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tcp_output.c
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tcp_output.c
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/* $OpenBSD: tcp_output.c,v 1.144 2024/04/17 20:48:51 bluhm Exp $ */
/* $NetBSD: tcp_output.c,v 1.16 1997/06/03 16:17:09 kml Exp $ */
/*
* 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.
*
* @(#)COPYRIGHT 1.1 (NRL) 17 January 1995
*
* NRL grants permission for redistribution and use in source and binary
* forms, with or without modification, of the software and documentation
* created at NRL 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. All advertising materials mentioning features or use of this software
* must display the following acknowledgements:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* This product includes software developed at the Information
* Technology Division, US Naval Research Laboratory.
* 4. Neither the name of the NRL nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THE SOFTWARE PROVIDED BY NRL IS PROVIDED BY NRL 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 NRL 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.
*
* The views and conclusions contained in the software and documentation
* are those of the authors and should not be interpreted as representing
* official policies, either expressed or implied, of the US Naval
* Research Laboratory (NRL).
*/
#include "pf.h"
#include "stoeplitz.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/mbuf.h>
#include <sys/protosw.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/kernel.h>
#include <net/if.h>
#include <net/if_var.h>
#include <net/route.h>
#if NPF > 0
#include <net/pfvar.h>
#endif
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/in_pcb.h>
#include <netinet/ip_var.h>
#include <netinet6/ip6_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/tcp_debug.h>
#ifdef notyet
extern struct mbuf *m_copypack();
#endif
extern int tcprexmtthresh;
#ifdef TCP_SACK_DEBUG
void tcp_print_holes(struct tcpcb *tp);
void
tcp_print_holes(struct tcpcb *tp)
{
struct sackhole *p = tp->snd_holes;
if (p == NULL)
return;
printf("Hole report: start--end dups rxmit\n");
while (p) {
printf("%x--%x d %d r %x\n", p->start, p->end, p->dups,
p->rxmit);
p = p->next;
}
printf("\n");
}
#endif /* TCP_SACK_DEBUG */
/*
* Returns pointer to a sackhole if there are any pending retransmissions;
* NULL otherwise.
*/
struct sackhole *
tcp_sack_output(struct tcpcb *tp)
{
struct sackhole *p;
if (!tp->sack_enable)
return (NULL);
p = tp->snd_holes;
while (p) {
if (p->dups >= tcprexmtthresh && SEQ_LT(p->rxmit, p->end)) {
if (SEQ_LT(p->rxmit, tp->snd_una)) {/* old SACK hole */
p = p->next;
continue;
}
#ifdef TCP_SACK_DEBUG
if (p)
tcp_print_holes(tp);
#endif
return (p);
}
p = p->next;
}
return (NULL);
}
/*
* After a timeout, the SACK list may be rebuilt. This SACK information
* should be used to avoid retransmitting SACKed data. This function
* traverses the SACK list to see if snd_nxt should be moved forward.
*/
void
tcp_sack_adjust(struct tcpcb *tp)
{
struct sackhole *cur = tp->snd_holes;
if (cur == NULL)
return; /* No holes */
if (SEQ_GEQ(tp->snd_nxt, tp->rcv_lastsack))
return; /* We're already beyond any SACKed blocks */
/*
* Two cases for which we want to advance snd_nxt:
* i) snd_nxt lies between end of one hole and beginning of another
* ii) snd_nxt lies between end of last hole and rcv_lastsack
*/
while (cur->next) {
if (SEQ_LT(tp->snd_nxt, cur->end))
return;
if (SEQ_GEQ(tp->snd_nxt, cur->next->start))
cur = cur->next;
else {
tp->snd_nxt = cur->next->start;
return;
}
}
if (SEQ_LT(tp->snd_nxt, cur->end))
return;
tp->snd_nxt = tp->rcv_lastsack;
return;
}
/*
* Tcp output routine: figure out what should be sent and send it.
