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freebsd/sys/netinet/tcp_output.c
Archie Cobbs 7734ea0612 Improve performance in the case where ip_output() returns an error. 
When this happens, we know for sure that the packet data was not
received by the peer. Therefore, back out any advancing of the
transmit sequence number so that we send the same data the next
time we transmit a packet, avoiding a guaranteed missed packet and
its resulting TCP transmit slowdown.

In most systems ip_output() probably never returns an error, and
so this problem is never seen. However, it is more likely to occur
with device drivers having short output queues (causing ENOBUFS to
be returned when they are full), not to mention low memory situations.

Moreover, because of this problem writers of slow devices were
required to make an unfortunate choice between (a) having a relatively
short output queue (with low latency but low TCP bandwidth because
of this problem) or (b) a long output queue (with high latency and
high TCP bandwidth). In my particular application (ISDN) it took
an output queue equal to ~5 seconds of transmission to avoid ENOBUFS.
A more reasonable output queue of 0.5 seconds resulted in only about
50% TCP throughput. With this patch full throughput was restored in
the latter case.

Reviewed by:	freebsd-net
2000-08-03 23:23:36 +00:00

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/*
* Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
* 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. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. 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 8.4 (Berkeley) 5/24/95
* $FreeBSD$
*/
#include "opt_inet6.h"
#include "opt_ipsec.h"
#include "opt_tcpdebug.h"
#include <stddef.h>
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/sysctl.h>
#include <sys/mbuf.h>
#include <sys/domain.h>
#include <sys/protosw.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <net/route.h>
#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/in_pcb.h>
#include <netinet/ip_var.h>
#ifdef INET6
#include <netinet6/in6_pcb.h>
#include <netinet/ip6.h>
#include <netinet6/ip6_var.h>
#endif
#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/tcpip.h>
#ifdef TCPDEBUG
#include <netinet/tcp_debug.h>
#endif
#ifdef IPSEC
#include <netinet6/ipsec.h>
#endif /*IPSEC*/
#include <machine/in_cksum.h>
#ifdef notyet
extern struct mbuf *m_copypack();
#endif
static int path_mtu_discovery = 1;
SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW,
&path_mtu_discovery, 1, "Enable Path MTU Discovery");
int ss_fltsz = 1;
SYSCTL_INT(_net_inet_tcp, OID_AUTO, slowstart_flightsize, CTLFLAG_RW,
&ss_fltsz, 1, "Slow start flight size");
int ss_fltsz_local = TCP_MAXWIN; /* something large */
SYSCTL_INT(_net_inet_tcp, OID_AUTO, local_slowstart_flightsize, CTLFLAG_RW,
&ss_fltsz_local, 1, "Slow start flight size for local networks");
int tcp_do_newreno = 1;
SYSCTL_INT(_net_inet_tcp, OID_AUTO, newreno, CTLFLAG_RW, &tcp_do_newreno,
0, "Enable NewReno Algorithms");
/*
* Tcp output routine: figure out what should be sent and send it.
*/
int
tcp_output(tp)
register struct tcpcb *tp;
{
register struct socket *so = tp->t_inpcb->inp_socket;
register long len, win;
int off, flags, error;
register struct mbuf *m;
struct ip *ip = NULL;
register struct ipovly *ipov = NULL;
#ifdef INET6
struct ip6_hdr *ip6 = NULL;
#endif /* INET6 */
register struct tcphdr *th;
u_char opt[TCP_MAXOLEN];
unsigned ipoptlen, optlen, hdrlen;
int idle, sendalot;
int maxburst = TCP_MAXBURST;
struct rmxp_tao *taop;
struct rmxp_tao tao_noncached;
#ifdef INET6
int isipv6;
#endif
#ifdef INET6
isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0;
#endif
/*
* 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 && (ticks - 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.
*
* Set the slow-start flight size depending on whether
* this is a local network or not.
