* Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.

/* $NetBSD: tcp_input.c,v 1.441 2024/10/08 06:17:14 rin Exp $ */

/*
* 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, 1999, 2001, 2005, 2006,
* 2011 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Coyote Point Systems, Inc.
* 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, 1994, 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_input.c 8.12 (Berkeley) 5/24/95
*/

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: tcp_input.c,v 1.441 2024/10/08 06:17:14 rin Exp $");

#ifdef _KERNEL_OPT
#include "opt_inet.h"
#include "opt_ipsec.h"
#include "opt_inet_csum.h"
#include "opt_tcp_debug.h"
#endif

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/protosw.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/errno.h>
#include <sys/syslog.h>
#include <sys/pool.h>
#include <sys/domain.h>
#include <sys/kernel.h>
#ifdef TCP_SIGNATURE
#include <sys/md5.h>
#endif
#include <sys/lwp.h> /* for lwp0 */
#include <sys/cprng.h>

#include <net/if.h>
#include <net/if_types.h>

#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/in_pcb.h>
#include <netinet/in_var.h>
#include <netinet/ip_var.h>
#include <netinet/in_offload.h>

#if NARP > 0
#include <netinet/if_inarp.h>
#endif
#ifdef INET6
#include <netinet/ip6.h>
#include <netinet6/ip6_var.h>
#include <netinet6/in6_pcb.h>
#include <netinet6/ip6_var.h>
#include <netinet6/in6_var.h>
#include <netinet/icmp6.h>
#include <netinet6/nd6.h>
#ifdef TCP_SIGNATURE
#include <netinet6/scope6_var.h>
#endif
#endif

#ifndef INET6
#include <netinet/ip6.h>
#endif

#include <netinet/tcp.h>
#include <netinet/tcp_fsm.h>
#include <netinet/tcp_seq.h>
#include <netinet/tcp_timer.h>
#include <netinet/tcp_var.h>
#include <netinet/tcp_private.h>
#include <netinet/tcp_congctl.h>
#include <netinet/tcp_debug.h>
#include <netinet/tcp_syncache.h>

#ifdef INET6
#include "faith.h"
#if defined(NFAITH) && NFAITH > 0
#include <net/if_faith.h>
#endif
#endif

#ifdef IPSEC
#include <netipsec/ipsec.h>
#include <netipsec/key.h>
#ifdef INET6
#include <netipsec/ipsec6.h>
#endif
#endif /* IPSEC*/

#include <netinet/tcp_vtw.h>

int tcprexmtthresh = 3;
int tcp_log_refused;

int tcp_do_autorcvbuf = 1;
int tcp_autorcvbuf_inc = 16 * 1024;
int tcp_autorcvbuf_max = 256 * 1024;
int tcp_msl = (TCPTV_MSL / PR_SLOWHZ);

int tcp_reass_maxqueuelen = 100;

static int tcp_rst_ppslim_count = 0;
static struct timeval tcp_rst_ppslim_last;
static int tcp_ackdrop_ppslim_count = 0;
static struct timeval tcp_ackdrop_ppslim_last;

#define TCP_PAWS_IDLE (24U * 24 * 60 * 60 * PR_SLOWHZ)

/* for modulo comparisons of timestamps */
#define TSTMP_LT(a,b) ((int)((a)-(b)) < 0)
#define TSTMP_GEQ(a,b) ((int)((a)-(b)) >= 0)

/*
* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint.
*/
static void
nd_hint(struct tcpcb *tp)
{
struct route *ro = NULL;
struct rtentry *rt;

if (tp == NULL)
return;

ro = &tp->t_inpcb->inp_route;
if (ro == NULL)
return;

rt = rtcache_validate(ro);
if (rt == NULL)
return;

switch (tp->t_family) {
#if NARP > 0
case AF_INET:
arp_nud_hint(rt);
break;
#endif
#ifdef INET6
case AF_INET6:
nd6_nud_hint(rt);
break;
#endif
}

rtcache_unref(rt, ro);
}

/*
* Compute ACK transmission behavior. Delay the ACK unless
* we have already delayed an ACK (must send an ACK every two segments).
* We also ACK immediately if we received a PUSH and the ACK-on-PUSH
* option is enabled.
*/
static void
tcp_setup_ack(struct tcpcb *tp, const struct tcphdr *th)
{

if (tp->t_flags & TF_DELACK ||
(tcp_ack_on_push && th->th_flags & TH_PUSH))
tp->t_flags |= TF_ACKNOW;
else
TCP_SET_DELACK(tp);
}

static void
icmp_check(struct tcpcb *tp, const struct tcphdr *th, int acked)
{

/*
* If we had a pending ICMP message that refers to data that have
* just been acknowledged, disregard the recorded ICMP message.
*/
if ((tp->t_flags & TF_PMTUD_PEND) &&
SEQ_GT(th->th_ack, tp->t_pmtud_th_seq))
tp->t_flags &= ~TF_PMTUD_PEND;

/*
* Keep track of the largest chunk of data
* acknowledged since last PMTU update
*/
if (tp->t_pmtud_mss_acked < acked)
tp->t_pmtud_mss_acked = acked;
}

/*
* Convert TCP protocol fields to host order for easier processing.
*/
static void
tcp_fields_to_host(struct tcphdr *th)
{

NTOHL(th->th_seq);
NTOHL(th->th_ack);
NTOHS(th->th_win);
NTOHS(th->th_urp);
}

/*
* ... and reverse the above.
*/
static void
tcp_fields_to_net(struct tcphdr *th)
{

HTONL(th->th_seq);
HTONL(th->th_ack);
HTONS(th->th_win);
HTONS(th->th_urp);
}

static void
tcp_urp_drop(struct tcphdr *th, int todrop, int *tiflags)
{
if (th->th_urp > todrop) {
th->th_urp -= todrop;
} else {
*tiflags &= ~TH_URG;
th->th_urp = 0;
}
}

#ifdef TCP_CSUM_COUNTERS
#include <sys/device.h>

extern struct evcnt tcp_hwcsum_ok;
extern struct evcnt tcp_hwcsum_bad;
extern struct evcnt tcp_hwcsum_data;
extern struct evcnt tcp_swcsum;
#if defined(INET6)
extern struct evcnt tcp6_hwcsum_ok;
extern struct evcnt tcp6_hwcsum_bad;
extern struct evcnt tcp6_hwcsum_data;
extern struct evcnt tcp6_swcsum;
#endif /* defined(INET6) */

#define TCP_CSUM_COUNTER_INCR(ev) (ev)->ev_count++

#else

#define TCP_CSUM_COUNTER_INCR(ev) /* nothing */

#endif /* TCP_CSUM_COUNTERS */

#ifdef TCP_REASS_COUNTERS
#include <sys/device.h>

extern struct evcnt tcp_reass_;
extern struct evcnt tcp_reass_empty;
extern struct evcnt tcp_reass_iteration[8];
extern struct evcnt tcp_reass_prependfirst;
extern struct evcnt tcp_reass_prepend;
extern struct evcnt tcp_reass_insert;
extern struct evcnt tcp_reass_inserttail;
extern struct evcnt tcp_reass_append;
extern struct evcnt tcp_reass_appendtail;
extern struct evcnt tcp_reass_overlaptail;
extern struct evcnt tcp_reass_overlapfront;
extern struct evcnt tcp_reass_segdup;
extern struct evcnt tcp_reass_fragdup;

#define TCP_REASS_COUNTER_INCR(ev) (ev)->ev_count++

#else

#define TCP_REASS_COUNTER_INCR(ev) /* nothing */

#endif /* TCP_REASS_COUNTERS */

static int tcp_reass(struct tcpcb *, const struct tcphdr *, struct mbuf *,
int);

static void tcp4_log_refused(const struct ip *, const struct tcphdr *);
#ifdef INET6
static void tcp6_log_refused(const struct ip6_hdr *, const struct tcphdr *);
#endif

#if defined(MBUFTRACE)
struct mowner tcp_reass_mowner = MOWNER_INIT("tcp", "reass");
#endif /* defined(MBUFTRACE) */

static struct pool tcpipqent_pool;

void
tcpipqent_init(void)
{

pool_init(&tcpipqent_pool, sizeof(struct ipqent), 0, 0, 0, "tcpipqepl",
NULL, IPL_VM);
}

struct ipqent *
tcpipqent_alloc(void)
{
struct ipqent *ipqe;
int s;

s = splvm();
ipqe = pool_get(&tcpipqent_pool, PR_NOWAIT);
splx(s);

return ipqe;
}

void
tcpipqent_free(struct ipqent *ipqe)
{
int s;

s = splvm();
pool_put(&tcpipqent_pool, ipqe);
splx(s);
}

/*
* Insert segment ti into reassembly queue of tcp with
* control block tp. Return TH_FIN if reassembly now includes
* a segment with FIN.
*/
static int
tcp_reass(struct tcpcb *tp, const struct tcphdr *th, struct mbuf *m, int tlen)
{
struct ipqent *p, *q, *nq, *tiqe = NULL;
struct socket *so = NULL;
int pkt_flags;
tcp_seq pkt_seq;
unsigned pkt_len;
u_long rcvpartdupbyte = 0;
u_long rcvoobyte;
#ifdef TCP_REASS_COUNTERS
u_int count = 0;
#endif
net_stat_ref_t tcps;

so = tp->t_inpcb->inp_socket;

TCP_REASS_LOCK_CHECK(tp);

/*
* Call with th==NULL after become established to
* force pre-ESTABLISHED data up to user socket.
*/
if (th == NULL)
goto present;

m_claimm(m, &tcp_reass_mowner);

rcvoobyte = tlen;
/*
* Copy these to local variables because the TCP header gets munged
* while we are collapsing mbufs.
*/
pkt_seq = th->th_seq;
pkt_len = tlen;
pkt_flags = th->th_flags;

TCP_REASS_COUNTER_INCR(&tcp_reass_);

if ((p = TAILQ_LAST(&tp->segq, ipqehead)) != NULL) {
/*
* When we miss a packet, the vast majority of time we get
* packets that follow it in order. So optimize for that.
*/
if (pkt_seq == p->ipqe_seq + p->ipqe_len) {
p->ipqe_len += pkt_len;
p->ipqe_flags |= pkt_flags;
m_cat(p->ipqe_m, m);
m = NULL;
tiqe = p;
TAILQ_REMOVE(&tp->timeq, p, ipqe_timeq);
TCP_REASS_COUNTER_INCR(&tcp_reass_appendtail);
goto skip_replacement;
}
/*
* While we're here, if the pkt is completely beyond
* anything we have, just insert it at the tail.
*/
if (SEQ_GT(pkt_seq, p->ipqe_seq + p->ipqe_len)) {
TCP_REASS_COUNTER_INCR(&tcp_reass_inserttail);
goto insert_it;
}
}

q = TAILQ_FIRST(&tp->segq);

if (q != NULL) {
/*
* If this segment immediately precedes the first out-of-order
* block, simply slap the segment in front of it and (mostly)
* skip the complicated logic.
*/
if (pkt_seq + pkt_len == q->ipqe_seq) {
q->ipqe_seq = pkt_seq;
q->ipqe_len += pkt_len;
q->ipqe_flags |= pkt_flags;
m_cat(m, q->ipqe_m);
q->ipqe_m = m;
tiqe = q;
TAILQ_REMOVE(&tp->timeq, q, ipqe_timeq);
TCP_REASS_COUNTER_INCR(&tcp_reass_prependfirst);
goto skip_replacement;
}
} else {
TCP_REASS_COUNTER_INCR(&tcp_reass_empty);
}

/*
* Find a segment which begins after this one does.
*/
for (p = NULL; q != NULL; q = nq) {
nq = TAILQ_NEXT(q, ipqe_q);
#ifdef TCP_REASS_COUNTERS
count++;
#endif

