/*
* Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
* 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 project 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 PROJECT 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 PROJECT 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).
*/
/*-
* Copyright (c) 1997, 1998, 2001, 2005, 2006 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Jason R. Thorpe and Kevin M. Lahey of the Numerical Aerospace Simulation
* Facility, NASA Ames Research Center.
* This code is derived from software contributed to The NetBSD Foundation
* by Charles M. Hannum.
* This code is derived from software contributed to The NetBSD Foundation
* by Rui Paulo.
*
* 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.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. 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 FOUNDATION 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 (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. 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
*/
/*
* Knob to enable Congestion Window Monitoring, and control
* the burst size it allows. Default burst is 4 packets, per
* the Internet draft.
*/
int tcp_cwm = 0;
int tcp_cwm_burstsize = 4;
int tcp_do_autosndbuf = 1;
int tcp_autosndbuf_inc = 8 * 1024;
int tcp_autosndbuf_max = 256 * 1024;
/*
* There may not be any room for data if mtu is too small. This
* includes zero-sized.
*/
if (size <= 0) {
return EMSGSIZE;
}
/*
* *rxsegsizep holds *estimated* inbound segment size (estimation
* assumes that path MTU is the same for both ways). this is only
* for silly window avoidance, do not use the value for other purposes.
*
* ipseclen is subtracted from both sides, this may not be right.
* I'm not quite sure about this (could someone comment).
*/
*txsegsizep = uimin(tp->t_peermss - optlen, size);
*rxsegsizep = uimin(tp->t_ourmss - optlen, size);
/*
* 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.
*/
if (so) {
*txsegsizep = uimin(so->so_snd.sb_hiwat >> 1, *txsegsizep);
}
/*
* A segment must at least store header + options
*/
if (*txsegsizep < hdrlen + optlen) {
return EMSGSIZE;
}
if (*txsegsizep != tp->t_segsz) {
/*
* If the new segment size is larger, we don't want to
* mess up the congestion window, but if it is smaller
* we'll have to reduce the congestion window to ensure
* that we don't get into trouble with initial windows
* and the rest. In any case, if the segment size
* has changed, chances are the path has, too, and
* our congestion window will be different.
*/
if (*txsegsizep < tp->t_segsz) {
tp->snd_cwnd = uimax((tp->snd_cwnd / tp->t_segsz)
* *txsegsizep, *txsegsizep);
tp->snd_ssthresh = uimax((tp->snd_ssthresh / tp->t_segsz)
* *txsegsizep, *txsegsizep);
}
tp->t_segsz = *txsegsizep;
}
return 0;
}
static int
tcp_build_datapkt(struct tcpcb *tp, struct socket *so, int off,
long len, int hdrlen, struct mbuf **mp)
{
struct mbuf *m, *m0;
net_stat_ref_t tcps;
/*
* XXX Because other code assumes headers will fit in
* XXX one header mbuf.
*
* (This code should almost *never* be run.)
*/
if (__predict_false((max_linkhdr + hdrlen) > MHLEN)) {
TCP_OUTPUT_COUNTER_INCR(&tcp_output_bigheader);
MCLGET(m, M_DONTWAIT);
if ((m->m_flags & M_EXT) == 0) {
m_freem(m);
return ENOBUFS;
}
}
m->m_data += max_linkhdr;
m->m_len = hdrlen;
/*
* To avoid traversing the whole sb_mb chain for correct
* data to send, remember last sent mbuf, its offset and
* the sent size. When called the next time, see if the
* data to send is directly following the previous transfer.
* This is important for large TCP windows.
*/
if (off == 0 || tp->t_lastm == NULL ||
(tp->t_lastoff + tp->t_lastlen) != off) {
TCP_OUTPUT_COUNTER_INCR(&tcp_output_predict_miss);
/*
* Either a new packet or a retransmit.
* Start from the beginning.
