--- /dev/null
+/*
+ * Copyright (c) 1982, 1986, 1988, 1990, 1993
+ * 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_output.c 8.3 (Berkeley) 12/30/93
+ * tcp_output.c,v 1.3 1994/09/15 10:36:55 davidg Exp
+ */
+
+/*
+ * Changes and additions relating to SLiRP
+ * Copyright (c) 1995 Danny Gasparovski.
+ *
+ * Please read the file COPYRIGHT for the
+ * terms and conditions of the copyright.
+ */
+
+#include <slirp.h>
+
+static const u_char tcp_outflags[TCP_NSTATES] = {
+ TH_RST|TH_ACK, 0, TH_SYN, TH_SYN|TH_ACK,
+ TH_ACK, TH_ACK, TH_FIN|TH_ACK, TH_FIN|TH_ACK,
+ TH_FIN|TH_ACK, TH_ACK, TH_ACK,
+};
+
+
+#undef MAX_TCPOPTLEN
+#define MAX_TCPOPTLEN 32 /* max # bytes that go in options */
+
+/*
+ * Tcp output routine: figure out what should be sent and send it.
+ */
+int
+tcp_output(struct tcpcb *tp)
+{
+ register struct socket *so = tp->t_socket;
+ register long len, win;
+ int off, flags, error;
+ register struct mbuf *m;
+ register struct tcpiphdr *ti;
+ u_char opt[MAX_TCPOPTLEN];
+ unsigned optlen, hdrlen;
+ int idle, sendalot;
+
+ DEBUG_CALL("tcp_output");
+ DEBUG_ARG("tp = %lx", (long )tp);
+
+ /*
+ * 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.
+ */
+ idle = (tp->snd_max == tp->snd_una);
+ if (idle && tp->t_idle >= tp->t_rxtcur)
+ /*
+ * We have been idle for "a while" and no acks are
+ * expected to clock out any data we send --
+ * slow start to get ack "clock" running again.
+ */
+ tp->snd_cwnd = tp->t_maxseg;
+again:
+ sendalot = 0;
+ off = tp->snd_nxt - tp->snd_una;
+ win = min(tp->snd_wnd, tp->snd_cwnd);
+
+ flags = tcp_outflags[tp->t_state];
+
+ DEBUG_MISC((dfd, " --- tcp_output flags = 0x%x\n",flags));
+
+ /*
+ * If in persist timeout with window of 0, send 1 byte.
+ * Otherwise, if window is small but nonzero
+ * and timer expired, we will send what we can
+ * and go to transmit state.
+ */
+ if (tp->t_force) {
+ if (win == 0) {
+ /*
+ * If we still have some data to send, then
+ * clear the FIN bit. Usually this would
+ * happen below when it realizes that we
+ * aren't sending all the data. However,
+ * if we have exactly 1 byte of unset data,
+ * then it won't clear the FIN bit below,
+ * and if we are in persist state, we wind
+ * up sending the packet without recording
+ * that we sent the FIN bit.
+ *
+ * We can't just blindly clear the FIN bit,
+ * because if we don't have any more data
+ * to send then the probe will be the FIN
+ * itself.
+ */
+ if (off < so->so_snd.sb_cc)
+ flags &= ~TH_FIN;
+ win = 1;
+ } else {
+ tp->t_timer[TCPT_PERSIST] = 0;
+ tp->t_rxtshift = 0;
+ }
+ }
+
+ len = min(so->so_snd.sb_cc, win) - off;
+
+ if (len < 0) {
+ /*
+ * If FIN has been sent but not acked,
+ * but we haven't been called to retransmit,
+ * len will be -1. Otherwise, window shrank
+ * after we sent into it. If window shrank to 0,
+ * cancel pending retransmit and pull snd_nxt
+ * back to (closed) window. We will enter persist
+ * state below. If the window didn't close completely,
+ * just wait for an ACK.
