field) {
-		case TCP_HC_TAO_CC:
-			hc_entry->rmx_tao.tao_cc = ccount;
-			break;
-
-		case TCP_HC_TAO_CCSENT:
-			hc_entry->rmx_tao.tao_ccsent = ccount;
-			break;
-
-		case TCP_HC_TAO_MSSOPT:
-			hc_entry->rmx_tao.tao_mssopt = mss;
-			break;
-	}
-
-	TAILQ_REMOVE(&hc_entry->rmx_head->hch_bucket, hc_entry, rmx_q);
-	TAILQ_INSERT_HEAD(&hc_entry->rmx_head->hch_bucket, hc_entry, rmx_q);
-	THC_UNLOCK(&hc_entry->rmx_head->hch_mtx);
-}
-
-/*
  * Sysctl function: prints the list and values of all hostcache entries in
  * unsorted order.
  */
diff --git a/sys/netinet/tcp_input.c b/sys/netinet/tcp_input.c
index b96b959..50e747d 100644
--- a/sys/netinet/tcp_input.c
+++ b/sys/netinet/tcp_input.c
@@ -98,7 +98,6 @@
 #include <machine/in_cksum.h>
 
 static const int tcprexmtthresh = 3;
-tcp_cc	tcp_ccgen;
 
 struct	tcpstat tcpstat;
 SYSCTL_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RW,
@@ -433,7 +432,6 @@ tcp_input(m, off0)
 	int todrop, acked, ourfinisacked, needoutput = 0;
 	u_long tiwin;
 	struct tcpopt to;		/* options in this segment */
-	struct rmxp_tao tao;		/* our TAO cache entry */
 	int headlocked = 0;
 #ifdef IPFIREWALL_FORWARD
 	struct m_tag *fwd_tag;
@@ -460,7 +458,6 @@ tcp_input(m, off0)
 #ifdef INET6
 	isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0;
 #endif
-	bzero(&tao, sizeof(tao));
 	bzero((char *)&to, sizeof(to));
 
 	tcpstat.tcps_rcvtotal++;
@@ -1090,8 +1087,6 @@ after_listen:
 			tp->ts_recent = to.to_tsval;
 			tp->ts_recent_age = ticks;
 		}
-		if (to.to_flags & (TOF_CC|TOF_CCNEW))
-			tp->t_flags |= TF_RCVD_CC;
 		if (to.to_flags & TOF_MSS)
 			tcp_mss(tp, to.to_mss);
 		if (tp->sack_enable) {
@@ -1132,16 +1127,8 @@ after_listen:
 	    ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) &&
 	    ((to.to_flags & TOF_TS) == 0 ||
 	     TSTMP_GEQ(to.to_tsval, tp->ts_recent)) &&
-	    /*
-	     * Using the CC option is compulsory if once started:
-	     *   the segment is OK if no T/TCP was negotiated or
-	     *   if the segment has a CC option equal to CCrecv
-	     */
-	    ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) ||
-	     ((to.to_flags & TOF_CC) != 0 && to.to_cc == tp->cc_recv)) &&
-	    th->th_seq == tp->rcv_nxt &&
-	    tiwin && tiwin == tp->snd_wnd &&
-	    tp->snd_nxt == tp->snd_max) {
+	     th->th_seq == tp->rcv_nxt && tiwin && tiwin == tp->snd_wnd &&
+	     tp->snd_nxt == tp->snd_max) {
 
 		/*
 		 * If last ACK falls within this segment's sequence numbers,
@@ -1345,26 +1332,11 @@ after_listen:
 	 *	continue processing rest of data/controls, beginning with URG
 	 */
 	case TCPS_SYN_SENT:
-		if (tcp_do_rfc1644)
-			tcp_hc_gettao(&inp->inp_inc, &tao);
-
 		if ((thflags & TH_ACK) &&
 		    (SEQ_LEQ(th->th_ack, tp->iss) ||
 		     SEQ_GT(th->th_ack, tp->snd_max))) {
-			/*
-			 * If we have a cached CCsent for the remote host,
-			 * hence we haven't just crashed and restarted,
-			 * do not send a RST.  This may be a retransmission
-			 * from the other side after our earlier ACK was lost.
-			 * Our new SYN, when it arrives, will serve as the
-			 * needed ACK.
-			 */
-			if (tao.tao_ccsent != 0)
-				goto drop;
-			else {
-				rstreason = BANDLIM_UNLIMITED;
-				goto dropwithreset;
-			}
+			rstreason = BANDLIM_UNLIMITED;
+			goto dropwithreset;
 		}
 		if (thflags & TH_RST) {
 			if (thflags & TH_ACK)
@@ -1374,30 +1346,10 @@ after_listen:
 		if ((thflags & TH_SYN) == 0)
 			goto drop;
 		tp->snd_wnd = th->th_win;	/* initial send window */
-		tp->cc_recv = to.to_cc;		/* foreign CC */
 
 		tp->irs = th->th_seq;
 		tcp_rcvseqinit(tp);
 		if (thflags & TH_ACK) {
-			/*
-			 * Our SYN was acked.  If segment contains CC.ECHO
-			 * option, check it to make sure this segment really
-			 * matches our SYN.  If not, just drop it as old
-			 * duplicate, but send an RST if we're still playing
-			 * by the old rules.  If no CC.ECHO option, make sure
-			 * we don't get fooled into using T/TCP.
-			 */
-			if (to.to_flags & TOF_CCECHO) {
-				if (tp->cc_send != to.to_ccecho) {
-					if (tao.tao_ccsent != 0)
-						goto drop;
-					else {
-						rstreason = BANDLIM_UNLIMITED;
-						goto dropwithreset;
-					}
-				}
-			} else
-				tp->t_flags &= ~TF_RCVD_CC;
 			tcpstat.tcps_connects++;
 			soisconnected(so);
 #ifdef MAC
@@ -1411,10 +1363,6 @@ after_listen:
 				tp->snd_scale = tp->requested_s_scale;
 				tp->rcv_scale = tp->request_r_scale;
 			}
-			/* Segment is acceptable, update cache if undefined. */
-			if (tao.tao_ccsent == 0 && tcp_do_rfc1644)
-				tcp_hc_updatetao(&inp->inp_inc, TCP_HC_TAO_CCSENT, to.to_ccecho, 0);
-
 			tp->rcv_adv += tp->rcv_wnd;
 			tp->snd_una++;		/* SYN is acked */
 			/*
@@ -1455,40 +1403,7 @@ after_listen:
 			 */
 			tp->t_flags |= TF_ACKNOW;
 			callout_stop(tp->tt_rexmt);
-			if (to.to_flags & TOF_CC) {
-				if (tao.tao_cc != 0 &&
-				    CC_GT(to.to_cc, tao.tao_cc)) {
-					/*
-					 * update cache and make transition:
-					 *        SYN-SENT -> ESTABLISHED*
-					 *        SYN-SENT* -> FIN-WAIT-1*
-					 */
-					tao.tao_cc = to.to_cc;
-					tcp_hc_updatetao(&inp->inp_inc,
-						TCP_HC_TAO_CC, to.to_cc, 0);
-					tp->t_starttime = ticks;
-					if (tp->t_flags & TF_NEEDFIN) {
-						tp->t_state = TCPS_FIN_WAIT_1;
-						tp->t_flags &= ~TF_NEEDFIN;
-					} else {
-						tp->t_state = TCPS_ESTABLISHED;
-						callout_reset(tp->tt_keep,
-							      tcp_keepidle,
-							      tcp_timer_keep,
-							      tp);
-					}
-					tp->t_flags |= TF_NEEDSYN;
-				} else
-					tp->t_state = TCPS_SYN_RECEIVED;
-			} else {
-				if (tcp_do_rfc1644) {
-					/* CC.NEW or no option => invalidate cache */
-					tao.tao_cc = 0;
-					tcp_hc_updatetao(&inp->inp_inc,
-						TCP_HC_TAO_CC, to.to_cc, 0);
-				}
-				tp->t_state = TCPS_SYN_RECEIVED;
-			}
+			tp->t_state = TCPS_SYN_RECEIVED;
 		}
 
 trimthenstep6:
@@ -1526,36 +1441,14 @@ trimthenstep6:
 