/*
* If the received segment is just right after this
* fragment, merge the two together and then check
* for further overlaps.
*/
if (q->ipqe_seq + q->ipqe_len == pkt_seq) {
pkt_len += q->ipqe_len;
pkt_flags |= q->ipqe_flags;
pkt_seq = q->ipqe_seq;
m_cat(q->ipqe_m, m);
m = q->ipqe_m;
TCP_REASS_COUNTER_INCR(&tcp_reass_append);
goto free_ipqe;
}

/*
* If the received segment is completely past this
* fragment, we need to go to the next fragment.
*/
if (SEQ_LT(q->ipqe_seq + q->ipqe_len, pkt_seq)) {
p = q;
continue;
}

/*
* If the fragment is past the received segment,
* it (or any following) can't be concatenated.
*/
if (SEQ_GT(q->ipqe_seq, pkt_seq + pkt_len)) {
TCP_REASS_COUNTER_INCR(&tcp_reass_insert);
break;
}

/*
* We've received all the data in this segment before.
* Mark it as a duplicate and return.
*/
if (SEQ_LEQ(q->ipqe_seq, pkt_seq) &&
SEQ_GEQ(q->ipqe_seq + q->ipqe_len, pkt_seq + pkt_len)) {
tcps = TCP_STAT_GETREF();
_NET_STATINC_REF(tcps, TCP_STAT_RCVDUPPACK);
_NET_STATADD_REF(tcps, TCP_STAT_RCVDUPBYTE, pkt_len);
TCP_STAT_PUTREF();
tcp_new_dsack(tp, pkt_seq, pkt_len);
m_freem(m);
if (tiqe != NULL) {
tcpipqent_free(tiqe);
}
TCP_REASS_COUNTER_INCR(&tcp_reass_segdup);
goto out;
}

/*
* Received segment completely overlaps this fragment
* so we drop the fragment (this keeps the temporal
* ordering of segments correct).
*/
if (SEQ_GEQ(q->ipqe_seq, pkt_seq) &&
SEQ_LEQ(q->ipqe_seq + q->ipqe_len, pkt_seq + pkt_len)) {
rcvpartdupbyte += q->ipqe_len;
m_freem(q->ipqe_m);
TCP_REASS_COUNTER_INCR(&tcp_reass_fragdup);
goto free_ipqe;
}

/*
* Received segment extends past the end of the fragment.
* Drop the overlapping bytes, merge the fragment and
* segment, and treat as a longer received packet.
*/
if (SEQ_LT(q->ipqe_seq, pkt_seq) &&
SEQ_GT(q->ipqe_seq + q->ipqe_len, pkt_seq)) {
int overlap = q->ipqe_seq + q->ipqe_len - pkt_seq;
m_adj(m, overlap);
rcvpartdupbyte += overlap;
m_cat(q->ipqe_m, m);
m = q->ipqe_m;
pkt_seq = q->ipqe_seq;
pkt_len += q->ipqe_len - overlap;
rcvoobyte -= overlap;
TCP_REASS_COUNTER_INCR(&tcp_reass_overlaptail);
goto free_ipqe;
}

/*
* Received segment extends past the front of the fragment.
* Drop the overlapping bytes on the received packet. The
* packet will then be concatenated with this fragment a
* bit later.
*/
if (SEQ_GT(q->ipqe_seq, pkt_seq) &&
SEQ_LT(q->ipqe_seq, pkt_seq + pkt_len)) {
int overlap = pkt_seq + pkt_len - q->ipqe_seq;
m_adj(m, -overlap);
pkt_len -= overlap;
rcvpartdupbyte += overlap;
TCP_REASS_COUNTER_INCR(&tcp_reass_overlapfront);
rcvoobyte -= overlap;
}

/*
* If the received segment immediately precedes this
* fragment then tack the fragment onto this segment
* and reinsert the data.
*/
if (q->ipqe_seq == pkt_seq + pkt_len) {
pkt_len += q->ipqe_len;
pkt_flags |= q->ipqe_flags;
m_cat(m, q->ipqe_m);
TAILQ_REMOVE(&tp->segq, q, ipqe_q);
TAILQ_REMOVE(&tp->timeq, q, ipqe_timeq);
tp->t_segqlen--;
KASSERT(tp->t_segqlen >= 0);
KASSERT(tp->t_segqlen != 0 ||
(TAILQ_EMPTY(&tp->segq) &&
TAILQ_EMPTY(&tp->timeq)));
if (tiqe == NULL) {
tiqe = q;
} else {
tcpipqent_free(q);
}
TCP_REASS_COUNTER_INCR(&tcp_reass_prepend);
break;
}

/*
* If the fragment is before the segment, remember it.
* When this loop is terminated, p will contain the
* pointer to the fragment that is right before the
* received segment.
*/
if (SEQ_LEQ(q->ipqe_seq, pkt_seq))
p = q;

continue;

/*
* This is a common operation. It also will allow
* to save doing a malloc/free in most instances.
*/
free_ipqe:
TAILQ_REMOVE(&tp->segq, q, ipqe_q);
TAILQ_REMOVE(&tp->timeq, q, ipqe_timeq);
tp->t_segqlen--;
KASSERT(tp->t_segqlen >= 0);
KASSERT(tp->t_segqlen != 0 ||
(TAILQ_EMPTY(&tp->segq) && TAILQ_EMPTY(&tp->timeq)));
if (tiqe == NULL) {
tiqe = q;
} else {
tcpipqent_free(q);
}
}

#ifdef TCP_REASS_COUNTERS
if (count > 7)
TCP_REASS_COUNTER_INCR(&tcp_reass_iteration[0]);
else if (count > 0)
TCP_REASS_COUNTER_INCR(&tcp_reass_iteration[count]);
#endif

insert_it:
/* limit tcp segments per reassembly queue */
if (tp->t_segqlen > tcp_reass_maxqueuelen) {
TCP_STATINC(TCP_STAT_RCVMEMDROP);
m_freem(m);
goto out;
}

/*
* Allocate a new queue entry (block) since the received segment
* did not collapse onto any other out-of-order block. If it had
* collapsed, tiqe would not be NULL and we would be reusing it.
*
* If the allocation fails, drop the packet.
*/
if (tiqe == NULL) {
tiqe = tcpipqent_alloc();
if (tiqe == NULL) {
TCP_STATINC(TCP_STAT_RCVMEMDROP);
m_freem(m);
goto out;
}
}

/*
* Update the counters.
*/
tp->t_rcvoopack++;
tcps = TCP_STAT_GETREF();
_NET_STATINC_REF(tcps, TCP_STAT_RCVOOPACK);
_NET_STATADD_REF(tcps, TCP_STAT_RCVOOBYTE, rcvoobyte);
if (rcvpartdupbyte) {
_NET_STATINC_REF(tcps, TCP_STAT_RCVPARTDUPPACK);
_NET_STATADD_REF(tcps, TCP_STAT_RCVPARTDUPBYTE,
rcvpartdupbyte);
}
TCP_STAT_PUTREF();

/*
* Insert the new fragment queue entry into both queues.
*/
tiqe->ipqe_m = m;
tiqe->ipqe_seq = pkt_seq;
tiqe->ipqe_len = pkt_len;
tiqe->ipqe_flags = pkt_flags;
if (p == NULL) {
TAILQ_INSERT_HEAD(&tp->segq, tiqe, ipqe_q);
} else {
TAILQ_INSERT_AFTER(&tp->segq, p, tiqe, ipqe_q);
}
tp->t_segqlen++;

skip_replacement:
TAILQ_INSERT_HEAD(&tp->timeq, tiqe, ipqe_timeq);

present:
/*
* Present data to user, advancing rcv_nxt through
* completed sequence space.
*/
if (TCPS_HAVEESTABLISHED(tp->t_state) == 0)
goto out;
q = TAILQ_FIRST(&tp->segq);
if (q == NULL || q->ipqe_seq != tp->rcv_nxt)
goto out;
if (tp->t_state == TCPS_SYN_RECEIVED && q->ipqe_len)
goto out;

tp->rcv_nxt += q->ipqe_len;
pkt_flags = q->ipqe_flags & TH_FIN;
nd_hint(tp);

TAILQ_REMOVE(&tp->segq, q, ipqe_q);
TAILQ_REMOVE(&tp->timeq, q, ipqe_timeq);
tp->t_segqlen--;
KASSERT(tp->t_segqlen >= 0);
KASSERT(tp->t_segqlen != 0 ||
(TAILQ_EMPTY(&tp->segq) && TAILQ_EMPTY(&tp->timeq)));
if (so->so_state & SS_CANTRCVMORE)
m_freem(q->ipqe_m);
else
sbappendstream(&so->so_rcv, q->ipqe_m);
tcpipqent_free(q);
TCP_REASS_UNLOCK(tp);
sorwakeup(so);
return pkt_flags;

out:
TCP_REASS_UNLOCK(tp);
return 0;
}

#ifdef INET6
int
tcp6_input(struct mbuf **mp, int *offp, int proto)
{
struct mbuf *m = *mp;

/*
* draft-itojun-ipv6-tcp-to-anycast
* better place to put this in?
*/
if (m->m_flags & M_ANYCAST6) {
struct ip6_hdr *ip6;
if (m->m_len < sizeof(struct ip6_hdr)) {
if ((m = m_pullup(m, sizeof(struct ip6_hdr))) == NULL) {
TCP_STATINC(TCP_STAT_RCVSHORT);
return IPPROTO_DONE;
}
}
ip6 = mtod(m, struct ip6_hdr *);
icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR,
(char *)&ip6->ip6_dst - (char *)ip6);
return IPPROTO_DONE;
}

tcp_input(m, *offp, proto);
return IPPROTO_DONE;
}
#endif

static void
tcp4_log_refused(const struct ip *ip, const struct tcphdr *th)
{
char src[INET_ADDRSTRLEN];
char dst[INET_ADDRSTRLEN];

if (ip) {
in_print(src, sizeof(src), &ip->ip_src);
in_print(dst, sizeof(dst), &ip->ip_dst);
} else {
strlcpy(src, "(unknown)", sizeof(src));
strlcpy(dst, "(unknown)", sizeof(dst));
}
log(LOG_INFO,
"Connection attempt to TCP %s:%d from %s:%d\n",
dst, ntohs(th->th_dport),
src, ntohs(th->th_sport));
}

#ifdef INET6
static void
tcp6_log_refused(const struct ip6_hdr *ip6, const struct tcphdr *th)
{
char src[INET6_ADDRSTRLEN];
char dst[INET6_ADDRSTRLEN];

if (ip6) {
in6_print(src, sizeof(src), &ip6->ip6_src);
in6_print(dst, sizeof(dst), &ip6->ip6_dst);
} else {
strlcpy(src, "(unknown v6)", sizeof(src));
strlcpy(dst, "(unknown v6)", sizeof(dst));
}
log(LOG_INFO,
"Connection attempt to TCP [%s]:%d from [%s]:%d\n",
dst, ntohs(th->th_dport),
src, ntohs(th->th_sport));
}
#endif

/*
* Checksum extended TCP header and data.
*/
int
tcp_input_checksum(int af, struct mbuf *m, const struct tcphdr *th,
int toff, int off, int tlen)
{
struct ifnet *rcvif;
int s;

/*
* XXX it's better to record and check if this mbuf is
* already checked.
*/

rcvif = m_get_rcvif(m, &s);
if (__predict_false(rcvif == NULL))
goto badcsum; /* XXX */

switch (af) {
case AF_INET:
switch (m->m_pkthdr.csum_flags &
((rcvif->if_csum_flags_rx & M_CSUM_TCPv4) |
M_CSUM_TCP_UDP_BAD | M_CSUM_DATA)) {
case M_CSUM_TCPv4|M_CSUM_TCP_UDP_BAD:
TCP_CSUM_COUNTER_INCR(&tcp_hwcsum_bad);
goto badcsum;

case M_CSUM_TCPv4|M_CSUM_DATA: {
u_int32_t hw_csum = m->m_pkthdr.csum_data;