*/
int
tcp_output(struct tcpcb *tp)
{
struct socket *so = tp->t_inpcb->inp_socket;
long len, win, txmaxseg;
int off, flags, error;
struct mbuf *m;
struct tcphdr *th;
u_int32_t optbuf[howmany(MAX_TCPOPTLEN, sizeof(u_int32_t))];
u_char *opt = (u_char *)optbuf;
unsigned int optlen, hdrlen, packetlen;
int idle, sendalot = 0;
int i, sack_rxmit = 0;
struct sackhole *p;
uint64_t now;
#ifdef TCP_SIGNATURE
unsigned int sigoff;
#endif /* TCP_SIGNATURE */
#ifdef TCP_ECN
int needect;
#endif
int tso;
if (tp->t_flags & TF_BLOCKOUTPUT) {
tp->t_flags |= TF_NEEDOUTPUT;
return (0);
} else
tp->t_flags &= ~TF_NEEDOUTPUT;
#if defined(TCP_SIGNATURE) && defined(DIAGNOSTIC)
if (tp->sack_enable && (tp->t_flags & TF_SIGNATURE))
return (EINVAL);
#endif /* defined(TCP_SIGNATURE) && defined(DIAGNOSTIC) */
now = tcp_now();
/*
* 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->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una);
if (idle && (now - tp->t_rcvtime) >= 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 = 2 * tp->t_maxseg;
/* remember 'idle' for next invocation of tcp_output */
if (idle && soissending(so)) {
tp->t_flags |= TF_LASTIDLE;
idle = 0;
} else
tp->t_flags &= ~TF_LASTIDLE;
again:
/*
* If we've recently taken a timeout, snd_max will be greater than
* snd_nxt. There may be SACK information that allows us to avoid
* resending already delivered data. Adjust snd_nxt accordingly.
*/
if (tp->sack_enable && SEQ_LT(tp->snd_nxt, tp->snd_max))
tcp_sack_adjust(tp);
off = tp->snd_nxt - tp->snd_una;
win = ulmin(tp->snd_wnd, tp->snd_cwnd);
flags = tcp_outflags[tp->t_state];
/*
* Send any SACK-generated retransmissions. If we're explicitly trying
* to send out new data (when sendalot is 1), bypass this function.
* If we retransmit in fast recovery mode, decrement snd_cwnd, since
* we're replacing a (future) new transmission with a retransmission
* now, and we previously incremented snd_cwnd in tcp_input().
*/
if (tp->sack_enable && !sendalot) {
if (tp->t_dupacks >= tcprexmtthresh &&
(p = tcp_sack_output(tp))) {
off = p->rxmit - tp->snd_una;
sack_rxmit = 1;
/* Coalesce holes into a single retransmission */
len = min(tp->t_maxseg, p->end - p->rxmit);
if (SEQ_LT(tp->snd_una, tp->snd_last))
tp->snd_cwnd -= tp->t_maxseg;
}
}
sendalot = 0;
tso = 0;
/*
* 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 {
TCP_TIMER_DISARM(tp, TCPT_PERSIST);
tp->t_rxtshift = 0;
}
}
if (!sack_rxmit) {
len = ulmin(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, pull snd_nxt back
* to (closed) window, and set the persist timer
* if it isn't already going. If the window didn't
* close completely, just wait for an ACK.
*/
len = 0;
if (win == 0) {
TCP_TIMER_DISARM(tp, TCPT_REXMT);
tp->t_rxtshift = 0;
tp->snd_nxt = tp->snd_una;
if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0)
tcp_setpersist(tp);
}
}
/*
* Never send more than half a buffer full. This insures that we can
* always keep 2 packets on the wire, no matter what SO_SNDBUF is, and
* therefore acks will never be delayed unless we run out of data to
* transmit.