*/
if (
#ifdef INET6
(isipv6 && in6_localaddr(&tp->t_inpcb->in6p_faddr)) ||
(!isipv6 &&
#endif
in_localaddr(tp->t_inpcb->inp_faddr)
#ifdef INET6
)
#endif
)
tp->snd_cwnd = tp->t_maxseg * ss_fltsz_local;
else
tp->snd_cwnd = tp->t_maxseg * ss_fltsz;
}
again:
sendalot = 0;
off = tp->snd_nxt - tp->snd_una;
win = min(tp->snd_wnd, tp->snd_cwnd);
flags = tcp_outflags[tp->t_state];
/*
* Get standard flags, and add SYN or FIN if requested by 'hidden'
* state flags.
*/
if (tp->t_flags & TF_NEEDFIN)
flags |= TH_FIN;
if (tp->t_flags & TF_NEEDSYN)
flags |= TH_SYN;
/*
* 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 unsent 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 {
callout_stop(tp->tt_persist);
tp->t_rxtshift = 0;
}
}
len = (long)ulmin(so->so_snd.sb_cc, win) - off;
if ((taop = tcp_gettaocache(tp->t_inpcb)) == NULL) {
taop = &tao_noncached;
bzero(taop, sizeof(*taop));
}
/*
* Lop off SYN bit if it has already been sent. However, if this
* is SYN-SENT state and if segment contains data and if we don't
* know that foreign host supports TAO, suppress sending segment.
*/
if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) {
flags &= ~TH_SYN;
off--, len++;
if (len > 0 && tp->t_state == TCPS_SYN_SENT &&
taop->tao_ccsent == 0)
return 0;
}
/*
* Be careful not to send data and/or FIN on SYN segments
* in cases when no CC option will be sent.
* This measure is needed to prevent interoperability problems
* with not fully conformant TCP implementations.
*/
if ((flags & TH_SYN) &&
((tp->t_flags & TF_NOOPT) || !(tp->t_flags & TF_REQ_CC) ||
((flags & TH_ACK) && !(tp->t_flags & TF_RCVD_CC)))) {
len = 0;
flags &= ~TH_FIN;
}
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) {
callout_stop(tp->tt_rexmt);
tp->t_rxtshift = 0;
tp->snd_nxt = tp->snd_una;
if (!callout_active(tp->tt_persist))
tcp_setpersist(tp);
}
}
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 (!(tp->t_flags & TF_MORETOCOME) &&
(idle || tp->t_flags & TF_NODELAY) &&
(tp->t_flags & TF_NOPUSH) == 0 &&
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_hiwat)
goto send;
}
/*
* Send if we owe peer an ACK.
*/
if (tp->t_flags & TF_ACKNOW)
goto send;
if ((flags & TH_RST) ||
((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0))
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
*
* callout_active(tp->tt_persist)
* is true when we are in persist state.
* tp->t_force
* is set when we are called to send a persist packet.
* callout_active(tp->tt_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 && !callout_active(tp->tt_rexmt) &&
!callout_active(tp->tt_persist)) {
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;
#ifdef INET6
if (isipv6)
hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr);
else
#endif
hdrlen = sizeof (struct tcpiphdr);
if (flags & TH_SYN) {
tp->snd_nxt = tp->iss;
if ((tp->t_flags & TF_NOOPT) == 0) {
u_short mss;
opt[0] = TCPOPT_MAXSEG;
opt[1] = TCPOLEN_MAXSEG;
mss = htons((u_short) tcp_mssopt(tp));
(void)memcpy(opt + 2, &mss, sizeof(mss));
optlen = TCPOLEN_MAXSEG;
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_ACK) == 0 ||
(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(ticks);
*lp = htonl(tp->ts_recent);
optlen += TCPOLEN_TSTAMP_APPA;
}
/*
* Send `CC-family' options if our side wants to use them (TF_REQ_CC),
* options are allowed (!TF_NOOPT) and it's not a RST.
