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freebsd-skq/sys/netinet/tcp_stacks/fastpath.c

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First cut of the modularization of our TCP stack. Still to do is to clean up the timer handling using the async-drain. Other optimizations may be coming to go with this. Whats here will allow differnet tcp implementations (one included). Reviewed by: jtl, hiren, transports Sponsored by: Netflix Inc. Differential Revision: D4055
2015-12-16 00:56:45 +00:00
/*-
* Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995
* The Regents of the University of California. All rights reserved.
* Copyright (c) 2007-2008,2010
* Swinburne University of Technology, Melbourne, Australia.
* Copyright (c) 2009-2010 Lawrence Stewart <lstewart@freebsd.org>
* Copyright (c) 2010 The FreeBSD Foundation
* Copyright (c) 2010-2011 Juniper Networks, Inc.
* Copyright (c) 2015 Netflix Inc.
* All rights reserved.
*
* Portions of this software were developed at the Centre for Advanced Internet
* Architectures, Swinburne University of Technology, by Lawrence Stewart,
* James Healy and David Hayes, made possible in part by a grant from the Cisco
* University Research Program Fund at Community Foundation Silicon Valley.
*
* Portions of this software were developed at the Centre for Advanced
* Internet Architectures, Swinburne University of Technology, Melbourne,
* Australia by David Hayes under sponsorship from the FreeBSD Foundation.
*
* Portions of this software were developed by Robert N. M. Watson under
* contract to Juniper Networks, Inc.
*
* Portions of this software were developed by Randall R. Stewart while
* working for Netflix Inc.
*
* 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.
* 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_input.c 8.12 (Berkeley) 5/24/95
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_ipfw.h" /* for ipfw_fwd */
#include "opt_inet.h"
#include "opt_inet6.h"
#include "opt_ipsec.h"
#include "opt_kdtrace.h"
#include "opt_tcpdebug.h"
#include <sys/param.h>
#include <sys/module.h>
#include <sys/kernel.h>
#include <sys/hhook.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/proc.h> /* for proc0 declaration */
#include <sys/protosw.h>
#include <sys/sdt.h>
#include <sys/signalvar.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/sysctl.h>
#include <sys/syslog.h>
#include <sys/systm.h>
#include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */
#include <vm/uma.h>
#include <net/if.h>
#include <net/if_var.h>
#include <net/route.h>
#include <net/vnet.h>
#define TCPSTATES /* for logging */
#include <netinet/cc.h>
#include <netinet/in.h>
#include <netinet/in_kdtrace.h>
#include <netinet/in_pcb.h>
#include <netinet/in_systm.h>
#include <netinet/in_var.h>
#include <netinet/ip.h>
#include <netinet/ip_icmp.h> /* required for icmp_var.h */
#include <netinet/icmp_var.h> /* for ICMP_BANDLIM */
#include <netinet/ip_var.h>
#include <netinet/ip_options.h>
#include <netinet/ip6.h>
#include <netinet/icmp6.h>
#include <netinet6/in6_pcb.h>
#include <netinet6/ip6_var.h>
#include <netinet6/nd6.h>
#include <netinet/tcp_fsm.h>
#include <netinet/tcp_seq.h>
#include <netinet/tcp_timer.h>
#include <netinet/tcp_var.h>
#include <netinet6/tcp6_var.h>
#include <netinet/tcpip.h>
#include <netinet/tcp_syncache.h>
#ifdef TCPDEBUG
#include <netinet/tcp_debug.h>
#endif /* TCPDEBUG */
#ifdef TCP_OFFLOAD
#include <netinet/tcp_offload.h>
#endif
#ifdef IPSEC
#include <netipsec/ipsec.h>
#include <netipsec/ipsec6.h>
#endif /*IPSEC*/
#include <machine/in_cksum.h>
#include <security/mac/mac_framework.h>
const int tcprexmtthresh;
VNET_DECLARE(int, tcp_autorcvbuf_inc);
#define V_tcp_autorcvbuf_inc VNET(tcp_autorcvbuf_inc)
VNET_DECLARE(int, tcp_autorcvbuf_max);
#define V_tcp_autorcvbuf_max VNET(tcp_autorcvbuf_max)
VNET_DECLARE(int, tcp_do_rfc3042);
#define V_tcp_do_rfc3042 VNET(tcp_do_rfc3042)
VNET_DECLARE(int, tcp_do_autorcvbuf);
#define V_tcp_do_autorcvbuf VNET(tcp_do_autorcvbuf)
VNET_DECLARE(int, tcp_insecure_rst);
#define V_tcp_insecure_rst VNET(tcp_insecure_rst)
VNET_DECLARE(int, tcp_insecure_syn);
#define V_tcp_insecure_syn VNET(tcp_insecure_syn)
static void tcp_do_segment_fastslow(struct mbuf *, struct tcphdr *,
struct socket *, struct tcpcb *, int, int, uint8_t,
int);
static void tcp_do_segment_fastack(struct mbuf *, struct tcphdr *,
struct socket *, struct tcpcb *, int, int, uint8_t,
int);
/*
* Indicate whether this ack should be delayed. We can delay the ack if
* following conditions are met:
* - There is no delayed ack timer in progress.
* - Our last ack wasn't a 0-sized window. We never want to delay
* the ack that opens up a 0-sized window.
* - LRO wasn't used for this segment. We make sure by checking that the
* segment size is not larger than the MSS.
* - Delayed acks are enabled or this is a half-synchronized T/TCP
* connection.
*/
#define DELAY_ACK(tp, tlen) \
((!tcp_timer_active(tp, TT_DELACK) && \
(tp->t_flags & TF_RXWIN0SENT) == 0) && \
(tlen <= tp->t_maxopd) && \
(V_tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN)))
/*
* So how is this faster than the normal fast ack?
* It basically allows us to also stay in the fastpath
* when a window-update ack also arrives. In testing
* we saw only 25-30% of connections doing fastpath
* due to the fact that along with moving forward
* in sequence the window was also updated.
*/
static void
tcp_do_fastack(struct mbuf *m, struct tcphdr *th, struct socket *so,
struct tcpcb *tp, struct tcpopt *to, int drop_hdrlen, int tlen,
int ti_locked, u_long tiwin)
{
int acked;
int winup_only=0;
#ifdef TCPDEBUG
/*
* The size of tcp_saveipgen must be the size of the max ip header,
* now IPv6.
*/
u_char tcp_saveipgen[IP6_HDR_LEN];
struct tcphdr tcp_savetcp;
short ostate = 0;
#endif
/*
* The following if statment will be true if
* we are doing the win_up_in_fp <and>
* - We have more new data (SEQ_LT(tp->snd_wl1, th->th_seq)) <or>
* - No more new data, but we have an ack for new data
* (tp->snd_wl1 == th->th_seq && SEQ_LT(tp->snd_wl2, th->th_ack))
* - No more new data, the same ack point but the window grew
* (tp->snd_wl1 == th->th_seq && tp->snd_wl2 == th->th_ack && twin > tp->snd_wnd)
*/
if ((SEQ_LT(tp->snd_wl1, th->th_seq) ||
(tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) ||
(tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) {
/* keep track of pure window updates */
if (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) {
winup_only = 1;
TCPSTAT_INC(tcps_rcvwinupd);
}
tp->snd_wnd = tiwin;
tp->snd_wl1 = th->th_seq;
tp->snd_wl2 = th->th_ack;
if (tp->snd_wnd > tp->max_sndwnd)
tp->max_sndwnd = tp->snd_wnd;
}
/*
* If last ACK falls within this segment's sequence numbers,
* record the timestamp.
* NOTE that the test is modified according to the latest
* proposal of the tcplw@cray.com list (Braden 1993/04/26).
*/
if ((to->to_flags & TOF_TS) != 0 &&
SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
tp->ts_recent_age = tcp_ts_getticks();
tp->ts_recent = to->to_tsval;
}
/*
* This is a pure ack for outstanding data.
*/
if (ti_locked == TI_RLOCKED) {
INP_INFO_RUNLOCK(&V_tcbinfo);
}
ti_locked = TI_UNLOCKED;
TCPSTAT_INC(tcps_predack);
/*
* "bad retransmit" recovery.
*/
if (tp->t_rxtshift == 1 &&
tp->t_flags & TF_PREVVALID &&
(int)(ticks - tp->t_badrxtwin) < 0) {
cc_cong_signal(tp, th, CC_RTO_ERR);
}
/*
* Recalculate the transmit timer / rtt.
*
* Some boxes send broken timestamp replies
* during the SYN+ACK phase, ignore
* timestamps of 0 or we could calculate a
* huge RTT and blow up the retransmit timer.
*/
if ((to->to_flags & TOF_TS) != 0 &&
to->to_tsecr) {
u_int t;
t = tcp_ts_getticks() - to->to_tsecr;
if (!tp->t_rttlow || tp->t_rttlow > t)
tp->t_rttlow = t;
tcp_xmit_timer(tp,
TCP_TS_TO_TICKS(t) + 1);
} else if (tp->t_rtttime &&
SEQ_GT(th->th_ack, tp->t_rtseq)) {
if (!tp->t_rttlow ||
tp->t_rttlow > ticks - tp->t_rtttime)
tp->t_rttlow = ticks - tp->t_rtttime;
tcp_xmit_timer(tp,
ticks - tp->t_rtttime);
}
if (winup_only == 0) {
acked = BYTES_THIS_ACK(tp, th);
/* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */
hhook_run_tcp_est_in(tp, th, to);
TCPSTAT_ADD(tcps_rcvackbyte, acked);
sbdrop(&so->so_snd, acked);
if (SEQ_GT(tp->snd_una, tp->snd_recover) &&
SEQ_LEQ(th->th_ack, tp->snd_recover))
tp->snd_recover = th->th_ack - 1;
/*
* Let the congestion control algorithm update
* congestion control related information. This
* typically means increasing the congestion
* window.
*/
cc_ack_received(tp, th, CC_ACK);
tp->snd_una = th->th_ack;
/*
* Pull snd_wl2 up to prevent seq wrap relative
* to th_ack.
*/
tp->snd_wl2 = th->th_ack;
tp->t_dupacks = 0;
m_freem(m);
/*
* If all outstanding data are acked, stop
* retransmit timer, otherwise restart timer
* using current (possibly backed-off) value.