 	/*
 	 * If the state is LAST_ACK or CLOSING or TIME_WAIT:
-	 *	if segment contains a SYN and CC [not CC.NEW] option:
-	 *              if state == TIME_WAIT and connection duration > MSL,
-	 *                  drop packet and send RST;
-	 *
-	 *		if SEG.CC > CCrecv then is new SYN, and can implicitly
-	 *		    ack the FIN (and data) in retransmission queue.
-	 *                  Complete close and delete TCPCB.  Then reprocess
-	 *                  segment, hoping to find new TCPCB in LISTEN state;
+	 *      do normal processing.
 	 *
-	 *		else must be old SYN; drop it.
-	 *      else do normal processing.
+	 * NB: Leftover from RFC1644 T/TCP.  Cases to be reused later.
 	 */
 	case TCPS_LAST_ACK:
 	case TCPS_CLOSING:
 	case TCPS_TIME_WAIT:
 		KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait"));
-		if ((thflags & TH_SYN) &&
-		    (to.to_flags & TOF_CC) && tp->cc_recv != 0) {
-			if (tp->t_state == TCPS_TIME_WAIT &&
-					(ticks - tp->t_starttime) > tcp_msl) {
-				rstreason = BANDLIM_UNLIMITED;
-				goto dropwithreset;
-			}
-			if (CC_GT(to.to_cc, tp->cc_recv)) {
-				tp = tcp_close(tp);
-				goto findpcb;
-			}
-			else
-				goto drop;
-		}
 		break;  /* continue normal processing */
 	}
 
@@ -1691,16 +1584,6 @@ trimthenstep6:
 	}
 
 	/*
-	 * T/TCP mechanism
-	 *   If T/TCP was negotiated and the segment doesn't have CC,
-	 *   or if its CC is wrong then drop the segment.
-	 *   RST segments do not have to comply with this.
-	 */
-	if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) &&
-	    ((to.to_flags & TOF_CC) == 0 || tp->cc_recv != to.to_cc))
-		goto dropafterack;
-
-	/*
 	 * In the SYN-RECEIVED state, validate that the packet belongs to
 	 * this connection before trimming the data to fit the receive
 	 * window.  Check the sequence number versus IRS since we know
@@ -1867,16 +1750,6 @@ trimthenstep6:
 			tp->rcv_scale = tp->request_r_scale;
 		}
 		/*
-		 * Upon successful completion of 3-way handshake,
-		 * update cache.CC, pass any queued data to the user,
-		 * and advance state appropriately.
-		 */
-		if (tcp_do_rfc1644) {
-			tao.tao_cc = tp->cc_recv;
-			tcp_hc_updatetao(&inp->inp_inc, TCP_HC_TAO_CC,
-					 tp->cc_recv, 0);
-		}
-		/*
 		 * Make transitions:
 		 *      SYN-RECEIVED  -> ESTABLISHED
 		 *      SYN-RECEIVED* -> FIN-WAIT-1
@@ -2682,34 +2555,6 @@ tcp_dooptions(tp, to, cp, cnt, is_syn, th)
 			    (char *)&to->to_tsecr, sizeof(to->to_tsecr));
 			to->to_tsecr = ntohl(to->to_tsecr);
 			break;
-		case TCPOPT_CC:
-			if (optlen != TCPOLEN_CC)
-				continue;
-			to->to_flags |= TOF_CC;
-			bcopy((char *)cp + 2,
-			    (char *)&to->to_cc, sizeof(to->to_cc));
-			to->to_cc = ntohl(to->to_cc);
-			break;
-		case TCPOPT_CCNEW:
-			if (optlen != TCPOLEN_CC)
-				continue;
-			if (!is_syn)
-				continue;
-			to->to_flags |= TOF_CCNEW;
-			bcopy((char *)cp + 2,
-			    (char *)&to->to_cc, sizeof(to->to_cc));
-			to->to_cc = ntohl(to->to_cc);
-			break;
-		case TCPOPT_CCECHO:
-			if (optlen != TCPOLEN_CC)
-				continue;
-			if (!is_syn)
-				continue;
-			to->to_flags |= TOF_CCECHO;
-			bcopy((char *)cp + 2,
-			    (char *)&to->to_ccecho, sizeof(to->to_ccecho));
-			to->to_ccecho = ntohl(to->to_ccecho);
-			break;
 #ifdef TCP_SIGNATURE
 		/*
 		 * XXX In order to reply to a host which has set the
@@ -2900,7 +2745,6 @@ tcp_mss(tp, offer)
 	struct inpcb *inp = tp->t_inpcb;
 	struct socket *so;
 	struct hc_metrics_lite metrics;
-	struct rmxp_tao tao;
 	int origoffer = offer;
 #ifdef INET6
 	int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0;
@@ -2910,7 +2754,6 @@ tcp_mss(tp, offer)
 #else
 	const size_t min_protoh = sizeof(struct tcpiphdr);
 #endif
-	bzero(&tao, sizeof(tao));
 
 	/* initialize */
 #ifdef INET6
@@ -2947,13 +2790,8 @@ tcp_mss(tp, offer)
 
 		case -1:
 			/*
-			 * Offer == -1 means that we didn't receive SYN yet,
-			 * use cached value in that case;
+			 * Offer == -1 means that we didn't receive SYN yet.
 			 */
-			if (tcp_do_rfc1644)
-				tcp_hc_gettao(&inp->inp_inc, &tao);
-			if (tao.tao_mssopt != 0)
-				offer = tao.tao_mssopt;
 			/* FALLTHROUGH */
 
 		default:
@@ -2969,9 +2807,6 @@ tcp_mss(tp, offer)
 			 * funny things may happen in tcp_output.
 			 */
 			offer = max(offer, 64);
-			if (tcp_do_rfc1644)
-				tcp_hc_updatetao(&inp->inp_inc,
-						 TCP_HC_TAO_MSSOPT, 0, offer);
 	}
 
 	/*
@@ -3013,18 +2848,13 @@ tcp_mss(tp, offer)
 	tp->t_maxopd = mss;
 
 	/*
-	 * In case of T/TCP, origoffer==-1 indicates, that no segments
-	 * were received yet.  In this case we just guess, otherwise
-	 * we do the same as before T/TCP.
+	 * origoffer==-1 indicates, that no segments were received yet.
+	 * In this case we just guess.
 	 */
 	if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&
 	    (origoffer == -1 ||
 	     (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP))
 		mss -= TCPOLEN_TSTAMP_APPA;
-	if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC &&
-	    (origoffer == -1 ||
-	     (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC))
-		mss -= TCPOLEN_CC_APPA;
 	tp->t_maxseg = mss;
 
 #if	(MCLBYTES & (MCLBYTES - 1)) == 0
@@ -3251,27 +3081,6 @@ tcp_timewait(tw, to, th, m, tlen)
 	if (thflags & TH_RST)
 		goto drop;
 
-	/*
-	 * If segment contains a SYN and CC [not CC.NEW] option:
-	 *	if connection duration > MSL, drop packet and send RST;
-	 *
-	 *	if SEG.CC > CCrecv then is new SYN.
-	 *	    Complete close and delete TCPCB.  Then reprocess
-	 *	    segment, hoping to find new TCPCB in LISTEN state;
-	 *
-	 *	else must be old SYN; drop it.
-	 * else do normal processing.
-	 */
-	if ((thflags & TH_SYN) && (to->to_flags & TOF_CC) && tw->cc_recv != 0) {
-		if ((ticks - tw->t_starttime) > tcp_msl)
-			goto reset;
-		if (CC_GT(to->to_cc, tw->cc_recv)) {
-			(void) tcp_twclose(tw, 0);
-			return (1);
-		}
-		goto drop;
-	}
-
 #if 0
 /* PAWS not needed at the moment */
 	/*
@@ -3323,7 +3132,6 @@ tcp_timewait(tw, to, th, m, tlen)
 		tcp_twrespond(tw, TH_ACK);
 	goto drop;
 
-reset:
 	/*
 	 * Generate a RST, dropping incoming segment.
 	 * Make ACK acceptable to originator of segment.
diff --git a/sys/netinet/tcp_output.c b/sys/netinet/tcp_output.c
index 2ad8ccb..0e36553 100644
--- a/sys/netinet/tcp_output.c
+++ b/sys/netinet/tcp_output.c
@@ -129,12 +129,10 @@ tcp_output(struct tcpcb *tp)
 #if 0
 	int maxburst = TCP_MAXBURST;
 #endif
-	struct rmxp_tao tao;
 #ifdef INET6
 	struct ip6_hdr *ip6 = NULL;
 	int isipv6;
 
-	bzero(&tao, sizeof(tao));
 	isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0;
 #endif
 