TCP_CSUM_COUNTER_INCR(&tcp_hwcsum_data);
if (m->m_pkthdr.csum_flags & M_CSUM_NO_PSEUDOHDR) {
const struct ip *ip =
mtod(m, const struct ip *);

hw_csum = in_cksum_phdr(ip->ip_src.s_addr,
ip->ip_dst.s_addr,
htons(hw_csum + tlen + off + IPPROTO_TCP));
}
if ((hw_csum ^ 0xffff) != 0)
goto badcsum;
break;
}

case M_CSUM_TCPv4:
/* Checksum was okay. */
TCP_CSUM_COUNTER_INCR(&tcp_hwcsum_ok);
break;

default:
/*
* Must compute it ourselves. Maybe skip checksum
* on loopback interfaces.
*/
if (__predict_true(!(rcvif->if_flags & IFF_LOOPBACK) ||
tcp_do_loopback_cksum)) {
TCP_CSUM_COUNTER_INCR(&tcp_swcsum);
if (in4_cksum(m, IPPROTO_TCP, toff,
tlen + off) != 0)
goto badcsum;
}
break;
}
break;

#ifdef INET6
case AF_INET6:
switch (m->m_pkthdr.csum_flags &
((rcvif->if_csum_flags_rx & M_CSUM_TCPv6) |
M_CSUM_TCP_UDP_BAD | M_CSUM_DATA)) {
case M_CSUM_TCPv6|M_CSUM_TCP_UDP_BAD:
TCP_CSUM_COUNTER_INCR(&tcp6_hwcsum_bad);
goto badcsum;

#if 0 /* notyet */
case M_CSUM_TCPv6|M_CSUM_DATA:
#endif

case M_CSUM_TCPv6:
/* Checksum was okay. */
TCP_CSUM_COUNTER_INCR(&tcp6_hwcsum_ok);
break;

default:
/*
* Must compute it ourselves. Maybe skip checksum
* on loopback interfaces.
*/
if (__predict_true((m->m_flags & M_LOOP) == 0 ||
tcp_do_loopback_cksum)) {
TCP_CSUM_COUNTER_INCR(&tcp6_swcsum);
if (in6_cksum(m, IPPROTO_TCP, toff,
tlen + off) != 0)
goto badcsum;
}
}
break;
#endif /* INET6 */
}
m_put_rcvif(rcvif, &s);

return 0;

badcsum:
m_put_rcvif(rcvif, &s);
TCP_STATINC(TCP_STAT_RCVBADSUM);
return -1;
}

/*
* When a packet arrives addressed to a vestigial tcpbp, we
* nevertheless have to respond to it per the spec.
*
* This code is duplicated from the one in tcp_input().
*/
static void tcp_vtw_input(struct tcphdr *th, vestigial_inpcb_t *vp,
struct mbuf *m, int tlen)
{
int tiflags;
int todrop;
uint32_t t_flags = 0;
net_stat_ref_t tcps;

tiflags = th->th_flags;
todrop = vp->rcv_nxt - th->th_seq;

if (todrop > 0) {
if (tiflags & TH_SYN) {
tiflags &= ~TH_SYN;
th->th_seq++;
tcp_urp_drop(th, 1, &tiflags);
todrop--;
}
if (todrop > tlen ||
(todrop == tlen && (tiflags & TH_FIN) == 0)) {
/*
* Any valid FIN or RST must be to the left of the
* window. At this point the FIN or RST must be a
* duplicate or out of sequence; drop it.
*/
if (tiflags & TH_RST)
goto drop;
tiflags &= ~(TH_FIN|TH_RST);

/*
* Send an ACK to resynchronize and drop any data.
* But keep on processing for RST or ACK.
*/
t_flags |= TF_ACKNOW;
todrop = tlen;
tcps = TCP_STAT_GETREF();
_NET_STATINC_REF(tcps, TCP_STAT_RCVDUPPACK);
_NET_STATADD_REF(tcps, TCP_STAT_RCVDUPBYTE, todrop);
TCP_STAT_PUTREF();
} else if ((tiflags & TH_RST) &&
th->th_seq != vp->rcv_nxt) {
/*
* Test for reset before adjusting the sequence
* number for overlapping data.
*/
goto dropafterack_ratelim;
} else {
tcps = TCP_STAT_GETREF();
_NET_STATINC_REF(tcps, TCP_STAT_RCVPARTDUPPACK);
_NET_STATADD_REF(tcps, TCP_STAT_RCVPARTDUPBYTE,
todrop);
TCP_STAT_PUTREF();
}

// tcp_new_dsack(tp, th->th_seq, todrop);
// hdroptlen += todrop; /*drop from head afterwards*/

th->th_seq += todrop;
tlen -= todrop;
tcp_urp_drop(th, todrop, &tiflags);
}

/*
* If new data are received on a connection after the
* user processes are gone, then RST the other end.
*/
if (tlen) {
TCP_STATINC(TCP_STAT_RCVAFTERCLOSE);
goto dropwithreset;
}

/*
* If segment ends after window, drop trailing data
* (and PUSH and FIN); if nothing left, just ACK.
*/
todrop = (th->th_seq + tlen) - (vp->rcv_nxt + vp->rcv_wnd);

if (todrop > 0) {
TCP_STATINC(TCP_STAT_RCVPACKAFTERWIN);
if (todrop >= tlen) {
/*
* The segment actually starts after the window.
* th->th_seq + tlen - vp->rcv_nxt - vp->rcv_wnd >= tlen
* th->th_seq - vp->rcv_nxt - vp->rcv_wnd >= 0
* th->th_seq >= vp->rcv_nxt + vp->rcv_wnd
*/
TCP_STATADD(TCP_STAT_RCVBYTEAFTERWIN, tlen);

/*
* If a new connection request is received
* while in TIME_WAIT, drop the old connection
* and start over if the sequence numbers
* are above the previous ones.
*/
if ((tiflags & TH_SYN) &&
SEQ_GT(th->th_seq, vp->rcv_nxt)) {
/*
* We only support this in the !NOFDREF case, which
* is to say: not here.
*/
goto dropwithreset;
}

/*
* 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 (if not RST) ack.
*/
if (vp->rcv_wnd == 0 && th->th_seq == vp->rcv_nxt) {
t_flags |= TF_ACKNOW;
TCP_STATINC(TCP_STAT_RCVWINPROBE);
} else {
goto dropafterack;
}
} else {
TCP_STATADD(TCP_STAT_RCVBYTEAFTERWIN, todrop);
}
m_adj(m, -todrop);
tlen -= todrop;
tiflags &= ~(TH_PUSH|TH_FIN);
}

if (tiflags & TH_RST) {
if (th->th_seq != vp->rcv_nxt)
goto dropafterack_ratelim;

vtw_del(vp->ctl, vp->vtw);
goto drop;
}

/*
* If the ACK bit is off we drop the segment and return.
*/
if ((tiflags & TH_ACK) == 0) {
if (t_flags & TF_ACKNOW)
goto dropafterack;
goto drop;
}

/*
* In TIME_WAIT state the only thing that should arrive
* is a retransmission of the remote FIN. Acknowledge
* it and restart the finack timer.
*/
vtw_restart(vp);
goto dropafterack;

dropafterack:
/*
* Generate an ACK dropping incoming segment if it occupies
* sequence space, where the ACK reflects our state.
*/
if (tiflags & TH_RST)
goto drop;
goto dropafterack2;

dropafterack_ratelim:
/*
* We may want to rate-limit ACKs against SYN/RST attack.
*/
if (ppsratecheck(&tcp_ackdrop_ppslim_last, &tcp_ackdrop_ppslim_count,
tcp_ackdrop_ppslim) == 0) {
/* XXX stat */
goto drop;
}
/* ...fall into dropafterack2... */

dropafterack2:
(void)tcp_respond(0, m, m, th, th->th_seq + tlen, th->th_ack, TH_ACK);
return;

dropwithreset:
/*
* Generate a RST, dropping incoming segment.
* Make ACK acceptable to originator of segment.
*/
if (tiflags & TH_RST)
goto drop;

if (tiflags & TH_ACK) {
tcp_respond(0, m, m, th, (tcp_seq)0, th->th_ack, TH_RST);
} else {
if (tiflags & TH_SYN)
++tlen;
(void)tcp_respond(0, m, m, th, th->th_seq + tlen, (tcp_seq)0,
TH_RST|TH_ACK);
}
return;
drop:
m_freem(m);
}

/*
* TCP input routine, follows pages 65-76 of RFC 793 very closely.
*/
void
tcp_input(struct mbuf *m, int off, int proto)
{
struct tcphdr *th;
struct ip *ip;
struct inpcb *inp;
#ifdef INET6
struct ip6_hdr *ip6;
#endif
u_int8_t *optp = NULL;
int optlen = 0;
int len, tlen, hdroptlen = 0;
struct tcpcb *tp = NULL;
int tiflags;
struct socket *so = NULL;
int todrop, acked, ourfinisacked, needoutput = 0;
bool dupseg;
#ifdef TCP_DEBUG
short ostate = 0;
#endif
u_long tiwin;
struct tcp_opt_info opti;
int thlen, iphlen;
int af; /* af on the wire */
struct mbuf *tcp_saveti = NULL;
uint32_t ts_rtt;
uint8_t iptos;
net_stat_ref_t tcps;
vestigial_inpcb_t vestige;

vestige.valid = 0;

MCLAIM(m, &tcp_rx_mowner);

TCP_STATINC(TCP_STAT_RCVTOTAL);

memset(&opti, 0, sizeof(opti));
opti.ts_present = 0;
opti.maxseg = 0;

/*
* RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN.
*
* TCP is, by definition, unicast, so we reject all
* multicast outright.
*
* Note, there are additional src/dst address checks in
* the AF-specific code below.
*/
if (m->m_flags & (M_BCAST|M_MCAST)) {
/* XXX stat */
goto drop;
}
#ifdef INET6
if (m->m_flags & M_ANYCAST6) {
/* XXX stat */
goto drop;
}
#endif

M_REGION_GET(th, struct tcphdr *, m, off, sizeof(struct tcphdr));
if (th == NULL) {
TCP_STATINC(TCP_STAT_RCVSHORT);
return;
}

/*
* Enforce alignment requirements that are violated in
* some cases, see kern/50766 for details.
*/
if (ACCESSIBLE_POINTER(th, struct tcphdr) == 0) {
m = m_copyup(m, off + sizeof(struct tcphdr), 0);
if (m == NULL) {
TCP_STATINC(TCP_STAT_RCVSHORT);
return;
}
th = (struct tcphdr *)(mtod(m, char *) + off);
}
KASSERT(ACCESSIBLE_POINTER(th, struct tcphdr));

/*
* Get IP and TCP header.
* Note: IP leaves IP header in first mbuf.
*/
ip = mtod(m, struct ip *);
#ifdef INET6
ip6 = mtod(m, struct ip6_hdr *);
#endif
switch (ip->ip_v) {
case 4:
af = AF_INET;
iphlen = sizeof(struct ip);

if (IN_MULTICAST(ip->ip_dst.s_addr) ||
in_broadcast(ip->ip_dst, m_get_rcvif_NOMPSAFE(m)))
goto drop;

/* We do the checksum after PCB lookup... */
len = ntohs(ip->ip_len);
tlen = len - off;
iptos = ip->ip_tos;
break;
#ifdef INET6
case 6:
iphlen = sizeof(struct ip6_hdr);
af = AF_INET6;