* If process is waiting for space,
* wakeup/selwakeup/signal. If data
* are ready to send, let tcp_output
* decide between more output or persist.
*/
#ifdef TCPDEBUG
if (so->so_options & SO_DEBUG)
tcp_trace(TA_INPUT, ostate, tp,
(void *)tcp_saveipgen,
&tcp_savetcp, 0);
#endif
if (tp->snd_una == tp->snd_max)
tcp_timer_activate(tp, TT_REXMT, 0);
else if (!tcp_timer_active(tp, TT_PERSIST))
tcp_timer_activate(tp, TT_REXMT,
tp->t_rxtcur);
} else {
/*
* Window update only, just free the mbufs and
* send out whatever we can.
*/
m_freem(m);
}
sowwakeup(so);
if (sbavail(&so->so_snd))
(void) tcp_output(tp);
KASSERT(ti_locked == TI_UNLOCKED, ("%s: check_delack ti_locked %d",
__func__, ti_locked));
INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
INP_WLOCK_ASSERT(tp->t_inpcb);
if (tp->t_flags & TF_DELACK) {
tp->t_flags &= ~TF_DELACK;
tcp_timer_activate(tp, TT_DELACK, tcp_delacktime);
}
INP_WUNLOCK(tp->t_inpcb);
}
/*
* Here nothing is really faster, its just that we
* have broken out the fast-data path also just like
* the fast-ack.
*/
static void
tcp_do_fastnewdata(struct mbuf *m, struct tcphdr *th, struct socket *so,
struct tcpcb *tp, struct tcpopt *to, int drop_hdrlen, int tlen,
int ti_locked, u_long tiwin)
{
int newsize = 0; /* automatic sockbuf scaling */
#ifdef TCPDEBUG
/*
* The size of tcp_saveipgen must be the size of the max ip header,
* now IPv6.
*/
u_char tcp_saveipgen[IP6_HDR_LEN];
struct tcphdr tcp_savetcp;
short ostate = 0;
#endif
/*
* If last ACK falls within this segment's sequence numbers,
* record the timestamp.
* NOTE that the test is modified according to the latest
* proposal of the tcplw@cray.com list (Braden 1993/04/26).
*/
if ((to->to_flags & TOF_TS) != 0 &&
SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
tp->ts_recent_age = tcp_ts_getticks();
tp->ts_recent = to->to_tsval;
}
/*
* This is a pure, in-sequence data packet with
* nothing on the reassembly queue and we have enough
* buffer space to take it.
*/
if (ti_locked == TI_RLOCKED) {
INP_INFO_RUNLOCK(&V_tcbinfo);
}
ti_locked = TI_UNLOCKED;
/* Clean receiver SACK report if present */
if ((tp->t_flags & TF_SACK_PERMIT) && tp->rcv_numsacks)
tcp_clean_sackreport(tp);
TCPSTAT_INC(tcps_preddat);
tp->rcv_nxt += tlen;
/*
* Pull snd_wl1 up to prevent seq wrap relative to
* th_seq.
*/
tp->snd_wl1 = th->th_seq;
/*
* Pull rcv_up up to prevent seq wrap relative to
* rcv_nxt.
*/
tp->rcv_up = tp->rcv_nxt;
TCPSTAT_ADD(tcps_rcvbyte, tlen);
#ifdef TCPDEBUG
if (so->so_options & SO_DEBUG)
tcp_trace(TA_INPUT, ostate, tp,
(void *)tcp_saveipgen, &tcp_savetcp, 0);
#endif
/*
* Automatic sizing of receive socket buffer. Often the send
* buffer size is not optimally adjusted to the actual network
* conditions at hand (delay bandwidth product). Setting the
* buffer size too small limits throughput on links with high
* bandwidth and high delay (eg. trans-continental/oceanic links).
*
* On the receive side the socket buffer memory is only rarely
* used to any significant extent. This allows us to be much
* more aggressive in scaling the receive socket buffer. For
* the case that the buffer space is actually used to a large
* extent and we run out of kernel memory we can simply drop
* the new segments; TCP on the sender will just retransmit it
* later. Setting the buffer size too big may only consume too
* much kernel memory if the application doesn't read() from
* the socket or packet loss or reordering makes use of the
* reassembly queue.
*
* The criteria to step up the receive buffer one notch are:
* 1. Application has not set receive buffer size with
* SO_RCVBUF. Setting SO_RCVBUF clears SB_AUTOSIZE.
* 2. the number of bytes received during the time it takes
* one timestamp to be reflected back to us (the RTT);
* 3. received bytes per RTT is within seven eighth of the
* current socket buffer size;
* 4. receive buffer size has not hit maximal automatic size;
*
* This algorithm does one step per RTT at most and only if
* we receive a bulk stream w/o packet losses or reorderings.
* Shrinking the buffer during idle times is not necessary as
* it doesn't consume any memory when idle.
*
* TODO: Only step up if the application is actually serving
* the buffer to better manage the socket buffer resources.
*/
if (V_tcp_do_autorcvbuf &&
(to->to_flags & TOF_TS) &&
to->to_tsecr &&
(so->so_rcv.sb_flags & SB_AUTOSIZE)) {
if (TSTMP_GT(to->to_tsecr, tp->rfbuf_ts) &&
to->to_tsecr - tp->rfbuf_ts < hz) {
if (tp->rfbuf_cnt >
(so->so_rcv.sb_hiwat / 8 * 7) &&
so->so_rcv.sb_hiwat <
V_tcp_autorcvbuf_max) {
newsize =
min(so->so_rcv.sb_hiwat +
V_tcp_autorcvbuf_inc,
V_tcp_autorcvbuf_max);
}
/* Start over with next RTT. */
tp->rfbuf_ts = 0;
tp->rfbuf_cnt = 0;
} else
tp->rfbuf_cnt += tlen; /* add up */
}
/* Add data to socket buffer. */
SOCKBUF_LOCK(&so->so_rcv);
if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
m_freem(m);
} else {
/*
* Set new socket buffer size.
* Give up when limit is reached.
*/
if (newsize)
if (!sbreserve_locked(&so->so_rcv,
newsize, so, NULL))
so->so_rcv.sb_flags &= ~SB_AUTOSIZE;
m_adj(m, drop_hdrlen); /* delayed header drop */
sbappendstream_locked(&so->so_rcv, m, 0);
}
/* NB: sorwakeup_locked() does an implicit unlock. */
sorwakeup_locked(so);
if (DELAY_ACK(tp, tlen)) {
tp->t_flags |= TF_DELACK;
} else {
tp->t_flags |= TF_ACKNOW;
tcp_output(tp);
}
KASSERT(ti_locked == TI_UNLOCKED, ("%s: check_delack ti_locked %d",
__func__, ti_locked));
INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
INP_WLOCK_ASSERT(tp->t_inpcb);
if (tp->t_flags & TF_DELACK) {
tp->t_flags &= ~TF_DELACK;
tcp_timer_activate(tp, TT_DELACK, tcp_delacktime);
}
INP_WUNLOCK(tp->t_inpcb);
}
/*
* The slow-path is the clone of the long long part
* of tcp_do_segment past all the fast-path stuff. We
* use it here by two different callers, the fast/slow and
* the fastack only.
*/
static void
tcp_do_slowpath(struct mbuf *m, struct tcphdr *th, struct socket *so,
struct tcpcb *tp, struct tcpopt *to, int drop_hdrlen, int tlen,
int ti_locked, u_long tiwin, int thflags)
{
int acked, ourfinisacked, needoutput = 0;
int rstreason, todrop, win;
char *s;
struct in_conninfo *inc;
struct mbuf *mfree = NULL;
#ifdef TCPDEBUG
/*
* The size of tcp_saveipgen must be the size of the max ip header,
* now IPv6.
*/
u_char tcp_saveipgen[IP6_HDR_LEN];
struct tcphdr tcp_savetcp;
short ostate = 0;
#endif
/*
* Calculate amount of space in receive window,
* and then do TCP input processing.
* Receive window is amount of space in rcv queue,
* but not less than advertised window.
*/
inc = &tp->t_inpcb->inp_inc;
win = sbspace(&so->so_rcv);
if (win < 0)
win = 0;
tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt));
/* Reset receive buffer auto scaling when not in bulk receive mode. */
tp->rfbuf_ts = 0;
tp->rfbuf_cnt = 0;
switch (tp->t_state) {
/*
* If the state is SYN_RECEIVED:
* if seg contains an ACK, but not for our SYN/ACK, send a RST.
*/
case TCPS_SYN_RECEIVED:
if ((thflags & TH_ACK) &&
(SEQ_LEQ(th->th_ack, tp->snd_una) ||
SEQ_GT(th->th_ack, tp->snd_max))) {
rstreason = BANDLIM_RST_OPENPORT;
goto dropwithreset;
}
break;
/*
* If the state is SYN_SENT:
* if seg contains an ACK, but not for our SYN, drop the input.
* if seg contains a RST, then drop the connection.
* if seg does not contain SYN, then drop it.
* Otherwise this is an acceptable SYN segment
* initialize tp->rcv_nxt and tp->irs
* if seg contains ack then advance tp->snd_una
* if seg contains an ECE and ECN support is enabled, the stream
* is ECN capable.
* if SYN has been acked change to ESTABLISHED else SYN_RCVD state
* arrange for segment to be acked (eventually)
* continue processing rest of data/controls, beginning with URG
*/
case TCPS_SYN_SENT:
if ((thflags & TH_ACK) &&
(SEQ_LEQ(th->th_ack, tp->iss) ||
SEQ_GT(th->th_ack, tp->snd_max))) {
rstreason = BANDLIM_UNLIMITED;
goto dropwithreset;
}
if ((thflags & (TH_ACK|TH_RST)) == (TH_ACK|TH_RST)) {
TCP_PROBE5(connect__refused, NULL, tp,
mtod(m, const char *), tp, th);
tp = tcp_drop(tp, ECONNREFUSED);
}
if (thflags & TH_RST)
goto drop;
if (!(thflags & TH_SYN))
goto drop;
tp->irs = th->th_seq;
tcp_rcvseqinit(tp);
if (thflags & TH_ACK) {
TCPSTAT_INC(tcps_connects);
soisconnected(so);
#ifdef MAC
mac_socketpeer_set_from_mbuf(m, so);
#endif
/* Do window scaling on this connection? */
if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
(TF_RCVD_SCALE|TF_REQ_SCALE)) {
tp->rcv_scale = tp->request_r_scale;
}
tp->rcv_adv += imin(tp->rcv_wnd,
TCP_MAXWIN << tp->rcv_scale);
tp->snd_una++; /* SYN is acked */
/*
* If there's data, delay ACK; if there's also a FIN
* ACKNOW will be turned on later.