@@ -329,22 +327,14 @@ after_sack_rexmit:
 	if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) {
 		flags &= ~TH_SYN;
 		off--, len++;
-		if (tcp_do_rfc1644)
-			tcp_hc_gettao(&tp->t_inpcb->inp_inc, &tao);
-		if (len > 0 && tp->t_state == TCPS_SYN_SENT &&
-		     tao.tao_ccsent == 0)
-			goto just_return;
 	}
 
 	/*
-	 * Be careful not to send data and/or FIN on SYN segments
-	 * in cases when no CC option will be sent.
+	 * Be careful not to send data and/or FIN on SYN segments.
 	 * This measure is needed to prevent interoperability problems
 	 * with not fully conformant TCP implementations.
 	 */
-	if ((flags & TH_SYN) &&
-	    ((tp->t_flags & TF_NOOPT) || !(tp->t_flags & TF_REQ_CC) ||
-	     ((flags & TH_ACK) && !(tp->t_flags & TF_RCVD_CC)))) {
+	if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) {
 		len = 0;
 		flags &= ~TH_FIN;
 	}
@@ -613,76 +603,6 @@ send:
 		*olp = htonl(TCPOPT_SACK_HDR|(TCPOLEN_SACK*count+2));
 		optlen += TCPOLEN_SACK*count + 4; /* including leading NOPs */
 	}
-	/*
-	 * Send `CC-family' options if our side wants to use them (TF_REQ_CC),
-	 * options are allowed (!TF_NOOPT) and it's not a RST.
-	 */
-	if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC &&
-	     (flags & TH_RST) == 0) {
-		switch (flags & (TH_SYN|TH_ACK)) {
-		/*
-		 * This is a normal ACK, send CC if we received CC before
-		 * from our peer.
-		 */
-		case TH_ACK:
-			if (!(tp->t_flags & TF_RCVD_CC))
-				break;
-			/*FALLTHROUGH*/
-
-		/*
-		 * We can only get here in T/TCP's SYN_SENT* state, when
-		 * we're a sending a non-SYN segment without waiting for
-		 * the ACK of our SYN.  A check above assures that we only
-		 * do this if our peer understands T/TCP.
-		 */
-		case 0:
-			opt[optlen++] = TCPOPT_NOP;
-			opt[optlen++] = TCPOPT_NOP;
-			opt[optlen++] = TCPOPT_CC;
-			opt[optlen++] = TCPOLEN_CC;
-			*(u_int32_t *)&opt[optlen] = htonl(tp->cc_send);
-
-			optlen += 4;
-			break;
-
-		/*
-		 * This is our initial SYN, check whether we have to use
-		 * CC or CC.new.
-		 */
-		case TH_SYN:
-			opt[optlen++] = TCPOPT_NOP;
-			opt[optlen++] = TCPOPT_NOP;
-			opt[optlen++] = tp->t_flags & TF_SENDCCNEW ?
-						TCPOPT_CCNEW : TCPOPT_CC;
-			opt[optlen++] = TCPOLEN_CC;
-			*(u_int32_t *)&opt[optlen] = htonl(tp->cc_send);
-			optlen += 4;
-			break;
-
-		/*
-		 * This is a SYN,ACK; send CC and CC.echo if we received
-		 * CC from our peer.
-		 */
-		case (TH_SYN|TH_ACK):
-			if (tp->t_flags & TF_RCVD_CC) {
-				opt[optlen++] = TCPOPT_NOP;
-				opt[optlen++] = TCPOPT_NOP;
-				opt[optlen++] = TCPOPT_CC;
-				opt[optlen++] = TCPOLEN_CC;
-				*(u_int32_t *)&opt[optlen] =
-					htonl(tp->cc_send);
-				optlen += 4;
-				opt[optlen++] = TCPOPT_NOP;
-				opt[optlen++] = TCPOPT_NOP;
-				opt[optlen++] = TCPOPT_CCECHO;
-				opt[optlen++] = TCPOLEN_CC;
-				*(u_int32_t *)&opt[optlen] =
-					htonl(tp->cc_recv);
-				optlen += 4;
-			}
-			break;
-		}
-	}
 
 #ifdef TCP_SIGNATURE
 #ifdef INET6
diff --git a/sys/netinet/tcp_reass.c b/sys/netinet/tcp_reass.c
index b96b959..50e747d 100644
--- a/sys/netinet/tcp_reass.c
+++ b/sys/netinet/tcp_reass.c
@@ -98,7 +98,6 @@
 #include <machine/in_cksum.h>
 
 static const int tcprexmtthresh = 3;
-tcp_cc	tcp_ccgen;
 
 struct	tcpstat tcpstat;
 SYSCTL_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RW,
@@ -433,7 +432,6 @@ tcp_input(m, off0)
 	int todrop, acked, ourfinisacked, needoutput = 0;
 	u_long tiwin;
 	struct tcpopt to;		/* options in this segment */
-	struct rmxp_tao tao;		/* our TAO cache entry */
 	int headlocked = 0;
 #ifdef IPFIREWALL_FORWARD
 	struct m_tag *fwd_tag;
@@ -460,7 +458,6 @@ tcp_input(m, off0)
 #ifdef INET6
 	isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0;
 #endif
-	bzero(&tao, sizeof(tao));
 	bzero((char *)&to, sizeof(to));
 
 	tcpstat.tcps_rcvtotal++;
@@ -1090,8 +1087,6 @@ after_listen:
 			tp->ts_recent = to.to_tsval;
 			tp->ts_recent_age = ticks;
 		}
-		if (to.to_flags & (TOF_CC|TOF_CCNEW))
-			tp->t_flags |= TF_RCVD_CC;
 		if (to.to_flags & TOF_MSS)
 			tcp_mss(tp, to.to_mss);
 		if (tp->sack_enable) {
@@ -1132,16 +1127,8 @@ after_listen:
 	    ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) &&
 	    ((to.to_flags & TOF_TS) == 0 ||
 	     TSTMP_GEQ(to.to_tsval, tp->ts_recent)) &&
-	    /*
-	     * Using the CC option is compulsory if once started:
-	     *   the segment is OK if no T/TCP was negotiated or
-	     *   if the segment has a CC option equal to CCrecv
-	     */
-	    ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) ||
-	     ((to.to_flags & TOF_CC) != 0 && to.to_cc == tp->cc_recv)) &&
-	    th->th_seq == tp->rcv_nxt &&
-	    tiwin && tiwin == tp->snd_wnd &&
-	    tp->snd_nxt == tp->snd_max) {
+	     th->th_seq == tp->rcv_nxt && tiwin && tiwin == tp->snd_wnd &&
+	     tp->snd_nxt == tp->snd_max) {
 
 		/*
 		 * If last ACK falls within this segment's sequence numbers,
@@ -1345,26 +1332,11 @@ after_listen:
 	 *	continue processing rest of data/controls, beginning with URG
 	 */
 	case TCPS_SYN_SENT:
-		if (tcp_do_rfc1644)
-			tcp_hc_gettao(&inp->inp_inc, &tao);
-
 		if ((thflags & TH_ACK) &&
 		    (SEQ_LEQ(th->th_ack, tp->iss) ||
 		     SEQ_GT(th->th_ack, tp->snd_max))) {
-			/*
-			 * If we have a cached CCsent for the remote host,
-			 * hence we haven't just crashed and restarted,
-			 * do not send a RST.  This may be a retransmission
-			 * from the other side after our earlier ACK was lost.
-			 * Our new SYN, when it arrives, will serve as the
-			 * needed ACK.
-			 */
-			if (tao.tao_ccsent != 0)
-				goto drop;
-			else {
-				rstreason = BANDLIM_UNLIMITED;
-				goto dropwithreset;
-			}
+			rstreason = BANDLIM_UNLIMITED;
+			goto dropwithreset;
 		}
 		if (thflags & TH_RST) {
 			if (thflags & TH_ACK)
@@ -1374,30 +1346,10 @@ after_listen:
 		if ((thflags & TH_SYN) == 0)
 			goto drop;
 		tp->snd_wnd = th->th_win;	/* initial send window */
-		tp->cc_recv = to.to_cc;		/* foreign CC */
 