*/
if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC &&
(flags & TH_RST) == 0) {
switch (flags & (TH_SYN|TH_ACK)) {
/*
* This is a normal ACK, send CC if we received CC before
* from our peer.
*/
case TH_ACK:
if (!(tp->t_flags & TF_RCVD_CC))
break;
/*FALLTHROUGH*/
/*
* We can only get here in T/TCP's SYN_SENT* state, when
* we're a sending a non-SYN segment without waiting for
* the ACK of our SYN. A check above assures that we only
* do this if our peer understands T/TCP.
*/
case 0:
opt[optlen++] = TCPOPT_NOP;
opt[optlen++] = TCPOPT_NOP;
opt[optlen++] = TCPOPT_CC;
opt[optlen++] = TCPOLEN_CC;
*(u_int32_t *)&opt[optlen] = htonl(tp->cc_send);
optlen += 4;
break;
/*
* This is our initial SYN, check whether we have to use
* CC or CC.new.
*/
case TH_SYN:
opt[optlen++] = TCPOPT_NOP;
opt[optlen++] = TCPOPT_NOP;
opt[optlen++] = tp->t_flags & TF_SENDCCNEW ?
TCPOPT_CCNEW : TCPOPT_CC;
opt[optlen++] = TCPOLEN_CC;
*(u_int32_t *)&opt[optlen] = htonl(tp->cc_send);
optlen += 4;
break;
/*
* This is a SYN,ACK; send CC and CC.echo if we received
* CC from our peer.
*/
case (TH_SYN|TH_ACK):
if (tp->t_flags & TF_RCVD_CC) {
opt[optlen++] = TCPOPT_NOP;
opt[optlen++] = TCPOPT_NOP;
opt[optlen++] = TCPOPT_CC;
opt[optlen++] = TCPOLEN_CC;
*(u_int32_t *)&opt[optlen] =
htonl(tp->cc_send);
optlen += 4;
opt[optlen++] = TCPOPT_NOP;
opt[optlen++] = TCPOPT_NOP;
opt[optlen++] = TCPOPT_CCECHO;
opt[optlen++] = TCPOLEN_CC;
*(u_int32_t *)&opt[optlen] =
htonl(tp->cc_recv);
optlen += 4;
}
break;
}
}
hdrlen += optlen;
#ifdef INET6
if (isipv6)
ipoptlen = ip6_optlen(tp->t_inpcb);
else
#endif
{
if (tp->t_inpcb->inp_options) {
ipoptlen = tp->t_inpcb->inp_options->m_len -
offsetof(struct ipoption, ipopt_list);
} else {
ipoptlen = 0;
}
}
#ifdef IPSEC
ipoptlen += ipsec_hdrsiz_tcp(tp);
#endif
/*
* 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 + optlen + ipoptlen > tp->t_maxopd) {
/*
* If there is still more to send, don't close the connection.