/*
* Be proactive about unspecified IPv6 address in source.
* As we use all-zero to indicate unbounded/unconnected pcb,
* unspecified IPv6 address can be used to confuse us.
*
* Note that packets with unspecified IPv6 destination is
* already dropped in ip6_input.
*/
if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
/* XXX stat */
goto drop;
}

/*
* Make sure destination address is not multicast.
* Source address checked in ip6_input().
*/
if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst)) {
/* XXX stat */
goto drop;
}

/* We do the checksum after PCB lookup... */
len = m->m_pkthdr.len;
tlen = len - off;
iptos = (ntohl(ip6->ip6_flow) >> 20) & 0xff;
break;
#endif
default:
m_freem(m);
return;
}

/*
* Check that TCP offset makes sense, pull out TCP options and
* adjust length.
*/
thlen = th->th_off << 2;
if (thlen < sizeof(struct tcphdr) || thlen > tlen) {
TCP_STATINC(TCP_STAT_RCVBADOFF);
goto drop;
}
tlen -= thlen;

if (thlen > sizeof(struct tcphdr)) {
M_REGION_GET(th, struct tcphdr *, m, off, thlen);
if (th == NULL) {
TCP_STATINC(TCP_STAT_RCVSHORT);
return;
}
KASSERT(ACCESSIBLE_POINTER(th, struct tcphdr));
optlen = thlen - sizeof(struct tcphdr);
optp = ((u_int8_t *)th) + sizeof(struct tcphdr);

/*
* Do quick retrieval of timestamp options.
*
* If timestamp is the only option and it's formatted as
* recommended in RFC 1323 appendix A, we quickly get the
* values now and don't bother calling tcp_dooptions(),
* etc.
*/
if ((optlen == TCPOLEN_TSTAMP_APPA ||
(optlen > TCPOLEN_TSTAMP_APPA &&
optp[TCPOLEN_TSTAMP_APPA] == TCPOPT_EOL)) &&
be32dec(optp) == TCPOPT_TSTAMP_HDR &&
(th->th_flags & TH_SYN) == 0) {
opti.ts_present = 1;
opti.ts_val = be32dec(optp + 4);
opti.ts_ecr = be32dec(optp + 8);
optp = NULL; /* we've parsed the options */
}
}
tiflags = th->th_flags;

/*
* Checksum extended TCP header and data
*/
if (tcp_input_checksum(af, m, th, off, thlen, tlen))
goto badcsum;

/*
* Locate pcb for segment.
*/
findpcb:
inp = NULL;
switch (af) {
case AF_INET:
inp = inpcb_lookup(&tcbtable, ip->ip_src, th->th_sport,
ip->ip_dst, th->th_dport, &vestige);
if (inp == NULL && !vestige.valid) {
TCP_STATINC(TCP_STAT_PCBHASHMISS);
inp = inpcb_lookup_bound(&tcbtable, ip->ip_dst,
th->th_dport);
}
#ifdef INET6
if (inp == NULL && !vestige.valid) {
struct in6_addr s, d;

/* mapped addr case */
in6_in_2_v4mapin6(&ip->ip_src, &s);
in6_in_2_v4mapin6(&ip->ip_dst, &d);
inp = in6pcb_lookup(&tcbtable, &s,
th->th_sport, &d, th->th_dport, 0, &vestige);
if (inp == NULL && !vestige.valid) {
TCP_STATINC(TCP_STAT_PCBHASHMISS);
inp = in6pcb_lookup_bound(&tcbtable, &d,
th->th_dport, 0);
}
}
#endif
if (inp == NULL && !vestige.valid) {
TCP_STATINC(TCP_STAT_NOPORT);
if (tcp_log_refused &&
(tiflags & (TH_RST|TH_ACK|TH_SYN)) == TH_SYN) {
tcp4_log_refused(ip, th);
}
tcp_fields_to_host(th);
goto dropwithreset_ratelim;
}
#if defined(IPSEC)
if (ipsec_used) {
if (inp && ipsec_in_reject(m, inp))
goto drop;
}
#endif /*IPSEC*/
break;
#ifdef INET6
case AF_INET6:
{
int faith;

#if defined(NFAITH) && NFAITH > 0
faith = faithprefix(&ip6->ip6_dst);
#else
faith = 0;
#endif
inp = in6pcb_lookup(&tcbtable, &ip6->ip6_src,
th->th_sport, &ip6->ip6_dst, th->th_dport, faith, &vestige);
if (inp == NULL && !vestige.valid) {
TCP_STATINC(TCP_STAT_PCBHASHMISS);
inp = in6pcb_lookup_bound(&tcbtable, &ip6->ip6_dst,
th->th_dport, faith);
}
if (inp == NULL && !vestige.valid) {
TCP_STATINC(TCP_STAT_NOPORT);
if (tcp_log_refused &&
(tiflags & (TH_RST|TH_ACK|TH_SYN)) == TH_SYN) {
tcp6_log_refused(ip6, th);
}
tcp_fields_to_host(th);
goto dropwithreset_ratelim;
}
#if defined(IPSEC)
if (ipsec_used && inp && ipsec_in_reject(m, inp))
goto drop;
#endif
break;
}
#endif
}

tcp_fields_to_host(th);

/*
* If the state is CLOSED (i.e., TCB does not exist) then
* all data in the incoming segment is discarded.
* If the TCB exists but is in CLOSED state, it is embryonic,
* but should either do a listen or a connect soon.
*/
tp = NULL;
so = NULL;
if (inp) {
/* Check the minimum TTL for socket. */
if (inp->inp_af == AF_INET && ip->ip_ttl < in4p_ip_minttl(inp))
goto drop;

tp = intotcpcb(inp);
so = inp->inp_socket;
} else if (vestige.valid) {
/* We do not support the resurrection of vtw tcpcps. */
tcp_vtw_input(th, &vestige, m, tlen);
m = NULL;
goto drop;
}

if (tp == NULL)
goto dropwithreset_ratelim;
if (tp->t_state == TCPS_CLOSED)
goto drop;

KASSERT(so->so_lock == softnet_lock);
KASSERT(solocked(so));

/* Unscale the window into a 32-bit value. */
if ((tiflags & TH_SYN) == 0)
tiwin = th->th_win << tp->snd_scale;
else
tiwin = th->th_win;

#ifdef INET6
/* save packet options if user wanted */
if (inp->inp_af == AF_INET6 && (inp->inp_flags & IN6P_CONTROLOPTS)) {
m_freem(inp->inp_options);
inp->inp_options = NULL;
ip6_savecontrol(inp, &inp->inp_options, ip6, m);
}
#endif

if (so->so_options & SO_DEBUG) {
#ifdef TCP_DEBUG
ostate = tp->t_state;
#endif

tcp_saveti = NULL;
if (iphlen + sizeof(struct tcphdr) > MHLEN)
goto nosave;

if (m->m_len > iphlen && (m->m_flags & M_EXT) == 0) {
tcp_saveti = m_copym(m, 0, iphlen, M_DONTWAIT);
if (tcp_saveti == NULL)
goto nosave;
} else {
MGETHDR(tcp_saveti, M_DONTWAIT, MT_HEADER);
if (tcp_saveti == NULL)
goto nosave;
MCLAIM(m, &tcp_mowner);
tcp_saveti->m_len = iphlen;
m_copydata(m, 0, iphlen,
mtod(tcp_saveti, void *));
}

if (M_TRAILINGSPACE(tcp_saveti) < sizeof(struct tcphdr)) {
m_freem(tcp_saveti);
tcp_saveti = NULL;
} else {
tcp_saveti->m_len += sizeof(struct tcphdr);
memcpy(mtod(tcp_saveti, char *) + iphlen, th,
sizeof(struct tcphdr));
}
nosave:;
}

if (so->so_options & SO_ACCEPTCONN) {
union syn_cache_sa src;
union syn_cache_sa dst;

KASSERT(tp->t_state == TCPS_LISTEN);

memset(&src, 0, sizeof(src));
memset(&dst, 0, sizeof(dst));
switch (af) {
case AF_INET:
src.sin.sin_len = sizeof(struct sockaddr_in);
src.sin.sin_family = AF_INET;
src.sin.sin_addr = ip->ip_src;
src.sin.sin_port = th->th_sport;

dst.sin.sin_len = sizeof(struct sockaddr_in);
dst.sin.sin_family = AF_INET;
dst.sin.sin_addr = ip->ip_dst;
dst.sin.sin_port = th->th_dport;
break;
#ifdef INET6
case AF_INET6:
src.sin6.sin6_len = sizeof(struct sockaddr_in6);
src.sin6.sin6_family = AF_INET6;
src.sin6.sin6_addr = ip6->ip6_src;
src.sin6.sin6_port = th->th_sport;

dst.sin6.sin6_len = sizeof(struct sockaddr_in6);
dst.sin6.sin6_family = AF_INET6;
dst.sin6.sin6_addr = ip6->ip6_dst;
dst.sin6.sin6_port = th->th_dport;
break;
#endif
}

if ((tiflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) {
if (tiflags & TH_RST) {
syn_cache_reset(&src.sa, &dst.sa, th);
} else if ((tiflags & (TH_ACK|TH_SYN)) ==
(TH_ACK|TH_SYN)) {
/*
* Received a SYN,ACK. This should never
* happen while we are in LISTEN. Send an RST.
*/
goto badsyn;
} else if (tiflags & TH_ACK) {
so = syn_cache_get(&src.sa, &dst.sa, th, so, m);
if (so == NULL) {
/*
* We don't have a SYN for this ACK;
* send an RST.
*/
goto badsyn;
} else if (so == (struct socket *)(-1)) {
/*
* We were unable to create the
* connection. If the 3-way handshake
* was completed, and RST has been
* sent to the peer. Since the mbuf
* might be in use for the reply, do
* not free it.
*/
m = NULL;
} else {
/*
* We have created a full-blown
* connection.
*/
inp = sotoinpcb(so);
tp = intotcpcb(inp);
if (tp == NULL)
goto badsyn; /*XXX*/
tiwin <<= tp->snd_scale;
goto after_listen;
}
} else {
/*
* None of RST, SYN or ACK was set.
* This is an invalid packet for a
* TCB in LISTEN state. Send a RST.
*/
goto badsyn;
}
} else {
/*
* Received a SYN.
*/

#ifdef INET6
/*
* If deprecated address is forbidden, we do
* not accept SYN to deprecated interface
* address to prevent any new inbound
* connection from getting established.
* When we do not accept SYN, we send a TCP
* RST, with deprecated source address (instead
* of dropping it). We compromise it as it is
* much better for peer to send a RST, and
* RST will be the final packet for the
* exchange.
*
* If we do not forbid deprecated addresses, we
* accept the SYN packet. RFC2462 does not
* suggest dropping SYN in this case.
* If we decipher RFC2462 5.5.4, it says like
* this:
* 1. use of deprecated addr with existing
* communication is okay - "SHOULD continue
* to be used"
* 2. use of it with new communication:
* (2a) "SHOULD NOT be used if alternate
* address with sufficient scope is
* available"
* (2b) nothing mentioned otherwise.
* Here we fall into (2b) case as we have no
* choice in our source address selection - we
* must obey the peer.
*
* The wording in RFC2462 is confusing, and
* there are multiple description text for
* deprecated address handling - worse, they
* are not exactly the same. I believe 5.5.4
* is the best one, so we follow 5.5.4.
*/
if (af == AF_INET6 && !ip6_use_deprecated) {
struct in6_ifaddr *ia6;
int s;
struct ifnet *rcvif = m_get_rcvif(m, &s);
if (rcvif == NULL)
goto dropwithreset; /* XXX */
if ((ia6 = in6ifa_ifpwithaddr(rcvif,
&ip6->ip6_dst)) &&
(ia6->ia6_flags & IN6_IFF_DEPRECATED)) {
tp = NULL;
m_put_rcvif(rcvif, &s);
goto dropwithreset;
}
m_put_rcvif(rcvif, &s);
}
#endif

