--- /dev/null
+/*
+ * Copyright (c) 1982, 1986, 1993, 1994
+ * The Regents of the University of California. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ * may be used to endorse or promote products derived from this software
+ * without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * @(#)tcp_var.h 8.3 (Berkeley) 4/10/94
+ * tcp_var.h,v 1.3 1994/08/21 05:27:39 paul Exp
+ */
+
+#ifndef _TCP_VAR_H_
+#define _TCP_VAR_H_
+
+#include "tcpip.h"
+#include "tcp_timer.h"
+
+/*
+ * Tcp control block, one per tcp; fields:
+ */
+struct tcpcb {
+ struct tcpiphdr *seg_next; /* sequencing queue */
+ struct tcpiphdr *seg_prev;
+ short t_state; /* state of this connection */
+ short t_timer[TCPT_NTIMERS]; /* tcp timers */
+ short t_rxtshift; /* log(2) of rexmt exp. backoff */
+ short t_rxtcur; /* current retransmit value */
+ short t_dupacks; /* consecutive dup acks recd */
+ u_short t_maxseg; /* maximum segment size */
+ char t_force; /* 1 if forcing out a byte */
+ u_short t_flags;
+#define TF_ACKNOW 0x0001 /* ack peer immediately */
+#define TF_DELACK 0x0002 /* ack, but try to delay it */
+#define TF_NODELAY 0x0004 /* don't delay packets to coalesce */
+#define TF_NOOPT 0x0008 /* don't use tcp options */
+#define TF_SENTFIN 0x0010 /* have sent FIN */
+#define TF_REQ_SCALE 0x0020 /* have/will request window scaling */
+#define TF_RCVD_SCALE 0x0040 /* other side has requested scaling */
+#define TF_REQ_TSTMP 0x0080 /* have/will request timestamps */
+#define TF_RCVD_TSTMP 0x0100 /* a timestamp was received in SYN */
+#define TF_SACK_PERMIT 0x0200 /* other side said I could SACK */
+
+ struct tcpiphdr t_template; /* static skeletal packet for xmit */
+
+ struct socket *t_socket; /* back pointer to socket */
+/*
+ * The following fields are used as in the protocol specification.
+ * See RFC783, Dec. 1981, page 21.
+ */
+/* send sequence variables */
+ tcp_seq snd_una; /* send unacknowledged */
+ tcp_seq snd_nxt; /* send next */
+ tcp_seq snd_up; /* send urgent pointer */
+ tcp_seq snd_wl1; /* window update seg seq number */
+ tcp_seq snd_wl2; /* window update seg ack number */
+ tcp_seq iss; /* initial send sequence number */
+ uint32_t snd_wnd; /* send window */
+/* receive sequence variables */
+ uint32_t rcv_wnd; /* receive window */
+ tcp_seq rcv_nxt; /* receive next */
+ tcp_seq rcv_up; /* receive urgent pointer */
+ tcp_seq irs; /* initial receive sequence number */
+/*
+ * Additional variables for this implementation.
+ */
+/* receive variables */
+ tcp_seq rcv_adv; /* advertised window */
+/* retransmit variables */
+ tcp_seq snd_max; /* highest sequence number sent;
+ * used to recognize retransmits
+ */
+/* congestion control (for slow start, source quench, retransmit after loss) */
+ uint32_t snd_cwnd; /* congestion-controlled window */
+ uint32_t snd_ssthresh; /* snd_cwnd size threshold for
+ * for slow start exponential to
+ * linear switch
+ */
+/*
+ * transmit timing stuff. See below for scale of srtt and rttvar.
+ * "Variance" is actually smoothed difference.
+ */
+ short t_idle; /* inactivity time */
+ short t_rtt; /* round trip time */
+ tcp_seq t_rtseq; /* sequence number being timed */
+ short t_srtt; /* smoothed round-trip time */
+ short t_rttvar; /* variance in round-trip time */
+ u_short t_rttmin; /* minimum rtt allowed */
+ uint32_t max_sndwnd; /* largest window peer has offered */
+
+/* out-of-band data */
+ char t_oobflags; /* have some */
+ char t_iobc; /* input character */
+#define TCPOOB_HAVEDATA 0x01
+#define TCPOOB_HADDATA 0x02
+ short t_softerror; /* possible error not yet reported */
+
+/* RFC 1323 variables */
+ u_char snd_scale; /* window scaling for send window */
+ u_char rcv_scale; /* window scaling for recv window */
+ u_char request_r_scale; /* pending window scaling */
+ u_char requested_s_scale;
+ uint32_t ts_recent; /* timestamp echo data */
+ uint32_t ts_recent_age; /* when last updated */
+ tcp_seq last_ack_sent;
+
+};
+
+#define sototcpcb(so) ((so)->so_tcpcb)
+
+/*
+ * The smoothed round-trip time and estimated variance
+ * are stored as fixed point numbers scaled by the values below.
+ * For convenience, these scales are also used in smoothing the average
+ * (smoothed = (1/scale)sample + ((scale-1)/scale)smoothed).
+ * With these scales, srtt has 3 bits to the right of the binary point,
+ * and thus an "ALPHA" of 0.875. rttvar has 2 bits to the right of the
+ * binary point, and is smoothed with an ALPHA of 0.75.
+ */
+#define TCP_RTT_SCALE 8 /* multiplier for srtt; 3 bits frac. */
+#define TCP_RTT_SHIFT 3 /* shift for srtt; 3 bits frac. */
+#define TCP_RTTVAR_SCALE 4 /* multiplier for rttvar; 2 bits */
+#define TCP_RTTVAR_SHIFT 2 /* multiplier for rttvar; 2 bits */
+
+/*
+ * The initial retransmission should happen at rtt + 4 * rttvar.
+ * Because of the way we do the smoothing, srtt and rttvar
+ * will each average +1/2 tick of bias. When we compute
+ * the retransmit timer, we want 1/2 tick of rounding and
+ * 1 extra tick because of +-1/2 tick uncertainty in the
+ * firing of the timer. The bias will give us exactly the
+ * 1.5 tick we need. But, because the bias is
+ * statistical, we have to test that we don't drop below
+ * the minimum feasible timer (which is 2 ticks).
+ * This macro assumes that the value of TCP_RTTVAR_SCALE
+ * is the same as the multiplier for rttvar.
+ */
+#define TCP_REXMTVAL(tp) \
+ (((tp)->t_srtt >> TCP_RTT_SHIFT) + (tp)->t_rttvar)
+
+#endif
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