+ */
+ len = 0;
+ if (win == 0) {
+ tp->t_timer[TCPT_REXMT] = 0;
+ tp->snd_nxt = tp->snd_una;
+ }
+ }
+
+ if (len > tp->t_maxseg) {
+ len = tp->t_maxseg;
+ sendalot = 1;
+ }
+ if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc))
+ flags &= ~TH_FIN;
+
+ win = sbspace(&so->so_rcv);
+
+ /*
+ * Sender silly window avoidance. If connection is idle
+ * and can send all data, a maximum segment,
+ * at least a maximum default-size segment do it,
+ * or are forced, do it; otherwise don't bother.
+ * If peer's buffer is tiny, then send
+ * when window is at least half open.
+ * If retransmitting (possibly after persist timer forced us
+ * to send into a small window), then must resend.
+ */
+ if (len) {
+ if (len == tp->t_maxseg)
+ goto send;
+ if ((1 || idle || tp->t_flags & TF_NODELAY) &&
+ len + off >= so->so_snd.sb_cc)
+ goto send;
+ if (tp->t_force)
+ goto send;
+ if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0)
+ goto send;
+ if (SEQ_LT(tp->snd_nxt, tp->snd_max))
+ goto send;
+ }
+
+ /*
+ * Compare available window to amount of window
+ * known to peer (as advertised window less
+ * next expected input). If the difference is at least two
+ * max size segments, or at least 50% of the maximum possible
+ * window, then want to send a window update to peer.
+ */
+ if (win > 0) {
+ /*
+ * "adv" is the amount we can increase the window,
+ * taking into account that we are limited by
+ * TCP_MAXWIN << tp->rcv_scale.
+ */
+ long adv = min(win, (long)TCP_MAXWIN << tp->rcv_scale) -
+ (tp->rcv_adv - tp->rcv_nxt);
+
+ if (adv >= (long) (2 * tp->t_maxseg))
+ goto send;
+ if (2 * adv >= (long) so->so_rcv.sb_datalen)
+ goto send;
+ }
+
+ /*
+ * Send if we owe peer an ACK.
+ */
+ if (tp->t_flags & TF_ACKNOW)
+ goto send;
+ if (flags & (TH_SYN|TH_RST))
+ goto send;
+ if (SEQ_GT(tp->snd_up, tp->snd_una))
+ goto send;
+ /*
+ * If our state indicates that FIN should be sent
+ * and we have not yet done so, or we're retransmitting the FIN,
+ * then we need to send.
+ */
+ if (flags & TH_FIN &&
+ ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una))
+ goto send;
+
+ /*
+ * 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 small or 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 too small, there is data to transmit, and no
+ * retransmit or persist is pending, then go to persist state.
+ * If nothing happens soon, send when timer expires:
+ * if window is nonzero, transmit what we can,
+ * otherwise force out a byte.
+ */
+ if (so->so_snd.sb_cc && tp->t_timer[TCPT_REXMT] == 0 &&
+ tp->t_timer[TCPT_PERSIST] == 0) {
+ tp->t_rxtshift = 0;
+ tcp_setpersist(tp);
+ }
+
+ /*
+ * No reason to send a segment, just return.
+ */
+ return (0);
+
+send:
+ /*
+ * Before ESTABLISHED, force sending of initial options
+ * unless TCP set not to do any options.
+ * NOTE: we assume that the IP/TCP header plus TCP options
+ * always fit in a single mbuf, leaving room for a maximum
+ * link header, i.e.
+ * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MHLEN
+ */
+ optlen = 0;
+ hdrlen = sizeof (struct tcpiphdr);
+ if (flags & TH_SYN) {
+ tp->snd_nxt = tp->iss;
+ if ((tp->t_flags & TF_NOOPT) == 0) {
+ uint16_t mss;
+
+ opt[0] = TCPOPT_MAXSEG;
+ opt[1] = 4;
+ mss = htons((uint16_t) tcp_mss(tp, 0));
+ memcpy((caddr_t)(opt + 2), (caddr_t)&mss, sizeof(mss));
+ optlen = 4;
+ }
+ }
+
+ hdrlen += optlen;
+
+ /*
+ * Adjust data length if insertion of options will
+ * bump the packet length beyond the t_maxseg length.