 		tp->irs = th->th_seq;
 		tcp_rcvseqinit(tp);
 		if (thflags & TH_ACK) {
-			/*
-			 * Our SYN was acked.  If segment contains CC.ECHO
-			 * option, check it to make sure this segment really
-			 * matches our SYN.  If not, just drop it as old
-			 * duplicate, but send an RST if we're still playing
-			 * by the old rules.  If no CC.ECHO option, make sure
-			 * we don't get fooled into using T/TCP.
-			 */
-			if (to.to_flags & TOF_CCECHO) {
-				if (tp->cc_send != to.to_ccecho) {
-					if (tao.tao_ccsent != 0)
-						goto drop;
-					else {
-						rstreason = BANDLIM_UNLIMITED;
-						goto dropwithreset;
-					}
-				}
-			} else
-				tp->t_flags &= ~TF_RCVD_CC;
 			tcpstat.tcps_connects++;
 			soisconnected(so);
 #ifdef MAC
@@ -1411,10 +1363,6 @@ after_listen:
 				tp->snd_scale = tp->requested_s_scale;
 				tp->rcv_scale = tp->request_r_scale;
 			}
-			/* Segment is acceptable, update cache if undefined. */
-			if (tao.tao_ccsent == 0 && tcp_do_rfc1644)
-				tcp_hc_updatetao(&inp->inp_inc, TCP_HC_TAO_CCSENT, to.to_ccecho, 0);
-
 			tp->rcv_adv += tp->rcv_wnd;
 			tp->snd_una++;		/* SYN is acked */
 			/*
@@ -1455,40 +1403,7 @@ after_listen:
 			 */
 			tp->t_flags |= TF_ACKNOW;
 			callout_stop(tp->tt_rexmt);
-			if (to.to_flags & TOF_CC) {
-				if (tao.tao_cc != 0 &&
-				    CC_GT(to.to_cc, tao.tao_cc)) {
-					/*
-					 * update cache and make transition:
-					 *        SYN-SENT -> ESTABLISHED*
-					 *        SYN-SENT* -> FIN-WAIT-1*
-					 */
-					tao.tao_cc = to.to_cc;
-					tcp_hc_updatetao(&inp->inp_inc,
-						TCP_HC_TAO_CC, to.to_cc, 0);
-					tp->t_starttime = ticks;
-					if (tp->t_flags & TF_NEEDFIN) {
-						tp->t_state = TCPS_FIN_WAIT_1;
-						tp->t_flags &= ~TF_NEEDFIN;
-					} else {
-						tp->t_state = TCPS_ESTABLISHED;
-						callout_reset(tp->tt_keep,
-							      tcp_keepidle,
-							      tcp_timer_keep,
-							      tp);
-					}
-					tp->t_flags |= TF_NEEDSYN;
-				} else
-					tp->t_state = TCPS_SYN_RECEIVED;
-			} else {
-				if (tcp_do_rfc1644) {
-					/* CC.NEW or no option => invalidate cache */
-					tao.tao_cc = 0;
-					tcp_hc_updatetao(&inp->inp_inc,
-						TCP_HC_TAO_CC, to.to_cc, 0);
-				}
-				tp->t_state = TCPS_SYN_RECEIVED;
-			}
+			tp->t_state = TCPS_SYN_RECEIVED;
 		}
 
 trimthenstep6:
@@ -1526,36 +1441,14 @@ trimthenstep6:
 
 	/*
 	 * If the state is LAST_ACK or CLOSING or TIME_WAIT:
-	 *	if segment contains a SYN and CC [not CC.NEW] option:
-	 *              if state == TIME_WAIT and connection duration > MSL,
-	 *                  drop packet and send RST;
-	 *
-	 *		if SEG.CC > CCrecv then is new SYN, and can implicitly
-	 *		    ack the FIN (and data) in retransmission queue.
-	 *                  Complete close and delete TCPCB.  Then reprocess
-	 *                  segment, hoping to find new TCPCB in LISTEN state;
+	 *      do normal processing.
 	 *
-	 *		else must be old SYN; drop it.
-	 *      else do normal processing.
+	 * NB: Leftover from RFC1644 T/TCP.  Cases to be reused later.
 	 */
 	case TCPS_LAST_ACK:
 	case TCPS_CLOSING:
 	case TCPS_TIME_WAIT:
 		KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait"));
-		if ((thflags & TH_SYN) &&
-		    (to.to_flags & TOF_CC) && tp->cc_recv != 0) {
-			if (tp->t_state == TCPS_TIME_WAIT &&
-					(ticks - tp->t_starttime) > tcp_msl) {
-				rstreason = BANDLIM_UNLIMITED;
-				goto dropwithreset;
-			}
-			if (CC_GT(to.to_cc, tp->cc_recv)) {
-				tp = tcp_close(tp);
-				goto findpcb;
-			}
-			else
-				goto drop;
-		}
 		break;  /* continue normal processing */
 	}
 
@@ -1691,16 +1584,6 @@ trimthenstep6:
 	}
 
 	/*
-	 * T/TCP mechanism
-	 *   If T/TCP was negotiated and the segment doesn't have CC,
-	 *   or if its CC is wrong then drop the segment.
-	 *   RST segments do not have to comply with this.
-	 */
-	if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) &&
-	    ((to.to_flags & TOF_CC) == 0 || tp->cc_recv != to.to_cc))
-		goto dropafterack;
-
-	/*
 	 * In the SYN-RECEIVED state, validate that the packet belongs to
 	 * this connection before trimming the data to fit the receive
 	 * window.  Check the sequence number versus IRS since we know
@@ -1867,16 +1750,6 @@ trimthenstep6:
 			tp->rcv_scale = tp->request_r_scale;
 		}
 		/*
-		 * Upon successful completion of 3-way handshake,
-		 * update cache.CC, pass any queued data to the user,
-		 * and advance state appropriately.
-		 */
-		if (tcp_do_rfc1644) {
-			tao.tao_cc = tp->cc_recv;
-			tcp_hc_updatetao(&inp->inp_inc, TCP_HC_TAO_CC,
-					 tp->cc_recv, 0);
-		}
-		/*
 		 * Make transitions:
 		 *      SYN-RECEIVED  -> ESTABLISHED
 		 *      SYN-RECEIVED* -> FIN-WAIT-1
@@ -2682,34 +2555,6 @@ tcp_dooptions(tp, to, cp, cnt, is_syn, th)
 			    (char *)&to->to_tsecr, sizeof(to->to_tsecr));
 			to->to_tsecr = ntohl(to->to_tsecr);
 			break;
-		case TCPOPT_CC:
-			if (optlen != TCPOLEN_CC)
-				continue;
-			to->to_flags |= TOF_CC;
-			bcopy((char *)cp + 2,
-			    (char *)&to->to_cc, sizeof(to->to_cc));
-			to->to_cc = ntohl(to->to_cc);
-			break;
-		case TCPOPT_CCNEW:
-			if (optlen != TCPOLEN_CC)
-				continue;
-			if (!is_syn)
-				continue;
-			to->to_flags |= TOF_CCNEW;
-			bcopy((char *)cp + 2,
-			    (char *)&to->to_cc, sizeof(to->to_cc));
-			to->to_cc = ntohl(to->to_cc);
-			break;
-		case TCPOPT_CCECHO:
-			if (optlen != TCPOLEN_CC)
-				continue;
-			if (!is_syn)
-				continue;
-			to->to_flags |= TOF_CCECHO;
-			bcopy((char *)cp + 2,
-			    (char *)&to->to_ccecho, sizeof(to->to_ccecho));
-			to->to_ccecho = ntohl(to->to_ccecho);
-			break;
 #ifdef TCP_SIGNATURE
 		/*
 		 * XXX In order to reply to a host which has set the
@@ -2900,7 +2745,6 @@ tcp_mss(tp, offer)
 	struct inpcb *inp = tp->t_inpcb;
 	struct socket *so;
 	struct hc_metrics_lite metrics;
-	struct rmxp_tao tao;
 	int origoffer = offer;
 #ifdef INET6
 	int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0;
@@ -2910,7 +2754,6 @@ tcp_mss(tp, offer)
 #else
 	const size_t min_protoh = sizeof(struct tcpiphdr);
 #endif
-	bzero(&tao, sizeof(tao));
 
 	/* initialize */
 #ifdef INET6
@@ -2947,13 +2790,8 @@ tcp_mss(tp, offer)
 
 		case -1:
 			/*
-			 * Offer == -1 means that we didn't receive SYN yet,
-			 * use cached value in that case;
+			 * Offer == -1 means that we didn't receive SYN yet.
 			 */
-			if (tcp_do_rfc1644)
-				tcp_hc_gettao(&inp->inp_inc, &tao);
-			if (tao.tao_mssopt != 0)
-				offer = tao.tao_mssopt;
 			/* FALLTHROUGH */
 
 		default:
@@ -2969,9 +2807,6 @@ tcp_mss(tp, offer)
 			 * funny things may happen in tcp_output.
 			 */
 			offer = max(offer, 64);
-			if (tcp_do_rfc1644)
-				tcp_hc_updatetao(&inp->inp_inc,
-						 TCP_HC_TAO_MSSOPT, 0, offer);
 	}
 
