u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;
u_long win = ulmin(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;
tcp_timers(tp, timer)	register struct tcpcb *tp;	int timer;{	register int rexmt;#ifdef TCP_SACK	struct sackhole *p, *q;	/*	 * Free SACK holes for 2MSL and REXMT timers.	 */	if (timer == TCPT_2MSL || timer == TCPT_REXMT) {		q = p = tp->snd_holes;		while (p != 0) {			q = p->next;			free(p, M_PCB);			p = q;		}		tp->snd_holes = 0;#if defined(TCP_SACK) && defined(TCP_FACK)		tp->snd_fack = tp->snd_una;		tp->retran_data = 0;		tp->snd_awnd = 0;#endif /* TCP_FACK */	}#endif /* TCP_SACK */	switch (timer) {	/*	 * 2 MSL timeout in shutdown went off.  If we're closed but	 * still waiting for peer to close and connection has been idle	 * too long, or if 2MSL time is up from TIME_WAIT, delete connection	 * control block.  Otherwise, check again in a bit.	 */	case TCPT_2MSL:		if (tp->t_state != TCPS_TIME_WAIT &&		    tp->t_idle <= tcp_maxidle)			tp->t_timer[TCPT_2MSL] = tcp_keepintvl;		else			tp = tcp_close(tp);		break;	/*	 * Retransmission timer went off.  Message has not	 * been acked within retransmit interval.  Back off	 * to a longer retransmit interval and retransmit one segment.	 */	case TCPT_REXMT:		if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {			tp->t_rxtshift = TCP_MAXRXTSHIFT;			tcpstat.tcps_timeoutdrop++;			tp = tcp_drop(tp, tp->t_softerror ?			    tp->t_softerror : ETIMEDOUT);			break;		}		tcpstat.tcps_rexmttimeo++;		rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];		TCPT_RANGESET((long) tp->t_rxtcur, rexmt,		    tp->t_rttmin, TCPTV_REXMTMAX);		tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;		/*		 * If losing, let the lower level know and try for		 * a better route.  Also, 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;		 * move the current srtt into rttvar to keep the current		 * retransmit times until then.		 */		if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {			in_losing(tp->t_inpcb);			tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);			tp->t_srtt = 0;		}		tp->snd_nxt = tp->snd_una;#if defined (TCP_NEWRENO) || defined (TCP_SACK)		tp->snd_last = tp->snd_una;#endif		/*		 * If timing a segment in this window, stop the timer.		 */		tp->t_rtt = 0;		/*		 * Close the congestion window down to one segment		 * (we'll open it by one segment for each ack we get).		 * Since we probably have a window's worth of unacked		 * data accumulated, this "slow start" keeps us from		 * dumping all that data as back-to-back packets (which		 * might overwhelm an intermediate gateway).		 *		 * There are two phases to the opening: Initially we		 * open by one mss on each ack.  This makes the window		 * size increase exponentially with time.  If the		 * window is larger than the path can handle, this		 * exponential growth results in dropped packet(s)		 * almost immediately.  To get more time between 		 * drops but still "push" the network to take advantage		 * of improving conditions, we switch from exponential		 * to linear window opening at some threshhold size.		 * For a threshhold, we use half the current window		 * size, truncated to a multiple of the mss.		 *		 * (the minimum cwnd that will give us exponential		 * growth is 2 mss.  We don't allow the threshhold		 * to go below this.)		 */		{		u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;		if (win < 2)			win = 2;		tp->snd_cwnd = tp->t_maxseg;		tp->snd_ssthresh = win * tp->t_maxseg;		tp->t_dupacks = 0;		}		(void) tcp_output(tp);		break;	/*	 * Persistance timer into zero window.	 * Force a byte to be output, if possible.	 */	case TCPT_PERSIST:		tcpstat.tcps_persisttimeo++;		/*		 * Hack: if the peer is dead/unreachable, we do not		 * time out if the window is closed.  After a full		 * backoff, drop the connection if the idle time		 * (no responses to probes) reaches the maximum		 * backoff that we would use if retransmitting.		 */		if (tp->t_rxtshift == TCP_MAXRXTSHIFT &&		    (tp->t_idle >= tcp_maxpersistidle ||		     tp->t_idle >= TCP_REXMTVAL(tp) * tcp_totbackoff)) {			tcpstat.tcps_persistdrop++;			tp = tcp_drop(tp, ETIMEDOUT);			break;		}		tcp_setpersist(tp);		tp->t_force = 1;		(void) tcp_output(tp);		tp->t_force = 0;		break;	/*	 * Keep-alive timer went off; send something	 * or drop connection if idle for too long.	 */	case TCPT_KEEP:		tcpstat.tcps_keeptimeo++;		if (TCPS_HAVEESTABLISHED(tp->t_state) == 0)			goto dropit;		if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE &&		    tp->t_state <= TCPS_CLOSE_WAIT) {			if (tp->t_idle >= tcp_keepidle + tcp_maxidle)				goto dropit;			/*			 * Send a packet designed to force a response			 * if the peer is up and reachable:			 * either an ACK if the connection is still alive,			 * or an RST if the peer has closed the connection			 * due to timeout or reboot.			 * Using sequence number tp->snd_una-1			 * causes the transmitted zero-length segment			 * to lie outside the receive window;			 * by the protocol spec, this requires the			 * correspondent TCP to respond.			 */			tcpstat.tcps_keepprobe++;#ifdef TCP_COMPAT_42			/*			 * The keepalive packet must have nonzero length			 * to get a 4.2 host to respond.			 */			tcp_respond(tp, tp->t_template, (struct mbuf *)NULL,			    tp->rcv_nxt - 1, tp->snd_una - 1, 0);#else			tcp_respond(tp, tp->t_template, (struct mbuf *)NULL,			    tp->rcv_nxt, tp->snd_una - 1, 0);#endif			tp->t_timer[TCPT_KEEP] = tcp_keepintvl;		} else			tp->t_timer[TCPT_KEEP] = tcp_keepidle;		break;	dropit:		tcpstat.tcps_keepdrops++;		tp = tcp_drop(tp, ETIMEDOUT);		break;	}	return (tp);}