/*
* LISTEN socket received a SYN from itself? This
* can't possibly be valid; drop the packet.
*/
if (th->th_sport == th->th_dport) {
int eq = 0;

switch (af) {
case AF_INET:
eq = in_hosteq(ip->ip_src, ip->ip_dst);
break;
#ifdef INET6
case AF_INET6:
eq = IN6_ARE_ADDR_EQUAL(&ip6->ip6_src,
&ip6->ip6_dst);
break;
#endif
}
if (eq) {
TCP_STATINC(TCP_STAT_BADSYN);
goto drop;
}
}

/*
* SYN looks ok; create compressed TCP
* state for it.
*/
if (so->so_qlen <= so->so_qlimit &&
syn_cache_add(&src.sa, &dst.sa, th, off,
so, m, optp, optlen, &opti))
m = NULL;
}

goto drop;
}

after_listen:
/*
* From here on, we're dealing with !LISTEN.
*/
KASSERT(tp->t_state != TCPS_LISTEN);

/*
* Segment received on connection.
* Reset idle time and keep-alive timer.
*/
tp->t_rcvtime = tcp_now;
if (TCPS_HAVEESTABLISHED(tp->t_state))
TCP_TIMER_ARM(tp, TCPT_KEEP, tp->t_keepidle);

/*
* Process options.
*/
#ifdef TCP_SIGNATURE
if (optp || (tp->t_flags & TF_SIGNATURE))
#else
if (optp)
#endif
if (tcp_dooptions(tp, optp, optlen, th, m, off, &opti) < 0)
goto drop;

if (TCP_SACK_ENABLED(tp)) {
tcp_del_sackholes(tp, th);
}

if (TCP_ECN_ALLOWED(tp)) {
if (tiflags & 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;
TCP_STATINC(TCP_STAT_ECN_CE);
break;
case IPTOS_ECN_ECT0:
TCP_STATINC(TCP_STAT_ECN_ECT);
break;
case IPTOS_ECN_ECT1:
/* XXX: ignore for now -- rpaulo */
break;
}
/*
* Congestion experienced.
* Ignore if we are already trying to recover.
*/
if ((tiflags & TH_ECE) && SEQ_GEQ(tp->snd_una, tp->snd_recover))
tp->t_congctl->cong_exp(tp);
}

if (opti.ts_present && opti.ts_ecr) {
/*
* Calculate the RTT from the returned time stamp and the
* connection's time base. If the time stamp is later than
* the current time, or is extremely old, fall back to non-1323
* RTT calculation. Since ts_rtt is unsigned, we can test both
* at the same time.
*
* Note that ts_rtt is in units of slow ticks (500
* ms). Since most earthbound RTTs are < 500 ms,
* observed values will have large quantization noise.
* Our smoothed RTT is then the fraction of observed
* samples that are 1 tick instead of 0 (times 500
* ms).
*
* ts_rtt is increased by 1 to denote a valid sample,
* with 0 indicating an invalid measurement. This
* extra 1 must be removed when ts_rtt is used, or
* else an erroneous extra 500 ms will result.
*/
ts_rtt = TCP_TIMESTAMP(tp) - opti.ts_ecr + 1;
if (ts_rtt > TCP_PAWS_IDLE)
ts_rtt = 0;
} else {
ts_rtt = 0;
}

/*
* Fast path: check for the two common cases of a uni-directional
* data transfer. If:
* o We are in the ESTABLISHED state, and
* o The packet has no control flags, and
* o The packet is in-sequence, and
* o The window didn't change, and
* o We are not retransmitting
* It's a candidate.
*
* If the length (tlen) is zero and the ack moved forward, we're
* the sender side of the transfer. Just free the data acked and
* 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.
*/
if (tp->t_state == TCPS_ESTABLISHED &&
(tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ECE|TH_CWR|TH_ACK))
== TH_ACK &&
(!opti.ts_present || TSTMP_GEQ(opti.ts_val, tp->ts_recent)) &&
th->th_seq == tp->rcv_nxt &&
tiwin && tiwin == tp->snd_wnd &&
tp->snd_nxt == tp->snd_max) {

/*
* 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 [email protected] list (Braden 1993/04/26).
*
* note that we already know
* TSTMP_GEQ(opti.ts_val, tp->ts_recent)
*/
if (opti.ts_present && SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
tp->ts_recent_age = tcp_now;
tp->ts_recent = opti.ts_val;
}

if (tlen == 0) {
/* Ack prediction. */
if (SEQ_GT(th->th_ack, tp->snd_una) &&
SEQ_LEQ(th->th_ack, tp->snd_max) &&
tp->snd_cwnd >= tp->snd_wnd &&
tp->t_partialacks < 0) {
/*
* this is a pure ack for outstanding data.
*/
if (ts_rtt)
tcp_xmit_timer(tp, ts_rtt - 1);
else if (tp->t_rtttime &&
SEQ_GT(th->th_ack, tp->t_rtseq))
tcp_xmit_timer(tp,
tcp_now - tp->t_rtttime);
acked = th->th_ack - tp->snd_una;
tcps = TCP_STAT_GETREF();
_NET_STATINC_REF(tcps, TCP_STAT_PREDACK);
_NET_STATINC_REF(tcps, TCP_STAT_RCVACKPACK);
_NET_STATADD_REF(tcps, TCP_STAT_RCVACKBYTE,
acked);
TCP_STAT_PUTREF();
nd_hint(tp);

if (acked > (tp->t_lastoff - tp->t_inoff))
tp->t_lastm = NULL;
sbdrop(&so->so_snd, acked);
tp->t_lastoff -= acked;

icmp_check(tp, th, acked);

tp->snd_una = th->th_ack;
tp->snd_fack = tp->snd_una;
if (SEQ_LT(tp->snd_high, tp->snd_una))
tp->snd_high = tp->snd_una;
/*
* drag snd_wl2 along so only newer
* ACKs can update the window size.
* also avoids the state where snd_wl2
* is eventually larger than th_ack and thus
* blocking the window update mechanism and
* the connection gets stuck for a loooong
* time in the zero sized send window state.
*
* see PR/kern 55567
*/
tp->snd_wl2 = tp->snd_una;

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/selnotify/signal. If data
* are ready to send, let tcp_output
* decide between more output or persist.
*/
if (tp->snd_una == tp->snd_max)
TCP_TIMER_DISARM(tp, TCPT_REXMT);
else if (TCP_TIMER_ISARMED(tp,
TCPT_PERSIST) == 0)
TCP_TIMER_ARM(tp, TCPT_REXMT,
tp->t_rxtcur);

sowwakeup(so);
if (so->so_snd.sb_cc) {
KERNEL_LOCK(1, NULL);
(void)tcp_output(tp);
KERNEL_UNLOCK_ONE(NULL);
}
m_freem(tcp_saveti);
return;
}
} else if (th->th_ack == tp->snd_una &&
TAILQ_FIRST(&tp->segq) == NULL &&
tlen <= sbspace(&so->so_rcv)) {
int newsize = 0;

/*
* this is a pure, in-sequence data packet
* with nothing on the reassembly queue and
* we have enough buffer space to take it.
*/
tp->rcv_nxt += tlen;

/*
* Pull rcv_up up to prevent seq wrap relative to
* rcv_nxt.
*/
tp->rcv_up = tp->rcv_nxt;

/*
* Pull snd_wl1 up to prevent seq wrap relative to
* th_seq.
*/
tp->snd_wl1 = th->th_seq;

tcps = TCP_STAT_GETREF();
_NET_STATINC_REF(tcps, TCP_STAT_PREDDAT);
_NET_STATINC_REF(tcps, TCP_STAT_RCVPACK);
_NET_STATADD_REF(tcps, TCP_STAT_RCVBYTE, tlen);
TCP_STAT_PUTREF();
nd_hint(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.
*
* 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. the number of bytes received during the time it takes
* one timestamp to be reflected back to us (the RTT);
* 2. received bytes per RTT is within seven eighth of the
* current socket buffer size;
* 3. 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 (tcp_do_autorcvbuf &&
opti.ts_ecr &&
(so->so_rcv.sb_flags & SB_AUTOSIZE)) {
if (opti.ts_ecr > tp->rfbuf_ts &&
opti.ts_ecr - tp->rfbuf_ts < PR_SLOWHZ) {
if (tp->rfbuf_cnt >
(so->so_rcv.sb_hiwat / 8 * 7) &&
so->so_rcv.sb_hiwat <
tcp_autorcvbuf_max) {
newsize =
uimin(so->so_rcv.sb_hiwat +
tcp_autorcvbuf_inc,
tcp_autorcvbuf_max);
}
/* Start over with next RTT. */
tp->rfbuf_ts = 0;
tp->rfbuf_cnt = 0;
} else
tp->rfbuf_cnt += tlen; /* add up */
}

/*
* Drop TCP, IP headers and TCP options then add data
* to socket buffer.
*/
if (so->so_state & SS_CANTRCVMORE) {
m_freem(m);
} else {
/*
* Set new socket buffer size.
* Give up when limit is reached.
*/
if (newsize)
if (!sbreserve(&so->so_rcv,
newsize, so))
so->so_rcv.sb_flags &= ~SB_AUTOSIZE;
m_adj(m, off + thlen);
sbappendstream(&so->so_rcv, m);
}
sorwakeup(so);
tcp_setup_ack(tp, th);
if (tp->t_flags & TF_ACKNOW) {
KERNEL_LOCK(1, NULL);
(void)tcp_output(tp);
KERNEL_UNLOCK_ONE(NULL);
}
m_freem(tcp_saveti);
return;
}
}

/*
* Compute mbuf offset to TCP data segment.
*/
hdroptlen = off + thlen;

/*
* Calculate amount of space in receive window. Receive window is
* amount of space in rcv queue, but not less than advertised
* window.
*/
{
int win;
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_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 a 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 ((tiflags & TH_ACK) &&
(SEQ_LEQ(th->th_ack, tp->iss) ||
SEQ_GT(th->th_ack, tp->snd_max)))
goto dropwithreset;
if (tiflags & TH_RST) {
if (tiflags & TH_ACK)
tp = tcp_drop(tp, ECONNREFUSED);
goto drop;
}
if ((tiflags & TH_SYN) == 0)
goto drop;
if (tiflags & TH_ACK) {
tp->snd_una = th->th_ack;
if (SEQ_LT(tp->snd_nxt, tp->snd_una))
tp->snd_nxt = tp->snd_una;
if (SEQ_LT(tp->snd_high, tp->snd_una))
tp->snd_high = tp->snd_una;
TCP_TIMER_DISARM(tp, TCPT_REXMT);

if ((tiflags & TH_ECE) && tcp_do_ecn) {
tp->t_flags |= TF_ECN_PERMIT;
TCP_STATINC(TCP_STAT_ECN_SHS);
}
}
tp->irs = th->th_seq;
tcp_rcvseqinit(tp);
tp->t_flags |= TF_ACKNOW;
tcp_mss_from_peer(tp, opti.maxseg);

