X-Git-Url: https://git.subgeniuskitty.com/unix-history/.git/blobdiff_plain/ae348eeadb89e419b478405d4e044baf8c26b383..cce93e4b226012d5eebcf7f7bd01cde8a8a07f51:/usr/src/sys/netinet/tcp_output.c

diff --git a/usr/src/sys/netinet/tcp_output.c b/usr/src/sys/netinet/tcp_output.c
index 9f82abf460..6dc94b5376 100644
--- a/usr/src/sys/netinet/tcp_output.c
+++ b/usr/src/sys/netinet/tcp_output.c
@@ -1,350 +1,329 @@
-/* tcp_output.c 4.4 81/10/31 */
+/*	tcp_output.c	4.49	82/12/14	*/
 
 #include "../h/param.h"
 #include "../h/systm.h"
 #include "../h/mbuf.h"
+#include "../h/protosw.h"
 #include "../h/socket.h"
-#include "../inet/inet.h"
-#include "../inet/inet_host.h"
-#include "../inet/inet_systm.h"
-#include "../inet/imp.h"
-#include "../inet/ip.h"
-#include "../inet/tcp.h"
-#include "../inet/tcp_fsm.h"
+#include "../h/socketvar.h"
+#include "../netinet/in.h"
+#include "../net/route.h"
+#include "../netinet/in_pcb.h"
+#include "../netinet/in_systm.h"
+#include "../netinet/ip.h"
+#include "../netinet/ip_var.h"
+#include "../netinet/tcp.h"
+#define	TCPOUTFLAGS
+#include "../netinet/tcp_fsm.h"
+#include "../netinet/tcp_seq.h"
+#include "../netinet/tcp_timer.h"
+#include "../netinet/tcp_var.h"
+#include "../netinet/tcpip.h"
+#include "../netinet/tcp_debug.h"
+#include <errno.h>
+
+char *tcpstates[]; /* XXX */
+
+/*
+ * Initial options.
+ */
+u_char	tcp_initopt[4] = { TCPOPT_MAXSEG, 4, 0x0, 0x0, };
 
 /*
- * Special routines to send control messages.
+ * Tcp output routine: figure out what should be sent and send it.
  */
-tcp_sndctl(tp)
-	struct tcb *tp;
+tcp_output(tp)
+	register struct tcpcb *tp;
 {
-COUNT(TCP_SNDCTL);
+	register struct socket *so = tp->t_inpcb->inp_socket;
+	register int len;
+	struct mbuf *m0;
+	int off, flags, win, error;
+	register struct mbuf *m;
+	register struct tcpiphdr *ti;
+	u_char *opt;
+	unsigned optlen = 0;
+	int sendalot;
 
-        if (tcp_send(tp))
-		return (1);
-	tcp_sndnull(tp);
-	return(0);
-}
 
-tcp_sndwin(tp)
-	struct tcb *tp;
-{
-	int ihave, hehas;
-COUNT(TCP_SNDWIN);
+	/*
+	 * Determine length of data that should be transmitted,
+	 * and flags that will be used.
+	 * If there is some data or critical controls (SYN, RST)
+	 * to send, then transmit; otherwise, investigate further.
+	 */
+again:
+	sendalot = 0;
+	off = tp->snd_nxt - tp->snd_una;
+	len = MIN(so->so_snd.sb_cc, tp->snd_wnd+tp->t_force) - off;
+	if (len < 0)
+		return (0);	/* ??? */	/* past FIN */
+	if (len > tp->t_maxseg) {
+		len = tp->t_maxseg;
+		sendalot = 1;
+	}
 
-	if (tp->rcv_adv) {
-		ihave = tp->t_ucb->uc_rhiwat -
-		    (tp->t_ucb->uc_rcc + tp->seqcnt);
-		hehas = tp->rcv_adv - tp->rcv_nxt;
-		if ((100*(ihave-hehas)/tp->t_ucb->uc_rhiwat) < 35)
-			return;
+	flags = tcp_outflags[tp->t_state];
+	if (tp->snd_nxt + len < tp->snd_una + so->so_snd.sb_cc)
+		flags &= ~TH_FIN;
+	if (flags & (TH_SYN|TH_RST|TH_FIN))
+		goto send;
+	if (SEQ_GT(tp->snd_up, tp->snd_una))
+		goto send;
+
+	/*
+	 * Sender silly window avoidance.  If can send all data,
+	 * a maximum segment, at least 1/4 of window do it,
+	 * or are forced, do it; otherwise don't bother.
+	 */
+	if (len) {
+		if (len == tp->t_maxseg || off+len >= so->so_snd.sb_cc)
+			goto send;
+		if (len * 4 >= tp->snd_wnd)		/* a lot */
+			goto send;
+		if (tp->t_force)
+			goto send;
 	}
-        if (tcp_send(tp))
-		return (1);
-	tcp_sndnull(tp);
-	return (0);
-}
 