+ */
+ if (len > tp->t_maxseg - optlen) {
+ len = tp->t_maxseg - optlen;
+ sendalot = 1;
+ }
+
+ /*
+ * Grab a header mbuf, attaching a copy of data to
+ * be transmitted, and initialize the header from
+ * the template for sends on this connection.
+ */
+ if (len) {
+ m = m_get(so->slirp);
+ if (m == NULL) {
+ error = 1;
+ goto out;
+ }
+ m->m_data += IF_MAXLINKHDR;
+ m->m_len = hdrlen;
+
+ sbcopy(&so->so_snd, off, (int) len, mtod(m, caddr_t) + hdrlen);
+ m->m_len += len;
+
+ /*
+ * If we're sending everything we've got, 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 (off + len == so->so_snd.sb_cc)
+ flags |= TH_PUSH;
+ } else {
+ m = m_get(so->slirp);
+ if (m == NULL) {
+ error = 1;
+ goto out;
+ }
+ m->m_data += IF_MAXLINKHDR;
+ m->m_len = hdrlen;
+ }
+
+ ti = mtod(m, struct tcpiphdr *);
+
+ memcpy((caddr_t)ti, &tp->t_template, sizeof (struct tcpiphdr));
+
+ /*
+ * Fill in fields, remembering maximum advertised
+ * window for use in delaying messages about window sizes.
+ * If resending a FIN, be sure not to use a new sequence number.
+ */
+ if (flags & TH_FIN && tp->t_flags & TF_SENTFIN &&
+ tp->snd_nxt == tp->snd_max)
+ tp->snd_nxt--;
+ /*
+ * If we are doing retransmissions, then snd_nxt will
+ * not reflect the first unsent octet. For ACK only
+ * packets, we do not want the sequence number of the
+ * retransmitted packet, we want the sequence number
+ * of the next unsent octet. So, if there is no data
+ * (and no SYN or FIN), use snd_max instead of snd_nxt
+ * when filling in ti_seq. But if we are in persist
+ * state, snd_max might reflect one byte beyond the
+ * right edge of the window, so use snd_nxt in that
+ * case, since we know we aren't doing a retransmission.
+ * (retransmit and persist are mutually exclusive...)
+ */
+ if (len || (flags & (TH_SYN|TH_FIN)) || tp->t_timer[TCPT_PERSIST])
+ ti->ti_seq = htonl(tp->snd_nxt);
+ else
+ ti->ti_seq = htonl(tp->snd_max);
+ ti->ti_ack = htonl(tp->rcv_nxt);
+ if (optlen) {
+ memcpy((caddr_t)(ti + 1), (caddr_t)opt, optlen);
+ ti->ti_off = (sizeof (struct tcphdr) + optlen) >> 2;
+ }
+ ti->ti_flags = flags;
+ /*
+ * Calculate receive window. Don't shrink window,
+ * but avoid silly window syndrome.
+ */
+ if (win < (long)(so->so_rcv.sb_datalen / 4) && win < (long)tp->t_maxseg)
+ win = 0;
+ if (win > (long)TCP_MAXWIN << tp->rcv_scale)
+ win = (long)TCP_MAXWIN << tp->rcv_scale;
+ if (win < (long)(tp->rcv_adv - tp->rcv_nxt))
+ win = (long)(tp->rcv_adv - tp->rcv_nxt);
+ ti->ti_win = htons((uint16_t) (win>>tp->rcv_scale));
+
+ if (SEQ_GT(tp->snd_up, tp->snd_una)) {
+ ti->ti_urp = htons((uint16_t)(tp->snd_up - ntohl(ti->ti_seq)));
+ 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 */
+
+ /*
+ * Put TCP length in extended header, and then
+ * checksum extended header and data.
