xnu-6153.121.1.tar.gz

[apple/xnu.git] / bsd / netinet / tcp_subr.c

/*
 * Copyright (c) 2000-2019 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 *
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 *
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 *
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */
/*
 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      @(#)tcp_subr.c  8.2 (Berkeley) 5/24/95
 */
/*
 * NOTICE: This file was modified by SPARTA, Inc. in 2005 to introduce
 * support for mandatory and extensible security protections.  This notice
 * is included in support of clause 2.2 (b) of the Apple Public License,
 * Version 2.0.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/callout.h>
#include <sys/kernel.h>
#include <sys/sysctl.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/domain.h>
#include <sys/proc.h>
#include <sys/kauth.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/protosw.h>
#include <sys/random.h>
#include <sys/syslog.h>
#include <sys/mcache.h>
#include <kern/locks.h>
#include <kern/zalloc.h>

#include <dev/random/randomdev.h>

#include <net/route.h>
#include <net/if.h>
#include <net/content_filter.h>
#include <net/ntstat.h>
#include <net/multi_layer_pkt_log.h>

#define tcp_minmssoverload fring
#define _IP_VHL
#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
#if INET6
#include <netinet/ip6.h>
#include <netinet/icmp6.h>
#endif
#include <netinet/in_pcb.h>
#if INET6
#include <netinet6/in6_pcb.h>
#endif
#include <netinet/in_var.h>
#include <netinet/ip_var.h>
#include <netinet/icmp_var.h>
#if INET6
#include <netinet6/ip6_var.h>
#endif
#include <netinet/mptcp_var.h>
#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_cc.h>
#include <netinet/tcp_cache.h>
#include <kern/thread_call.h>

#if INET6
#include <netinet6/tcp6_var.h>
#endif
#include <netinet/tcpip.h>
#if TCPDEBUG
#include <netinet/tcp_debug.h>
#endif
#include <netinet/tcp_log.h>

#include <netinet6/ip6protosw.h>

#if IPSEC
#include <netinet6/ipsec.h>
#if INET6
#include <netinet6/ipsec6.h>
#endif
#endif /* IPSEC */

#if NECP
#include <net/necp.h>
#endif /* NECP */

#undef tcp_minmssoverload

#if CONFIG_MACF_NET
#include <security/mac_framework.h>
#endif /* MAC_NET */

#include <corecrypto/ccaes.h>
#include <libkern/crypto/aes.h>
#include <libkern/crypto/md5.h>
#include <sys/kdebug.h>
#include <mach/sdt.h>
#include <atm/atm_internal.h>
#include <pexpert/pexpert.h>

#include <netinet/lro_ext.h>

#define DBG_FNC_TCP_CLOSE       NETDBG_CODE(DBG_NETTCP, ((5 << 8) | 2))

static tcp_cc tcp_ccgen;
extern int tcp_lq_overflow;

extern struct tcptimerlist tcp_timer_list;
extern struct tcptailq tcp_tw_tailq;

SYSCTL_SKMEM_TCP_INT(TCPCTL_MSSDFLT, mssdflt, CTLFLAG_RW | CTLFLAG_LOCKED,
    int, tcp_mssdflt, TCP_MSS, "Default TCP Maximum Segment Size");

#if INET6
SYSCTL_SKMEM_TCP_INT(TCPCTL_V6MSSDFLT, v6mssdflt,
    CTLFLAG_RW | CTLFLAG_LOCKED, int, tcp_v6mssdflt, TCP6_MSS,
    "Default TCP Maximum Segment Size for IPv6");
#endif

int tcp_sysctl_fastopenkey(struct sysctl_oid *, void *, int,
    struct sysctl_req *);
SYSCTL_PROC(_net_inet_tcp, OID_AUTO, fastopen_key, CTLTYPE_STRING | CTLFLAG_WR,
    0, 0, tcp_sysctl_fastopenkey, "S", "TCP Fastopen key");

/* Current count of half-open TFO connections */
int     tcp_tfo_halfcnt = 0;

