diff options
Diffstat (limited to 'src/VBox/Devices/Network/slirp/tcp_output.c')
| -rw-r--r-- | src/VBox/Devices/Network/slirp/tcp_output.c | 739 |
1 files changed, 739 insertions, 0 deletions
diff --git a/src/VBox/Devices/Network/slirp/tcp_output.c b/src/VBox/Devices/Network/slirp/tcp_output.c new file mode 100644 index 00000000..9e61e77b --- /dev/null +++ b/src/VBox/Devices/Network/slirp/tcp_output.c @@ -0,0 +1,739 @@ +/* $Id: tcp_output.c $ */ +/** @file + * NAT - TCP output. + */ + +/* + * Copyright (C) 2006-2023 Oracle and/or its affiliates. + * + * This file is part of VirtualBox base platform packages, as + * available from https://www.virtualbox.org. + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation, in version 3 of the + * License. + * + * This program is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, see <https://www.gnu.org/licenses>. + * + * SPDX-License-Identifier: GPL-3.0-only + */ + +/* + * This code is based on: + * + * 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> + +/* + * Since this is only used in "stats socket", we give meaning + * names instead of the REAL names + */ +const char * const tcpstates[] = +{ +/* "CLOSED", "LISTEN", "SYN_SENT", "SYN_RCVD", */ + "REDIRECT", "LISTEN", "SYN_SENT", "SYN_RCVD", + "ESTABLISHED", "CLOSE_WAIT", "FIN_WAIT_1", "CLOSING", + "LAST_ACK", "FIN_WAIT_2", "TIME_WAIT", +}; + +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, +}; + + +#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(PNATState pData, register struct tcpcb *tp) +{ + register struct socket *so = tp->t_socket; + register long len, win; + int off, flags, error; + register struct mbuf *m = NULL; + register struct tcpiphdr *ti; + u_char opt[MAX_TCPOPTLEN]; + unsigned optlen, hdrlen; + int idle, sendalot; + int size = 0; + + LogFlowFunc(("ENTER: tcp_output: tp = %R[tcpcb793]\n", 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]; + + Log2((" --- 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 < SBUF_LEN(&so->so_snd)) + flags &= ~TH_FIN; + win = 1; + } + else + { + tp->t_timer[TCPT_PERSIST] = 0; + tp->t_rxtshift = 0; + } + } + + len = min(SBUF_LEN(&so->so_snd), 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 + SBUF_LEN(&so->so_snd))) + 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 >= SBUF_LEN(&so->so_snd)) + 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); + if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) + adv -= tp->rcv_adv - tp->rcv_nxt; + + if (adv >= (long) (2 * tp->t_maxseg)) + goto send; + if (2 * adv >= (long) SBUF_SIZE(&so->so_rcv)) + 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 ( SBUF_LEN(&so->so_snd) + && 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. + */ + tcpstat.tcps_didnuttin++; + + LogFlowFuncLeave(); + return (0); + +send: + LogFlowFunc(("send\n")); + /* + * 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) + { + u_int16_t mss; + + opt[0] = TCPOPT_MAXSEG; + opt[1] = 4; + mss = RT_H2N_U16((u_int16_t) tcp_mss(pData, tp, 0)); + memcpy((caddr_t)(opt + 2), (caddr_t)&mss, sizeof(mss)); + optlen = 4; + +#if 0 + if ( (tp->t_flags & TF_REQ_SCALE) + && ( (flags & TH_ACK) == 0 + || (tp->t_flags & TF_RCVD_SCALE))) + { + *((u_int32_t *) (opt + optlen)) = RT_H2N_U32( TCPOPT_NOP << 24 + | TCPOPT_WINDOW << 16 + | TCPOLEN_WINDOW << 8 + | tp->request_r_scale); + optlen += 4; + } +#endif + } + } + + /* + * Send a timestamp and echo-reply if this is a SYN and our side + * wants to use timestamps (TF_REQ_TSTMP is set) or both our side + * and our peer have sent timestamps in our SYN's. + */ +#if 0 + if ( (tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP + && (flags & TH_RST) == 0 + && ( (flags & (TH_SYN|TH_ACK)) == TH_SYN + || (tp->t_flags & TF_RCVD_TSTMP))) + { + u_int32_t *lp = (u_int32_t *)(opt + optlen); + + /* Form timestamp option as shown in appendix A of RFC 1323. */ + *lp++ = RT_H2N_U32_C(TCPOPT_TSTAMP_HDR); + *lp++ = RT_H2N_U32(tcp_now); + *lp = RT_H2N_U32(tp->ts_recent); + optlen += TCPOLEN_TSTAMP_APPA; + } +#endif + 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) + { + if (tp->t_force && len == 1) + tcpstat.tcps_sndprobe++; + else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) + { + tcpstat.tcps_sndrexmitpack++; + tcpstat.tcps_sndrexmitbyte += len; + } + else + { + tcpstat.tcps_sndpack++; + tcpstat.tcps_sndbyte += len; + } + + size = MCLBYTES; + if ((len + hdrlen + ETH_HLEN) < MSIZE) + size = MCLBYTES; + else if ((len + hdrlen + ETH_HLEN) < MCLBYTES) + size = MCLBYTES; + else if((len + hdrlen + ETH_HLEN) < MJUM9BYTES) + size = MJUM9BYTES; + else