*/
if (DELAY_ACK(tp, tlen) && tlen != 0)
tcp_timer_activate(tp, TT_DELACK,
tcp_delacktime);
else
tp->t_flags |= TF_ACKNOW;
if ((thflags & TH_ECE) && V_tcp_do_ecn) {
tp->t_flags |= TF_ECN_PERMIT;
TCPSTAT_INC(tcps_ecn_shs);
}
/*
* Received <SYN,ACK> in SYN_SENT[*] state.
* Transitions:
* SYN_SENT --> ESTABLISHED
* SYN_SENT* --> FIN_WAIT_1
*/
tp->t_starttime = ticks;
if (tp->t_flags & TF_NEEDFIN) {
tcp_state_change(tp, TCPS_FIN_WAIT_1);
tp->t_flags &= ~TF_NEEDFIN;
thflags &= ~TH_SYN;
} else {
tcp_state_change(tp, TCPS_ESTABLISHED);
TCP_PROBE5(connect__established, NULL, tp,
mtod(m, const char *), tp, th);
cc_conn_init(tp);
tcp_timer_activate(tp, TT_KEEP,
TP_KEEPIDLE(tp));
}
} else {
/*
* Received initial SYN in SYN-SENT[*] state =>
* simultaneous open.
* If it succeeds, connection is * half-synchronized.
* Otherwise, do 3-way handshake:
* SYN-SENT -> SYN-RECEIVED
* SYN-SENT* -> SYN-RECEIVED*
*/
tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN);
tcp_timer_activate(tp, TT_REXMT, 0);
tcp_state_change(tp, TCPS_SYN_RECEIVED);
}
KASSERT(ti_locked == TI_RLOCKED, ("%s: trimthenstep6: "
"ti_locked %d", __func__, ti_locked));
INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
INP_WLOCK_ASSERT(tp->t_inpcb);
/*
* Advance th->th_seq to correspond to first data byte.
* If data, trim to stay within window,
* dropping FIN if necessary.
*/
th->th_seq++;
if (tlen > tp->rcv_wnd) {
todrop = tlen - tp->rcv_wnd;
m_adj(m, -todrop);
tlen = tp->rcv_wnd;
thflags &= ~TH_FIN;
TCPSTAT_INC(tcps_rcvpackafterwin);
TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop);
}
tp->snd_wl1 = th->th_seq - 1;
tp->rcv_up = th->th_seq;
/*
* Client side of transaction: already sent SYN and data.
* If the remote host used T/TCP to validate the SYN,
* our data will be ACK'd; if so, enter normal data segment
* processing in the middle of step 5, ack processing.
* Otherwise, goto step 6.
*/
if (thflags & TH_ACK)
goto process_ACK;
goto step6;
/*
* If the state is LAST_ACK or CLOSING or TIME_WAIT:
* do normal processing.
*
* NB: Leftover from RFC1644 T/TCP. Cases to be reused later.
*/
case TCPS_LAST_ACK:
case TCPS_CLOSING:
break; /* continue normal processing */
}
/*
* States other than LISTEN or SYN_SENT.
* First check the RST flag and sequence number since reset segments
* are exempt from the timestamp and connection count tests. This
* fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix
* below which allowed reset segments in half the sequence space
* to fall though and be processed (which gives forged reset
* segments with a random sequence number a 50 percent chance of
* killing a connection).
* Then check timestamp, if present.
* Then check the connection count, if present.
* Then check that at least some bytes of segment are within
* receive window. If segment begins before rcv_nxt,
* drop leading data (and SYN); if nothing left, just ack.
*/
if (thflags & TH_RST) {
/*
* RFC5961 Section 3.2
*
* - RST drops connection only if SEG.SEQ == RCV.NXT.
* - If RST is in window, we send challenge ACK.
*
* Note: to take into account delayed ACKs, we should
* test against last_ack_sent instead of rcv_nxt.
* Note 2: we handle special case of closed window, not
* covered by the RFC.
*/
if ((SEQ_GEQ(th->th_seq, tp->last_ack_sent) &&
SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) ||
(tp->rcv_wnd == 0 && tp->last_ack_sent == th->th_seq)) {
INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
KASSERT(ti_locked == TI_RLOCKED,
("%s: TH_RST ti_locked %d, th %p tp %p",
__func__, ti_locked, th, tp));
KASSERT(tp->t_state != TCPS_SYN_SENT,
("%s: TH_RST for TCPS_SYN_SENT th %p tp %p",
__func__, th, tp));
if (V_tcp_insecure_rst ||
tp->last_ack_sent == th->th_seq) {
TCPSTAT_INC(tcps_drops);
/* Drop the connection. */
switch (tp->t_state) {
case TCPS_SYN_RECEIVED:
so->so_error = ECONNREFUSED;
goto close;
case TCPS_ESTABLISHED:
case TCPS_FIN_WAIT_1:
case TCPS_FIN_WAIT_2:
case TCPS_CLOSE_WAIT:
so->so_error = ECONNRESET;
close:
tcp_state_change(tp, TCPS_CLOSED);
/* FALLTHROUGH */
default:
tp = tcp_close(tp);
}
} else {
TCPSTAT_INC(tcps_badrst);
/* Send challenge ACK. */
tcp_respond(tp, mtod(m, void *), th, m,
tp->rcv_nxt, tp->snd_nxt, TH_ACK);
tp->last_ack_sent = tp->rcv_nxt;
m = NULL;
}
}
goto drop;
}
/*
* RFC5961 Section 4.2
* Send challenge ACK for any SYN in synchronized state.
*/
if ((thflags & TH_SYN) && tp->t_state != TCPS_SYN_SENT) {
KASSERT(ti_locked == TI_RLOCKED,
("tcp_do_segment: TH_SYN ti_locked %d", ti_locked));
INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
TCPSTAT_INC(tcps_badsyn);
if (V_tcp_insecure_syn &&
SEQ_GEQ(th->th_seq, tp->last_ack_sent) &&
SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) {
tp = tcp_drop(tp, ECONNRESET);
rstreason = BANDLIM_UNLIMITED;
} else {
/* Send challenge ACK. */
tcp_respond(tp, mtod(m, void *), th, m, tp->rcv_nxt,
tp->snd_nxt, TH_ACK);
tp->last_ack_sent = tp->rcv_nxt;
m = NULL;
}
goto drop;
}
/*
* RFC 1323 PAWS: If we have a timestamp reply on this segment
* and it's less than ts_recent, drop it.
*/
if ((to->to_flags & TOF_TS) != 0 && tp->ts_recent &&
TSTMP_LT(to->to_tsval, tp->ts_recent)) {
/* Check to see if ts_recent is over 24 days old. */
if (tcp_ts_getticks() - tp->ts_recent_age > TCP_PAWS_IDLE) {
/*
* Invalidate ts_recent. If this segment updates
* ts_recent, the age will be reset later and ts_recent
* will get a valid value. If it does not, setting
* ts_recent to zero will at least satisfy the
* requirement that zero be placed in the timestamp
* echo reply when ts_recent isn't valid. The
* age isn't reset until we get a valid ts_recent
* because we don't want out-of-order segments to be
* dropped when ts_recent is old.
*/
tp->ts_recent = 0;
} else {
TCPSTAT_INC(tcps_rcvduppack);
TCPSTAT_ADD(tcps_rcvdupbyte, tlen);
TCPSTAT_INC(tcps_pawsdrop);
if (tlen)
goto dropafterack;
goto drop;
}
}
/*
* In the SYN-RECEIVED state, validate that the packet belongs to
* this connection before trimming the data to fit the receive
* window. Check the sequence number versus IRS since we know
* the sequence numbers haven't wrapped. This is a partial fix
* for the "LAND" DoS attack.
*/
if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) {
rstreason = BANDLIM_RST_OPENPORT;
goto dropwithreset;
}
todrop = tp->rcv_nxt - th->th_seq;
if (todrop > 0) {
if (thflags & TH_SYN) {
thflags &= ~TH_SYN;
th->th_seq++;
if (th->th_urp > 1)
th->th_urp--;
else
thflags &= ~TH_URG;
todrop--;
}
/*
* Following if statement from Stevens, vol. 2, p. 960.
*/
if (todrop > tlen
|| (todrop == tlen && (thflags & TH_FIN) == 0)) {
/*
* Any valid FIN must be to the left of the window.
* At this point the FIN must be a duplicate or out
* of sequence; drop it.
*/
thflags &= ~TH_FIN;
/*
* Send an ACK to resynchronize and drop any data.
* But keep on processing for RST or ACK.
*/
tp->t_flags |= TF_ACKNOW;
todrop = tlen;
TCPSTAT_INC(tcps_rcvduppack);
TCPSTAT_ADD(tcps_rcvdupbyte, todrop);
} else {
TCPSTAT_INC(tcps_rcvpartduppack);
TCPSTAT_ADD(tcps_rcvpartdupbyte, todrop);
}
drop_hdrlen += todrop; /* drop from the top afterwards */
th->th_seq += todrop;
tlen -= todrop;
if (th->th_urp > todrop)
th->th_urp -= todrop;
else {
thflags &= ~TH_URG;
th->th_urp = 0;
}
}
/*
* If new data are received on a connection after the
* user processes are gone, then RST the other end.
*/
if ((so->so_state & SS_NOFDREF) &&
tp->t_state > TCPS_CLOSE_WAIT && tlen) {
KASSERT(ti_locked == TI_RLOCKED, ("%s: SS_NOFDEREF && "
"CLOSE_WAIT && tlen ti_locked %d", __func__, ti_locked));
INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
log(LOG_DEBUG, "%s; %s: %s: Received %d bytes of data "
"after socket was closed, "
"sending RST and removing tcpcb\n",
s, __func__, tcpstates[tp->t_state], tlen);
free(s, M_TCPLOG);
}
tp = tcp_close(tp);
TCPSTAT_INC(tcps_rcvafterclose);
rstreason = BANDLIM_UNLIMITED;
goto dropwithreset;
}
/*
* If segment ends after window, drop trailing data
* (and PUSH and FIN); if nothing left, just ACK.