-tcp_sndnull(tp)
-	register struct tcb *tp;
-{
-COUNT(TCP_SNDNULL);
+	/*
+	 * Send if we owe peer an ACK.
+	 */
+	if (tp->t_flags&TF_ACKNOW)
+		goto send;
 
-	tcp_output(tp, 0, 0, (struct mbuf *)0);
-        tp->tc_flags &= ~TC_ACK_DUE;
-}
 
-tcp_sndrst(tp, n)
-	register struct tcb *tp;
-	register struct th *n;
-{
-COUNT(TCP_SNDRST);
+	/*
+	 * Calculate available window in i, and also amount
+	 * of window known to peer (as advertised window less
+	 * next expected input.)  If this is 35% or more of the
+	 * maximum possible window, then want to send a segment to peer.
+	 */
+	win = sbspace(&so->so_rcv);
+	if (win > 0 &&
+	    ((100*(win-(tp->rcv_adv-tp->rcv_nxt))/so->so_rcv.sb_hiwat) >= 35))
+		goto send;
 
-        /* don't send a reset in response to a reset */
-	if (n->th_flags&TH_RST)
-		return;
-	tp->tc_flags |= TC_SND_RST;
-	if (n->th_flags&TH_ACK)
-		tp->snd_nxt = n->t_ackno;
-	tp->tc_flags &= ~TC_SYN_RCVD;
-	tcp_sndnull(tp);
-	tp->tc_flags &= ~TC_SND_RST;
-}
+	/*
+	 * TCP window updates are not reliable, rather a polling protocol
+	 * using ``persist'' packets is used to insure receipt of window
+	 * updates.  The three ``states'' for the output side are:
+	 *	idle			not doing retransmits or persists
+	 *	persisting		to move a zero window
+	 *	(re)transmitting	and thereby not persisting
+	 *
+	 * tp->t_timer[TCPT_PERSIST]
+	 *	is set when we are in persist state.
+	 * tp->t_force
+	 *	is set when we are called to send a persist packet.
+	 * tp->t_timer[TCPT_REXMT]
+	 *	is set when we are retransmitting
+	 * The output side is idle when both timers are zero.
+	 *
+	 * If send window is closed, there is data to transmit, and no
+	 * retransmit or persist is pending, then go to persist state,
+	 * arranging to force out a byte to get more current window information
+	 * if nothing happens soon.
+	 */
+	if (tp->snd_wnd == 0 && so->so_snd.sb_cc &&
+	    tp->t_timer[TCPT_REXMT] == 0 && tp->t_timer[TCPT_PERSIST] == 0) {
+		tp->t_rxtshift = 0;
+		tcp_setpersist(tp);
+	}
 
-/*
- * Tcp segment output routine.
- */
-tcp_send(tp)
-	register struct tcb *tp;
-{
-	register struct ucb *up;
-	register unsigned long last, wind;
-	struct mbuf *m;
-	int flags = 0, forced, sent;
-	struct mbuf *tcp_sndcopy();
-	int len;
+	/*
+	 * No reason to send a segment, just return.
+	 */
+	return (0);
 