*/
flags &= ~TH_FIN;
len = tp->t_maxopd - optlen - ipoptlen;
sendalot = 1;
}
/*#ifdef DIAGNOSTIC*/
#ifdef INET6
if (max_linkhdr + hdrlen > MCLBYTES)
panic("tcphdr too big");
#else
if (max_linkhdr + hdrlen > MHLEN)
panic("tcphdr too big");
#endif
/*#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.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;
}
#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) {
error = ENOBUFS;
goto out;
}
#ifdef INET6
if (MHLEN < hdrlen + max_linkhdr) {
MCLGET(m, M_DONTWAIT);
if ((m->m_flags & M_EXT) == 0) {
m_freem(m);
error = ENOBUFS;
goto out;
}
}
#endif
m->m_data += max_linkhdr;
m->m_len = hdrlen;
if (len <= MHLEN - hdrlen - max_linkhdr) {
m_copydata(so->so_snd.sb_mb, off, (int) len,
mtod(m, caddr_t) + hdrlen);
m->m_len += len;
} else {
m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len);
if (m->m_next == 0) {
(void) m_free(m);
error = ENOBUFS;
goto out;
}
}
#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)
flags |= TH_PUSH;
} else {
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++;
MGETHDR(m, M_DONTWAIT, MT_HEADER);
if (m == NULL) {
error = ENOBUFS;
goto out;
}
#ifdef INET6
if (isipv6 && (MHLEN < hdrlen + max_linkhdr) &&
MHLEN >= hdrlen) {
MH_ALIGN(m, hdrlen);
} else
#endif
m->m_data += max_linkhdr;
m->m_len = hdrlen;
}
m->m_pkthdr.rcvif = (struct ifnet *)0;
if (tp->t_template == 0)
panic("tcp_output");
#ifdef INET6
if (isipv6) {
ip6 = mtod(m, struct ip6_hdr *);
th = (struct tcphdr *)(ip6 + 1);
bcopy((caddr_t)tp->t_template->tt_ipgen, (caddr_t)ip6,
sizeof(struct ip6_hdr));
bcopy((caddr_t)&tp->t_template->tt_t, (caddr_t)th,
sizeof(struct tcphdr));
} else
#endif /* INET6 */
{
ip = mtod(m, struct ip *);
ipov = (struct ipovly *)ip;
th = (struct tcphdr *)(ip + 1);
/* this picks up the pseudo header (w/o the length) */
bcopy((caddr_t)tp->t_template->tt_ipgen, (caddr_t)ip,
sizeof(struct ip));
bcopy((caddr_t)&tp->t_template->tt_t, (caddr_t)th,
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))
|| callout_active(tp->tt_persist))
th->th_seq = htonl(tp->snd_nxt);
else
th->th_seq = htonl(tp->snd_max);
th->th_ack = htonl(tp->rcv_nxt);
if (optlen) {
bcopy(opt, th + 1, optlen);
th->th_off = (sizeof (struct tcphdr) + optlen) >> 2;
}
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)(tp->rcv_adv - tp->rcv_nxt))
win = (long)(tp->rcv_adv - tp->rcv_nxt);
if (win > (long)TCP_MAXWIN << tp->rcv_scale)
win = (long)TCP_MAXWIN << tp->rcv_scale;
th->th_win = htons((u_short) (win>>tp->rcv_scale));
if (SEQ_GT(tp->snd_up, tp->snd_nxt)) {
th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt));
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 */
/*
* Put TCP length in extended header, and then
* checksum extended header and data.
*/
m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */
#ifdef INET6
if (isipv6)
/*
* ip6_plen is not need to be filled now, and will be filled
* in ip6_output.
*/
th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr),
sizeof(struct tcphdr) + optlen + len);
else
#endif /* INET6 */
{
m->m_pkthdr.csum_flags = CSUM_TCP;
m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
if (len + optlen)
th->th_sum = in_addword(th->th_sum,
htons((u_short)(optlen + len)));
/* IP version must be set here for ipv4/ipv6 checking later */
KASSERT(ip->ip_v == IPVERSION,
("%s: IP version incorrect: %d", __FUNCTION__, ip->ip_v));
}
/*
* In transmit state, time the transmission and arrange for
* the retransmit. In persist state, just set snd_max.
*/
if (tp->t_force == 0 || !callout_active(tp->tt_persist)) {
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_rtttime == 0) {
tp->t_rtttime = ticks;
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 (!callout_active(tp->tt_rexmt) &&
tp->snd_nxt != tp->snd_una) {
if (callout_active(tp->tt_persist)) {
callout_stop(tp->tt_persist);
tp->t_rxtshift = 0;
}
callout_reset(tp->tt_rexmt, tp->t_rxtcur,
tcp_timer_rexmt, tp);
}
} else
if (SEQ_GT(tp->snd_nxt + len, tp->snd_max))
tp->snd_max = tp->snd_nxt + len;
#ifdef TCPDEBUG
/*
* Trace.
*/
if (so->so_options & SO_DEBUG)
tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0);
#endif
/*
* 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_pkthdr.len should have been set before cksum calcuration,
* because in6_cksum() need it.