*/
todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd);
if (todrop > 0) {
TCPSTAT_INC(tcps_rcvpackafterwin);
if (todrop >= tlen) {
TCPSTAT_ADD(tcps_rcvbyteafterwin, tlen);
/*
* If window is closed can only take segments at
* window edge, and have to drop data and PUSH from
* incoming segments. Continue processing, but
* remember to ack. Otherwise, drop segment
* and ack.
*/
if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) {
tp->t_flags |= TF_ACKNOW;
TCPSTAT_INC(tcps_rcvwinprobe);
} else
goto dropafterack;
} else
TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop);
m_adj(m, -todrop);
tlen -= todrop;
thflags &= ~(TH_PUSH|TH_FIN);
}
/*
* If last ACK falls within this segment's sequence numbers,
* record its timestamp.
* NOTE:
* 1) That the test incorporates suggestions from the latest
* proposal of the tcplw@cray.com list (Braden 1993/04/26).
* 2) That updating only on newer timestamps interferes with
* our earlier PAWS tests, so this check should be solely
* predicated on the sequence space of this segment.
* 3) That we modify the segment boundary check to be
* Last.ACK.Sent <= SEG.SEQ + SEG.Len
* instead of RFC1323's
* Last.ACK.Sent < SEG.SEQ + SEG.Len,
* This modified check allows us to overcome RFC1323's
* limitations as described in Stevens TCP/IP Illustrated
* Vol. 2 p.869. In such cases, we can still calculate the
* RTT correctly when RCV.NXT == Last.ACK.Sent.
*/
if ((to->to_flags & TOF_TS) != 0 &&
SEQ_LEQ(th->th_seq, tp->last_ack_sent) &&
SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen +
((thflags & (TH_SYN|TH_FIN)) != 0))) {
tp->ts_recent_age = tcp_ts_getticks();
tp->ts_recent = to->to_tsval;
}
/*
* If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN
* flag is on (half-synchronized state), then queue data for
* later processing; else drop segment and return.
*/
if ((thflags & TH_ACK) == 0) {
if (tp->t_state == TCPS_SYN_RECEIVED ||
(tp->t_flags & TF_NEEDSYN))
goto step6;
else if (tp->t_flags & TF_ACKNOW)
goto dropafterack;
else
goto drop;
}
/*
* Ack processing.
*/
switch (tp->t_state) {
/*
* In SYN_RECEIVED state, the ack ACKs our SYN, so enter
* ESTABLISHED state and continue processing.
* The ACK was checked above.
*/
case TCPS_SYN_RECEIVED:
TCPSTAT_INC(tcps_connects);
soisconnected(so);
/* Do window scaling? */
if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
(TF_RCVD_SCALE|TF_REQ_SCALE)) {
tp->rcv_scale = tp->request_r_scale;
tp->snd_wnd = tiwin;
}
/*
* Make transitions:
* SYN-RECEIVED -> ESTABLISHED
* SYN-RECEIVED* -> FIN-WAIT-1
*/
tp->t_starttime = ticks;
if (tp->t_flags & TF_NEEDFIN) {
tcp_state_change(tp, TCPS_FIN_WAIT_1);
tp->t_flags &= ~TF_NEEDFIN;
} else {
tcp_state_change(tp, TCPS_ESTABLISHED);
TCP_PROBE5(accept__established, NULL, tp,
mtod(m, const char *), tp, th);
cc_conn_init(tp);
tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp));
}
/*
* If segment contains data or ACK, will call tcp_reass()
* later; if not, do so now to pass queued data to user.
*/
if (tlen == 0 && (thflags & TH_FIN) == 0)
(void) tcp_reass(tp, (struct tcphdr *)0, 0,
(struct mbuf *)0);
tp->snd_wl1 = th->th_seq - 1;
/* FALLTHROUGH */
/*
* In ESTABLISHED state: drop duplicate ACKs; ACK out of range
* ACKs. If the ack is in the range
* tp->snd_una < th->th_ack <= tp->snd_max
* then advance tp->snd_una to th->th_ack and drop
* data from the retransmission queue. If this ACK reflects
* more up to date window information we update our window information.
*/
case TCPS_ESTABLISHED:
case TCPS_FIN_WAIT_1:
case TCPS_FIN_WAIT_2:
case TCPS_CLOSE_WAIT:
case TCPS_CLOSING:
case TCPS_LAST_ACK:
if (SEQ_GT(th->th_ack, tp->snd_max)) {
TCPSTAT_INC(tcps_rcvacktoomuch);
goto dropafterack;
}
if ((tp->t_flags & TF_SACK_PERMIT) &&
((to->to_flags & TOF_SACK) ||
!TAILQ_EMPTY(&tp->snd_holes)))
tcp_sack_doack(tp, to, th->th_ack);
else
/*
* Reset the value so that previous (valid) value
* from the last ack with SACK doesn't get used.
*/
tp->sackhint.sacked_bytes = 0;
/* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */
hhook_run_tcp_est_in(tp, th, to);
if (SEQ_LEQ(th->th_ack, tp->snd_una)) {
if (tlen == 0 && tiwin == tp->snd_wnd) {
/*
* If this is the first time we've seen a
* FIN from the remote, this is not a
* duplicate and it needs to be processed
* normally. This happens during a
* simultaneous close.
*/
if ((thflags & TH_FIN) &&
(TCPS_HAVERCVDFIN(tp->t_state) == 0)) {
tp->t_dupacks = 0;
break;
}
TCPSTAT_INC(tcps_rcvdupack);
/*
* If we have outstanding data (other than
* a window probe), this is a completely
* duplicate ack (ie, window info didn't
* change and FIN isn't set),
* the ack is the biggest we've
* seen and we've seen exactly our rexmt
* threshhold of them, assume a packet
* has been dropped and retransmit it.
* Kludge snd_nxt & the congestion
* window so we send only this one
* packet.
*
* We know we're losing at the current
* window size so do congestion avoidance
* (set ssthresh to half the current window
* and pull our congestion window back to
* the new ssthresh).
*
* Dup acks mean that packets have left the
* network (they're now cached at the receiver)
* so bump cwnd by the amount in the receiver
* to keep a constant cwnd packets in the
* network.
*
* When using TCP ECN, notify the peer that
* we reduced the cwnd.
*/
if (!tcp_timer_active(tp, TT_REXMT) ||
th->th_ack != tp->snd_una)
tp->t_dupacks = 0;
else if (++tp->t_dupacks > tcprexmtthresh ||
IN_FASTRECOVERY(tp->t_flags)) {
cc_ack_received(tp, th, CC_DUPACK);
if ((tp->t_flags & TF_SACK_PERMIT) &&
IN_FASTRECOVERY(tp->t_flags)) {
int awnd;
/*
* Compute the amount of data in flight first.
* We can inject new data into the pipe iff
* we have less than 1/2 the original window's
* worth of data in flight.
*/
if (V_tcp_do_rfc6675_pipe)
awnd = tcp_compute_pipe(tp);
else
awnd = (tp->snd_nxt - tp->snd_fack) +
tp->sackhint.sack_bytes_rexmit;
if (awnd < tp->snd_ssthresh) {
tp->snd_cwnd += tp->t_maxseg;
if (tp->snd_cwnd > tp->snd_ssthresh)
tp->snd_cwnd = tp->snd_ssthresh;
}
} else
tp->snd_cwnd += tp->t_maxseg;
(void) tp->t_fb->tfb_tcp_output(tp);
goto drop;
} else if (tp->t_dupacks == tcprexmtthresh) {
tcp_seq onxt = tp->snd_nxt;
/*
* If we're doing sack, check to
* see if we're already in sack
* recovery. If we're not doing sack,
* check to see if we're in newreno
* recovery.
*/
if (tp->t_flags & TF_SACK_PERMIT) {
if (IN_FASTRECOVERY(tp->t_flags)) {
tp->t_dupacks = 0;
break;
}
} else {
if (SEQ_LEQ(th->th_ack,
tp->snd_recover)) {
tp->t_dupacks = 0;
break;
}
}
/* Congestion signal before ack. */
cc_cong_signal(tp, th, CC_NDUPACK);
cc_ack_received(tp, th, CC_DUPACK);
tcp_timer_activate(tp, TT_REXMT, 0);
tp->t_rtttime = 0;
if (tp->t_flags & TF_SACK_PERMIT) {
TCPSTAT_INC(
tcps_sack_recovery_episode);
tp->sack_newdata = tp->snd_nxt;
tp->snd_cwnd = tp->t_maxseg;
(void) tp->t_fb->tfb_tcp_output(tp);
goto drop;
}
tp->snd_nxt = th->th_ack;
tp->snd_cwnd = tp->t_maxseg;
(void) tp->t_fb->tfb_tcp_output(tp);
KASSERT(tp->snd_limited <= 2,
("%s: tp->snd_limited too big",
__func__));
tp->snd_cwnd = tp->snd_ssthresh +
tp->t_maxseg *
(tp->t_dupacks - tp->snd_limited);
if (SEQ_GT(onxt, tp->snd_nxt))
tp->snd_nxt = onxt;
goto drop;
} else if (V_tcp_do_rfc3042) {
/*
* Process first and second duplicate
* ACKs. Each indicates a segment
* leaving the network, creating room
* for more. Make sure we can send a
* packet on reception of each duplicate
* ACK by increasing snd_cwnd by one
* segment. Restore the original
* snd_cwnd after packet transmission.
*/
cc_ack_received(tp, th, CC_DUPACK);
u_long oldcwnd = tp->snd_cwnd;
tcp_seq oldsndmax = tp->snd_max;
u_int sent;
int avail;
KASSERT(tp->t_dupacks == 1 ||
tp->t_dupacks == 2,
("%s: dupacks not 1 or 2",
__func__));
if (tp->t_dupacks == 1)
tp->snd_limited = 0;
tp->snd_cwnd =
(tp->snd_nxt - tp->snd_una) +
(tp->t_dupacks - tp->snd_limited) *
tp->t_maxseg;
/*
* Only call tcp_output when there
* is new data available to be sent.
* Otherwise we would send pure ACKs.