/*
* Initialize the initial congestion window. If we
* had to retransmit the SYN, we must initialize cwnd
* to 1 segment (i.e. the Loss Window).
*/
if (tp->t_flags & TF_SYN_REXMT)
tp->snd_cwnd = tp->t_peermss;
else {
int ss = tcp_init_win;
if (inp->inp_af == AF_INET && in_localaddr(in4p_faddr(inp)))
ss = tcp_init_win_local;
#ifdef INET6
else if (inp->inp_af == AF_INET6 && in6_localaddr(&in6p_faddr(inp)))
ss = tcp_init_win_local;
#endif
tp->snd_cwnd = TCP_INITIAL_WINDOW(ss, tp->t_peermss);
}

tcp_rmx_rtt(tp);
if (tiflags & TH_ACK) {
TCP_STATINC(TCP_STAT_CONNECTS);
/*
* move tcp_established before soisconnected
* because upcall handler can drive tcp_output
* functionality.
* XXX we might call soisconnected at the end of
* all processing
*/
tcp_established(tp);
soisconnected(so);
/* Do window scaling on this connection? */
if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
(TF_RCVD_SCALE|TF_REQ_SCALE)) {
tp->snd_scale = tp->requested_s_scale;
tp->rcv_scale = tp->request_r_scale;
}
TCP_REASS_LOCK(tp);
(void)tcp_reass(tp, NULL, NULL, tlen);
/*
* if we didn't have to retransmit the SYN,
* use its rtt as our initial srtt & rtt var.
*/
if (tp->t_rtttime)
tcp_xmit_timer(tp, tcp_now - tp->t_rtttime);
} else {
tp->t_state = TCPS_SYN_RECEIVED;
}

/*
* 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;
tiflags &= ~TH_FIN;
tcps = TCP_STAT_GETREF();
_NET_STATINC_REF(tcps, TCP_STAT_RCVPACKAFTERWIN);
_NET_STATADD_REF(tcps, TCP_STAT_RCVBYTEAFTERWIN,
todrop);
TCP_STAT_PUTREF();
}
tp->snd_wl1 = th->th_seq - 1;
tp->rcv_up = th->th_seq;
goto step6;

/*
* If the state is SYN_RECEIVED:
* If seg contains an ACK, but not for our SYN, drop the input
* and generate an RST. See page 36, rfc793
*/
case TCPS_SYN_RECEIVED:
if ((tiflags & TH_ACK) &&
(SEQ_LEQ(th->th_ack, tp->iss) ||
SEQ_GT(th->th_ack, tp->snd_max)))
goto dropwithreset;
break;
}

/*
* From here on, we're dealing with !LISTEN and !SYN_SENT.
*/
KASSERT(tp->t_state != TCPS_LISTEN &&
tp->t_state != TCPS_SYN_SENT);

/*
* RFC1323 PAWS: if we have a timestamp reply on this segment and
* it's less than ts_recent, drop it.
*/
if (opti.ts_present && (tiflags & TH_RST) == 0 && tp->ts_recent &&
TSTMP_LT(opti.ts_val, tp->ts_recent)) {
/* Check to see if ts_recent is over 24 days old. */
if (tcp_now - 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 {
tcps = TCP_STAT_GETREF();
_NET_STATINC_REF(tcps, TCP_STAT_RCVDUPPACK);
_NET_STATADD_REF(tcps, TCP_STAT_RCVDUPBYTE, tlen);
_NET_STATINC_REF(tcps, TCP_STAT_PAWSDROP);
TCP_STAT_PUTREF();
tcp_new_dsack(tp, th->th_seq, tlen);
goto dropafterack;
}
}

/*
* Check that at least some bytes of the segment are within the
* receive window. If segment begins before rcv_nxt, drop leading
* data (and SYN); if nothing left, just ack.
*/
todrop = tp->rcv_nxt - th->th_seq;
dupseg = false;
if (todrop > 0) {
if (tiflags & TH_SYN) {
tiflags &= ~TH_SYN;
th->th_seq++;
tcp_urp_drop(th, 1, &tiflags);
todrop--;
}
if (todrop > tlen ||
(todrop == tlen && (tiflags & TH_FIN) == 0)) {
/*
* Any valid FIN or RST must be to the left of the
* window. At this point the FIN or RST must be a
* duplicate or out of sequence; drop it.
*/
if (tiflags & TH_RST)
goto drop;
tiflags &= ~(TH_FIN|TH_RST);

/*
* Send an ACK to resynchronize and drop any data.
* But keep on processing for RST or ACK.
*/
tp->t_flags |= TF_ACKNOW;
todrop = tlen;
dupseg = true;
tcps = TCP_STAT_GETREF();
_NET_STATINC_REF(tcps, TCP_STAT_RCVDUPPACK);
_NET_STATADD_REF(tcps, TCP_STAT_RCVDUPBYTE, todrop);
TCP_STAT_PUTREF();
} else if ((tiflags & TH_RST) && th->th_seq != tp->rcv_nxt) {
/*
* Test for reset before adjusting the sequence
* number for overlapping data.
*/
goto dropafterack_ratelim;
} else {
tcps = TCP_STAT_GETREF();
_NET_STATINC_REF(tcps, TCP_STAT_RCVPARTDUPPACK);
_NET_STATADD_REF(tcps, TCP_STAT_RCVPARTDUPBYTE,
todrop);
TCP_STAT_PUTREF();
}
tcp_new_dsack(tp, th->th_seq, todrop);
hdroptlen += todrop; /* drop from head afterwards (m_adj) */
th->th_seq += todrop;
tlen -= todrop;
tcp_urp_drop(th, todrop, &tiflags);
}

/*
* If new data is 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) {
tp = tcp_close(tp);
TCP_STATINC(TCP_STAT_RCVAFTERCLOSE);
goto dropwithreset;
}

/*
* If the segment ends after the 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) {
TCP_STATINC(TCP_STAT_RCVPACKAFTERWIN);
if (todrop >= tlen) {
/*
* The segment actually starts after the window.
* th->th_seq + tlen - tp->rcv_nxt - tp->rcv_wnd >= tlen
* th->th_seq - tp->rcv_nxt - tp->rcv_wnd >= 0
* th->th_seq >= tp->rcv_nxt + tp->rcv_wnd
*/
TCP_STATADD(TCP_STAT_RCVBYTEAFTERWIN, tlen);

/*
* If a new connection request is received while in
* TIME_WAIT, drop the old connection and start over
* if the sequence numbers are above the previous
* ones.
*
* NOTE: We need to put the header fields back into
* network order.
*/
if ((tiflags & TH_SYN) &&
tp->t_state == TCPS_TIME_WAIT &&
SEQ_GT(th->th_seq, tp->rcv_nxt)) {
tp = tcp_close(tp);
tcp_fields_to_net(th);
m_freem(tcp_saveti);
tcp_saveti = NULL;
goto findpcb;
}

/*
* 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 (if not RST) ack.
*/
if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) {
KASSERT(todrop == tlen);
tp->t_flags |= TF_ACKNOW;
TCP_STATINC(TCP_STAT_RCVWINPROBE);
} else {
goto dropafterack;
}
} else {
TCP_STATADD(TCP_STAT_RCVBYTEAFTERWIN, todrop);
}
m_adj(m, -todrop);
tlen -= todrop;
tiflags &= ~(TH_PUSH|TH_FIN);
}

/*
* If last ACK falls within this segment's sequence numbers,
* record the timestamp.
* NOTE:
* 1) That the test incorporates suggestions from the latest
* proposal of the [email protected] 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 (opti.ts_present &&
SEQ_LEQ(th->th_seq, tp->last_ack_sent) &&
SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen +
((tiflags & (TH_SYN|TH_FIN)) != 0))) {
tp->ts_recent_age = tcp_now;
tp->ts_recent = opti.ts_val;
}

/*
* If the RST bit is set examine the state:
* RECEIVED state:
* If passive open, return to LISTEN state.
* If active open, inform user that connection was refused.
* ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT states:
* Inform user that connection was reset, and close tcb.
* CLOSING, LAST_ACK, TIME_WAIT states:
* Close the tcb.
*/
if (tiflags & TH_RST) {
if (th->th_seq != tp->rcv_nxt)
goto dropafterack_ratelim;

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:
tp->t_state = TCPS_CLOSED;
TCP_STATINC(TCP_STAT_DROPS);
tp = tcp_close(tp);
goto drop;

case TCPS_CLOSING:
case TCPS_LAST_ACK:
case TCPS_TIME_WAIT:
tp = tcp_close(tp);
goto drop;
}
}

/*
* Since we've covered the SYN-SENT and SYN-RECEIVED states above
* we must be in a synchronized state. RFC793 states (under Reset
* Generation) that any unacceptable segment (an out-of-order SYN
* qualifies) received in a synchronized state must elicit only an
* empty acknowledgment segment ... and the connection remains in
* the same state.
*/
if (tiflags & TH_SYN) {
if (tp->rcv_nxt == th->th_seq) {
tcp_respond(tp, m, m, th, (tcp_seq)0, th->th_ack - 1,
TH_ACK);
m_freem(tcp_saveti);
return;
}

goto dropafterack_ratelim;
}

/*
* If the ACK bit is off we drop the segment and return.
*/
if ((tiflags & TH_ACK) == 0) {
if (tp->t_flags & TF_ACKNOW)
goto dropafterack;
goto drop;
}

/*
* From here on, we're doing ACK processing.
*/

switch (tp->t_state) {
/*
* In SYN_RECEIVED state if the ack ACKs our SYN then enter
* ESTABLISHED state and continue processing, otherwise
* send an RST.
*/
case TCPS_SYN_RECEIVED:
if (SEQ_GT(tp->snd_una, th->th_ack) ||
SEQ_GT(th->th_ack, tp->snd_max))
goto dropwithreset;
TCP_STATINC(TCP_STAT_CONNECTS);
soisconnected(so);
tcp_established(tp);
/* Do window scaling? */
if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
(TF_RCVD_SCALE|TF_REQ_SCALE)) {
tp->snd_scale = tp->requested_s_scale;
tp->rcv_scale = tp->request_r_scale;
}
TCP_REASS_LOCK(tp);
(void)tcp_reass(tp, NULL, NULL, tlen);
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:
case TCPS_TIME_WAIT:
if (SEQ_LEQ(th->th_ack, tp->snd_una)) {
if (tlen == 0 && !dupseg && tiwin == tp->snd_wnd) {
TCP_STATINC(TCP_STAT_RCVDUPACK);
/*
* If we have outstanding data (other than
* a window probe), this is a completely
* duplicate ack (ie, window info didn't
* change), the ack is the biggest we've
* seen and we've seen exactly our rexmt
* threshold of them, assume a packet
* has been dropped and retransmit it.
* Kludge snd_nxt & the congestion
* window so we send only this one
* packet.
*/
if (TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 ||
th->th_ack != tp->snd_una)
tp->t_dupacks = 0;
else if (tp->t_partialacks < 0 &&
(++tp->t_dupacks == tcprexmtthresh ||
TCP_FACK_FASTRECOV(tp))) {
/*
* Do the fast retransmit, and adjust
* congestion control parameters.
*/
if (tp->t_congctl->fast_retransmit(tp, th)) {
/* False fast retransmit */
break;
}
goto drop;
} else if (tp->t_dupacks > tcprexmtthresh) {
tp->snd_cwnd += tp->t_segsz;
KERNEL_LOCK(1, NULL);
(void)tcp_output(tp);
KERNEL_UNLOCK_ONE(NULL);
goto drop;
}
} else {
/*
* If the ack appears to be very old, only
* allow data that is in-sequence. This
* makes it somewhat more difficult to insert
* forged data by guessing sequence numbers.
* Sent an ack to try to update the send
* sequence number on the other side.
*/
if (tlen && th->th_seq != tp->rcv_nxt &&
SEQ_LT(th->th_ack,
tp->snd_una - tp->max_sndwnd))
goto dropafterack;
}
break;
}
/*
* If the congestion window was inflated to account
* for the other side's cached packets, retract it.
*/
tp->t_congctl->fast_retransmit_newack(tp, th);

if (SEQ_GT(th->th_ack, tp->snd_max)) {
TCP_STATINC(TCP_STAT_RCVACKTOOMUCH);
goto dropafterack;
}
acked = th->th_ack - tp->snd_una;
tcps = TCP_STAT_GETREF();
_NET_STATINC_REF(tcps, TCP_STAT_RCVACKPACK);
_NET_STATADD_REF(tcps, TCP_STAT_RCVACKBYTE, acked);
TCP_STAT_PUTREF();