if ((len + hdrlen + ETH_HLEN) < MJUM16BYTES) + size = MJUM16BYTES; + else + AssertMsgFailed(("Unsupported size")); + m = m_getjcl(pData, M_NOWAIT, MT_HEADER, M_PKTHDR, size); + if (m == NULL) + { +/* error = ENOBUFS; */ + error = 1; + goto out; + } + m->m_data += if_maxlinkhdr; + m->m_pkthdr.header = mtod(m, void *); + m->m_len = hdrlen; + + /* + * This will always succeed, since we make sure our mbufs + * are big enough to hold one MSS packet + header + ... etc. + */ +#if 0 + if (len <= MHLEN - hdrlen - max_linkhdr) + { +#endif + sbcopy(&so->so_snd, off, (int) len, mtod(m, caddr_t) + hdrlen); + m->m_len += len; +#if 0 + } + else + { + m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len); + if (m->m_next == 0) + len = 0; + } +#endif + /* + * 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 == (ssize_t)SBUF_LEN(&so->so_snd)) + flags |= TH_PUSH; + } + else + { + bool fUninitializedTemplate = false; + if (tp->t_flags & TF_ACKNOW) + tcpstat.tcps_sndacks++; + else if (flags & (TH_SYN|TH_FIN|TH_RST)) + tcpstat.tcps_sndctrl++; + else if (SEQ_GT(tp->snd_up, tp->snd_una)) + tcpstat.tcps_sndurg++; + else + tcpstat.tcps_sndwinup++; + + if ((hdrlen + ETH_HLEN) < MSIZE) + { + size = MCLBYTES; + } + else if ((hdrlen + ETH_HLEN) < MCLBYTES) + { + size = MCLBYTES; + } + else if((hdrlen + ETH_HLEN) < MJUM9BYTES) + { + size = MJUM9BYTES; + } + else if ((hdrlen + ETH_HLEN) < MJUM16BYTES) + { + size = MJUM16BYTES; + } + else + { + AssertMsgFailed(("Unsupported size")); + } + m = m_getjcl(pData, M_NOWAIT, MT_HEADER, M_PKTHDR, size); + if (m == NULL) + { +/* error = ENOBUFS; */ + error = 1; + goto out; + } + m->m_data += if_maxlinkhdr; + m->m_pkthdr.header = mtod(m, void *); + m->m_len = hdrlen; + /* + * Uninitialized TCP template looks very suspicious at this processing state, thus why we have + * to workaround the problem till right fix. Warning appears once at release log. + */ + fUninitializedTemplate = RT_BOOL(( tp->t_template.ti_src.s_addr == INADDR_ANY + || tp->t_template.ti_dst.s_addr == INADDR_ANY)); +#ifndef DEBUG_vvl + if (fUninitializedTemplate) + { + static bool fWarn; + tcp_template(tp); + if(!fWarn) + { + LogRel(("NAT: TCP: TCP template was created forcely from socket information\n")); + fWarn = true; + } + } +#else + Assert((!fUninitializedTemplate)); +#endif + } + + 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 = RT_H2N_U32(tp->snd_nxt); + else + ti->ti_seq = RT_H2N_U32(tp->snd_max); + ti->ti_ack = RT_H2N_U32(tp->rcv_nxt); + if (optlen) + { + memcpy((caddr_t)(ti + 1), (caddr_t)opt, optlen); + ti->ti_off = (uint8_t)((sizeof (struct tcphdr) + optlen) >> 2); + } + ti->ti_flags = flags; + /* + * Calculate receive window. Don't shrink window, + * but avoid silly window syndrome. + */ + if (win < (long)(SBUF_SIZE(&so->so_rcv) / 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)(int32_t)(tp->rcv_adv - tp->rcv_nxt)) + win = (long)(int32_t)(tp->rcv_adv - tp->rcv_nxt); + ti->ti_win = RT_H2N_U16((u_int16_t) (win>>tp->rcv_scale)); + +#if 0 + if (SEQ_GT(tp->snd_up, tp->snd_nxt)) + { + ti->ti_urp = RT_H2N_U16((u_int16_t)(tp->snd_up - tp->snd_nxt)); +#else + if (SEQ_GT(tp->snd_up, tp->snd_una)) + { + ti->ti_urp = RT_H2N_U16((u_int16_t)(tp->snd_up - RT_N2H_U32(ti->ti_seq))); +#endif + 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 = RT_H2N_U16((u_int16_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; + tcpstat.tcps_segstimed++; + } + } + + /* + * 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_ASSERTPKTHDR(m); + m->m_pkthdr.header = mtod(m, void *); + 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 = ip_defttl; + ((struct ip *)ti)->ip_tos = so->so_iptos; + + /* #if BSD >= 43 */ + /* Don't do IP options... */ +#if 0 + error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route, + so->so_options & SO_DONTROUTE, 0); +#endif + error = ip_output(pData, so, m); + +#if 0 +/* #else */ + error = ip_output(m, (struct mbuf *)0, &tp->t_inpcb->inp_route, + so->so_options & SO_DONTROUTE); +/* #endif */ +#endif + } + if (error) + { +out: +#if 0 + if (error == ENOBUFS) + { + tcp_quench(tp->t_inpcb, 0); + return (0); + } + + if ( ( error == EHOSTUNREACH + || error == ENETDOWN) + && TCPS_HAVERCVDSYN(tp->t_state)) + { + tp->t_softerror = error; + return (0); + } +#endif + if (m != NULL) + m_freem(pData, m); + return (error); + } + tcpstat.tcps_sndtotal++; + + /* + * 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; + +#if 0 + if (tp->t_timer[TCPT_REXMT]) + panic("tcp_output REXMT"); +#endif + /* + * 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++; +} |