*/
tp->t_lastm = so->so_snd.sb_mb;
tp->t_inoff = off;
} else {
TCP_OUTPUT_COUNTER_INCR(&tcp_output_predict_hit);
tp->t_inoff += tp->t_lastlen;
}
/* Traverse forward to next packet */
while (tp->t_inoff > 0) {
if (tp->t_lastm == NULL)
panic("tp->t_lastm == NULL");
if (tp->t_inoff < tp->t_lastm->m_len)
break;
tp->t_inoff -= tp->t_lastm->m_len;
tp->t_lastm = tp->t_lastm->m_next;
}
/*
* Tcp output routine: figure out what should be sent and send it.
*/
int
tcp_output(struct tcpcb *tp)
{
struct rtentry *rt = NULL;
struct socket *so;
struct route *ro;
long len, win;
int off, flags, error;
struct mbuf *m;
struct ip *ip;
#ifdef INET6
struct ip6_hdr *ip6;
#endif
struct tcphdr *th;
u_char opt[MAX_TCPOPTLEN], *optp;
#define OPT_FITS(more) ((optlen + (more)) <= sizeof(opt))
unsigned optlen, hdrlen, packetlen;
unsigned int sack_numblks;
int idle, sendalot, txsegsize, rxsegsize;
int txsegsize_nosack;
int maxburst = TCP_MAXBURST;
int af; /* address family on the wire */
int iphdrlen;
int has_tso4, has_tso6;
int has_tso, use_tso;
bool alwaysfrag;
int sack_rxmit;
int sack_bytes_rxmt;
int ecn_tos;
struct sackhole *p;
#ifdef TCP_SIGNATURE
int sigoff = 0;
#endif
net_stat_ref_t tcps;
so = tp->t_inpcb->inp_socket;
ro = &tp->t_inpcb->inp_route;
switch (af = tp->t_family) {
case AF_INET:
case AF_INET6:
if (tp->t_inpcb)
break;
return EINVAL;
default:
return EAFNOSUPPORT;
}
if (tcp_segsize(tp, &txsegsize, &rxsegsize, &alwaysfrag))
return EMSGSIZE;
idle = (tp->snd_max == tp->snd_una);
/*
* Determine if we can use TCP segmentation offload:
* - If we're using IPv4
* - If there is not an IPsec policy that prevents it
* - If the interface can do it
*/
has_tso4 = has_tso6 = false;
/*
* Restart Window computation. From draft-floyd-incr-init-win-03:
*
* Optionally, a TCP MAY set the restart window to the
* minimum of the value used for the initial window and
* the current value of cwnd (in other words, using a
* larger value for the restart window should never increase
* the size of cwnd).
*/
if (tcp_cwm) {
/*
* Hughes/Touch/Heidemann Congestion Window Monitoring.
* Count the number of packets currently pending
* acknowledgement, and limit our congestion window
* to a pre-determined allowed burst size plus that count.
* This prevents bursting once all pending packets have
* been acknowledged (i.e. transmission is idle).
*
* XXX Link this to Initial Window?
*/
tp->snd_cwnd = uimin(tp->snd_cwnd,
(tcp_cwm_burstsize * txsegsize) +
(tp->snd_nxt - tp->snd_una));
} else {
if (idle && (tcp_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.
*/
int ss = tcp_init_win;
if (tp->t_inpcb->inp_af == AF_INET &&
in_localaddr(in4p_faddr(tp->t_inpcb)))
ss = tcp_init_win_local;
#ifdef INET6
else if (tp->t_inpcb->inp_af == AF_INET6 &&
in6_localaddr(&in6p_faddr(tp->t_inpcb)))
ss = tcp_init_win_local;
#endif
tp->snd_cwnd = uimin(tp->snd_cwnd,
TCP_INITIAL_WINDOW(ss, txsegsize));
}
}
/*
* Determine length of data that should be transmitted, and
* flags that should be used. If there is some data or critical
* controls (SYN, RST) to send, then transmit; otherwise,
* investigate further.
*
* Readjust SACK information to avoid resending duplicate data.
*/
if (TCP_SACK_ENABLED(tp) && SEQ_LT(tp->snd_nxt, tp->snd_max))
tcp_sack_adjust(tp);
sendalot = 0;
off = tp->snd_nxt - tp->snd_una;
win = uimin(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().