+ */
+ if (len + optlen)
+ ti->ti_len = htons((uint16_t)(sizeof (struct tcphdr) +
+ optlen + len));
+ ti->ti_sum = cksum(m, (int)(hdrlen + len));
+
+ /*
+ * In transmit state, time the transmission and arrange for
+ * the retransmit. In persist state, just set snd_max.
+ */
+ if (tp->t_force == 0 || tp->t_timer[TCPT_PERSIST] == 0) {
+ tcp_seq startseq = tp->snd_nxt;
+
+ /*
+ * Advance snd_nxt over sequence space of this segment.
+ */
+ if (flags & (TH_SYN|TH_FIN)) {
+ if (flags & TH_SYN)
+ tp->snd_nxt++;
+ if (flags & TH_FIN) {
+ tp->snd_nxt++;
+ tp->t_flags |= TF_SENTFIN;
+ }
+ }
+ tp->snd_nxt += len;
+ if (SEQ_GT(tp->snd_nxt, tp->snd_max)) {
+ tp->snd_max = tp->snd_nxt;
+ /*
+ * Time this transmission if not a retransmission and
+ * not currently timing anything.
+ */
+ if (tp->t_rtt == 0) {
+ tp->t_rtt = 1;
+ tp->t_rtseq = startseq;
+ }
+ }
+
+ /*
+ * Set retransmit timer if not currently set,
+ * and not doing an ack or a keep-alive probe.
+ * Initial value for retransmit timer is smoothed
+ * round-trip time + 2 * round-trip time variance.
+ * Initialize shift counter which is used for backoff
+ * of retransmit time.
+ */
+ if (tp->t_timer[TCPT_REXMT] == 0 &&
+ tp->snd_nxt != tp->snd_una) {
+ tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
+ if (tp->t_timer[TCPT_PERSIST]) {
+ tp->t_timer[TCPT_PERSIST] = 0;
+ tp->t_rxtshift = 0;
+ }
+ }
+ } else
+ if (SEQ_GT(tp->snd_nxt + len, tp->snd_max))
+ tp->snd_max = tp->snd_nxt + len;
+
+ /*
+ * Fill in IP length and desired time to live and
+ * send to IP level. There should be a better way
+ * to handle ttl and tos; we could keep them in
+ * the template, but need a way to checksum without them.
+ */
+ m->m_len = hdrlen + len; /* XXX Needed? m_len should be correct */
+
+ {
+
+ ((struct ip *)ti)->ip_len = m->m_len;
+
+ ((struct ip *)ti)->ip_ttl = IPDEFTTL;
+ ((struct ip *)ti)->ip_tos = so->so_iptos;
+
+ error = ip_output(so, m);
+ }
+ if (error) {
+out:
+ return (error);
+ }
+
+ /*
+ * 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.
+ * Any pending ACK has now been sent.
+ */
+ if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv))
+ tp->rcv_adv = tp->rcv_nxt + win;
+ tp->last_ack_sent = tp->rcv_nxt;
+ tp->t_flags &= ~(TF_ACKNOW|TF_DELACK);
+ if (sendalot)
+ goto again;
+
+ return (0);
+}
+
+void
+tcp_setpersist(struct tcpcb *tp)
+{
+ int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1;
+
+ /*
+ * Start/restart persistence timer.
+ */
+ TCPT_RANGESET(tp->t_timer[TCPT_PERSIST],
+ t * tcp_backoff[tp->t_rxtshift],
+ TCPTV_PERSMIN, TCPTV_PERSMAX);
+ if (tp->t_rxtshift < TCP_MAXRXTSHIFT)
+ tp->t_rxtshift++;
+}
Code Review / kvmfornfv.git / blobdiff