-COUNT(TCP_SEND);
-	up = tp->t_ucb;
-	tp->snd_lst = tp->snd_nxt;
-	forced = 0;
-	m = NULL;
-	if (tp->snd_nxt == tp->iss) {
-		flags |= TH_SYN;
-		tp->snd_lst++;
+send:
+	/*
+	 * Grab a header mbuf, attaching a copy of data to
+	 * be transmitted, and initialize the header from
+	 * the template for sends on this connection.
+	 */
+	MGET(m, M_DONTWAIT, MT_DATA);
+	if (m == 0)
+		return (ENOBUFS);
+	m->m_off = MMAXOFF - sizeof (struct tcpiphdr);
+	m->m_len = sizeof (struct tcpiphdr);
+	if (len) {
+		m->m_next = m_copy(so->so_snd.sb_mb, off, len);
+		if (m->m_next == 0)
+			len = 0;
 	}
-	last = tp->snd_off;
-	for (m = up->uc_sbuf; m != NULL; m = m->m_next)
-		last += m->m_len;
-	if (tp->snd_nxt > last) {
-		if ((tp->tc_flags&TC_SND_FIN) &&
-		    (tp->seq_fin == tp->iss || tp->snd_nxt <= tp->seq_fin)) {
+	ti = mtod(m, struct tcpiphdr *);
+	if (tp->t_template == 0)
+		panic("tcp_output");
+	bcopy((caddr_t)tp->t_template, (caddr_t)ti, sizeof (struct tcpiphdr));
 
-			flags |= TH_FIN;
-			tp->seq_fin = tp->snd_lst++;
-		}
+	/*
+	 * Fill in fields, remembering maximum advertised
+	 * window for use in delaying messages about window sizes.
+	 */
+	ti->ti_seq = tp->snd_nxt;
+	ti->ti_ack = tp->rcv_nxt;
+	ti->ti_seq = htonl(ti->ti_seq);
+	ti->ti_ack = htonl(ti->ti_ack);
+	/*
+	 * Before ESTABLISHED, force sending of initial options
+	 * unless TCP set to not do any options.
+	 */
+	if (tp->t_state < TCPS_ESTABLISHED) {
+		if (tp->t_flags&TF_NOOPT)
+			goto noopt;
+		opt = tcp_initopt;
+		optlen = sizeof (tcp_initopt);
+		*(u_short *)(opt + 2) = MIN(so->so_rcv.sb_hiwat / 2, 1024);
+		*(u_short *)(opt + 2) = htons(*(u_short *)(opt + 2));
 	} else {
-		if (tp->tc_flags&TC_SYN_ACKED) {
-			wind = tp->snd_una + tp->snd_wnd;
-			tp->snd_lst = min(last, wind);
-			if ((len = tp->snd_lst - tp->snd_nxt) > 1024)
-				tp->snd_lst -= len - 1024;
-			if (tp->snd_lst >= wind)
-				tp->t_persist = T_PERS;
-		}
-		if ((tp->tc_flags&TC_FORCE_ONE) && (tp->snd_lst == wind)) {
-			tp->snd_lst = tp->snd_nxt + 1;
-			forced = 1;
-		}
-		m = tcp_sndcopy(tp, max(tp->iss+1,tp->snd_nxt), tp->snd_lst);
-		if (tp->snd_end > tp->iss && tp->snd_end <= tp->snd_lst)
-			flags |= TH_EOL;
-		if ((tp->tc_flags&TC_SND_FIN) && !forced &&
-		    tp->snd_lst == last &&
-		    (tp->seq_fin == tp->iss || tp->snd_nxt <= tp->seq_fin)) {
-			flags |= TH_FIN;
-			tp->seq_fin = tp->snd_lst++;
-		}
+		if (tp->t_tcpopt == 0)
+			goto noopt;
+		opt = mtod(tp->t_tcpopt, u_char *);
+		optlen = tp->t_tcpopt->m_len;
 	}
-	if (tp->snd_nxt >= tp->snd_lst)
-		return (0);
-	if (tp->tc_flags & TC_SND_URG)
-		flags |= TH_URG;
-	sent = tcp_output(tp, flags, tp->snd_lst - tp->snd_nxt, m);
-	if (!forced) {
-		tp->t_rexmt = tp->t_xmtime;
-		tp->t_rexmt_val = tp->snd_lst;
-		if ((tp->tc_flags&TC_REXMT) == 0) {
-			tp->t_rexmttl = T_REXMTTL;
-			tp->t_rtl_val = tp->snd_lst;
+	if (opt) {
+		m0 = m->m_next;
+		m->m_next = m_get(M_DONTWAIT, MT_DATA);
+		if (m->m_next == 0) {
+			(void) m_free(m);
+			m_freem(m0);
+			return (ENOBUFS);
 		}
+		m->m_next->m_next = m0;
+		m0 = m->m_next;
+		m0->m_len = optlen;
+		bcopy((caddr_t)opt, mtod(m0, caddr_t), optlen);
+		opt = (u_char *)(mtod(m0, caddr_t) + optlen);
+		while (m0->m_len & 0x3) {
+			*opt++ = TCPOPT_EOL;
+			m0->m_len++;
+		}
+		optlen = m0->m_len;
+		ti->ti_off = (sizeof (struct tcphdr) + optlen) >> 2;
 	}
-	if (sent)
-		tp->snd_nxt = tp->snd_lst;
-	if ((tp->tc_flags&TC_SYN_ACKED) &&
-	    tp->snd_una > tp->t_xmt_val) {
-		tp->t_xmt = 0;
-		tp->t_xmt_val = tp->snd_lst;
-	}
-	tp->tc_flags &= ~(TC_ACK_DUE|TC_REXMT|TC_FORCE_ONE);
-	tp->snd_hi = max(tp->snd_nxt, tp->snd_hi);
-	return (1);
-}
+noopt:
+	ti->ti_flags = flags;
+	win = sbspace(&so->so_rcv);
+	if (win < so->so_rcv.sb_hiwat / 4)	/* avoid silly window */
+		win = 0;
+	if (win > 0)
+		ti->ti_win = htons((u_short)win);
+	if (SEQ_GT(tp->snd_up, tp->snd_nxt)) {
+		ti->ti_urp = tp->snd_up - tp->snd_nxt;
+		ti->ti_urp = htons(ti->ti_urp);
+		ti->ti_flags |= TH_URG;
+	} else
+		/*
+		 * If no urgent pointer to send, then we pull
+		 * the urgent pointer to the left edge of the send window
+		 * so that it doesn't drift into the send window on sequence
+		 * number wraparound.
+		 */
+		tp->snd_up = tp->snd_una;		/* drag it along */
+	/*
+	 * If anything to send and we can send it all, set PUSH.
+	 * (This will keep happy those implementations which only
+	 * give data to the user when a buffer fills or a PUSH comes in.
+	 */
+	if (len && off+len == so->so_snd.sb_cc)
+		ti->ti_flags |= TH_PUSH;
 