*/
/*
* Still in sack recovery, reset rxmit flag to zero.
*/
sack_rxmit = 0;
sack_bytes_rxmt = 0;
len = 0;
p = NULL;
do {
long cwin;
if (!TCP_SACK_ENABLED(tp))
break;
if (tp->t_partialacks < 0)
break;
p = tcp_sack_output(tp, &sack_bytes_rxmt);
if (p == NULL)
break;
cwin = uimin(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt;
if (cwin < 0)
cwin = 0;
/* Do not retransmit SACK segments beyond snd_recover */
if (SEQ_GT(p->end, tp->snd_recover)) {
/*
* (At least) part of sack hole extends beyond
* snd_recover. Check to see if we can rexmit data
* for this hole.
*/
if (SEQ_GEQ(p->rxmit, tp->snd_recover)) {
/*
* Can't rexmit any more data for this hole.
* That data will be rexmitted in the next
* sack recovery episode, when snd_recover
* moves past p->rxmit.
*/
p = NULL;
break;
}
/* Can rexmit part of the current hole */
len = ((long)ulmin(cwin, tp->snd_recover - p->rxmit));
} else
len = ((long)ulmin(cwin, p->end - p->rxmit));
off = p->rxmit - tp->snd_una;
if (off + len > so->so_snd.sb_cc) {
/* 1 for TH_FIN */
KASSERT(off + len == so->so_snd.sb_cc + 1);
KASSERT(p->rxmit + len == tp->snd_max);
len = so->so_snd.sb_cc - off;
}
if (len > 0) {
sack_rxmit = 1;
sendalot = 1;
}
} while (/*CONSTCOND*/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 == 0) {
if (TCP_SACK_ENABLED(tp) && tp->t_partialacks >= 0) {
long cwin;
/*
* We are inside of a SACK recovery episode and are
* sending new data, having retransmitted all the
* data possible in the scoreboard.
*/
if (tp->snd_wnd < so->so_snd.sb_cc) {
len = tp->snd_wnd - off;
flags &= ~TH_FIN;
} else {
len = so->so_snd.sb_cc - off;
}
/*
* From FreeBSD:
* Don't remove this (len > 0) check !
* We explicitly check for len > 0 here (although it
* isn't really necessary), to work around a gcc
* optimization issue - to force gcc to compute
* len above. Without this check, the computation
* of len is bungled by the optimizer.
*/
if (len > 0) {
cwin = tp->snd_cwnd -
(tp->snd_nxt - tp->sack_newdata) -
sack_bytes_rxmt;
if (cwin < 0)
cwin = 0;
if (cwin < len) {
len = cwin;
flags &= ~TH_FIN;
}
}
} else if (win < so->so_snd.sb_cc) {
len = win - off;
flags &= ~TH_FIN;
} else {
len = so->so_snd.sb_cc - 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.
*
* If we have a pending FIN, either it has already been
* transmitted or it is outside the window, so drop it.
* If the FIN has been transmitted, but this is not a
* retransmission, then len must be -1. Therefore we also
* prevent here the sending of `gratuitous FINs'. This
* eliminates the need to check for that case below (e.g.
* to back up snd_nxt before the FIN so that the sequence
* number is correct).
*/
len = 0;
flags &= ~TH_FIN;
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);
}
}
/*
* Automatic sizing enables the performance of large buffers
* and most of the efficiency of small ones by only allocating
* space when it is needed.
*
* The criteria to step up the send buffer one notch are:
* 1. receive window of remote host is larger than send buffer
* (with a fudge factor of 5/4th);
* 2. send buffer is filled to 7/8th with data (so we actually
* have data to make use of it);
* 3. send buffer fill has not hit maximal automatic size;
* 4. our send window (slow start and cogestion controlled) is
* larger than sent but unacknowledged data in send buffer.
*
* The remote host receive window scaling factor may limit the
* growing of the send buffer before it reaches its allowed
* maximum.