/* Maximum of half-open TFO connection backlog */
SYSCTL_SKMEM_TCP_INT(OID_AUTO, fastopen_backlog,
    CTLFLAG_RW | CTLFLAG_LOCKED, int, tcp_tfo_backlog, 10,
    "Backlog queue for half-open TFO connections");

SYSCTL_SKMEM_TCP_INT(OID_AUTO, fastopen, CTLFLAG_RW | CTLFLAG_LOCKED,
    int, tcp_fastopen, TCP_FASTOPEN_CLIENT | TCP_FASTOPEN_SERVER,
    "Enable TCP Fastopen (RFC 7413)");

SYSCTL_SKMEM_TCP_INT(OID_AUTO, now_init, CTLFLAG_RD | CTLFLAG_LOCKED,
    uint32_t, tcp_now_init, 0, "Initial tcp now value");

SYSCTL_SKMEM_TCP_INT(OID_AUTO, microuptime_init, CTLFLAG_RD | CTLFLAG_LOCKED,
    uint32_t, tcp_microuptime_init, 0, "Initial tcp uptime value in micro seconds");

/*
 * Minimum MSS we accept and use. This prevents DoS attacks where
 * we are forced to a ridiculous low MSS like 20 and send hundreds
 * of packets instead of one. The effect scales with the available
 * bandwidth and quickly saturates the CPU and network interface
 * with packet generation and sending. Set to zero to disable MINMSS
 * checking. This setting prevents us from sending too small packets.
 */
SYSCTL_SKMEM_TCP_INT(OID_AUTO, minmss, CTLFLAG_RW | CTLFLAG_LOCKED,
    int, tcp_minmss, TCP_MINMSS, "Minmum TCP Maximum Segment Size");
int tcp_do_rfc1323 = 1;
#if (DEVELOPMENT || DEBUG)
SYSCTL_INT(_net_inet_tcp, TCPCTL_DO_RFC1323, rfc1323,
    CTLFLAG_RW | CTLFLAG_LOCKED, &tcp_do_rfc1323, 0,
    "Enable rfc1323 (high performance TCP) extensions");
#endif /* (DEVELOPMENT || DEBUG) */

// Not used
static int      tcp_do_rfc1644 = 0;
SYSCTL_INT(_net_inet_tcp, TCPCTL_DO_RFC1644, rfc1644,
    CTLFLAG_RW | CTLFLAG_LOCKED, &tcp_do_rfc1644, 0,
    "Enable rfc1644 (TTCP) extensions");

SYSCTL_SKMEM_TCP_INT(OID_AUTO, do_tcpdrain, CTLFLAG_RW | CTLFLAG_LOCKED,
    static int, do_tcpdrain, 0,
    "Enable tcp_drain routine for extra help when low on mbufs");

SYSCTL_INT(_net_inet_tcp, OID_AUTO, pcbcount, CTLFLAG_RD | CTLFLAG_LOCKED,
    &tcbinfo.ipi_count, 0, "Number of active PCBs");

SYSCTL_INT(_net_inet_tcp, OID_AUTO, tw_pcbcount, CTLFLAG_RD | CTLFLAG_LOCKED,
    &tcbinfo.ipi_twcount, 0, "Number of pcbs in time-wait state");

SYSCTL_SKMEM_TCP_INT(OID_AUTO, icmp_may_rst, CTLFLAG_RW | CTLFLAG_LOCKED,
    static int, icmp_may_rst, 1,
    "Certain ICMP unreachable messages may abort connections in SYN_SENT");

static int      tcp_strict_rfc1948 = 0;
static int      tcp_isn_reseed_interval = 0;
#if (DEVELOPMENT || DEBUG)
SYSCTL_INT(_net_inet_tcp, OID_AUTO, strict_rfc1948, CTLFLAG_RW | CTLFLAG_LOCKED,
    &tcp_strict_rfc1948, 0, "Determines if RFC1948 is followed exactly");

SYSCTL_INT(_net_inet_tcp, OID_AUTO, isn_reseed_interval,
    CTLFLAG_RW | CTLFLAG_LOCKED,
    &tcp_isn_reseed_interval, 0, "Seconds between reseeding of ISN secret");
#endif /* (DEVELOPMENT || DEBUG) */