*/
SOCKBUF_LOCK(&so->so_snd);
avail = sbavail(&so->so_snd) -
(tp->snd_nxt - tp->snd_una);
SOCKBUF_UNLOCK(&so->so_snd);
if (avail > 0)
(void) tp->t_fb->tfb_tcp_output(tp);
sent = tp->snd_max - oldsndmax;
if (sent > tp->t_maxseg) {
KASSERT((tp->t_dupacks == 2 &&
tp->snd_limited == 0) ||
(sent == tp->t_maxseg + 1 &&
tp->t_flags & TF_SENTFIN),
("%s: sent too much",
__func__));
tp->snd_limited = 2;
} else if (sent > 0)
++tp->snd_limited;
tp->snd_cwnd = oldcwnd;
goto drop;
}
} else
tp->t_dupacks = 0;
break;
}
KASSERT(SEQ_GT(th->th_ack, tp->snd_una),
("%s: th_ack <= snd_una", __func__));
/*
* If the congestion window was inflated to account
* for the other side's cached packets, retract it.
*/
if (IN_FASTRECOVERY(tp->t_flags)) {
if (SEQ_LT(th->th_ack, tp->snd_recover)) {
if (tp->t_flags & TF_SACK_PERMIT)
tcp_sack_partialack(tp, th);
else
tcp_newreno_partial_ack(tp, th);
} else
cc_post_recovery(tp, th);
}
tp->t_dupacks = 0;
/*
* If we reach this point, ACK is not a duplicate,
* i.e., it ACKs something we sent.
*/
if (tp->t_flags & TF_NEEDSYN) {
/*
* T/TCP: Connection was half-synchronized, and our
* SYN has been ACK'd (so connection is now fully
* synchronized). Go to non-starred state,
* increment snd_una for ACK of SYN, and check if
* we can do window scaling.
*/
tp->t_flags &= ~TF_NEEDSYN;
tp->snd_una++;
/* Do window scaling? */
if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
(TF_RCVD_SCALE|TF_REQ_SCALE)) {
tp->rcv_scale = tp->request_r_scale;
/* Send window already scaled. */
}
}
process_ACK:
INP_WLOCK_ASSERT(tp->t_inpcb);
acked = BYTES_THIS_ACK(tp, th);
TCPSTAT_INC(tcps_rcvackpack);
TCPSTAT_ADD(tcps_rcvackbyte, acked);
/*
* If we just performed our first retransmit, and the ACK
* arrives within our recovery window, then it was a mistake
* to do the retransmit in the first place. Recover our
* original cwnd and ssthresh, and proceed to transmit where
* we left off.
*/
if (tp->t_rxtshift == 1 && tp->t_flags & TF_PREVVALID &&
(int)(ticks - tp->t_badrxtwin) < 0)
cc_cong_signal(tp, th, CC_RTO_ERR);
/*
* If we have a timestamp reply, update smoothed
* round trip time. If no timestamp is present but
* transmit timer is running and timed sequence
* number was acked, update smoothed round trip time.
* Since we now have an rtt measurement, cancel the
* timer backoff (cf., Phil Karn's retransmit alg.).
* Recompute the initial retransmit timer.
*
* Some boxes send broken timestamp replies
* during the SYN+ACK phase, ignore
* timestamps of 0 or we could calculate a
* huge RTT and blow up the retransmit timer.
*/
if ((to->to_flags & TOF_TS) != 0 && to->to_tsecr) {
u_int t;
t = tcp_ts_getticks() - to->to_tsecr;
if (!tp->t_rttlow || tp->t_rttlow > t)
tp->t_rttlow = t;
tcp_xmit_timer(tp, TCP_TS_TO_TICKS(t) + 1);
} else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) {
if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime)
tp->t_rttlow = ticks - tp->t_rtttime;
tcp_xmit_timer(tp, ticks - tp->t_rtttime);
}
/*
* If all outstanding data is acked, stop retransmit
* timer and remember to restart (more output or persist).
* If there is more data to be acked, restart retransmit
* timer, using current (possibly backed-off) value.
*/
if (th->th_ack == tp->snd_max) {
tcp_timer_activate(tp, TT_REXMT, 0);
needoutput = 1;
} else if (!tcp_timer_active(tp, TT_PERSIST))
tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
/*
* If no data (only SYN) was ACK'd,
* skip rest of ACK processing.
*/
if (acked == 0)
goto step6;
/*
* Let the congestion control algorithm update congestion
* control related information. This typically means increasing
* the congestion window.
*/
cc_ack_received(tp, th, CC_ACK);
SOCKBUF_LOCK(&so->so_snd);
if (acked > sbavail(&so->so_snd)) {
tp->snd_wnd -= sbavail(&so->so_snd);
mfree = sbcut_locked(&so->so_snd,
(int)sbavail(&so->so_snd));
ourfinisacked = 1;
} else {
mfree = sbcut_locked(&so->so_snd, acked);
tp->snd_wnd -= acked;
ourfinisacked = 0;
}
/* NB: sowwakeup_locked() does an implicit unlock. */
sowwakeup_locked(so);
m_freem(mfree);
/* Detect una wraparound. */
if (!IN_RECOVERY(tp->t_flags) &&
SEQ_GT(tp->snd_una, tp->snd_recover) &&
SEQ_LEQ(th->th_ack, tp->snd_recover))
tp->snd_recover = th->th_ack - 1;
/* XXXLAS: Can this be moved up into cc_post_recovery? */
if (IN_RECOVERY(tp->t_flags) &&
SEQ_GEQ(th->th_ack, tp->snd_recover)) {
EXIT_RECOVERY(tp->t_flags);
}
tp->snd_una = th->th_ack;
if (tp->t_flags & TF_SACK_PERMIT) {
if (SEQ_GT(tp->snd_una, tp->snd_recover))
tp->snd_recover = tp->snd_una;
}
if (SEQ_LT(tp->snd_nxt, tp->snd_una))
tp->snd_nxt = tp->snd_una;
switch (tp->t_state) {
/*
* In FIN_WAIT_1 STATE in addition to the processing
* for the ESTABLISHED state if our FIN is now acknowledged
* then enter FIN_WAIT_2.
*/
case TCPS_FIN_WAIT_1:
if (ourfinisacked) {
/*
* If we can't receive any more
* data, then closing user can proceed.
* Starting the timer is contrary to the
* specification, but if we don't get a FIN
* we'll hang forever.
*
* XXXjl:
* we should release the tp also, and use a
* compressed state.
*/
if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
soisdisconnected(so);
tcp_timer_activate(tp, TT_2MSL,
(tcp_fast_finwait2_recycle ?
tcp_finwait2_timeout :
TP_MAXIDLE(tp)));
}
tcp_state_change(tp, TCPS_FIN_WAIT_2);
}
break;
/*
* In CLOSING STATE in addition to the processing for
* the ESTABLISHED state if the ACK acknowledges our FIN
* then enter the TIME-WAIT state, otherwise ignore
* the segment.
*/
case TCPS_CLOSING:
if (ourfinisacked) {
INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
tcp_twstart(tp);
INP_INFO_RUNLOCK(&V_tcbinfo);
m_freem(m);
return;
}
break;
/*
* In LAST_ACK, we may still be waiting for data to drain
* and/or to be acked, as well as for the ack of our FIN.
* If our FIN is now acknowledged, delete the TCB,
* enter the closed state and return.
*/
case TCPS_LAST_ACK:
if (ourfinisacked) {
INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
tp = tcp_close(tp);
goto drop;
}
break;
}
}
step6:
INP_WLOCK_ASSERT(tp->t_inpcb);
/*
* Update window information.
* Don't look at window if no ACK: TAC's send garbage on first SYN.
*/
if ((thflags & TH_ACK) &&
(SEQ_LT(tp->snd_wl1, th->th_seq) ||
(tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) ||
(tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) {
/* keep track of pure window updates */
if (tlen == 0 &&
tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)
TCPSTAT_INC(tcps_rcvwinupd);
tp->snd_wnd = tiwin;
tp->snd_wl1 = th->th_seq;
tp->snd_wl2 = th->th_ack;
if (tp->snd_wnd > tp->max_sndwnd)
tp->max_sndwnd = tp->snd_wnd;
needoutput = 1;
}
/*
* Process segments with URG.
*/
if ((thflags & TH_URG) && th->th_urp &&
TCPS_HAVERCVDFIN(tp->t_state) == 0) {
/*
* This is a kludge, but if we receive and accept
* random urgent pointers, we'll crash in
* soreceive. It's hard to imagine someone
* actually wanting to send this much urgent data.
*/
SOCKBUF_LOCK(&so->so_rcv);
if (th->th_urp + sbavail(&so->so_rcv) > sb_max) {
th->th_urp = 0; /* XXX */
thflags &= ~TH_URG; /* XXX */
SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */
goto dodata; /* XXX */
}
/*
* If this segment advances the known urgent pointer,
* then mark the data stream. This should not happen
* in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
* a FIN has been received from the remote side.
* In these states we ignore the URG.
*
* According to RFC961 (Assigned Protocols),
* the urgent pointer points to the last octet
* of urgent data. We continue, however,
* to consider it to indicate the first octet
* of data past the urgent section as the original
* spec states (in one of two places).
*/
if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) {
tp->rcv_up = th->th_seq + th->th_urp;
so->so_oobmark = sbavail(&so->so_rcv) +
(tp->rcv_up - tp->rcv_nxt) - 1;
if (so->so_oobmark == 0)
so->so_rcv.sb_state |= SBS_RCVATMARK;
sohasoutofband(so);
tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA);
}
SOCKBUF_UNLOCK(&so->so_rcv);
/*
* Remove out of band data so doesn't get presented to user.
* This can happen independent of advancing the URG pointer,
* but if two URG's are pending at once, some out-of-band
* data may creep in... ick.
*/
if (th->th_urp <= (u_long)tlen &&
!(so->so_options & SO_OOBINLINE)) {
/* hdr drop is delayed */
tcp_pulloutofband(so, th, m, drop_hdrlen);
}
} else {
/*
* If no out of band data is expected,
* pull receive urgent pointer along
* with the receive window.
*/
if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
tp->rcv_up = tp->rcv_nxt;
}
dodata: /* XXX */
INP_WLOCK_ASSERT(tp->t_inpcb);
/*
* Process the segment text, merging it into the TCP sequencing queue,
* and arranging for acknowledgment of receipt if necessary.
* This process logically involves adjusting tp->rcv_wnd as data
* is presented to the user (this happens in tcp_usrreq.c,
* case PRU_RCVD). If a FIN has already been received on this
* connection then we just ignore the text.