*
* It scales directly with slow start or congestion window
* and does at most one step per received ACK. This fast
* scaling has the drawback of growing the send buffer beyond
* what is strictly necessary to make full use of a given
* delay*bandwidth product. However testing has shown this not
* to be much of a problem. At worst we are trading wasting
* of available bandwidth (the non-use of it) for wasting some
* socket buffer memory.
*
* TODO: Shrink send buffer during idle periods together
* with congestion window. Requires another timer.
*/
if (tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) {
if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat &&
so->so_snd.sb_cc >= (so->so_snd.sb_hiwat / 8 * 7) &&
so->so_snd.sb_cc < tcp_autosndbuf_max &&
win >= (so->so_snd.sb_cc - (tp->snd_nxt - tp->snd_una))) {
if (!sbreserve(&so->so_snd,
uimin(so->so_snd.sb_hiwat + tcp_autosndbuf_inc,
tcp_autosndbuf_max), so))
so->so_snd.sb_flags &= ~SB_AUTOSIZE;
}
}
if (len > txsegsize) {
if (use_tso) {
/*
* Truncate TSO transfers to IP_MAXPACKET, and make
* sure that we send equal size transfers down the
* stack (rather than big-small-big-small-...).
*/
#ifdef INET6
CTASSERT(IPV6_MAXPACKET == IP_MAXPACKET);
#endif
len = (uimin(len, IP_MAXPACKET) / txsegsize) * txsegsize;
if (len <= txsegsize) {
use_tso = 0;
}
} else
len = txsegsize;
flags &= ~TH_FIN;
sendalot = 1;
} else
use_tso = 0;
if (sack_rxmit) {
if (SEQ_LT(p->rxmit + 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 >= txsegsize)
goto send;
if ((so->so_state & SS_MORETOCOME) == 0 &&
((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)
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 twice the size of the largest segment
* we expect to receive (i.e. two 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 recwin = uimin(win, (long)TCP_MAXWIN << tp->rcv_scale);
long oldwin, adv;
/*
* rcv_nxt may overtake rcv_adv when we accept a
* zero-window probe.
*/
if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt))
oldwin = tp->rcv_adv - tp->rcv_nxt;
else
oldwin = 0;
/*
* If the new window size ends up being the same as or
* less than the old size when it is scaled, then
* don't force a window update.
*/
if (recwin >> tp->rcv_scale <= oldwin >> tp->rcv_scale)
goto dontupdate;
/*
* Send if we owe peer an ACK.
*/
if (tp->t_flags & TF_ACKNOW)
goto send;
if (flags & (TH_SYN|TH_FIN|TH_RST))
goto send;
if (SEQ_GT(tp->snd_up, 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 (TCP_SACK_ENABLED(tp) && SEQ_GT(tp->snd_max, tp->snd_una) &&
!TCP_TIMER_ISARMED(tp, TCPT_REXMT) &&
!TCP_TIMER_ISARMED(tp, TCPT_PERSIST)) {
TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur);
goto just_return;
}
/*
* 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.
*/
just_return:
TCP_REASS_UNLOCK(tp);
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 + IP_header + TCP_header + optlen <= MCLBYTES
*/
optlen = 0;
optp = opt;
switch (af) {
case AF_INET:
iphdrlen = sizeof(struct ip) + sizeof(struct tcphdr);
break;
#ifdef INET6
case AF_INET6:
iphdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
break;
#endif
default: /*pacify gcc*/
iphdrlen = 0;
break;
}
hdrlen = iphdrlen;
if (flags & TH_SYN) {
struct rtentry *synrt;
/*
* 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))) {
int alen = 0;
while (optlen % 4 != 2) {
optlen += TCPOLEN_NOP;
*optp++ = TCPOPT_NOP;
alen++;
}
if (OPT_FITS(TCPOLEN_TIMESTAMP)) {
*optp++ = TCPOPT_TIMESTAMP;
*optp++ = TCPOLEN_TIMESTAMP;
uint32_t *lp = (uint32_t *)optp;
/* Form timestamp option (appendix A of RFC 1323) */
*lp++ = htonl(TCP_TIMESTAMP(tp));
*lp = htonl(tp->ts_recent);
optp += TCPOLEN_TIMESTAMP - 2;
optlen += TCPOLEN_TIMESTAMP;
/* Terminate and pad TCP options to a 4 byte boundary. */
if (optlen % 4) {
if (!OPT_FITS(TCPOLEN_EOL)) {
reset: TCP_REASS_UNLOCK(tp);
error = ECONNABORTED;
goto out;
}
optlen += TCPOLEN_EOL;
*optp++ = TCPOPT_EOL;
}
/*
* According to RFC 793 (STD0007):
* "The content of the header beyond the End-of-Option option
* must be header padding (i.e., zero)."