SYSCTL_SKMEM_TCP_INT(OID_AUTO, rtt_min, CTLFLAG_RW | CTLFLAG_LOCKED,
    int, tcp_TCPTV_MIN, 100, "min rtt value allowed");

SYSCTL_SKMEM_TCP_INT(OID_AUTO, rexmt_slop, CTLFLAG_RW,
    int, tcp_rexmt_slop, TCPTV_REXMTSLOP, "Slop added to retransmit timeout");

SYSCTL_SKMEM_TCP_INT(OID_AUTO, randomize_ports, CTLFLAG_RW | CTLFLAG_LOCKED,
    __private_extern__ int, tcp_use_randomport, 0,
    "Randomize TCP port numbers");

SYSCTL_SKMEM_TCP_INT(OID_AUTO, win_scale_factor, CTLFLAG_RW | CTLFLAG_LOCKED,
    __private_extern__ int, tcp_win_scale, 3, "Window scaling factor");

#if (DEVELOPMENT || DEBUG)
SYSCTL_SKMEM_TCP_INT(OID_AUTO, init_rtt_from_cache,
    CTLFLAG_RW | CTLFLAG_LOCKED, static int, tcp_init_rtt_from_cache, 1,
    "Initalize RTT from route cache");
#else
SYSCTL_SKMEM_TCP_INT(OID_AUTO, init_rtt_from_cache,
    CTLFLAG_RD | CTLFLAG_LOCKED, static int, tcp_init_rtt_from_cache, 1,
    "Initalize RTT from route cache");
#endif /* (DEVELOPMENT || DEBUG) */

static void     tcp_cleartaocache(void);
static void     tcp_notify(struct inpcb *, int);

struct zone     *sack_hole_zone;
struct zone     *tcp_reass_zone;
struct zone     *tcp_bwmeas_zone;
struct zone     *tcp_rxt_seg_zone;

extern int slowlink_wsize;      /* window correction for slow links */
extern int path_mtu_discovery;

static void tcp_sbrcv_grow_rwin(struct tcpcb *tp, struct sockbuf *sb);

#define TCP_BWMEAS_BURST_MINSIZE 6
#define TCP_BWMEAS_BURST_MAXSIZE 25

static uint32_t bwmeas_elm_size;

/*
 * Target size of TCP PCB hash tables. Must be a power of two.
 *
 * Note that this can be overridden by the kernel environment
 * variable net.inet.tcp.tcbhashsize
 */
#ifndef TCBHASHSIZE
#define TCBHASHSIZE     CONFIG_TCBHASHSIZE
#endif

__private_extern__ int  tcp_tcbhashsize = TCBHASHSIZE;
SYSCTL_INT(_net_inet_tcp, OID_AUTO, tcbhashsize, CTLFLAG_RD | CTLFLAG_LOCKED,
    &tcp_tcbhashsize, 0, "Size of TCP control-block hashtable");

/*
 * This is the actual shape of what we allocate using the zone
 * allocator.  Doing it this way allows us to protect both structures
 * using the same generation count, and also eliminates the overhead
 * of allocating tcpcbs separately.  By hiding the structure here,
 * we avoid changing most of the rest of the code (although it needs
 * to be changed, eventually, for greater efficiency).
 */
#define ALIGNMENT       32
struct  inp_tp {
        struct  inpcb   inp;
        struct  tcpcb   tcb __attribute__((aligned(ALIGNMENT)));
};
#undef ALIGNMENT

int  get_inpcb_str_size(void);
int  get_tcp_str_size(void);

os_log_t tcp_mpkl_log_object = NULL;

static void tcpcb_to_otcpcb(struct tcpcb *, struct otcpcb *);

static lck_attr_t *tcp_uptime_mtx_attr = NULL;
static lck_grp_t *tcp_uptime_mtx_grp = NULL;
static lck_grp_attr_t *tcp_uptime_mtx_grp_attr = NULL;
int tcp_notsent_lowat_check(struct socket *so);
static void tcp_flow_lim_stats(struct ifnet_stats_per_flow *ifs,
    struct if_lim_perf_stat *stat);
static void tcp_flow_ecn_perf_stats(struct ifnet_stats_per_flow *ifs,
    struct if_tcp_ecn_perf_stat *stat);

static aes_encrypt_ctx tfo_ctx; /* Crypto-context for TFO */

void
tcp_tfo_gen_cookie(struct inpcb *inp, u_char *out, size_t blk_size)
{
        u_char in[CCAES_BLOCK_SIZE];
#if INET6
        int isipv6 = inp->inp_vflag & INP_IPV6;
#endif