*/
if ((tlen || (thflags & TH_FIN)) &&
TCPS_HAVERCVDFIN(tp->t_state) == 0) {
tcp_seq save_start = th->th_seq;
m_adj(m, drop_hdrlen); /* delayed header drop */
/*
* Insert segment which includes th into TCP reassembly queue
* with control block tp. Set thflags to whether reassembly now
* includes a segment with FIN. This handles the common case
* inline (segment is the next to be received on an established
* connection, and the queue is empty), avoiding linkage into
* and removal from the queue and repetition of various
* conversions.
* Set DELACK for segments received in order, but ack
* immediately when segments are out of order (so
* fast retransmit can work).
*/
if (th->th_seq == tp->rcv_nxt &&
LIST_EMPTY(&tp->t_segq) &&
TCPS_HAVEESTABLISHED(tp->t_state)) {
if (DELAY_ACK(tp, tlen))
tp->t_flags |= TF_DELACK;
else
tp->t_flags |= TF_ACKNOW;
tp->rcv_nxt += tlen;
thflags = th->th_flags & TH_FIN;
TCPSTAT_INC(tcps_rcvpack);
TCPSTAT_ADD(tcps_rcvbyte, tlen);
SOCKBUF_LOCK(&so->so_rcv);
if (so->so_rcv.sb_state & SBS_CANTRCVMORE)
m_freem(m);
else
sbappendstream_locked(&so->so_rcv, m, 0);
/* NB: sorwakeup_locked() does an implicit unlock. */
sorwakeup_locked(so);
} else {
/*
* XXX: Due to the header drop above "th" is
* theoretically invalid by now. Fortunately
* m_adj() doesn't actually frees any mbufs
* when trimming from the head.
*/
thflags = tcp_reass(tp, th, &tlen, m);
tp->t_flags |= TF_ACKNOW;
}
if (tlen > 0 && (tp->t_flags & TF_SACK_PERMIT))
tcp_update_sack_list(tp, save_start, save_start + tlen);
#if 0
/*
* Note the amount of data that peer has sent into
* our window, in order to estimate the sender's
* buffer size.
* XXX: Unused.
*/
if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt))
len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt);
else
len = so->so_rcv.sb_hiwat;
#endif
} else {
m_freem(m);
thflags &= ~TH_FIN;
}
/*
* If FIN is received ACK the FIN and let the user know
* that the connection is closing.
*/
if (thflags & TH_FIN) {
if (TCPS_HAVERCVDFIN(tp->t_state) == 0) {
socantrcvmore(so);
/*
* If connection is half-synchronized
* (ie NEEDSYN flag on) then delay ACK,
* so it may be piggybacked when SYN is sent.
* Otherwise, since we received a FIN then no
* more input can be expected, send ACK now.
*/
if (tp->t_flags & TF_NEEDSYN)
tp->t_flags |= TF_DELACK;
else
tp->t_flags |= TF_ACKNOW;
tp->rcv_nxt++;
}
switch (tp->t_state) {
/*
* In SYN_RECEIVED and ESTABLISHED STATES
* enter the CLOSE_WAIT state.
*/
case TCPS_SYN_RECEIVED:
tp->t_starttime = ticks;
/* FALLTHROUGH */
case TCPS_ESTABLISHED:
tcp_state_change(tp, TCPS_CLOSE_WAIT);
break;
/*
* If still in FIN_WAIT_1 STATE FIN has not been acked so
* enter the CLOSING state.
*/
case TCPS_FIN_WAIT_1:
tcp_state_change(tp, TCPS_CLOSING);
break;
/*
* In FIN_WAIT_2 state enter the TIME_WAIT state,
* starting the time-wait timer, turning off the other
* standard timers.
*/
case TCPS_FIN_WAIT_2:
INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
KASSERT(ti_locked == TI_RLOCKED, ("%s: dodata "
"TCP_FIN_WAIT_2 ti_locked: %d", __func__,
ti_locked));
tcp_twstart(tp);
INP_INFO_RUNLOCK(&V_tcbinfo);
return;
}
}
if (ti_locked == TI_RLOCKED) {
INP_INFO_RUNLOCK(&V_tcbinfo);
}
ti_locked = TI_UNLOCKED;
#ifdef TCPDEBUG
if (so->so_options & SO_DEBUG)
tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen,
&tcp_savetcp, 0);
#endif
TCP_PROBE3(debug__input, tp, th, mtod(m, const char *));
/*
* Return any desired output.
*/
if (needoutput || (tp->t_flags & TF_ACKNOW))
(void) tp->t_fb->tfb_tcp_output(tp);
KASSERT(ti_locked == TI_UNLOCKED, ("%s: check_delack ti_locked %d",
__func__, ti_locked));
INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
INP_WLOCK_ASSERT(tp->t_inpcb);
if (tp->t_flags & TF_DELACK) {
tp->t_flags &= ~TF_DELACK;
tcp_timer_activate(tp, TT_DELACK, tcp_delacktime);
}
INP_WUNLOCK(tp->t_inpcb);
return;
dropafterack:
/*
* Generate an ACK dropping incoming segment if it occupies
* sequence space, where the ACK reflects our state.
*
* We can now skip the test for the RST flag since all
* paths to this code happen after packets containing
* RST have been dropped.
*
* In the SYN-RECEIVED state, don't send an ACK unless the
* segment we received passes the SYN-RECEIVED ACK test.
* If it fails send a RST. This breaks the loop in the
* "LAND" DoS attack, and also prevents an ACK storm
* between two listening ports that have been sent forged
* SYN segments, each with the source address of the other.
*/
if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) &&
(SEQ_GT(tp->snd_una, th->th_ack) ||
SEQ_GT(th->th_ack, tp->snd_max)) ) {
rstreason = BANDLIM_RST_OPENPORT;
goto dropwithreset;
}
#ifdef TCPDEBUG
if (so->so_options & SO_DEBUG)
tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
&tcp_savetcp, 0);
#endif
TCP_PROBE3(debug__input, tp, th, mtod(m, const char *));
if (ti_locked == TI_RLOCKED) {
INP_INFO_RUNLOCK(&V_tcbinfo);
}
ti_locked = TI_UNLOCKED;
tp->t_flags |= TF_ACKNOW;
(void) tp->t_fb->tfb_tcp_output(tp);
INP_WUNLOCK(tp->t_inpcb);
m_freem(m);
return;
dropwithreset:
if (ti_locked == TI_RLOCKED) {
INP_INFO_RUNLOCK(&V_tcbinfo);
}
ti_locked = TI_UNLOCKED;
if (tp != NULL) {
tcp_dropwithreset(m, th, tp, tlen, rstreason);
INP_WUNLOCK(tp->t_inpcb);
} else
tcp_dropwithreset(m, th, NULL, tlen, rstreason);
return;
drop:
if (ti_locked == TI_RLOCKED) {
INP_INFO_RUNLOCK(&V_tcbinfo);
ti_locked = TI_UNLOCKED;
}
#ifdef INVARIANTS
else
INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
#endif
/*
* Drop space held by incoming segment and return.
*/
#ifdef TCPDEBUG
if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
&tcp_savetcp, 0);
#endif
TCP_PROBE3(debug__input, tp, th, mtod(m, const char *));
if (tp != NULL)
INP_WUNLOCK(tp->t_inpcb);
m_freem(m);
}
/*
* Do fast slow is a combination of the original
* tcp_dosegment and a split fastpath, one function
* for the fast-ack which also includes allowing fastpath
* for window advanced in sequence acks. And also a
* sub-function that handles the insequence data.
*/
void
tcp_do_segment_fastslow(struct mbuf *m, struct tcphdr *th, struct socket *so,
struct tcpcb *tp, int drop_hdrlen, int tlen, uint8_t iptos,
int ti_locked)
{
int thflags;
u_long tiwin;
char *s;
int can_enter;
struct in_conninfo *inc;
struct tcpopt to;
thflags = th->th_flags;
tp->sackhint.last_sack_ack = 0;
inc = &tp->t_inpcb->inp_inc;
/*
* If this is either a state-changing packet or current state isn't
* established, we require a write lock on tcbinfo. Otherwise, we
* allow the tcbinfo to be in either alocked or unlocked, as the
* caller may have unnecessarily acquired a write lock due to a race.
*/
if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0 ||
tp->t_state != TCPS_ESTABLISHED) {
KASSERT(ti_locked == TI_RLOCKED, ("%s ti_locked %d for "
"SYN/FIN/RST/!EST", __func__, ti_locked));
INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
} else {
#ifdef INVARIANTS
if (ti_locked == TI_RLOCKED) {
INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
} else {
KASSERT(ti_locked == TI_UNLOCKED, ("%s: EST "
"ti_locked: %d", __func__, ti_locked));
INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
}
#endif
}
INP_WLOCK_ASSERT(tp->t_inpcb);
KASSERT(tp->t_state > TCPS_LISTEN, ("%s: TCPS_LISTEN",
__func__));
KASSERT(tp->t_state != TCPS_TIME_WAIT, ("%s: TCPS_TIME_WAIT",
__func__));
/*
* Segment received on connection.
* Reset idle time and keep-alive timer.
* XXX: This should be done after segment
* validation to ignore broken/spoofed segs.
*/
tp->t_rcvtime = ticks;
if (TCPS_HAVEESTABLISHED(tp->t_state))
tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp));
/*
* Unscale the window into a 32-bit value.
* For the SYN_SENT state the scale is zero.
*/
tiwin = th->th_win << tp->snd_scale;
/*
* TCP ECN processing.
*/
if (tp->t_flags & TF_ECN_PERMIT) {
if (thflags & TH_CWR)
tp->t_flags &= ~TF_ECN_SND_ECE;
switch (iptos & IPTOS_ECN_MASK) {
case IPTOS_ECN_CE:
tp->t_flags |= TF_ECN_SND_ECE;
TCPSTAT_INC(tcps_ecn_ce);
break;
case IPTOS_ECN_ECT0:
TCPSTAT_INC(tcps_ecn_ect0);
break;
case IPTOS_ECN_ECT1:
TCPSTAT_INC(tcps_ecn_ect1);
break;
}
/* Congestion experienced. */
if (thflags & TH_ECE) {
cc_cong_signal(tp, th, CC_ECN);
}
}
/*
* Parse options on any incoming segment.