* and later: "The padding is composed of zeros."
*/
while (optlen % 4) {
if (!OPT_FITS(TCPOLEN_PAD))
goto reset;
optlen += TCPOLEN_PAD;
*optp++ = TCPOPT_PAD;
}
TCP_REASS_UNLOCK(tp);
hdrlen += optlen;
#ifdef DIAGNOSTIC
if (!use_tso && len > txsegsize)
panic("tcp data to be sent is larger than segment");
else if (use_tso && len > IP_MAXPACKET)
panic("tcp data to be sent is larger than max TSO size");
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) {
error = tcp_build_datapkt(tp, so, off, len, hdrlen, &m);
if (error)
goto out;
/*
* 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 {
tcps = TCP_STAT_GETREF();
if (tp->t_flags & TF_ACKNOW)
_NET_STATINC_REF(tcps, TCP_STAT_SNDACKS);
else if (flags & (TH_SYN|TH_FIN|TH_RST))
_NET_STATINC_REF(tcps, TCP_STAT_SNDCTRL);
else if (SEQ_GT(tp->snd_up, tp->snd_una))
_NET_STATINC_REF(tcps, TCP_STAT_SNDURG);
else
_NET_STATINC_REF(tcps, TCP_STAT_SNDWINUP);
TCP_STAT_PUTREF();
/*
* If we are starting a connection, send ECN setup
* SYN packet. If we are on a retransmit, we may
* resend those bits a number of times as per
* RFC 3168.
*/
if (tp->t_state == TCPS_SYN_SENT && tcp_do_ecn) {
if (tp->t_flags & TF_SYN_REXMT) {
if (tp->t_ecn_retries--)
flags |= TH_ECE|TH_CWR;
} else {
flags |= TH_ECE|TH_CWR;
tp->t_ecn_retries = tcp_ecn_maxretries;
}
}
if (TCP_ECN_ALLOWED(tp)) {
/*
* If the peer has ECN, mark data packets
* ECN capable. Ignore pure ack packets, retransmissions
* and window probes.
*/
if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) &&
!(tp->t_force && len == 1)) {
ecn_tos = IPTOS_ECN_ECT0;
TCP_STATINC(TCP_STAT_ECN_ECT);
}
/*
* Reply with proper ECN notifications.
*/
if (tp->t_flags & TF_ECN_SND_CWR) {
flags |= TH_CWR;
tp->t_flags &= ~TF_ECN_SND_CWR;
}
if (tp->t_flags & TF_ECN_SND_ECE) {
flags |= TH_ECE;
}
}
/*
* 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 (TCP_SACK_ENABLED(tp) && sack_rxmit) {
th->th_seq = htonl(p->rxmit);
p->rxmit += len;
} else {
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);
}
th->th_ack = htonl(tp->rcv_nxt);
if (optlen) {
memcpy(th + 1, opt, 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)rxsegsize)
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);
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 */
/*
* Set ourselves up to be checksummed just before the packet
* hits the wire.
*/
switch (af) {
case AF_INET:
m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
if (use_tso) {
m->m_pkthdr.segsz = txsegsize;
m->m_pkthdr.csum_flags = M_CSUM_TSOv4;
} else {
m->m_pkthdr.csum_flags = M_CSUM_TCPv4;
if (len + optlen) {
/* Fixup the pseudo-header checksum. */
/* XXXJRT Not IP Jumbogram safe. */
th->th_sum = in_cksum_addword(th->th_sum,
htons((u_int16_t) (len + optlen)));
}
}
break;
#ifdef INET6
case AF_INET6:
m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
if (use_tso) {
m->m_pkthdr.segsz = txsegsize;
m->m_pkthdr.csum_flags = M_CSUM_TSOv6;
} else {
m->m_pkthdr.csum_flags = M_CSUM_TCPv6;
if (len + optlen) {
/* Fixup the pseudo-header checksum. */
/* XXXJRT: Not IPv6 Jumbogram safe. */
th->th_sum = in_cksum_addword(th->th_sum,
htons((u_int16_t) (len + optlen)));
}
}
break;
#endif
}
/*
* 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.