 	/*
@@ -3013,18 +2848,13 @@ tcp_mss(tp, offer)
 	tp->t_maxopd = mss;
 
 	/*
-	 * In case of T/TCP, origoffer==-1 indicates, that no segments
-	 * were received yet.  In this case we just guess, otherwise
-	 * we do the same as before T/TCP.
+	 * origoffer==-1 indicates, that no segments were received yet.
+	 * In this case we just guess.
 	 */
 	if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&
 	    (origoffer == -1 ||
 	     (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP))
 		mss -= TCPOLEN_TSTAMP_APPA;
-	if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC &&
-	    (origoffer == -1 ||
-	     (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC))
-		mss -= TCPOLEN_CC_APPA;
 	tp->t_maxseg = mss;
 
 #if	(MCLBYTES & (MCLBYTES - 1)) == 0
@@ -3251,27 +3081,6 @@ tcp_timewait(tw, to, th, m, tlen)
 	if (thflags & TH_RST)
 		goto drop;
 
-	/*
-	 * If segment contains a SYN and CC [not CC.NEW] option:
-	 *	if connection duration > MSL, drop packet and send RST;
-	 *
-	 *	if SEG.CC > CCrecv then is new SYN.
-	 *	    Complete close and delete TCPCB.  Then reprocess
-	 *	    segment, hoping to find new TCPCB in LISTEN state;
-	 *
-	 *	else must be old SYN; drop it.
-	 * else do normal processing.
-	 */
-	if ((thflags & TH_SYN) && (to->to_flags & TOF_CC) && tw->cc_recv != 0) {
-		if ((ticks - tw->t_starttime) > tcp_msl)
-			goto reset;
-		if (CC_GT(to->to_cc, tw->cc_recv)) {
-			(void) tcp_twclose(tw, 0);
-			return (1);
-		}
-		goto drop;
-	}
-
 #if 0
 /* PAWS not needed at the moment */
 	/*
@@ -3323,7 +3132,6 @@ tcp_timewait(tw, to, th, m, tlen)
 		tcp_twrespond(tw, TH_ACK);
 	goto drop;
 
-reset:
 	/*
 	 * Generate a RST, dropping incoming segment.
 	 * Make ACK acceptable to originator of segment.
diff --git a/sys/netinet/tcp_seq.h b/sys/netinet/tcp_seq.h
index c029b12..d2bf224 100644
--- a/sys/netinet/tcp_seq.h
+++ b/sys/netinet/tcp_seq.h
@@ -77,7 +77,4 @@
 #define TCP_PAWS_IDLE	(24 * 24 * 60 * 60 * hz)
 					/* timestamp wrap-around time */
 
-#ifdef _KERNEL
-extern tcp_cc	tcp_ccgen;		/* global connection count */
-#endif /* _KERNEL */
 #endif /* _NETINET_TCP_SEQ_H_ */
diff --git a/sys/netinet/tcp_subr.c b/sys/netinet/tcp_subr.c
index 03610b3..0c91656 100644
--- a/sys/netinet/tcp_subr.c
+++ b/sys/netinet/tcp_subr.c
@@ -155,10 +155,6 @@ int	tcp_do_rfc1323 = 1;
 SYSCTL_INT(_net_inet_tcp, TCPCTL_DO_RFC1323, rfc1323, CTLFLAG_RW,
     &tcp_do_rfc1323 , 0, "Enable rfc1323 (high performance TCP) extensions");
 
-int	tcp_do_rfc1644 = 0;
-SYSCTL_INT(_net_inet_tcp, TCPCTL_DO_RFC1644, rfc1644, CTLFLAG_RW,
-    &tcp_do_rfc1644 , 0, "Enable rfc1644 (TTCP) extensions");
-
 static int	tcp_tcbhashsize = 0;
 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tcbhashsize, CTLFLAG_RDTUN,
      &tcp_tcbhashsize, 0, "Size of TCP control-block hashtable");
@@ -246,8 +242,6 @@ tcp_init()
 {
 	int hashsize = TCBHASHSIZE;
 
-	tcp_ccgen = 1;
-
 	tcp_delacktime = TCPTV_DELACK;
 	tcp_keepinit = TCPTV_KEEP_INIT;
 	tcp_keepidle = TCPTV_KEEP_IDLE;
@@ -613,8 +607,6 @@ tcp_newtcpcb(inp)
 
 	if (tcp_do_rfc1323)
 		tp->t_flags = (TF_REQ_SCALE|TF_REQ_TSTMP);
-	if (tcp_do_rfc1644)
-		tp->t_flags |= TF_REQ_CC;
 	tp->sack_enable = tcp_do_sack;
 	tp->t_inpcb = inp;	/* XXX */
 	/*
@@ -1409,7 +1401,6 @@ tcp_mtudisc(inp, errno)
 	int errno;
 {
 	struct tcpcb *tp = intotcpcb(inp);
-	struct rmxp_tao tao;
 	struct socket *so = inp->inp_socket;
 	u_int maxmtu;
 	u_int romtu;
@@ -1417,7 +1408,6 @@ tcp_mtudisc(inp, errno)
 #ifdef INET6
 	int isipv6;
 #endif /* INET6 */
-	bzero(&tao, sizeof(tao));
 
 	if (tp != NULL) {
 #ifdef INET6
@@ -1452,11 +1442,6 @@ tcp_mtudisc(inp, errno)
 #endif /* INET6 */
 			;
 
-		if (tcp_do_rfc1644) {
-			tcp_hc_gettao(&inp->inp_inc, &tao);
-			if (tao.tao_mssopt)
-				mss = min(mss, tao.tao_mssopt);
-		}
 		/*
 		 * XXX - The above conditional probably violates the TCP
 		 * spec.  The problem is that, since we don't know the
@@ -1481,9 +1466,6 @@ tcp_mtudisc(inp, errno)
 		if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&
 		    (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)
 			mss -= TCPOLEN_TSTAMP_APPA;
-		if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC &&
-		    (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC)
-			mss -= TCPOLEN_CC_APPA;
 #if	(MCLBYTES & (MCLBYTES - 1)) == 0
 		if (mss > MCLBYTES)
 			mss &= ~(MCLBYTES-1);
@@ -1659,8 +1641,6 @@ tcp_twstart(tp)
 	tw->rcv_nxt = tp->rcv_nxt;
 	tw->iss     = tp->iss;
 	tw->irs     = tp->irs;
-	tw->cc_recv = tp->cc_recv;
-	tw->cc_send = tp->cc_send;
 	tw->t_starttime = tp->t_starttime;
 	tw->tw_time = 0;
 
@@ -1669,15 +1649,8 @@ tcp_twstart(tp)
  * be used for fin-wait-2 state also, then we may need
  * a ts_recent from the last segment.
  */
-	/* Shorten TIME_WAIT [RFC-1644, p.28] */
-	if (tp->cc_recv != 0 && (ticks - tp->t_starttime) < tcp_msl) {
-		tw_time = tp->t_rxtcur * TCPTV_TWTRUNC;
-		/* For T/TCP client, force ACK now. */
-		acknow = 1;
-	} else {
-		tw_time = 2 * tcp_msl;
-		acknow = tp->t_flags & TF_ACKNOW;
-	}
+	tw_time = 2 * tcp_msl;
+	acknow = tp->t_flags & TF_ACKNOW;
 	tcp_discardcb(tp);
 	so = inp->inp_socket;
 	ACCEPT_LOCK();
@@ -1803,16 +1776,6 @@ tcp_twrespond(struct tcptw *tw, int flags)
 		optp += TCPOLEN_TSTAMP_APPA;
 	}
 