        VERIFY(blk_size == CCAES_BLOCK_SIZE);

        bzero(&in[0], CCAES_BLOCK_SIZE);
        bzero(&out[0], CCAES_BLOCK_SIZE);

#if INET6
        if (isipv6) {
                memcpy(in, &inp->in6p_faddr, sizeof(struct in6_addr));
        } else
#endif /* INET6 */
        memcpy(in, &inp->inp_faddr, sizeof(struct in_addr));

        aes_encrypt_cbc(in, NULL, 1, out, &tfo_ctx);
}

__private_extern__ int
tcp_sysctl_fastopenkey(__unused struct sysctl_oid *oidp, __unused void *arg1,
    __unused int arg2, struct sysctl_req *req)
{
        int error = 0;
        /*
         * TFO-key is expressed as a string in hex format
         * (+1 to account for \0 char)
         */
        char keystring[TCP_FASTOPEN_KEYLEN * 2 + 1];
        u_int32_t key[TCP_FASTOPEN_KEYLEN / sizeof(u_int32_t)];
        int i;

        /* -1, because newlen is len without the terminating \0 character */
        if (req->newlen != (sizeof(keystring) - 1)) {
                error = EINVAL;
                goto exit;
        }

        /*
         * sysctl_io_string copies keystring into the oldptr of the sysctl_req.
         * Make sure everything is zero, to avoid putting garbage in there or
         * leaking the stack.
         */
        bzero(keystring, sizeof(keystring));

        error = sysctl_io_string(req, keystring, sizeof(keystring), 0, NULL);
        if (error) {
                goto exit;
        }

        for (i = 0; i < (TCP_FASTOPEN_KEYLEN / sizeof(u_int32_t)); i++) {
                /*
                 * We jump over the keystring in 8-character (4 byte in hex)
                 * steps
                 */
                if (sscanf(&keystring[i * 8], "%8x", &key[i]) != 1) {
                        error = EINVAL;
                        goto exit;
                }
        }

        aes_encrypt_key128((u_char *)key, &tfo_ctx);

exit:
        return error;
}

int
get_inpcb_str_size(void)
{
        return sizeof(struct inpcb);
}

int
get_tcp_str_size(void)
{
        return sizeof(struct tcpcb);
}

static int scale_to_powerof2(int size);

/*
 * This helper routine returns one of the following scaled value of size:
 * 1. Rounded down power of two value of size if the size value passed as
 *    argument is not a power of two and the rounded up value overflows.
 * OR
 * 2. Rounded up power of two value of size if the size value passed as
 *    argument is not a power of two and the rounded up value does not overflow
 * OR
 * 3. Same value as argument size if it is already a power of two.
 */
static int
scale_to_powerof2(int size)
{
        /* Handle special case of size = 0 */
        int ret = size ? size : 1;

        if (!powerof2(ret)) {
                while (!powerof2(size)) {
                        /*
                         * Clear out least significant
                         * set bit till size is left with
                         * its highest set bit at which point
                         * it is rounded down power of two.
                         */
                        size = size & (size - 1);
                }

                /* Check for overflow when rounding up */
                if (0 == (size << 1)) {
                        ret = size;
                } else {
                        ret = size << 1;
                }
        }

        return ret;
}

static void
tcp_tfo_init(void)
{
        u_char key[TCP_FASTOPEN_KEYLEN];

        read_frandom(key, sizeof(key));
        aes_encrypt_key128(key, &tfo_ctx);
}

/*
 * Tcp initialization
 */
void
tcp_init(struct protosw *pp, struct domain *dp)
{
#pragma unused(dp)
        static int tcp_initialized = 0;
        vm_size_t str_size;
        struct inpcbinfo *pcbinfo;
        uint32_t logging_config;