/*
* 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.
*/
if (ts_rtt)
tcp_xmit_timer(tp, ts_rtt - 1);
else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq))
tcp_xmit_timer(tp, tcp_now - 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_DISARM(tp, TCPT_REXMT);
needoutput = 1;
} else if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0)
TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur);

/*
* New data has been acked, adjust the congestion window.
*/
tp->t_congctl->newack(tp, th);

nd_hint(tp);
if (acked > so->so_snd.sb_cc) {
tp->snd_wnd -= so->so_snd.sb_cc;
sbdrop(&so->so_snd, (int)so->so_snd.sb_cc);
ourfinisacked = 1;
} else {
if (acked > (tp->t_lastoff - tp->t_inoff))
tp->t_lastm = NULL;
sbdrop(&so->so_snd, acked);
tp->t_lastoff -= acked;
if (tp->snd_wnd > acked)
tp->snd_wnd -= acked;
else
tp->snd_wnd = 0;
ourfinisacked = 0;
}
sowwakeup(so);

icmp_check(tp, th, acked);

tp->snd_una = th->th_ack;
if (SEQ_GT(tp->snd_una, tp->snd_fack))
tp->snd_fack = tp->snd_una;
if (SEQ_LT(tp->snd_nxt, tp->snd_una))
tp->snd_nxt = tp->snd_una;
if (SEQ_LT(tp->snd_high, tp->snd_una))
tp->snd_high = 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.
*/
if (so->so_state & SS_CANTRCVMORE) {
soisdisconnected(so);
if (tp->t_maxidle > 0)
TCP_TIMER_ARM(tp, TCPT_2MSL,
tp->t_maxidle);
}
tp->t_state = 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) {
tp->t_state = TCPS_TIME_WAIT;
tcp_canceltimers(tp);
TCP_TIMER_ARM(tp, TCPT_2MSL, 2 * tp->t_msl);
soisdisconnected(so);
}
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) {
tp = tcp_close(tp);
goto drop;
}
break;

/*
* In TIME_WAIT state the only thing that should arrive
* is a retransmission of the remote FIN. Acknowledge
* it and restart the finack timer.
*/
case TCPS_TIME_WAIT:
TCP_TIMER_ARM(tp, TCPT_2MSL, 2 * tp->t_msl);
goto dropafterack;
}
}

step6:
/*
* Update window information.
* Don't look at window if no ACK: TAC's send garbage on first SYN.
*/
if ((tiflags & 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)
TCP_STATINC(TCP_STAT_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 ((tiflags & 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.
*/
if (th->th_urp + so->so_rcv.sb_cc > sb_max) {
th->th_urp = 0; /* XXX */
tiflags &= ~TH_URG; /* 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 = so->so_rcv.sb_cc +
(tp->rcv_up - tp->rcv_nxt) - 1;
if (so->so_oobmark == 0)
so->so_state |= SS_RCVATMARK;
sohasoutofband(so);
tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA);
}

/*
* 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_int16_t)tlen &&
(so->so_options & SO_OOBINLINE) == 0)
tcp_pulloutofband(so, th, m, hdroptlen);
} 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:

/*
* Process the segment text, merging it into the TCP sequencing queue,
* and arranging for acknowledgement 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,
* tcp_rcvd()). If a FIN has already been received on this
* connection then we just ignore the text.
*/
if ((tlen || (tiflags & TH_FIN)) &&
TCPS_HAVERCVDFIN(tp->t_state) == 0) {
/*
* Handle the common case:
* o Segment is the next to be received, and
* o The queue is empty, and
* o The connection is established
* In this case, we avoid calling tcp_reass.
*
* tcp_setup_ack: set DELACK for segments received in order,
* but ack immediately when segments are out of order (so that
* fast retransmit can work).
*/
TCP_REASS_LOCK(tp);
if (th->th_seq == tp->rcv_nxt &&
TAILQ_FIRST(&tp->segq) == NULL &&
tp->t_state == TCPS_ESTABLISHED) {
tcp_setup_ack(tp, th);
tp->rcv_nxt += tlen;
tiflags = th->th_flags & TH_FIN;
tcps = TCP_STAT_GETREF();
_NET_STATINC_REF(tcps, TCP_STAT_RCVPACK);
_NET_STATADD_REF(tcps, TCP_STAT_RCVBYTE, tlen);
TCP_STAT_PUTREF();
nd_hint(tp);
if (so->so_state & SS_CANTRCVMORE) {
m_freem(m);
} else {
m_adj(m, hdroptlen);
sbappendstream(&(so)->so_rcv, m);
}
TCP_REASS_UNLOCK(tp);
sorwakeup(so);
} else {
m_adj(m, hdroptlen);
tiflags = tcp_reass(tp, th, m, tlen);
tp->t_flags |= TF_ACKNOW;
}

/*
* Note the amount of data that peer has sent into
* our window, in order to estimate the sender's
* buffer size.
*/
len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt);
} else {
m_freem(m);
m = NULL;
tiflags &= ~TH_FIN;
}

/*
* If FIN is received ACK the FIN and let the user know
* that the connection is closing. Ignore a FIN received before
* the connection is fully established.
*/
if ((tiflags & TH_FIN) && TCPS_HAVEESTABLISHED(tp->t_state)) {
if (TCPS_HAVERCVDFIN(tp->t_state) == 0) {
socantrcvmore(so);
tp->t_flags |= TF_ACKNOW;
tp->rcv_nxt++;
}
switch (tp->t_state) {

/*
* In ESTABLISHED STATE enter the CLOSE_WAIT state.
*/
case TCPS_ESTABLISHED:
tp->t_state = 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:
tp->t_state = 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:
tp->t_state = TCPS_TIME_WAIT;
tcp_canceltimers(tp);
TCP_TIMER_ARM(tp, TCPT_2MSL, 2 * tp->t_msl);
soisdisconnected(so);
break;

/*
* In TIME_WAIT state restart the 2 MSL time_wait timer.
*/
case TCPS_TIME_WAIT:
TCP_TIMER_ARM(tp, TCPT_2MSL, 2 * tp->t_msl);
break;
}
}
#ifdef TCP_DEBUG
if (so->so_options & SO_DEBUG)
tcp_trace(TA_INPUT, ostate, tp, tcp_saveti, 0);
#endif

/*
* Return any desired output.
*/
if (needoutput || (tp->t_flags & TF_ACKNOW)) {
KERNEL_LOCK(1, NULL);
(void)tcp_output(tp);
KERNEL_UNLOCK_ONE(NULL);
}
m_freem(tcp_saveti);

if (tp->t_state == TCPS_TIME_WAIT
&& (so->so_state & SS_NOFDREF)
&& (tp->t_inpcb || af != AF_INET || af != AF_INET6)
&& ((af == AF_INET ? tcp4_vtw_enable : tcp6_vtw_enable) & 1) != 0
&& TAILQ_EMPTY(&tp->segq)
&& vtw_add(af, tp)) {
;
}
return;

badsyn:
/*
* Received a bad SYN. Increment counters and dropwithreset.
*/
TCP_STATINC(TCP_STAT_BADSYN);
tp = NULL;
goto dropwithreset;

dropafterack:
/*
* Generate an ACK dropping incoming segment if it occupies
* sequence space, where the ACK reflects our state.
*/
if (tiflags & TH_RST)
goto drop;
goto dropafterack2;

dropafterack_ratelim:
/*
* We may want to rate-limit ACKs against SYN/RST attack.
*/
if (ppsratecheck(&tcp_ackdrop_ppslim_last, &tcp_ackdrop_ppslim_count,
tcp_ackdrop_ppslim) == 0) {
/* XXX stat */
goto drop;
}

dropafterack2:
m_freem(m);
tp->t_flags |= TF_ACKNOW;
KERNEL_LOCK(1, NULL);
(void)tcp_output(tp);
KERNEL_UNLOCK_ONE(NULL);
m_freem(tcp_saveti);
return;

dropwithreset_ratelim:
/*
* We may want to rate-limit RSTs in certain situations,
* particularly if we are sending an RST in response to
* an attempt to connect to or otherwise communicate with
* a port for which we have no socket.
*/
if (ppsratecheck(&tcp_rst_ppslim_last, &tcp_rst_ppslim_count,
tcp_rst_ppslim) == 0) {
/* XXX stat */
goto drop;
}

dropwithreset:
/*
* Generate a RST, dropping incoming segment.
* Make ACK acceptable to originator of segment.
*/
if (tiflags & TH_RST)
goto drop;
if (tiflags & TH_ACK) {
(void)tcp_respond(tp, m, m, th, (tcp_seq)0, th->th_ack, TH_RST);
} else {
if (tiflags & TH_SYN)
tlen++;
(void)tcp_respond(tp, m, m, th, th->th_seq + tlen, (tcp_seq)0,
TH_RST|TH_ACK);
}
m_freem(tcp_saveti);
return;

badcsum:
drop:
/*
* Drop space held by incoming segment and return.
*/
if (tp) {
so = tp->t_inpcb->inp_socket;
#ifdef TCP_DEBUG
if (so && (so->so_options & SO_DEBUG) != 0)
tcp_trace(TA_DROP, ostate, tp, tcp_saveti, 0);
#endif
}
m_freem(tcp_saveti);
m_freem(m);
return;
}

#ifdef TCP_SIGNATURE
int
tcp_signature_apply(void *fstate, void *data, u_int len)
{

MD5Update(fstate, (u_char *)data, len);
return (0);
}

struct secasvar *
tcp_signature_getsav(struct mbuf *m)
{
struct ip *ip;
struct ip6_hdr *ip6;

ip = mtod(m, struct ip *);
switch (ip->ip_v) {
case 4:
ip = mtod(m, struct ip *);
ip6 = NULL;
break;
case 6:
ip = NULL;
ip6 = mtod(m, struct ip6_hdr *);
break;
default:
return (NULL);
}

#ifdef IPSEC
union sockaddr_union dst;

/* Extract the destination from the IP header in the mbuf. */
memset(&dst, 0, sizeof(union sockaddr_union));
if (ip != NULL) {
dst.sa.sa_len = sizeof(struct sockaddr_in);
dst.sa.sa_family = AF_INET;
dst.sin.sin_addr = ip->ip_dst;
} else {
dst.sa.sa_len = sizeof(struct sockaddr_in6);
dst.sa.sa_family = AF_INET6;
dst.sin6.sin6_addr = ip6->ip6_dst;
}