* There are no states in which we send both a SYN and a FIN,
* so we collapse the tests for these flags.
*/
if (flags & (TH_SYN|TH_FIN))
tp->snd_nxt++;
if (sack_rxmit)
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 = tcp_now;
tp->t_rtseq = startseq;
TCP_STATINC(TCP_STAT_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 (TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0) {
if ((sack_rxmit && tp->snd_nxt != tp->snd_max)
|| tp->snd_nxt != tp->snd_una) {
if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST)) {
TCP_TIMER_DISARM(tp, TCPT_PERSIST);
tp->t_rxtshift = 0;
}
TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur);
} else if (len == 0 && so->so_snd.sb_cc > 0
&& TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) {
/*
* If we are sending a window probe and there's
* unacked data in the socket, make sure at
* least the persist timer is running.
*/
tp->t_rxtshift = 0;
tcp_setpersist(tp);
}
}
} else
if (SEQ_GT(tp->snd_nxt + len, tp->snd_max))
tp->snd_max = tp->snd_nxt + len;
#ifdef TCP_DEBUG
/*
* Trace.
*/
if (so->so_options & SO_DEBUG)
tcp_trace(TA_OUTPUT, tp->t_state, tp, m, 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 = hdrlen + len;
switch (af) {
case AF_INET:
ip->ip_len = htons(m->m_pkthdr.len);
packetlen = m->m_pkthdr.len;
if (tp->t_inpcb->inp_af == AF_INET) {
ip->ip_ttl = in4p_ip(tp->t_inpcb).ip_ttl;
ip->ip_tos = in4p_ip(tp->t_inpcb).ip_tos | ecn_tos;
}
#ifdef INET6
else if (tp->t_inpcb->inp_af == AF_INET6) {
ip->ip_ttl = in6pcb_selecthlim(tp->t_inpcb, NULL); /*XXX*/
ip->ip_tos = ecn_tos; /*XXX*/
}
#endif
break;
#ifdef INET6
case AF_INET6:
packetlen = m->m_pkthdr.len;
ip6->ip6_nxt = IPPROTO_TCP;
if (tp->t_family == AF_INET6) {
/*
* 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 = in6pcb_selecthlim_rt(tp->t_inpcb);
}
ip6->ip6_flow |= htonl(ecn_tos << 20);
/* ip6->ip6_flow = ??? (from template) */
/* ip6_plen will be filled in ip6_output(). */
break;
#endif
default: /*pacify gcc*/
packetlen = 0;
break;
}
/*
* 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;
TCP_CLEAR_DELACK(tp);
#ifdef DIAGNOSTIC
if (maxburst < 0)
printf("tcp_output: maxburst exceeded by %d\n", -maxburst);
#endif
if (sendalot && (tp->t_congctl == &tcp_reno_ctl || --maxburst))
goto again;
return 0;
}
void
tcp_setpersist(struct tcpcb *tp)
{
int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> (1 + 2);
int nticks;
if (TCP_TIMER_ISARMED(tp, TCPT_REXMT))
panic("tcp_output REXMT");
/*
* Start/restart persistance timer.
*/
if (t < tp->t_rttmin)
t = tp->t_rttmin;
TCPT_RANGESET(nticks, t * tcp_backoff[tp->t_rxtshift],
TCPTV_PERSMIN, TCPTV_PERSMAX);
TCP_TIMER_ARM(tp, TCPT_PERSIST, nticks);
if (tp->t_rxtshift < TCP_MAXRXTSHIFT)
tp->t_rxtshift++;
}