*/
txmaxseg = ulmin(so->so_snd.sb_hiwat / 2, tp->t_maxseg);
if (len > txmaxseg) {
if (tcp_do_tso &&
tp->t_inpcb->inp_options == NULL &&
tp->t_inpcb->inp_outputopts6 == NULL &&
#ifdef TCP_SIGNATURE
((tp->t_flags & TF_SIGNATURE) == 0) &&
#endif
len >= 2 * tp->t_maxseg &&
tp->rcv_numsacks == 0 && sack_rxmit == 0 &&
!(flags & (TH_SYN|TH_RST|TH_FIN))) {
tso = 1;
/* avoid small chopped packets */
if (len > (len / tp->t_maxseg) * tp->t_maxseg) {
len = (len / tp->t_maxseg) * tp->t_maxseg;
sendalot = 1;
}
} else {
len = txmaxseg;
sendalot = 1;
}
}
if (off + len < so->so_snd.sb_cc)
flags &= ~TH_FIN;
win = sbspace(so, &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 >= txmaxseg)
goto send;
if ((idle || (tp->t_flags & TF_NODELAY)) &&
len + off >= so->so_snd.sb_cc && !soissending(so) &&
(tp->t_flags & TF_NOPUSH) == 0)
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;
if (sack_rxmit)
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 = lmin(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_hiwat)
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;
/*
* In SACK, it is possible for tcp_output to fail to send a segment
* after the retransmission timer has been turned off. Make sure
* that the retransmission timer is set.
*/
if (SEQ_GT(tp->snd_max, tp->snd_una) &&
TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 &&
TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) {
TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur);
return (0);
}
/*
* 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 && TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 &&
TCP_TIMER_ISARMED(tp, 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(network header) + sizeof(struct tcphdr +
* optlen <= MHLEN
*/
optlen = 0;
switch (tp->pf) {
case 0: /*default to PF_INET*/
case PF_INET:
hdrlen = sizeof(struct ip) + sizeof(struct tcphdr);
break;
#ifdef INET6
case PF_INET6:
hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
break;
#endif /* INET6 */
default:
return (EPFNOSUPPORT);
}
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 = htons((u_int16_t) tcp_mss(tp, 0));
memcpy(opt + 2, &mss, sizeof(mss));
optlen = 4;
if (flags & TH_ACK)
tcp_mss_update(tp);
/*
* If this is the first SYN of connection (not a SYN
* ACK), include SACK_PERMIT_HDR option. If this is a
* SYN ACK, include SACK_PERMIT_HDR option if peer has
* already done so.
*/
if (tp->sack_enable && ((flags & TH_ACK) == 0 ||
(tp->t_flags & TF_SACK_PERMIT))) {
*((u_int32_t *) (opt + optlen)) =
htonl(TCPOPT_SACK_PERMIT_HDR);
optlen += 4;
}
if ((tp->t_flags & TF_REQ_SCALE) &&
((flags & TH_ACK) == 0 ||
(tp->t_flags & TF_RCVD_SCALE))) {
*((u_int32_t *) (opt + optlen)) = htonl(
TCPOPT_NOP << 24 |
TCPOPT_WINDOW << 16 |
TCPOLEN_WINDOW << 8 |
tp->request_r_scale);
optlen += 4;
}
}
}
/*
* 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 ((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++ = htonl(TCPOPT_TSTAMP_HDR);
*lp++ = htonl(now + tp->ts_modulate);
*lp = htonl(tp->ts_recent);
optlen += TCPOLEN_TSTAMP_APPA;
}
/* Set receive buffer autosizing timestamp. */
if (tp->rfbuf_ts == 0) {
tp->rfbuf_ts = now;
tp->rfbuf_cnt = 0;
}
#ifdef TCP_SIGNATURE
if (tp->t_flags & TF_SIGNATURE) {
u_int8_t *bp = (u_int8_t *)(opt + optlen);
/* Send signature option */
*(bp++) = TCPOPT_SIGNATURE;
*(bp++) = TCPOLEN_SIGNATURE;
sigoff = optlen + 2;
{
unsigned int i;
for (i = 0; i < 16; i++)
*(bp++) = 0;
}
/* Pad options list to the next 32 bit boundary and
* terminate it.