-/*
- * Create template to be used to send tcp packets on a connection.
- * Call after host entry created, allocates an mbuf and fills
- * in a skeletal tcp/ip header, minimizing the amount of work
- * necessary when the connection is used.
- */
-struct th *
-tcp_template(tp)
-	struct tcb *tp;
-{
-	register struct host *h = tp->t_ucb->uc_host;
-	register struct mbuf *m;
-	register struct th *n;
-	register struct ip *ip;
+	/*
+	 * Put TCP length in extended header, and then
+	 * checksum extended header and data.
+	 */
+	if (len + optlen) {
+		ti->ti_len = sizeof (struct tcphdr) + optlen + len;
+		ti->ti_len = htons((u_short)ti->ti_len);
+	}
+	ti->ti_sum = in_cksum(m, sizeof (struct tcpiphdr) + (int)optlen + len);
 
-	if (h == 0)
-		return (0);
-	m = m_get(1);
-	if (m == 0)
-		return (0);
-	m->m_off = MMAXOFF - sizeof (struct th);
-	m->m_len = sizeof (struct th);
-	n = mtod(m, struct th *);
-	n->t_next = n->t_prev = 0;
-	n->t_x1 = 0;
-	n->t_pr = TCPROTO;
-	n->t_len = htons(sizeof (struct th) - sizeof (struct ip));
-	n->t_s.s_addr = n_lhost.s_addr;
-	n->t_d.s_addr = h->h_addr.s_addr;
-	n->t_src = htons(tp->t_lport);
-	n->t_dst = htons(tp->t_fport);
-	n->t_seq = 0;
-	n->t_ackno = 0;
-	n->t_x2 = 0;
-	n->t_off = 5;
-	n->th_flags = 0;
-	n->t_win = 0;
-	n->t_sum = 0;
-	n->t_urp = 0;
-	return (n);
-}
+	/*
+	 * In transmit state, time the transmission and arrange for
+	 * the retransmit.  In persist state, reset persist time for
+	 * next persist.
+	 */
+	if (tp->t_force == 0) {
+		/*
+		 * Advance snd_nxt over sequence space of this segment.
+		 */
+		if (flags & (TH_SYN|TH_FIN))
+			tp->snd_nxt++;
+		tp->snd_nxt += len;
+		if (SEQ_GT(tp->snd_nxt, tp->snd_max))
+			tp->snd_max = tp->snd_nxt;
 