        VERIFY((pp->pr_flags & (PR_INITIALIZED | PR_ATTACHED)) == PR_ATTACHED);

        if (tcp_initialized) {
                return;
        }
        tcp_initialized = 1;

        tcp_ccgen = 1;
        tcp_cleartaocache();

        tcp_keepinit = TCPTV_KEEP_INIT;
        tcp_keepidle = TCPTV_KEEP_IDLE;
        tcp_keepintvl = TCPTV_KEEPINTVL;
        tcp_keepcnt = TCPTV_KEEPCNT;
        tcp_maxpersistidle = TCPTV_KEEP_IDLE;
        tcp_msl = TCPTV_MSL;

        microuptime(&tcp_uptime);
        read_frandom(&tcp_now, sizeof(tcp_now));

        /* Starts tcp internal clock at a random value */
        tcp_now = tcp_now & 0x3fffffff;

        /* expose initial uptime/now via systcl for utcp to keep time sync */
        tcp_now_init = tcp_now;
        tcp_microuptime_init =
            tcp_uptime.tv_usec + (tcp_uptime.tv_sec * USEC_PER_SEC);
        SYSCTL_SKMEM_UPDATE_FIELD(tcp.microuptime_init, tcp_microuptime_init);
        SYSCTL_SKMEM_UPDATE_FIELD(tcp.now_init, tcp_now_init);

        tcp_tfo_init();

        LIST_INIT(&tcb);
        tcbinfo.ipi_listhead = &tcb;

        pcbinfo = &tcbinfo;
        /*
         * allocate lock group attribute and group for tcp pcb mutexes
         */
        pcbinfo->ipi_lock_grp_attr = lck_grp_attr_alloc_init();
        pcbinfo->ipi_lock_grp = lck_grp_alloc_init("tcppcb",
            pcbinfo->ipi_lock_grp_attr);

        /*
         * allocate the lock attribute for tcp pcb mutexes
         */
        pcbinfo->ipi_lock_attr = lck_attr_alloc_init();

        if ((pcbinfo->ipi_lock = lck_rw_alloc_init(pcbinfo->ipi_lock_grp,
            pcbinfo->ipi_lock_attr)) == NULL) {
                panic("%s: unable to allocate PCB lock\n", __func__);
                /* NOTREACHED */
        }

        if (tcp_tcbhashsize == 0) {
                /* Set to default */
                tcp_tcbhashsize = 512;
        }

        if (!powerof2(tcp_tcbhashsize)) {
                int old_hash_size = tcp_tcbhashsize;
                tcp_tcbhashsize = scale_to_powerof2(tcp_tcbhashsize);
                /* Lower limit of 16  */
                if (tcp_tcbhashsize < 16) {
                        tcp_tcbhashsize = 16;
                }
                printf("WARNING: TCB hash size not a power of 2, "
                    "scaled from %d to %d.\n",
                    old_hash_size,
                    tcp_tcbhashsize);
        }

        tcbinfo.ipi_hashbase = hashinit(tcp_tcbhashsize, M_PCB,
            &tcbinfo.ipi_hashmask);
        tcbinfo.ipi_porthashbase = hashinit(tcp_tcbhashsize, M_PCB,
            &tcbinfo.ipi_porthashmask);
        str_size = P2ROUNDUP(sizeof(struct inp_tp), sizeof(u_int64_t));
        tcbinfo.ipi_zone = zinit(str_size, 120000 * str_size, 8192, "tcpcb");
        zone_change(tcbinfo.ipi_zone, Z_CALLERACCT, FALSE);
        zone_change(tcbinfo.ipi_zone, Z_EXPAND, TRUE);

        tcbinfo.ipi_gc = tcp_gc;
        tcbinfo.ipi_timer = tcp_itimer;
        in_pcbinfo_attach(&tcbinfo);

        str_size = P2ROUNDUP(sizeof(struct sackhole), sizeof(u_int64_t));
        sack_hole_zone = zinit(str_size, 120000 * str_size, 8192,
            "sack_hole zone");
        zone_change(sack_hole_zone, Z_CALLERACCT, FALSE);
        zone_change(sack_hole_zone, Z_EXPAND, TRUE);