*/
tcp_dooptions(&to, (u_char *)(th + 1),
(th->th_off << 2) - sizeof(struct tcphdr),
(thflags & TH_SYN) ? TO_SYN : 0);
/*
* If echoed timestamp is later than the current time,
* fall back to non RFC1323 RTT calculation. Normalize
* timestamp if syncookies were used when this connection
* was established.
*/
if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) {
to.to_tsecr -= tp->ts_offset;
if (TSTMP_GT(to.to_tsecr, tcp_ts_getticks()))
to.to_tsecr = 0;
}
/*
* If timestamps were negotiated during SYN/ACK they should
* appear on every segment during this session and vice versa.
*/
if ((tp->t_flags & TF_RCVD_TSTMP) && !(to.to_flags & TOF_TS)) {
if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
log(LOG_DEBUG, "%s; %s: Timestamp missing, "
"no action\n", s, __func__);
free(s, M_TCPLOG);
}
}
if (!(tp->t_flags & TF_RCVD_TSTMP) && (to.to_flags & TOF_TS)) {
if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
log(LOG_DEBUG, "%s; %s: Timestamp not expected, "
"no action\n", s, __func__);
free(s, M_TCPLOG);
}
}
/*
* Process options only when we get SYN/ACK back. The SYN case
* for incoming connections is handled in tcp_syncache.
* According to RFC1323 the window field in a SYN (i.e., a <SYN>
* or <SYN,ACK>) segment itself is never scaled.
* XXX this is traditional behavior, may need to be cleaned up.
*/
if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) {
if ((to.to_flags & TOF_SCALE) &&
(tp->t_flags & TF_REQ_SCALE)) {
tp->t_flags |= TF_RCVD_SCALE;
tp->snd_scale = to.to_wscale;
}
/*
* Initial send window. It will be updated with
* the next incoming segment to the scaled value.
*/
tp->snd_wnd = th->th_win;
if (to.to_flags & TOF_TS) {
tp->t_flags |= TF_RCVD_TSTMP;
tp->ts_recent = to.to_tsval;
tp->ts_recent_age = tcp_ts_getticks();
}
if (to.to_flags & TOF_MSS)
tcp_mss(tp, to.to_mss);
if ((tp->t_flags & TF_SACK_PERMIT) &&
(to.to_flags & TOF_SACKPERM) == 0)
tp->t_flags &= ~TF_SACK_PERMIT;
}
can_enter = 0;
if (__predict_true((tlen == 0))) {
/*
* The ack moved forward and we have a window (non-zero)
* <or>
* The ack did not move forward, but the window increased.
*/
if (__predict_true((SEQ_GT(th->th_ack, tp->snd_una) && tiwin) ||
((th->th_ack == tp->snd_una) && tiwin && (tiwin > tp->snd_wnd)))) {
can_enter = 1;
}
} else {
/*
* Data incoming, use the old entry criteria
* for fast-path with data.
*/
if ((tiwin && tiwin == tp->snd_wnd)) {
can_enter = 1;
}
}
/*
* Header prediction: check for the two common cases
* of a uni-directional data xfer. If the packet has
* no control flags, is in-sequence, the window didn't
* change and we're not retransmitting, it's a
* candidate. If the length is zero and the ack moved
* forward, we're the sender side of the xfer. Just
* free the data acked & wake any higher level process
* that was blocked waiting for space. If the length
* is non-zero and the ack didn't move, we're the
* receiver side. If we're getting packets in-order
* (the reassembly queue is empty), add the data to
* the socket buffer and note that we need a delayed ack.
* Make sure that the hidden state-flags are also off.
* Since we check for TCPS_ESTABLISHED first, it can only
* be TH_NEEDSYN.
*/
if (__predict_true(tp->t_state == TCPS_ESTABLISHED &&
th->th_seq == tp->rcv_nxt &&
(thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
tp->snd_nxt == tp->snd_max &&
can_enter &&
((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) &&
LIST_EMPTY(&tp->t_segq) &&
((to.to_flags & TOF_TS) == 0 ||
TSTMP_GEQ(to.to_tsval, tp->ts_recent)))) {
if (__predict_true((tlen == 0) &&
(SEQ_LEQ(th->th_ack, tp->snd_max) &&
!IN_RECOVERY(tp->t_flags) &&
(to.to_flags & TOF_SACK) == 0 &&
TAILQ_EMPTY(&tp->snd_holes)))) {
/* We are done */
tcp_do_fastack(m, th, so, tp, &to, drop_hdrlen, tlen,
ti_locked, tiwin);
return;
} else if ((tlen) &&
(th->th_ack == tp->snd_una &&
tlen <= sbspace(&so->so_rcv))) {
tcp_do_fastnewdata(m, th, so, tp, &to, drop_hdrlen, tlen,
ti_locked, tiwin);
/* We are done */
return;
}
}
tcp_do_slowpath(m, th, so, tp, &to, drop_hdrlen, tlen,
ti_locked, tiwin, thflags);
}
/*
* This subfunction is used to try to highly optimize the
* fast path. We again allow window updates that are
* in sequence to remain in the fast-path. We also add
* in the __predict's to attempt to help the compiler.
* Note that if we return a 0, then we can *not* process
* it and the caller should push the packet into the
* slow-path.
*/
static int
tcp_fastack(struct mbuf *m, struct tcphdr *th, struct socket *so,
struct tcpcb *tp, struct tcpopt *to, int drop_hdrlen, int tlen,
int ti_locked, u_long tiwin)
{
int acked;
int winup_only=0;
#ifdef TCPDEBUG
/*
* The size of tcp_saveipgen must be the size of the max ip header,
* now IPv6.
*/
u_char tcp_saveipgen[IP6_HDR_LEN];
struct tcphdr tcp_savetcp;
short ostate = 0;
#endif
if (__predict_false(SEQ_LEQ(th->th_ack, tp->snd_una))) {
/* Old ack, behind (or duplicate to) the last one rcv'd */
return (0);
}
if (__predict_false(th->th_ack == tp->snd_una) &&
__predict_false(tiwin <= tp->snd_wnd)) {
/* duplicate ack <or> a shrinking dup ack with shrinking window */
return (0);
}
if (__predict_false(tiwin == 0)) {
/* zero window */
return (0);
}
if (__predict_false(SEQ_GT(th->th_ack, tp->snd_max))) {
/* Above what we have sent? */
return (0);
}
if (__predict_false(tp->snd_nxt != tp->snd_max)) {
/* We are retransmitting */
return (0);
}
if (__predict_false(tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN))) {
/* We need a SYN or a FIN, unlikely.. */
return (0);
}
if((to->to_flags & TOF_TS) && __predict_false(TSTMP_LT(to->to_tsval, tp->ts_recent))) {
/* Timestamp is behind .. old ack with seq wrap? */
return (0);
}
if (__predict_false(IN_RECOVERY(tp->t_flags))) {
/* Still recovering */
return (0);
}
if (__predict_false(to->to_flags & TOF_SACK)) {
/* Sack included in the ack.. */
return (0);
}
if (!TAILQ_EMPTY(&tp->snd_holes)) {
/* We have sack holes on our scoreboard */
return (0);
}
/* Ok if we reach here, we can process a fast-ack */
/* Did the window get updated? */
if (tiwin != tp->snd_wnd) {
/* keep track of pure window updates */
if (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) {
winup_only = 1;
TCPSTAT_INC(tcps_rcvwinupd);
}
tp->snd_wnd = tiwin;
tp->snd_wl1 = th->th_seq;
if (tp->snd_wnd > tp->max_sndwnd)
tp->max_sndwnd = tp->snd_wnd;
}
/*
* Pull snd_wl2 up to prevent seq wrap relative
* to th_ack.
*/
tp->snd_wl2 = th->th_ack;
/*
* If last ACK falls within this segment's sequence numbers,
* record the timestamp.
* NOTE that the test is modified according to the latest
* proposal of the tcplw@cray.com list (Braden 1993/04/26).
*/
if ((to->to_flags & TOF_TS) != 0 &&
SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
tp->ts_recent_age = tcp_ts_getticks();
tp->ts_recent = to->to_tsval;
}
/*
* This is a pure ack for outstanding data.
*/
if (ti_locked == TI_RLOCKED) {
INP_INFO_RUNLOCK(&V_tcbinfo);
}
ti_locked = TI_UNLOCKED;
TCPSTAT_INC(tcps_predack);
/*
* "bad retransmit" recovery.
*/
if (tp->t_rxtshift == 1 &&
tp->t_flags & TF_PREVVALID &&
(int)(ticks - tp->t_badrxtwin) < 0) {
cc_cong_signal(tp, th, CC_RTO_ERR);
}
/*
* Recalculate the transmit timer / rtt.
*
* Some boxes send broken timestamp replies
* during the SYN+ACK phase, ignore
* timestamps of 0 or we could calculate a
* huge RTT and blow up the retransmit timer.
*/
if ((to->to_flags & TOF_TS) != 0 &&
to->to_tsecr) {
u_int t;
t = tcp_ts_getticks() - to->to_tsecr;
if (!tp->t_rttlow || tp->t_rttlow > t)
tp->t_rttlow = t;
tcp_xmit_timer(tp,
TCP_TS_TO_TICKS(t) + 1);
} else if (tp->t_rtttime &&
SEQ_GT(th->th_ack, tp->t_rtseq)) {
if (!tp->t_rttlow ||
tp->t_rttlow > ticks - tp->t_rtttime)
tp->t_rttlow = ticks - tp->t_rtttime;
tcp_xmit_timer(tp,
ticks - tp->t_rtttime);
}
if (winup_only == 0) {
acked = BYTES_THIS_ACK(tp, th);
/* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */
hhook_run_tcp_est_in(tp, th, to);
TCPSTAT_ADD(tcps_rcvackbyte, acked);
sbdrop(&so->so_snd, acked);
if (SEQ_GT(tp->snd_una, tp->snd_recover) &&
SEQ_LEQ(th->th_ack, tp->snd_recover))
tp->snd_recover = th->th_ack - 1;
/*
* Let the congestion control algorithm update
* congestion control related information. This
* typically means increasing the congestion
* window.
*/
cc_ack_received(tp, th, CC_ACK);
tp->snd_una = th->th_ack;
tp->t_dupacks = 0;
m_freem(m);
/*
* If all outstanding data are acked, stop
* retransmit timer, otherwise restart timer
* using current (possibly backed-off) value.