*/
*bp++ = TCPOPT_NOP;
*bp++ = TCPOPT_NOP;
optlen += TCPOLEN_SIGLEN;
}
#endif /* TCP_SIGNATURE */
/*
* Send SACKs if necessary. This should be the last option processed.
* Only as many SACKs are sent as are permitted by the maximum options
* size. No more than three SACKs are sent.
*/
if (tp->sack_enable && tp->t_state == TCPS_ESTABLISHED &&
(tp->t_flags & (TF_SACK_PERMIT|TF_NOOPT)) == TF_SACK_PERMIT &&
tp->rcv_numsacks) {
u_int32_t *lp = (u_int32_t *)(opt + optlen);
u_int32_t *olp = lp++;
int count = 0; /* actual number of SACKs inserted */
int maxsack = (MAX_TCPOPTLEN - (optlen + 4))/TCPOLEN_SACK;
tcpstat_inc(tcps_sack_snd_opts);
maxsack = min(maxsack, TCP_MAX_SACK);
for (i = 0; (i < tp->rcv_numsacks && count < maxsack); i++) {
struct sackblk sack = tp->sackblks[i];
if (sack.start == 0 && sack.end == 0)
continue;
*lp++ = htonl(sack.start);
*lp++ = htonl(sack.end);
count++;
}
*olp = htonl(TCPOPT_SACK_HDR|(TCPOLEN_SACK*count+2));
optlen += TCPOLEN_SACK*count + 4; /* including leading NOPs */
}
#ifdef DIAGNOSTIC
if (optlen > MAX_TCPOPTLEN)
panic("tcp_output: options too long");
#endif /* DIAGNOSTIC */
hdrlen += optlen;
/*
* Adjust data length if insertion of options will
* bump the packet length beyond the t_maxopd length.
* Clear the FIN bit because we cut off the tail of
* the segment.
*/
if (len > tp->t_maxopd - optlen) {
if (tso) {
if (len + hdrlen + max_linkhdr > MAXMCLBYTES) {
len = MAXMCLBYTES - hdrlen - max_linkhdr;
sendalot = 1;
}
} else {
len = tp->t_maxopd - optlen;
sendalot = 1;
}
flags &= ~TH_FIN;
}
#ifdef DIAGNOSTIC
if (max_linkhdr + hdrlen > MCLBYTES)
panic("tcphdr too big");
#endif
/*
* 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_inc(tcps_sndprobe);
else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) {
tcpstat_pkt(tcps_sndrexmitpack, tcps_sndrexmitbyte,
len);
tp->t_sndrexmitpack++;
} else {
tcpstat_pkt(tcps_sndpack, tcps_sndbyte, len);
}
#ifdef notyet
if ((m = m_copypack(so->so_snd.sb_mb, off,
(int)len, max_linkhdr + hdrlen)) == 0) {
error = ENOBUFS;
goto out;
}
/*
* m_copypack left space for our hdr; use it.