-	/*
-	 * Send `CC-family' options if needed, and it's not a RST.
-	 */
-	if (tw->cc_recv != 0 && flags == TH_ACK) {
-		u_int32_t *lp = (u_int32_t *)optp;
-
-		*lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CC));
-		*lp   = htonl(tw->cc_send);
-		optp += TCPOLEN_CC_APPA;
-	}
 	optlen = optp - (u_int8_t *)(th + 1);
 
 	m->m_len = hdrlen + optlen;
diff --git a/sys/netinet/tcp_syncache.c b/sys/netinet/tcp_syncache.c
index e648fc9..ffb3cc7 100644
--- a/sys/netinet/tcp_syncache.c
+++ b/sys/netinet/tcp_syncache.c
@@ -694,16 +694,6 @@ syncache_socket(sc, lso, m)
 		tp->ts_recent = sc->sc_tsrecent;
 		tp->ts_recent_age = ticks;
 	}
-	if (sc->sc_flags & SCF_CC) {
-		/*
-		 * Initialization of the tcpcb for transaction;
-		 *   set SND.WND = SEG.WND,
-		 *   initialize CCsend and CCrecv.
-		 */
-		tp->t_flags |= TF_REQ_CC|TF_RCVD_CC;
-		tp->cc_send = sc->sc_cc_send;
-		tp->cc_recv = sc->sc_cc_recv;
-	}
 #ifdef TCP_SIGNATURE
 	if (sc->sc_flags & SCF_SIGNATURE)
 		tp->t_flags |= TF_SIGNATURE;
@@ -831,7 +821,6 @@ syncache_add(inc, to, th, sop, m)
 	struct syncache *sc = NULL;
 	struct syncache_head *sch;
 	struct mbuf *ipopts = NULL;
-	struct rmxp_tao tao;
 	u_int32_t flowtmp;
 	int i, win;
 
@@ -839,7 +828,6 @@ syncache_add(inc, to, th, sop, m)
 
 	so = *sop;
 	tp = sototcpcb(so);
-	bzero(&tao, sizeof(tao));
 
 	/*
 	 * Remember the IP options, if any.
@@ -989,17 +977,6 @@ syncache_add(inc, to, th, sop, m)
 			sc->sc_flags |= SCF_WINSCALE;
 		}
 	}
-	if (tcp_do_rfc1644) {
-		/*
-		 * A CC or CC.new option received in a SYN makes
-		 * it ok to send CC in subsequent segments.
-		 */
-		if (to->to_flags & (TOF_CC|TOF_CCNEW)) {
-			sc->sc_cc_recv = to->to_cc;
-			sc->sc_cc_send = CC_INC(tcp_ccgen);
-			sc->sc_flags |= SCF_CC;
-		}
-	}
 	if (tp->t_flags & TF_NOOPT)
 		sc->sc_flags = SCF_NOOPT;
 #ifdef TCP_SIGNATURE
@@ -1018,58 +995,7 @@ syncache_add(inc, to, th, sop, m)
 		sc->sc_flags |= SCF_SACK;
 
 	/*
-	 * XXX
-	 * We have the option here of not doing TAO (even if the segment
-	 * qualifies) and instead fall back to a normal 3WHS via the syncache.
-	 * This allows us to apply synflood protection to TAO-qualifying SYNs
-	 * also. However, there should be a hueristic to determine when to
-	 * do this, and is not present at the moment.
-	 */
-
-	/*
-	 * Perform TAO test on incoming CC (SEG.CC) option, if any.
-	 * - compare SEG.CC against cached CC from the same host, if any.
-	 * - if SEG.CC > chached value, SYN must be new and is accepted
-	 *	immediately: save new CC in the cache, mark the socket
-	 *	connected, enter ESTABLISHED state, turn on flag to
-	 *	send a SYN in the next segment.
-	 *	A virtual advertised window is set in rcv_adv to
-	 *	initialize SWS prevention.  Then enter normal segment
-	 *	processing: drop SYN, process data and FIN.
-	 * - otherwise do a normal 3-way handshake.
-	 */
-	if (tcp_do_rfc1644)
-		tcp_hc_gettao(&sc->sc_inc, &tao);
-
-	if ((to->to_flags & TOF_CC) != 0) {
-		if (((tp->t_flags & TF_NOPUSH) != 0) &&
-		    sc->sc_flags & SCF_CC && tao.tao_cc != 0 &&
-		    CC_GT(to->to_cc, tao.tao_cc)) {
-			sc->sc_rxtslot = 0;
-			so = syncache_socket(sc, *sop, m);
-			if (so != NULL) {
-				tao.tao_cc = to->to_cc;
-				tcp_hc_updatetao(&sc->sc_inc, TCP_HC_TAO_CC,
-						 tao.tao_cc, 0);
-				*sop = so;
-			}
-			syncache_free(sc);
-			return (so != NULL);
-		}
-	} else {
-		/*
-		 * No CC option, but maybe CC.NEW: invalidate cached value.
-		 */
-		if (tcp_do_rfc1644) {
-			tao.tao_cc = 0;
-			tcp_hc_updatetao(&sc->sc_inc, TCP_HC_TAO_CC,
-					 tao.tao_cc, 0);
-		}
-	}
-
-	/*
-	 * TAO test failed or there was no CC option,
-	 *    do a standard 3-way handshake.
+	 * Do a standard 3-way handshake.
 	 */
 #ifdef TCPDEBUG
 	if (syncache_respond(sc, m, so) == 0) {
@@ -1127,8 +1053,7 @@ syncache_respond(sc, m)
 	} else {
 		optlen = TCPOLEN_MAXSEG +
 		    ((sc->sc_flags & SCF_WINSCALE) ? 4 : 0) +
-		    ((sc->sc_flags & SCF_TIMESTAMP) ? TCPOLEN_TSTAMP_APPA : 0) +
-		    ((sc->sc_flags & SCF_CC) ? TCPOLEN_CC_APPA * 2 : 0);
+		    ((sc->sc_flags & SCF_TIMESTAMP) ? TCPOLEN_TSTAMP_APPA : 0);
 #ifdef TCP_SIGNATURE
 		optlen += (sc->sc_flags & SCF_SIGNATURE) ?
 		    TCPOLEN_SIGNATURE + 2 : 0;
@@ -1240,19 +1165,6 @@ syncache_respond(sc, m)
 			optp += TCPOLEN_TSTAMP_APPA;
 		}
 
-		/*
-		 * Send CC and CC.echo if we received CC from our peer.
-		 */
-		if (sc->sc_flags & SCF_CC) {
-			u_int32_t *lp = (u_int32_t *)(optp);
-
-			*lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CC));
-			*lp++ = htonl(sc->sc_cc_send);
-			*lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CCECHO));
-			*lp   = htonl(sc->sc_cc_recv);
-			optp += TCPOLEN_CC_APPA * 2;
-		}
-
 #ifdef TCP_SIGNATURE
 		/*
 		 * Handle TCP-MD5 passive opener response.
diff --git a/sys/netinet/tcp_timer.c b/sys/netinet/tcp_timer.c
index 65d9d65..1ecf33d 100644
--- a/sys/netinet/tcp_timer.c
+++ b/sys/netinet/tcp_timer.c
@@ -541,14 +541,14 @@ tcp_timer_rexmt(xtp)
 	TCPT_RANGESET(tp->t_rxtcur, rexmt,
 		      tp->t_rttmin, TCPTV_REXMTMAX);
 	/*
-	 * Disable rfc1323 and rfc1644 if we havn't got any response to
+	 * Disable rfc1323 if we havn't got any response to
 	 * our third SYN to work-around some broken terminal servers
 	 * (most of which have hopefully been retired) that have bad VJ
 	 * header compression code which trashes TCP segments containing
 	 * unknown-to-them TCP options.
 	 */
 	if ((tp->t_state == TCPS_SYN_SENT) && (tp->t_rxtshift == 3))
-		tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP|TF_REQ_CC);
+		tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP);
 	/*
 	 * If we backed off this far, our srtt estimate is probably bogus.
 	 * Clobber it so we'll take the next rtt measurement as our srtt;
diff --git a/sys/netinet/tcp_timewait.c b/sys/netinet/tcp_timewait.c
index 03610b3..0c91656 100644
--- a/sys/netinet/tcp_timewait.c
+++ b/sys/netinet/tcp_timewait.c
@@ -155,10 +155,6 @@ int	tcp_do_rfc1323 = 1;
 SYSCTL_INT(_net_inet_tcp, TCPCTL_DO_RFC1323, rfc1323, CTLFLAG_RW,
     &tcp_do_rfc1323 , 0, "Enable rfc1323 (high performance TCP) extensions");
 