-tcp_output(tp, flags, len, dat)
-	register struct tcb *tp;
-	register int flags;
-	int len;
-	struct mbuf *dat;
-{
-	register struct mbuf *m;
-	register struct th *t;
-	register struct ip *ip;
-	int i;
-#ifdef TCPDEBUG
-	struct tcp_debug tdb;
-#endif
-COUNT(SEND_TCP);
+		/*
+		 * Time this transmission if not a retransmission and
+		 * not currently timing anything.
+		 */
+		if (SEQ_GT(tp->snd_nxt, tp->snd_max) && tp->t_rtt == 0) {
+			tp->t_rtt = 1;
+			tp->t_rtseq = tp->snd_nxt - len;
+		}
 
-	if ((t = tp->t_ucb->uc_template) == 0)
-		return (0);
-	MGET(m, 0);
-	if (m == 0)
-		return (0);
-	m->m_off = MMAXOFF - sizeof(struct th);
-	m->m_len = sizeof (struct th);
-	m->m_next = dat;
-	if (flags & TH_SYN)
-		len--;
-	if (flags & TH_FIN)
-		len--;
-	bcopy((caddr_t)t, mtod(m, caddr_t), sizeof (struct th));
-	t = mtod(m, struct th *);
-	if (tp->tc_flags&TC_SND_RST) {
-		flags &= ~TH_SYN;
-		flags |= TH_RST;
-	}
-	if (tp->tc_flags&TC_SYN_RCVD)
-		flags |= TH_ACK;
-	t->th_flags = flags;
-	if (flags & TH_URG)
-		t->t_urp = htons(tp->snd_urp);
-	t->t_win =
-	    tp->t_ucb->uc_rhiwat - (tp->t_ucb->uc_rcc + tp->seqcnt);
-	if (tp->rcv_nxt + t->t_win > tp->rcv_adv)
-		tp->rcv_adv = tp->rcv_nxt + t->t_win;
-	if (len)
-		t->t_len = htons(len + TCPSIZE);
-	t->t_win = htons(t->t_win);
-#ifdef TCPDEBUG
-	if ((tp->t_ucb->uc_flags & UDEBUG) || tcpconsdebug) {
-		t->t_seq = tp->snd_nxt;
-		t->t_ackno = tp->rcv_nxt;
-		tdb_setup(tp, t, INSEND, &tdb);
-		tdb_stuff(&tdb, -2);
+		/*
+		 * Set retransmit timer if not currently set.
+		 * Initial value for retransmit timer to tcp_beta*tp->t_srtt.
+		 * Initialize shift counter which is used for exponential
+		 * backoff of retransmit time.
+		 */
+		if (tp->t_timer[TCPT_REXMT] == 0 &&
+		    tp->snd_nxt != tp->snd_una) {
+			TCPT_RANGESET(tp->t_timer[TCPT_REXMT],
+			    tcp_beta * tp->t_srtt, TCPTV_MIN, TCPTV_MAX);
+			tp->t_rtt = 0;
+			tp->t_rxtshift = 0;
+		}
+		tp->t_timer[TCPT_PERSIST] = 0;
+	} else {
+		if (SEQ_GT(tp->snd_una+1, tp->snd_max))
+			tp->snd_max = tp->snd_una+1;
 	}
-#endif
-	t->t_seq = htonl(tp->snd_nxt);
-	t->t_ackno = htonl(tp->rcv_nxt);
-	t->t_sum = cksum(m, len + sizeof(struct th));
-	ip = (struct ip *)t;
-	ip->ip_v = IPVERSION;
-	ip->ip_hl = 5;
-	ip->ip_tos = 0;
-	ip->ip_len = len + sizeof(struct th);
-	ip->ip_id = ip_id++;
-	ip->ip_off = 0;
-	ip->ip_ttl = MAXTTL;
-	i = ip_send(ip);
-	return(i);
-}
 