*/
m->m_len += hdrlen;
m->m_data -= hdrlen;
#else
MGETHDR(m, M_DONTWAIT, MT_HEADER);
if (m != NULL && max_linkhdr + hdrlen > MHLEN) {
MCLGET(m, M_DONTWAIT);
if ((m->m_flags & M_EXT) == 0) {
m_freem(m);
m = NULL;
}
}
if (m == NULL) {
error = ENOBUFS;
goto out;
}
m->m_data += max_linkhdr;
m->m_len = hdrlen;
if (len <= m_trailingspace(m)) {
m_copydata(so->so_snd.sb_mb, off, (int) len,
mtod(m, caddr_t) + hdrlen);
m->m_len += len;
} else {
m->m_next = m_copym(so->so_snd.sb_mb, off, (int) len,
M_NOWAIT);
if (m->m_next == 0) {
(void) m_free(m);
error = ENOBUFS;
goto out;
}
}
if (so->so_snd.sb_mb->m_flags & M_PKTHDR)
m->m_pkthdr.ph_loopcnt =
so->so_snd.sb_mb->m_pkthdr.ph_loopcnt;
#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 == so->so_snd.sb_cc && !soissending(so))
flags |= TH_PUSH;
tp->t_sndtime = now;
} else {
if (tp->t_flags & TF_ACKNOW)
tcpstat_inc(tcps_sndacks);
else if (flags & (TH_SYN|TH_FIN|TH_RST))
tcpstat_inc(tcps_sndctrl);
else if (SEQ_GT(tp->snd_up, tp->snd_una))
tcpstat_inc(tcps_sndurg);
else
tcpstat_inc(tcps_sndwinup);
MGETHDR(m, M_DONTWAIT, MT_HEADER);
if (m != NULL && max_linkhdr + hdrlen > MHLEN) {
MCLGET(m, M_DONTWAIT);
if ((m->m_flags & M_EXT) == 0) {
m_freem(m);
m = NULL;
}
}
if (m == NULL) {
error = ENOBUFS;
goto out;
}
m->m_data += max_linkhdr;
m->m_len = hdrlen;
}
m->m_pkthdr.ph_ifidx = 0;
m->m_pkthdr.len = hdrlen + len;
/* Enable TSO and specify the size of the resulting segments. */
if (tso) {
SET(m->m_pkthdr.csum_flags, M_TCP_TSO);
m->m_pkthdr.ph_mss = tp->t_maxseg;
}
if (!tp->t_template)
panic("tcp_output");
#ifdef DIAGNOSTIC
if (tp->t_template->m_len != hdrlen - optlen)
panic("tcp_output: template len != hdrlen - optlen");
#endif /* DIAGNOSTIC */
memcpy(mtod(m, caddr_t), mtod(tp->t_template, caddr_t),
tp->t_template->m_len);
th = (struct tcphdr *)(mtod(m, caddr_t) + tp->t_template->m_len -
sizeof(struct tcphdr));
/*
* 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)) ||
TCP_TIMER_ISARMED(tp, TCPT_PERSIST))
th->th_seq = htonl(tp->snd_nxt);
else
th->th_seq = htonl(tp->snd_max);
if (sack_rxmit) {
/*
* If sendalot was turned on (due to option stuffing), turn it
* off. Properly set th_seq field. Advance the ret'x pointer
* by len.
*/
if (sendalot)
sendalot = 0;
th->th_seq = htonl(p->rxmit);
p->rxmit += len;
tcpstat_pkt(tcps_sack_rexmits, tcps_sack_rexmit_bytes, len);
}
th->th_ack = htonl(tp->rcv_nxt);
if (optlen) {
memcpy(th + 1, opt, optlen);
th->th_off = (sizeof (struct tcphdr) + optlen) >> 2;
}
#ifdef TCP_ECN
if (tcp_do_ecn) {
/*
* if we have received congestion experienced segs,
* set ECE bit.
*/
if (tp->t_flags & TF_RCVD_CE) {
flags |= TH_ECE;
tcpstat_inc(tcps_ecn_sndece);
}
if (!(tp->t_flags & TF_DISABLE_ECN)) {
/*
* if this is a SYN seg, set ECE and CWR.
* set only ECE for SYN-ACK if peer supports ECN.
*/
if ((flags & (TH_SYN|TH_ACK)) == TH_SYN)
flags |= (TH_ECE|TH_CWR);
else if ((tp->t_flags & TF_ECN_PERMIT) &&
(flags & (TH_SYN|TH_ACK)) == (TH_SYN|TH_ACK))
flags |= TH_ECE;
}
/*
* if we have reduced the congestion window, notify
* the peer by setting CWR bit.