-int	tcp_do_rfc1644 = 0;
-SYSCTL_INT(_net_inet_tcp, TCPCTL_DO_RFC1644, rfc1644, CTLFLAG_RW,
-    &tcp_do_rfc1644 , 0, "Enable rfc1644 (TTCP) extensions");
-
 static int	tcp_tcbhashsize = 0;
 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tcbhashsize, CTLFLAG_RDTUN,
      &tcp_tcbhashsize, 0, "Size of TCP control-block hashtable");
@@ -246,8 +242,6 @@ tcp_init()
 {
 	int hashsize = TCBHASHSIZE;
 
-	tcp_ccgen = 1;
-
 	tcp_delacktime = TCPTV_DELACK;
 	tcp_keepinit = TCPTV_KEEP_INIT;
 	tcp_keepidle = TCPTV_KEEP_IDLE;
@@ -613,8 +607,6 @@ tcp_newtcpcb(inp)
 
 	if (tcp_do_rfc1323)
 		tp->t_flags = (TF_REQ_SCALE|TF_REQ_TSTMP);
-	if (tcp_do_rfc1644)
-		tp->t_flags |= TF_REQ_CC;
 	tp->sack_enable = tcp_do_sack;
 	tp->t_inpcb = inp;	/* XXX */
 	/*
@@ -1409,7 +1401,6 @@ tcp_mtudisc(inp, errno)
 	int errno;
 {
 	struct tcpcb *tp = intotcpcb(inp);
-	struct rmxp_tao tao;
 	struct socket *so = inp->inp_socket;
 	u_int maxmtu;
 	u_int romtu;
@@ -1417,7 +1408,6 @@ tcp_mtudisc(inp, errno)
 #ifdef INET6
 	int isipv6;
 #endif /* INET6 */
-	bzero(&tao, sizeof(tao));
 
 	if (tp != NULL) {
 #ifdef INET6
@@ -1452,11 +1442,6 @@ tcp_mtudisc(inp, errno)
 #endif /* INET6 */
 			;
 
-		if (tcp_do_rfc1644) {
-			tcp_hc_gettao(&inp->inp_inc, &tao);
-			if (tao.tao_mssopt)
-				mss = min(mss, tao.tao_mssopt);
-		}
 		/*
 		 * XXX - The above conditional probably violates the TCP
 		 * spec.  The problem is that, since we don't know the
@@ -1481,9 +1466,6 @@ tcp_mtudisc(inp, errno)
 		if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&
 		    (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)
 			mss -= TCPOLEN_TSTAMP_APPA;
-		if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC &&
-		    (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC)
-			mss -= TCPOLEN_CC_APPA;
 #if	(MCLBYTES & (MCLBYTES - 1)) == 0
 		if (mss > MCLBYTES)
 			mss &= ~(MCLBYTES-1);
@@ -1659,8 +1641,6 @@ tcp_twstart(tp)
 	tw->rcv_nxt = tp->rcv_nxt;
 	tw->iss     = tp->iss;
 	tw->irs     = tp->irs;
-	tw->cc_recv = tp->cc_recv;
-	tw->cc_send = tp->cc_send;
 	tw->t_starttime = tp->t_starttime;
 	tw->tw_time = 0;
 
@@ -1669,15 +1649,8 @@ tcp_twstart(tp)
  * be used for fin-wait-2 state also, then we may need
  * a ts_recent from the last segment.
  */
-	/* Shorten TIME_WAIT [RFC-1644, p.28] */
-	if (tp->cc_recv != 0 && (ticks - tp->t_starttime) < tcp_msl) {
-		tw_time = tp->t_rxtcur * TCPTV_TWTRUNC;
-		/* For T/TCP client, force ACK now. */
-		acknow = 1;
-	} else {
-		tw_time = 2 * tcp_msl;
-		acknow = tp->t_flags & TF_ACKNOW;
-	}
+	tw_time = 2 * tcp_msl;
+	acknow = tp->t_flags & TF_ACKNOW;
 	tcp_discardcb(tp);
 	so = inp->inp_socket;
 	ACCEPT_LOCK();
@@ -1803,16 +1776,6 @@ tcp_twrespond(struct tcptw *tw, int flags)
 		optp += TCPOLEN_TSTAMP_APPA;
 	}
 
-	/*
-	 * Send `CC-family' options if needed, and it's not a RST.
-	 */
-	if (tw->cc_recv != 0 && flags == TH_ACK) {
-		u_int32_t *lp = (u_int32_t *)optp;
-
-		*lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CC));
-		*lp   = htonl(tw->cc_send);
-		optp += TCPOLEN_CC_APPA;
-	}
 	optlen = optp - (u_int8_t *)(th + 1);
 
 	m->m_len = hdrlen + optlen;
diff --git a/sys/netinet/tcp_usrreq.c b/sys/netinet/tcp_usrreq.c
index 525b48a..f2a9cad 100644
--- a/sys/netinet/tcp_usrreq.c
+++ b/sys/netinet/tcp_usrreq.c
@@ -815,14 +815,10 @@ tcp_connect(tp, nam, td)
 {
 	struct inpcb *inp = tp->t_inpcb, *oinp;
 	struct socket *so = inp->inp_socket;
-	struct tcptw *otw;
-	struct rmxp_tao tao;
 	struct in_addr laddr;
 	u_short lport;
 	int error;
 
-	bzero(&tao, sizeof(tao));
-
 	if (inp->inp_lport == 0) {
 		error = in_pcbbind(inp, (struct sockaddr *)0, td->td_ucred);
 		if (error)
@@ -840,17 +836,8 @@ tcp_connect(tp, nam, td)
 	    &inp->inp_faddr.s_addr, &inp->inp_fport, &oinp, td->td_ucred);
 	if (error && oinp == NULL)
 		return error;
-	if (oinp) {
-		if (oinp != inp &&
-		    (oinp->inp_vflag & INP_TIMEWAIT) &&
-		    (ticks - (otw = intotw(oinp))->t_starttime) < tcp_msl &&
-		    otw->cc_recv != 0) {
-			inp->inp_faddr = oinp->inp_faddr;
-			inp->inp_fport = oinp->inp_fport;
-			(void) tcp_twclose(otw, 0);
-		} else
-			return EADDRINUSE;
-	}
+	if (oinp)
+		return EADDRINUSE;
 	inp->inp_laddr = laddr;
 	in_pcbrehash(inp);
 
@@ -867,26 +854,6 @@ tcp_connect(tp, nam, td)
 	tp->t_bw_rtseq = tp->iss;
 	tcp_sendseqinit(tp);
 
-	/*
-	 * Generate a CC value for this connection and
-	 * check whether CC or CCnew should be used.
-	 */
-	if (tcp_do_rfc1644)
-		tcp_hc_gettao(&inp->inp_inc, &tao);
-
-	tp->cc_send = CC_INC(tcp_ccgen);
-	if (tao.tao_ccsent != 0 &&
-	    CC_GEQ(tp->cc_send, tao.tao_ccsent)) {
-		tao.tao_ccsent = tp->cc_send;
-	} else {
-		tao.tao_ccsent = 0;
-		tp->t_flags |= TF_SENDCCNEW;
-	}
-
-	if (tcp_do_rfc1644)
-		tcp_hc_updatetao(&inp->inp_inc, TCP_HC_TAO_CCSENT,
-				 tao.tao_ccsent, 0);
-
 	return 0;
 }
 
@@ -899,14 +866,10 @@ tcp6_connect(tp, nam, td)
 {
 	struct inpcb *inp = tp->t_inpcb, *oinp;
 	struct socket *so = inp->inp_socket;
-	struct tcptw *otw;
 	struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)nam;
 	struct in6_addr *addr6;
-	struct rmxp_tao tao;
 	int error;
 
-	bzero(&tao, sizeof(tao));
-
 	if (inp->inp_lport == 0) {
 		error = in6_pcbbind(inp, (struct sockaddr *)0, td->td_ucred);
 		if (error)
@@ -927,17 +890,8 @@ tcp6_connect(tp, nam, td)
 				  ? addr6
 				  : &inp->in6p_laddr,
 				  inp->inp_lport,  0, NULL);
-	if (oinp) {
-		if (oinp != inp &&
-		    (oinp->inp_vflag & INP_TIMEWAIT) &&
-		    (ticks - (otw = intotw(oinp))->t_starttime) < tcp_msl &&
-		    otw->cc_recv != 0) {
-			inp->inp_faddr = oinp->inp_faddr;
-			inp->inp_fport = oinp->inp_fport;
-			(void) tcp_twclose(otw, 0);
-		} else
-			return EADDRINUSE;
-	}
+	if (oinp)
+		return EADDRINUSE;
 	if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr))
 		inp->in6p_laddr = *addr6;
 	inp->in6p_faddr = sin6->sin6_addr;
@@ -962,25 +916,6 @@ tcp6_connect(tp, nam, td)
 	tp->t_bw_rtseq = tp->iss;
 	tcp_sendseqinit(tp);
 