        str_size = P2ROUNDUP(sizeof(struct tseg_qent), sizeof(u_int64_t));
        tcp_reass_zone = zinit(str_size, (nmbclusters >> 4) * str_size,
            0, "tcp_reass_zone");
        if (tcp_reass_zone == NULL) {
                panic("%s: failed allocating tcp_reass_zone", __func__);
                /* NOTREACHED */
        }
        zone_change(tcp_reass_zone, Z_CALLERACCT, FALSE);
        zone_change(tcp_reass_zone, Z_EXPAND, TRUE);

        bwmeas_elm_size = P2ROUNDUP(sizeof(struct bwmeas), sizeof(u_int64_t));
        tcp_bwmeas_zone = zinit(bwmeas_elm_size, (100 * bwmeas_elm_size), 0,
            "tcp_bwmeas_zone");
        if (tcp_bwmeas_zone == NULL) {
                panic("%s: failed allocating tcp_bwmeas_zone", __func__);
                /* NOTREACHED */
        }
        zone_change(tcp_bwmeas_zone, Z_CALLERACCT, FALSE);
        zone_change(tcp_bwmeas_zone, Z_EXPAND, TRUE);

        str_size = P2ROUNDUP(sizeof(struct tcp_ccstate), sizeof(u_int64_t));
        tcp_cc_zone = zinit(str_size, 20000 * str_size, 0, "tcp_cc_zone");
        zone_change(tcp_cc_zone, Z_CALLERACCT, FALSE);
        zone_change(tcp_cc_zone, Z_EXPAND, TRUE);

        str_size = P2ROUNDUP(sizeof(struct tcp_rxt_seg), sizeof(u_int64_t));
        tcp_rxt_seg_zone = zinit(str_size, 10000 * str_size, 0,
            "tcp_rxt_seg_zone");
        zone_change(tcp_rxt_seg_zone, Z_CALLERACCT, FALSE);
        zone_change(tcp_rxt_seg_zone, Z_EXPAND, TRUE);

#if INET6
#define TCP_MINPROTOHDR (sizeof(struct ip6_hdr) + sizeof(struct tcphdr))
#else /* INET6 */
#define TCP_MINPROTOHDR (sizeof(struct tcpiphdr))
#endif /* INET6 */
        if (max_protohdr < TCP_MINPROTOHDR) {
                _max_protohdr = TCP_MINPROTOHDR;
                _max_protohdr = max_protohdr;   /* round it up */
        }
        if (max_linkhdr + max_protohdr > MCLBYTES) {
                panic("tcp_init");
        }
#undef TCP_MINPROTOHDR

        /* Initialize time wait and timer lists */
        TAILQ_INIT(&tcp_tw_tailq);

        bzero(&tcp_timer_list, sizeof(tcp_timer_list));
        LIST_INIT(&tcp_timer_list.lhead);
        /*
         * allocate lock group attribute, group and attribute for
         * the tcp timer list
         */
        tcp_timer_list.mtx_grp_attr = lck_grp_attr_alloc_init();
        tcp_timer_list.mtx_grp = lck_grp_alloc_init("tcptimerlist",
            tcp_timer_list.mtx_grp_attr);
        tcp_timer_list.mtx_attr = lck_attr_alloc_init();
        if ((tcp_timer_list.mtx = lck_mtx_alloc_init(tcp_timer_list.mtx_grp,
            tcp_timer_list.mtx_attr)) == NULL) {
                panic("failed to allocate memory for tcp_timer_list.mtx\n");
        }
        ;
        tcp_timer_list.call = thread_call_allocate(tcp_run_timerlist, NULL);
        if (tcp_timer_list.call == NULL) {
                panic("failed to allocate call entry 1 in tcp_init\n");
        }