*/
if ((tp->t_flags & TF_ECN_PERMIT) &&
(tp->t_flags & TF_SEND_CWR)) {
flags |= TH_CWR;
tp->t_flags &= ~TF_SEND_CWR;
tcpstat_inc(tcps_ecn_sndcwr);
}
}
#endif
th->th_flags = flags;
/*
* Calculate receive window. Don't shrink window,
* but avoid silly window syndrome.
*/
if (win < (long)(so->so_rcv.sb_hiwat / 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);
if (flags & TH_RST)
win = 0;
th->th_win = htons((u_int16_t) (win>>tp->rcv_scale));
if (th->th_win == 0)
tp->t_sndzerowin++;
if (SEQ_GT(tp->snd_up, tp->snd_nxt)) {
u_int32_t urp = tp->snd_up - tp->snd_nxt;
if (urp > IP_MAXPACKET)
urp = IP_MAXPACKET;
th->th_urp = htons((u_int16_t)urp);
th->th_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 */
#ifdef TCP_SIGNATURE
if (tp->t_flags & TF_SIGNATURE) {
int iphlen;
union sockaddr_union src, dst;
struct tdb *tdb;
bzero(&src, sizeof(union sockaddr_union));
bzero(&dst, sizeof(union sockaddr_union));
switch (tp->pf) {
case 0: /*default to PF_INET*/
case AF_INET:
iphlen = sizeof(struct ip);
src.sa.sa_len = sizeof(struct sockaddr_in);
src.sa.sa_family = AF_INET;
src.sin.sin_addr = mtod(m, struct ip *)->ip_src;
dst.sa.sa_len = sizeof(struct sockaddr_in);
dst.sa.sa_family = AF_INET;
dst.sin.sin_addr = mtod(m, struct ip *)->ip_dst;
break;
#ifdef INET6
case AF_INET6:
iphlen = sizeof(struct ip6_hdr);
src.sa.sa_len = sizeof(struct sockaddr_in6);
src.sa.sa_family = AF_INET6;
src.sin6.sin6_addr = mtod(m, struct ip6_hdr *)->ip6_src;
dst.sa.sa_len = sizeof(struct sockaddr_in6);
dst.sa.sa_family = AF_INET6;
dst.sin6.sin6_addr = mtod(m, struct ip6_hdr *)->ip6_dst;
break;
#endif /* INET6 */
}
tdb = gettdbbysrcdst(rtable_l2(tp->t_inpcb->inp_rtableid),
0, &src, &dst, IPPROTO_TCP);
if (tdb == NULL) {
m_freem(m);
return (EPERM);
}
if (tcp_signature(tdb, tp->pf, m, th, iphlen, 0,
mtod(m, caddr_t) + hdrlen - optlen + sigoff) < 0) {
m_freem(m);
tdb_unref(tdb);
return (EINVAL);
}
tdb_unref(tdb);
}
#endif /* TCP_SIGNATURE */
/* Defer checksumming until later (ip_output() or hardware) */
m->m_pkthdr.csum_flags |= M_TCP_CSUM_OUT;
/*
* In transmit state, time the transmission and arrange for
* the retransmit. In persist state, just set snd_max.
*/
if (tp->t_force == 0 || TCP_TIMER_ISARMED(tp, 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;
}
}
if (tp->sack_enable) {
if (sack_rxmit && (p->rxmit != tp->snd_nxt)) {
goto timer;
}
}
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_rtttime == 0) {
tp->t_rtttime = now;
tp->t_rtseq = startseq;
tcpstat_inc(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.
*/
timer:
if (tp->sack_enable && sack_rxmit &&
TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 &&
tp->snd_nxt != tp->snd_max) {
TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur);
if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST)) {
TCP_TIMER_DISARM(tp, TCPT_PERSIST);
tp->t_rxtshift = 0;
}
}
if (TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 &&
tp->snd_nxt != tp->snd_una) {
TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur);
if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST)) {
TCP_TIMER_DISARM(tp, TCPT_PERSIST);
tp->t_rxtshift = 0;
}
}