*/
#ifdef INET6
if (isipv6) {
/*
* we separately set hoplimit for every segment, since the
* user might want to change the value via setsockopt.
* Also, desired default hop limit might be changed via
* Neighbor Discovery.
*/
ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb,
tp->t_inpcb->in6p_route.ro_rt ?
tp->t_inpcb->in6p_route.ro_rt->rt_ifp
: NULL);
/* TODO: IPv6 IP6TOS_ECT bit on */
#ifdef IPSEC
ipsec_setsocket(m, so);
#endif /*IPSEC*/
error = ip6_output(m,
tp->t_inpcb->in6p_outputopts,
&tp->t_inpcb->in6p_route,
(so->so_options & SO_DONTROUTE), NULL, NULL);
} else
#endif /* INET6 */
{
struct rtentry *rt;
ip->ip_len = m->m_pkthdr.len;
#ifdef INET6
if (INP_CHECK_SOCKAF(so, AF_INET6))
ip->ip_ttl = in6_selecthlim(tp->t_inpcb,
tp->t_inpcb->in6p_route.ro_rt ?
tp->t_inpcb->in6p_route.ro_rt->rt_ifp
: NULL);
else
#endif /* INET6 */
ip->ip_ttl = tp->t_inpcb->inp_ip_ttl; /* XXX */
ip->ip_tos = tp->t_inpcb->inp_ip_tos; /* XXX */
/*
* See if we should do MTU discovery. We do it only if the following
* are true:
* 1) we have a valid route to the destination
* 2) the MTU is not locked (if it is, then discovery has been
* disabled)
*/
if (path_mtu_discovery
&& (rt = tp->t_inpcb->inp_route.ro_rt)
&& rt->rt_flags & RTF_UP
&& !(rt->rt_rmx.rmx_locks & RTV_MTU)) {
ip->ip_off |= IP_DF;
}
#ifdef IPSEC
ipsec_setsocket(m, so);
#endif /*IPSEC*/
error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route,
(so->so_options & SO_DONTROUTE), 0);
}
if (error) {
/*
* We know that the packet was lost, so back out the
* sequence number advance, if any.
*/
if (tp->t_force == 0 || !callout_active(tp->tt_persist)) {
/*
* No need to check for TH_FIN here because
* the TF_SENTFIN flag handles that case.
*/
if (flags & TH_SYN)
tp->snd_nxt--;
tp->snd_nxt -= len;
}
out:
if (error == ENOBUFS) {
if (!callout_active(tp->tt_rexmt) &&
!callout_active(tp->tt_persist))
callout_reset(tp->tt_rexmt, tp->t_rxtcur,
tcp_timer_rexmt, tp);
tcp_quench(tp->t_inpcb, 0);
return (0);
}
if (error == EMSGSIZE) {
/*
* ip_output() will have already fixed the route
* for us. tcp_mtudisc() will, as its last action,
* initiate retransmission, so it is important to
* not do so here.
*/
tcp_mtudisc(tp->t_inpcb, 0);
return 0;
}
if ((error == EHOSTUNREACH || error == ENETDOWN)
&& TCPS_HAVERCVDSYN(tp->t_state)) {
tp->t_softerror = error;
return (0);
}
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;
if (tcp_delack_enabled)
callout_stop(tp->tt_delack);
if (sendalot && (!tcp_do_newreno || --maxburst))
goto again;
return (0);
}
void
tcp_setpersist(tp)
register struct tcpcb *tp;
{
int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1;
int tt;
if (callout_active(tp->tt_rexmt))
panic("tcp_setpersist: retransmit pending");
/*
* Start/restart persistance timer.
*/
TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift],
TCPTV_PERSMIN, TCPTV_PERSMAX);
callout_reset(tp->tt_persist, tt, tcp_timer_persist, tp);
if (tp->t_rxtshift < TCP_MAXRXTSHIFT)
tp->t_rxtshift++;
}
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