-	/*
-	 * Generate a CC value for this connection and
-	 * check whether CC or CCnew should be used.
-	 */
-	if (tcp_do_rfc1644)
-		tcp_hc_gettao(&inp->inp_inc, &tao);
-
-	tp->cc_send = CC_INC(tcp_ccgen);
-	if (tao.tao_ccsent != 0 &&
-	    CC_GEQ(tp->cc_send, tao.tao_ccsent)) {
-		tao.tao_ccsent = tp->cc_send;
-	} else {
-		tao.tao_ccsent = 0;
-		tp->t_flags |= TF_SENDCCNEW;
-	}
-	if (tcp_do_rfc1644)
-		tcp_hc_updatetao(&inp->inp_inc, TCP_HC_TAO_CCSENT,
-				 tao.tao_ccsent, 0);
-
 	return 0;
 }
 #endif /* INET6 */
diff --git a/sys/netinet/tcp_var.h b/sys/netinet/tcp_var.h
index 3155101..8dbf4a5 100644
--- a/sys/netinet/tcp_var.h
+++ b/sys/netinet/tcp_var.h
@@ -39,7 +39,6 @@
  * Kernel variables for tcp.
  */
 extern int	tcp_do_rfc1323;
-extern int	tcp_do_rfc1644;
 
 /* TCP segment queue entry */
 struct tseg_qent {
@@ -102,9 +101,6 @@ struct tcpcb {
 #define	TF_NEEDSYN	0x000400	/* send SYN (implicit state) */
 #define	TF_NEEDFIN	0x000800	/* send FIN (implicit state) */
 #define	TF_NOPUSH	0x001000	/* don't push */
-#define	TF_REQ_CC	0x002000	/* have/will request CC */
-#define	TF_RCVD_CC	0x004000	/* a CC was received in SYN */
-#define	TF_SENDCCNEW	0x008000	/* send CCnew instead of CC in SYN */
 #define	TF_MORETOCOME	0x010000	/* More data to be appended to sock */
 #define	TF_LQ_OVERFLOW	0x020000	/* listen queue overflow */
 #define	TF_LASTIDLE	0x040000	/* connection was previously idle */
@@ -177,9 +173,6 @@ struct tcpcb {
 
 	u_long	ts_recent_age;		/* when last updated */
 	tcp_seq	last_ack_sent;
-/* RFC 1644 variables */
-	tcp_cc	cc_send;		/* send connection count */
-	tcp_cc	cc_recv;		/* receive connection count */
 /* experimental */
 	u_long	snd_cwnd_prev;		/* cwnd prior to retransmit */
 	u_long	snd_ssthresh_prev;	/* ssthresh prior to retransmit */
@@ -231,9 +224,6 @@ struct tcpcb {
 struct tcpopt {
 	u_long		to_flags;	/* which options are present */
 #define TOF_TS		0x0001		/* timestamp */
-#define TOF_CC		0x0002		/* CC and CCnew are exclusive */
-#define TOF_CCNEW	0x0004
-#define	TOF_CCECHO	0x0008
 #define	TOF_MSS		0x0010
 #define	TOF_SCALE	0x0020
 #define	TOF_SIGNATURE	0x0040		/* signature option present */
@@ -241,8 +231,6 @@ struct tcpopt {
 #define	TOF_SACK	0x0100		/* Peer sent SACK option */
 	u_int32_t	to_tsval;
 	u_int32_t	to_tsecr;
-	tcp_cc		to_cc;		/* holds CC or CCnew */
-	tcp_cc		to_ccecho;
 	u_int16_t	to_mss;
 	u_int8_t	to_requested_s_scale;
 	u_int8_t	to_pad;
@@ -256,8 +244,6 @@ struct syncache {
 	struct		in_conninfo sc_inc;	/* addresses */
 	u_int32_t	sc_tsrecent;
 	u_int32_t	sc_flowlabel;		/* IPv6 flowlabel */
-	tcp_cc		sc_cc_send;		/* holds CC or CCnew */
-	tcp_cc		sc_cc_recv;
 	tcp_seq		sc_irs;			/* seq from peer */
 	tcp_seq		sc_iss;			/* our ISS */
 	u_long		sc_rxttime;		/* retransmit time */
@@ -270,7 +256,6 @@ struct syncache {
 #define SCF_NOOPT	0x01			/* no TCP options */
 #define SCF_WINSCALE	0x02			/* negotiated window scaling */
 #define SCF_TIMESTAMP	0x04			/* negotiated timestamps */
-#define SCF_CC		0x08			/* negotiated CC */
 #define SCF_UNREACH	0x10			/* icmp unreachable received */
 #define SCF_SIGNATURE	0x20			/* send MD5 digests */
 #define SCF_SACK	0x80			/* send SACK option */
@@ -303,8 +288,6 @@ struct tcptw {
 	tcp_seq		rcv_nxt;
 	tcp_seq		iss;
 	tcp_seq		irs;
-	tcp_cc		cc_recv;
-	tcp_cc		cc_send;
 	u_short		last_win;	/* cached window value */
 	u_short		tw_so_options;	/* copy of so_options */
 	struct ucred	*tw_cred;	/* user credentials */
@@ -314,21 +297,6 @@ struct tcptw {
 	LIST_ENTRY(tcptw) tw_2msl;
 };
 
-/*
- * The TAO cache entry which is stored in the tcp hostcache.
- */
-struct rmxp_tao {
-	tcp_cc	tao_cc;			/* latest CC in valid SYN */
-	tcp_cc	tao_ccsent;		/* latest CC sent to peer */
-	u_short	tao_mssopt;		/* peer's cached MSS */
-#ifdef notyet
-	u_short	tao_flags;		/* cache status flags */
-#define	TAOF_DONT	0x0001		/* peer doesn't understand rfc1644 */
-#define	TAOF_OK		0x0002		/* peer does understand rfc1644 */
-#define	TAOF_UNDEF	0		/* we don't know yet */
-#endif /* notyet */
-};
-
 #define	intotcpcb(ip)	((struct tcpcb *)(ip)->inp_ppcb)
 #define	intotw(ip)	((struct tcptw *)(ip)->inp_ppcb)
 #define	sototcpcb(so)	(intotcpcb(sotoinpcb(so)))
@@ -487,7 +455,6 @@ struct	xtcpcb {
  * Names for TCP sysctl objects
  */
 #define	TCPCTL_DO_RFC1323	1	/* use RFC-1323 extensions */
-#define	TCPCTL_DO_RFC1644	2	/* use RFC-1644 extensions */
 #define	TCPCTL_MSSDFLT		3	/* MSS default */
 #define TCPCTL_STATS		4	/* statistics (read-only) */
 #define	TCPCTL_RTTDFLT		5	/* default RTT estimate */
@@ -505,7 +472,6 @@ struct	xtcpcb {
 #define TCPCTL_NAMES { \
 	{ 0, 0 }, \
 	{ "rfc1323", CTLTYPE_INT }, \
-	{ "rfc1644", CTLTYPE_INT }, \
 	{ "mssdflt", CTLTYPE_INT }, \
 	{ "stats", CTLTYPE_STRUCT }, \
 	{ "rttdflt", CTLTYPE_INT }, \
@@ -600,14 +566,8 @@ void	 syncache_badack(struct in_conninfo *);
 void	 tcp_hc_init(void);
 void	 tcp_hc_get(struct in_conninfo *, struct hc_metrics_lite *);
 u_long	 tcp_hc_getmtu(struct in_conninfo *);
-void	 tcp_hc_gettao(struct in_conninfo *, struct rmxp_tao *);
 void	 tcp_hc_updatemtu(struct in_conninfo *, u_long);
 void	 tcp_hc_update(struct in_conninfo *, struct hc_metrics_lite *);
-void	 tcp_hc_updatetao(struct in_conninfo *, int, tcp_cc, u_short);
-/* update which tao field */
-#define	TCP_HC_TAO_CC		0x1
-#define TCP_HC_TAO_CCSENT	0x2
-#define TCP_HC_TAO_MSSOPT	0x3
 
 extern	struct pr_usrreqs tcp_usrreqs;
 extern	u_long tcp_sendspace;