        /*
         * allocate lock group attribute, group and attribute for
         * tcp_uptime_lock
         */
        tcp_uptime_mtx_grp_attr = lck_grp_attr_alloc_init();
        tcp_uptime_mtx_grp = lck_grp_alloc_init("tcpuptime",
            tcp_uptime_mtx_grp_attr);
        tcp_uptime_mtx_attr = lck_attr_alloc_init();
        tcp_uptime_lock = lck_spin_alloc_init(tcp_uptime_mtx_grp,
            tcp_uptime_mtx_attr);

        /* Initialize TCP LRO data structures */
        tcp_lro_init();

        /* Initialize TCP Cache */
        tcp_cache_init();

        tcp_mpkl_log_object = MPKL_CREATE_LOGOBJECT("com.apple.xnu.tcp");
        if (tcp_mpkl_log_object == NULL) {
                panic("MPKL_CREATE_LOGOBJECT failed");
        }

        logging_config = atm_get_diagnostic_config();
        if (logging_config & 0x80000000) {
                tcp_log_privacy = 1;
        }

        PE_parse_boot_argn("tcp_log", &tcp_log_enable_flags, sizeof(tcp_log_enable_flags));

        /*
         * If more than 60 MB of mbuf pool is available, increase the
         * maximum allowed receive and send socket buffer size.
         */
        if (nmbclusters > 30720) {
                tcp_autorcvbuf_max = 2 * 1024 * 1024;
                tcp_autosndbuf_max = 2 * 1024 * 1024;

                SYSCTL_SKMEM_UPDATE_FIELD(tcp.autorcvbufmax, tcp_autorcvbuf_max);
                SYSCTL_SKMEM_UPDATE_FIELD(tcp.autosndbufmax, tcp_autosndbuf_max);
        }
}

/*
 * Fill in the IP and TCP headers for an outgoing packet, given the tcpcb.
 * tcp_template used to store this data in mbufs, but we now recopy it out
 * of the tcpcb each time to conserve mbufs.
 */
void
tcp_fillheaders(struct tcpcb *tp, void *ip_ptr, void *tcp_ptr)
{
        struct inpcb *inp = tp->t_inpcb;
        struct tcphdr *tcp_hdr = (struct tcphdr *)tcp_ptr;

#if INET6
        if ((inp->inp_vflag & INP_IPV6) != 0) {
                struct ip6_hdr *ip6;

                ip6 = (struct ip6_hdr *)ip_ptr;
                ip6->ip6_flow = (ip6->ip6_flow & ~IPV6_FLOWINFO_MASK) |
                    (inp->inp_flow & IPV6_FLOWINFO_MASK);
                ip6->ip6_vfc = (ip6->ip6_vfc & ~IPV6_VERSION_MASK) |
                    (IPV6_VERSION & IPV6_VERSION_MASK);
                ip6->ip6_plen = htons(sizeof(struct tcphdr));
                ip6->ip6_nxt = IPPROTO_TCP;
                ip6->ip6_hlim = 0;
                ip6->ip6_src = inp->in6p_laddr;
                ip6->ip6_dst = inp->in6p_faddr;
                tcp_hdr->th_sum = in6_pseudo(&inp->in6p_laddr, &inp->in6p_faddr,
                    htonl(sizeof(struct tcphdr) + IPPROTO_TCP));
        } else
#endif
        {
                struct ip *ip = (struct ip *) ip_ptr;

                ip->ip_vhl = IP_VHL_BORING;
                ip->ip_tos = 0;
                ip->ip_len = 0;
                ip->ip_id = 0;
                ip->ip_off = 0;
                ip->ip_ttl = 0;
                ip->ip_sum = 0;
                ip->ip_p = IPPROTO_TCP;
                ip->ip_src = inp->inp_laddr;
                ip->ip_dst = inp->inp_faddr;
                tcp_hdr->th_sum =
                    in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
                    htons(sizeof(struct tcphdr) + IPPROTO_TCP));
        }

        tcp_hdr->th_sport = inp->inp_lport;
        tcp_hdr->th_dport = inp->inp_fport;
        tcp_hdr->th_seq = 0;
        tcp_hdr->th_ack = 0;
        tcp_hdr->th_x2 = 0;
        tcp_hdr->th_off = 5;
        tcp_hdr->th_flags = 0;
        tcp_hdr->th_win = 0;
        tcp_hdr->th_urp = 0;
}