/*
* Look up an SADB entry which matches the address of the peer.
*/
return KEY_LOOKUP_SA(&dst, IPPROTO_TCP, htonl(TCP_SIG_SPI), 0, 0);
#else
return NULL;
#endif
}

int
tcp_signature(struct mbuf *m, struct tcphdr *th, int thoff,
struct secasvar *sav, char *sig)
{
MD5_CTX ctx;
struct ip *ip;
struct ipovly *ipovly;
#ifdef INET6
struct ip6_hdr *ip6;
struct ip6_hdr_pseudo ip6pseudo;
#endif
struct ippseudo ippseudo;
struct tcphdr th0;
int l, tcphdrlen;

if (sav == NULL)
return (-1);

tcphdrlen = th->th_off * 4;

switch (mtod(m, struct ip *)->ip_v) {
case 4:
MD5Init(&ctx);
ip = mtod(m, struct ip *);
memset(&ippseudo, 0, sizeof(ippseudo));
ipovly = (struct ipovly *)ip;
ippseudo.ippseudo_src = ipovly->ih_src;
ippseudo.ippseudo_dst = ipovly->ih_dst;
ippseudo.ippseudo_pad = 0;
ippseudo.ippseudo_p = IPPROTO_TCP;
ippseudo.ippseudo_len = htons(m->m_pkthdr.len - thoff);
MD5Update(&ctx, (char *)&ippseudo, sizeof(ippseudo));
break;
#if INET6
case 6:
MD5Init(&ctx);
ip6 = mtod(m, struct ip6_hdr *);
memset(&ip6pseudo, 0, sizeof(ip6pseudo));
ip6pseudo.ip6ph_src = ip6->ip6_src;
in6_clearscope(&ip6pseudo.ip6ph_src);
ip6pseudo.ip6ph_dst = ip6->ip6_dst;
in6_clearscope(&ip6pseudo.ip6ph_dst);
ip6pseudo.ip6ph_len = htons(m->m_pkthdr.len - thoff);
ip6pseudo.ip6ph_nxt = IPPROTO_TCP;
MD5Update(&ctx, (char *)&ip6pseudo, sizeof(ip6pseudo));
break;
#endif
default:
return (-1);
}

th0 = *th;
th0.th_sum = 0;
MD5Update(&ctx, (char *)&th0, sizeof(th0));

l = m->m_pkthdr.len - thoff - tcphdrlen;
if (l > 0)
m_apply(m, thoff + tcphdrlen,
m->m_pkthdr.len - thoff - tcphdrlen,
tcp_signature_apply, &ctx);

MD5Update(&ctx, _KEYBUF(sav->key_auth), _KEYLEN(sav->key_auth));
MD5Final(sig, &ctx);

return (0);
}
#endif

/*
* Parse and process tcp options.
*
* Returns -1 if this segment should be dropped. (eg. wrong signature)
* Otherwise returns 0.
*/
int
tcp_dooptions(struct tcpcb *tp, const u_char *cp, int cnt, struct tcphdr *th,
struct mbuf *m, int toff, struct tcp_opt_info *oi)
{
u_int16_t mss;
int opt, optlen = 0;
#ifdef TCP_SIGNATURE
void *sigp = NULL;
char sigbuf[TCP_SIGLEN];
struct secasvar *sav = NULL;
#endif

for (; cp && cnt > 0; cnt -= optlen, cp += optlen) {
opt = cp[0];
if (opt == TCPOPT_EOL)
break;
if (opt == TCPOPT_NOP)
optlen = 1;
else {
if (cnt < 2)
break;
optlen = cp[1];
if (optlen < 2 || optlen > cnt)
break;
}
switch (opt) {

default:
continue;

case TCPOPT_MAXSEG:
if (optlen != TCPOLEN_MAXSEG)
continue;
if (!(th->th_flags & TH_SYN))
continue;
if (TCPS_HAVERCVDSYN(tp->t_state))
continue;
memcpy(&mss, cp + 2, sizeof(mss));
oi->maxseg = ntohs(mss);
break;

case TCPOPT_WINDOW:
if (optlen != TCPOLEN_WINDOW)
continue;
if (!(th->th_flags & TH_SYN))
continue;
if (TCPS_HAVERCVDSYN(tp->t_state))
continue;
tp->t_flags |= TF_RCVD_SCALE;
tp->requested_s_scale = cp[2];
if (tp->requested_s_scale > TCP_MAX_WINSHIFT) {
char buf[INET6_ADDRSTRLEN];
struct ip *ip = mtod(m, struct ip *);
#ifdef INET6
struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
#endif

switch (ip->ip_v) {
case 4:
in_print(buf, sizeof(buf),
&ip->ip_src);
break;
#ifdef INET6
case 6:
in6_print(buf, sizeof(buf),
&ip6->ip6_src);
break;
#endif
default:
strlcpy(buf, "(unknown)", sizeof(buf));
break;
}

log(LOG_ERR, "TCP: invalid wscale %d from %s, "
"assuming %d\n",
tp->requested_s_scale, buf,
TCP_MAX_WINSHIFT);
tp->requested_s_scale = TCP_MAX_WINSHIFT;
}
break;

case TCPOPT_TIMESTAMP:
if (optlen != TCPOLEN_TIMESTAMP)
continue;
oi->ts_present = 1;
memcpy(&oi->ts_val, cp + 2, sizeof(oi->ts_val));
NTOHL(oi->ts_val);
memcpy(&oi->ts_ecr, cp + 6, sizeof(oi->ts_ecr));
NTOHL(oi->ts_ecr);

if (!(th->th_flags & TH_SYN))
continue;
if (TCPS_HAVERCVDSYN(tp->t_state))
continue;
/*
* A timestamp received in a SYN makes
* it ok to send timestamp requests and replies.
*/
tp->t_flags |= TF_RCVD_TSTMP;
tp->ts_recent = oi->ts_val;
tp->ts_recent_age = tcp_now;
break;

case TCPOPT_SACK_PERMITTED:
if (optlen != TCPOLEN_SACK_PERMITTED)
continue;
if (!(th->th_flags & TH_SYN))
continue;
if (TCPS_HAVERCVDSYN(tp->t_state))
continue;
if (tcp_do_sack) {
tp->t_flags |= TF_SACK_PERMIT;
tp->t_flags |= TF_WILL_SACK;
}
break;

case TCPOPT_SACK:
tcp_sack_option(tp, th, cp, optlen);
break;
#ifdef TCP_SIGNATURE
case TCPOPT_SIGNATURE:
if (optlen != TCPOLEN_SIGNATURE)
continue;
if (sigp &&
!consttime_memequal(sigp, cp + 2, TCP_SIGLEN))
return (-1);

sigp = sigbuf;
memcpy(sigbuf, cp + 2, TCP_SIGLEN);
tp->t_flags |= TF_SIGNATURE;
break;
#endif
}
}

#ifndef TCP_SIGNATURE
return 0;
#else
if (tp->t_flags & TF_SIGNATURE) {
sav = tcp_signature_getsav(m);
if (sav == NULL && tp->t_state == TCPS_LISTEN)
return (-1);
}

if ((sigp ? TF_SIGNATURE : 0) ^ (tp->t_flags & TF_SIGNATURE))
goto out;

if (sigp) {
char sig[TCP_SIGLEN];

tcp_fields_to_net(th);
if (tcp_signature(m, th, toff, sav, sig) < 0) {
tcp_fields_to_host(th);
goto out;
}
tcp_fields_to_host(th);

if (!consttime_memequal(sig, sigp, TCP_SIGLEN)) {
TCP_STATINC(TCP_STAT_BADSIG);
goto out;
} else
TCP_STATINC(TCP_STAT_GOODSIG);

key_sa_recordxfer(sav, m);
KEY_SA_UNREF(&sav);
}
return 0;
out:
if (sav != NULL)
KEY_SA_UNREF(&sav);
return -1;
#endif
}

/*
* Pull out of band byte out of a segment so
* it doesn't appear in the user's data queue.
* It is still reflected in the segment length for
* sequencing purposes.
*/
void
tcp_pulloutofband(struct socket *so, struct tcphdr *th,
struct mbuf *m, int off)
{
int cnt = off + th->th_urp - 1;

while (cnt >= 0) {
if (m->m_len > cnt) {
char *cp = mtod(m, char *) + cnt;
struct tcpcb *tp = sototcpcb(so);

tp->t_iobc = *cp;
tp->t_oobflags |= TCPOOB_HAVEDATA;
memmove(cp, cp + 1, (unsigned)(m->m_len - cnt - 1));
m->m_len--;
return;
}
cnt -= m->m_len;
m = m->m_next;
if (m == NULL)
break;
}
panic("tcp_pulloutofband");
}

/*
* Collect new round-trip time estimate
* and update averages and current timeout.
*
* rtt is in units of slow ticks (typically 500 ms) -- essentially the
* difference of two timestamps.
*/
void
tcp_xmit_timer(struct tcpcb *tp, uint32_t rtt)
{
int32_t delta;

TCP_STATINC(TCP_STAT_RTTUPDATED);
if (tp->t_srtt != 0) {
/*
* Compute the amount to add to srtt for smoothing,
* *alpha, or 2^(-TCP_RTT_SHIFT). Because
* srtt is stored in 1/32 slow ticks, we conceptually
* shift left 5 bits, subtract srtt to get the
* difference, and then shift right by TCP_RTT_SHIFT
* (3) to obtain 1/8 of the difference.
*/
delta = (rtt << 2) - (tp->t_srtt >> TCP_RTT_SHIFT);
/*
* This can never happen, because delta's lowest
* possible value is 1/8 of t_srtt. But if it does,
* set srtt to some reasonable value, here chosen
* as 1/8 tick.
*/
if ((tp->t_srtt += delta) <= 0)
tp->t_srtt = 1 << 2;
/*
* RFC2988 requires that rttvar be updated first.
* This code is compliant because "delta" is the old
* srtt minus the new observation (scaled).
*
* RFC2988 says:
* rttvar = (1-beta) * rttvar + beta * |srtt-observed|
*
* delta is in units of 1/32 ticks, and has then been
* divided by 8. This is equivalent to being in 1/16s
* units and divided by 4. Subtract from it 1/4 of
* the existing rttvar to form the (signed) amount to
* adjust.
*/
if (delta < 0)
delta = -delta;
delta -= (tp->t_rttvar >> TCP_RTTVAR_SHIFT);
/*
* As with srtt, this should never happen. There is
* no support in RFC2988 for this operation. But 1/4s
* as rttvar when faced with something arguably wrong
* is ok.
*/
if ((tp->t_rttvar += delta) <= 0)
tp->t_rttvar = 1 << 2;

/*
* If srtt exceeds .01 second, ensure we use the 'remote' MSL
* Problem is: it doesn't work. Disabled by defaulting
* tcp_rttlocal to 0; see corresponding code in
* tcp_subr that selects local vs remote in a different way.
*
* The static branch prediction hint here should be removed
* when the rtt estimator is fixed and the rtt_enable code
* is turned back on.
*/
if (__predict_false(tcp_rttlocal) && tcp_msl_enable
&& tp->t_srtt > tcp_msl_remote_threshold
&& tp->t_msl < tcp_msl_remote) {
tp->t_msl = MIN(tcp_msl_remote, TCP_MAXMSL);
}
} else {
/*
* This is the first measurement. Per RFC2988, 2.2,
* set rtt=R and srtt=R/2.
* For srtt, storage representation is 1/32 ticks,
* so shift left by 5.
* For rttvar, storage representation is 1/16 ticks,
* So shift left by 4, but then right by 1 to halve.
*/
tp->t_srtt = rtt << (TCP_RTT_SHIFT + 2);
tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT + 2 - 1);
}
tp->t_rtttime = 0;
tp->t_rxtshift = 0;

/*
* the retransmit should happen at rtt + 4 * rttvar.
* Because of the way we do the smoothing, srtt and rttvar
* will each average +1/2 tick of bias. When we compute
* the retransmit timer, we want 1/2 tick of rounding and
* 1 extra tick because of +-1/2 tick uncertainty in the
* firing of the timer. The bias will give us exactly the
* 1.5 tick we need. But, because the bias is
* statistical, we have to test that we don't drop below
* the minimum feasible timer (which is 2 ticks).
*/
TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
uimax(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX);

/*
* We received an ack for a packet that wasn't retransmitted;
* it is probably safe to discard any error indications we've
* received recently. This isn't quite right, but close enough
* for now (a route might have failed after we sent a segment,
* and the return path might not be symmetrical).
*/
tp->t_softerror = 0;
}