* If process is waiting for space,
* wakeup/selwakeup/signal. If data
* are ready to send, let tcp_output
* decide between more output or persist.
*/
#ifdef TCPDEBUG
if (so->so_options & SO_DEBUG)
tcp_trace(TA_INPUT, ostate, tp,
(void *)tcp_saveipgen,
&tcp_savetcp, 0);
#endif
if (tp->snd_una == tp->snd_max)
tcp_timer_activate(tp, TT_REXMT, 0);
else if (!tcp_timer_active(tp, TT_PERSIST))
tcp_timer_activate(tp, TT_REXMT,
tp->t_rxtcur);
/* Wake up the socket if we have room to write more */
sowwakeup(so);
} else {
/*
* Window update only, just free the mbufs and
* send out whatever we can.
*/
m_freem(m);
}
if (sbavail(&so->so_snd))
(void) tcp_output(tp);
KASSERT(ti_locked == TI_UNLOCKED, ("%s: check_delack ti_locked %d",
__func__, ti_locked));
INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
INP_WLOCK_ASSERT(tp->t_inpcb);
if (tp->t_flags & TF_DELACK) {
tp->t_flags &= ~TF_DELACK;
tcp_timer_activate(tp, TT_DELACK, tcp_delacktime);
}
INP_WUNLOCK(tp->t_inpcb);
return (1);
}
/*
* This tcp-do-segment concentrates on making the fastest
* ack processing path. It does not have a fast-path for
* data (it possibly could which would then eliminate the
* need for fast-slow above). For a content distributor having
* large outgoing elephants and very very little coming in
* having no fastpath for data does not really help (since you
* don't get much data in). The most important thing is
* processing ack's quickly and getting the rest of the data
* output to the peer as quickly as possible. This routine
* seems to be about an overall 3% faster then the old
* tcp_do_segment and keeps us in the fast-path for packets
* much more (by allowing window updates to also stay in the fastpath).
*/
void
tcp_do_segment_fastack(struct mbuf *m, struct tcphdr *th, struct socket *so,
struct tcpcb *tp, int drop_hdrlen, int tlen, uint8_t iptos,
int ti_locked)
{
int thflags;
u_long tiwin;
char *s;
struct in_conninfo *inc;
struct tcpopt to;
thflags = th->th_flags;
tp->sackhint.last_sack_ack = 0;
inc = &tp->t_inpcb->inp_inc;
/*
* If this is either a state-changing packet or current state isn't
* established, we require a write lock on tcbinfo. Otherwise, we
* allow the tcbinfo to be in either alocked or unlocked, as the
* caller may have unnecessarily acquired a write lock due to a race.
*/
if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0 ||
tp->t_state != TCPS_ESTABLISHED) {
KASSERT(ti_locked == TI_RLOCKED, ("%s ti_locked %d for "
"SYN/FIN/RST/!EST", __func__, ti_locked));
INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
} else {
#ifdef INVARIANTS
if (ti_locked == TI_RLOCKED) {
INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
} else {
KASSERT(ti_locked == TI_UNLOCKED, ("%s: EST "
"ti_locked: %d", __func__, ti_locked));
INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
}
#endif
}
INP_WLOCK_ASSERT(tp->t_inpcb);
KASSERT(tp->t_state > TCPS_LISTEN, ("%s: TCPS_LISTEN",
__func__));
KASSERT(tp->t_state != TCPS_TIME_WAIT, ("%s: TCPS_TIME_WAIT",
__func__));
/*
* Segment received on connection.
* Reset idle time and keep-alive timer.
* XXX: This should be done after segment
* validation to ignore broken/spoofed segs.
*/
tp->t_rcvtime = ticks;
if (TCPS_HAVEESTABLISHED(tp->t_state))
tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp));
/*
* Unscale the window into a 32-bit value.
* For the SYN_SENT state the scale is zero.
*/
tiwin = th->th_win << tp->snd_scale;
/*
* TCP ECN processing.
*/
if (tp->t_flags & TF_ECN_PERMIT) {
if (thflags & TH_CWR)
tp->t_flags &= ~TF_ECN_SND_ECE;
switch (iptos & IPTOS_ECN_MASK) {
case IPTOS_ECN_CE:
tp->t_flags |= TF_ECN_SND_ECE;
TCPSTAT_INC(tcps_ecn_ce);
break;
case IPTOS_ECN_ECT0:
TCPSTAT_INC(tcps_ecn_ect0);
break;
case IPTOS_ECN_ECT1:
TCPSTAT_INC(tcps_ecn_ect1);
break;
}
/* Congestion experienced. */
if (thflags & TH_ECE) {
cc_cong_signal(tp, th, CC_ECN);
}
}
/*
* Parse options on any incoming segment.
*/
tcp_dooptions(&to, (u_char *)(th + 1),
(th->th_off << 2) - sizeof(struct tcphdr),
(thflags & TH_SYN) ? TO_SYN : 0);
/*
* If echoed timestamp is later than the current time,
* fall back to non RFC1323 RTT calculation. Normalize
* timestamp if syncookies were used when this connection
* was established.
*/
if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) {
to.to_tsecr -= tp->ts_offset;
if (TSTMP_GT(to.to_tsecr, tcp_ts_getticks()))
to.to_tsecr = 0;
}
/*
* If timestamps were negotiated during SYN/ACK they should
* appear on every segment during this session and vice versa.
*/
if ((tp->t_flags & TF_RCVD_TSTMP) && !(to.to_flags & TOF_TS)) {
if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
log(LOG_DEBUG, "%s; %s: Timestamp missing, "
"no action\n", s, __func__);
free(s, M_TCPLOG);
}
}
if (!(tp->t_flags & TF_RCVD_TSTMP) && (to.to_flags & TOF_TS)) {
if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
log(LOG_DEBUG, "%s; %s: Timestamp not expected, "
"no action\n", s, __func__);
free(s, M_TCPLOG);
}
}
/*
* Process options only when we get SYN/ACK back. The SYN case
* for incoming connections is handled in tcp_syncache.
* According to RFC1323 the window field in a SYN (i.e., a <SYN>
* or <SYN,ACK>) segment itself is never scaled.
* XXX this is traditional behavior, may need to be cleaned up.
*/
if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) {
if ((to.to_flags & TOF_SCALE) &&
(tp->t_flags & TF_REQ_SCALE)) {
tp->t_flags |= TF_RCVD_SCALE;
tp->snd_scale = to.to_wscale;
}
/*
* Initial send window. It will be updated with
* the next incoming segment to the scaled value.
*/
tp->snd_wnd = th->th_win;
if (to.to_flags & TOF_TS) {
tp->t_flags |= TF_RCVD_TSTMP;
tp->ts_recent = to.to_tsval;
tp->ts_recent_age = tcp_ts_getticks();
}
if (to.to_flags & TOF_MSS)
tcp_mss(tp, to.to_mss);
if ((tp->t_flags & TF_SACK_PERMIT) &&
(to.to_flags & TOF_SACKPERM) == 0)
tp->t_flags &= ~TF_SACK_PERMIT;
}
/*
* Header prediction: check for the two common cases
* of a uni-directional data xfer. If the packet has
* no control flags, is in-sequence, the window didn't
* change and we're not retransmitting, it's a
* candidate. If the length is zero and the ack moved
* forward, we're the sender side of the xfer. Just
* free the data acked & wake any higher level process
* that was blocked waiting for space. If the length
* is non-zero and the ack didn't move, we're the
* receiver side. If we're getting packets in-order
* (the reassembly queue is empty), add the data to
* the socket buffer and note that we need a delayed ack.
* Make sure that the hidden state-flags are also off.
* Since we check for TCPS_ESTABLISHED first, it can only
* be TH_NEEDSYN.
*/
if (__predict_true(tp->t_state == TCPS_ESTABLISHED) &&
__predict_true(((to.to_flags & TOF_SACK) == 0)) &&
__predict_true(tlen == 0) &&
__predict_true((thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK) &&
__predict_true(LIST_EMPTY(&tp->t_segq)) &&
__predict_true(th->th_seq == tp->rcv_nxt)) {
if (tcp_fastack(m, th, so, tp, &to, drop_hdrlen, tlen,
ti_locked, tiwin)) {
return;
}
}
tcp_do_slowpath(m, th, so, tp, &to, drop_hdrlen, tlen,
ti_locked, tiwin, thflags);
}
struct tcp_function_block __tcp_fastslow = {
"fastslow",
tcp_output,
tcp_do_segment_fastslow,
tcp_default_ctloutput,
NULL,
NULL,
NULL,
NULL,
NULL,
NULL,
NULL,
0,
0
};
struct tcp_function_block __tcp_fastack = {
"fastack",
tcp_output,
tcp_do_segment_fastack,
tcp_default_ctloutput,
NULL,
NULL,
NULL,
NULL,
NULL,
NULL,
NULL,
0,
0
};
static int
tcp_addfastpaths(module_t mod, int type, void *data)
{
int err=0;
switch (type) {
case MOD_LOAD:
err = register_tcp_functions(&__tcp_fastack, M_WAITOK);
if (err) {
printf("Failed to register fastack module -- err:%d\n", err);
return(err);
}
err = register_tcp_functions(&__tcp_fastslow, M_WAITOK);
if (err) {
printf("Failed to register fastslow module -- err:%d\n", err);
deregister_tcp_functions(&__tcp_fastack);
return(err);
}
break;
case MOD_QUIESCE:
if ((__tcp_fastslow.tfb_refcnt) ||( __tcp_fastack.tfb_refcnt)) {
return(EBUSY);
}
break;
case MOD_UNLOAD:
err = deregister_tcp_functions(&__tcp_fastack);
if (err == EBUSY)
break;
err = deregister_tcp_functions(&__tcp_fastslow);
if (err == EBUSY)
break;
err = 0;
break;
default:
return (EOPNOTSUPP);
}
return (err);
}
static moduledata_t new_tcp_fastpaths = {
.name = "tcp_fastpaths",
.evhand = tcp_addfastpaths,
.priv = 0
};
MODULE_VERSION(kern_tcpfastpaths, 1);
DECLARE_MODULE(kern_tcpfastpaths, new_tcp_fastpaths, SI_SUB_PSEUDO, SI_ORDER_ANY);
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