-firstempty(tp)
-	register struct tcb *tp;
-{
-	register struct th *p, *q;
-COUNT(FIRSTEMPTY);
+	/*
+	 * Trace.
+	 */
+	if (so->so_options & SO_DEBUG)
+		tcp_trace(TA_OUTPUT, tp->t_state, tp, ti, 0);
 
-	if ((p = tp->t_rcv_next) == (struct th *)tp || tp->rcv_nxt < p->t_seq)
-		return (tp->rcv_nxt);
-	while ((q = p->t_next) != (struct th *)tp &&
-	    (t_end(p) + 1) == q->t_seq)
-		p = q;
-	return (t_end(p) + 1);
-}
-
-struct mbuf *
-tcp_sndcopy(tp, start, end)
-	struct tcb *tp;
-	u_long start, end;
-{
-	register struct mbuf *m, *n, **np;
-	u_long off;
-	register int len;
-	int adj;
-	struct mbuf *top, *p;
-COUNT(SND_COPY);
+	/*
+	 * Fill in IP length and desired time to live and
+	 * send to IP level.
+	 */
+	((struct ip *)ti)->ip_len = sizeof (struct tcpiphdr) + optlen + len;
+	((struct ip *)ti)->ip_ttl = TCP_TTL;
+	if (error = ip_output(m, tp->t_ipopt, (so->so_options & SO_DONTROUTE) ?
+	    &routetoif : &tp->t_inpcb->inp_route, 0))
+		return (error);
 
-	if (start >= end)    
-		return(NULL);
-	off = tp->snd_off;
-	m = tp->t_ucb->uc_sbuf;
-	while (m != NULL && start >= (off + m->m_len)) {
-		off += m->m_len;
-		m = m->m_next;
-	}
-	np = &top;
-	top = 0;
-	adj = start - off;
-	len = end - start;
-	while (m && len > 0) {
-		MGET(n, 1);
-		*np = n;
-		if (n == 0)
-			goto nospace;
-		n->m_len = MIN(len, m->m_len - adj);
-		if (m->m_off > MMAXOFF) {
-			p = mtod(m, struct mbuf *);
-			n->m_off = ((int)p - (int)n) + adj;
-			mprefcnt[mtopf(p)]++;
-		} else {
-			n->m_off = MMINOFF;
-			bcopy(mtod(m, caddr_t)+adj, mtod(n, caddr_t),
-			    n->m_len);
-		}
-		len -= n->m_len;
-		adj = 0;
-		m = m->m_next;
-		/* SHOULD TRY PACKING INTO SMALL MBUFS HERE */
-		np = &n->m_next;
-	}
-	/* SHOULD NEVER RUN OUT OF m WHEN LEN */
-	if (len)
-		printf("snd_copy: m %x len %d\n", m, len);
-	return (top);
-nospace:
-	printf("snd_copy: no space\n");
-	m_freem(top);
+	/*
+	 * Data sent (as far as we can tell).
+	 * If this advertises a larger window than any other segment,
+	 * then remember the size of the advertised window.
+	 * Drop send for purpose of ACK requirements.
+	 */
+	if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv))
+		tp->rcv_adv = tp->rcv_nxt + win;
+	tp->t_flags &= ~(TF_ACKNOW|TF_DELACK);
+	if (sendalot && tp->t_force == 0)
+		goto again;
 	return (0);
 }
 
-tcp_enq(p, prev)
-	register struct th *p;
-	register struct th *prev;
-{
-
-	p->t_prev = prev;
-	p->t_next = prev->t_next;
-	prev->t_next->t_prev = p;
-	prev->t_next = p;
-}
- 
-tcp_deq(p)
-	register struct th *p;
+tcp_setpersist(tp)
+	register struct tcpcb *tp;
 {
 
-	p->t_prev->t_next = p->t_next;
-	p->t_next->t_prev = p->t_prev;
+	if (tp->t_timer[TCPT_REXMT])
+		panic("tcp_output REXMT");
+	/*
+	 * Start/restart persistance timer.
+	 */
+	TCPT_RANGESET(tp->t_timer[TCPT_PERSIST],
+	    ((int)(tcp_beta * tp->t_srtt)) << tp->t_rxtshift,
+	    TCPTV_PERSMIN, TCPTV_MAX);
+	tp->t_rxtshift++;
+	if (tp->t_rxtshift >= TCP_MAXRXTSHIFT)
+		tp->t_rxtshift = 0;
 }