/*
 * Create template to be used to send tcp packets on a connection.
 * Allocates an mbuf and fills in a skeletal tcp/ip header.  The only
 * use for this function is in keepalives, which use tcp_respond.
 */
struct tcptemp *
tcp_maketemplate(struct tcpcb *tp)
{
        struct mbuf *m;
        struct tcptemp *n;

        m = m_get(M_DONTWAIT, MT_HEADER);
        if (m == NULL) {
                return 0;
        }
        m->m_len = sizeof(struct tcptemp);
        n = mtod(m, struct tcptemp *);

        tcp_fillheaders(tp, (void *)&n->tt_ipgen, (void *)&n->tt_t);
        return n;
}

/*
 * Send a single message to the TCP at address specified by
 * the given TCP/IP header.  If m == 0, then we make a copy
 * of the tcpiphdr at ti and send directly to the addressed host.
 * This is used to force keep alive messages out using the TCP
 * template for a connection.  If flags are given then we send
 * a message back to the TCP which originated the * segment ti,
 * and discard the mbuf containing it and any other attached mbufs.
 *
 * In any case the ack and sequence number of the transmitted
 * segment are as specified by the parameters.
 *
 * NOTE: If m != NULL, then ti must point to *inside* the mbuf.
 */
void
tcp_respond(struct tcpcb *tp, void *ipgen, struct tcphdr *th, struct mbuf *m,
    tcp_seq ack, tcp_seq seq, int flags, struct tcp_respond_args *tra)
{
        int tlen;
        int win = 0;
        struct route *ro = 0;
        struct route sro;
        struct ip *ip;
        struct tcphdr *nth;
#if INET6
        struct route_in6 *ro6 = 0;
        struct route_in6 sro6;
        struct ip6_hdr *ip6;
        int isipv6;
#endif /* INET6 */
        struct ifnet *outif;
        int sotc = SO_TC_UNSPEC;

#if INET6
        isipv6 = IP_VHL_V(((struct ip *)ipgen)->ip_vhl) == 6;
        ip6 = ipgen;
#endif /* INET6 */
        ip = ipgen;

        if (tp) {
                if (!(flags & TH_RST)) {
                        win = tcp_sbspace(tp);
                        if (win > (int32_t)TCP_MAXWIN << tp->rcv_scale) {
                                win = (int32_t)TCP_MAXWIN << tp->rcv_scale;
                        }
                }
#if INET6
                if (isipv6) {
                        ro6 = &tp->t_inpcb->in6p_route;
                } else
#endif /* INET6 */
                ro = &tp->t_inpcb->inp_route;
        } else {
#if INET6
                if (isipv6) {
                        ro6 = &sro6;
                        bzero(ro6, sizeof(*ro6));
                } else
#endif /* INET6 */
                {
                        ro = &sro;
                        bzero(ro, sizeof(*ro));
                }
        }
        if (m == 0) {
                m = m_gethdr(M_DONTWAIT, MT_HEADER);    /* MAC-OK */
                if (m == NULL) {
                        return;
                }
                tlen = 0;
                m->m_data += max_linkhdr;
#if INET6
                if (isipv6) {
                        VERIFY((MHLEN - max_linkhdr) >=
                            (sizeof(*ip6) + sizeof(*nth)));
                        bcopy((caddr_t)ip6, mtod(m, caddr_t),
                            sizeof(struct ip6_hdr));
                        ip6 = mtod(m, struct ip6_hdr *);
                        nth = (struct tcphdr *)(void *)(ip6 + 1);
                } else
#endif /* INET6 */
                {
                        VERIFY((MHLEN - max_linkhdr) >=
                            (sizeof(*ip) + sizeof(*nth)));
                        bcopy((caddr_t)ip, mtod(m, caddr_t), sizeof(struct ip));
                        ip = mtod(m, struct ip *);
                        nth = (struct tcphdr *)(void *)(ip + 1);
                }
                bcopy((caddr_t)th, (caddr_t)nth, sizeof(struct tcphdr));
#if MPTCP
                if ((tp) && (tp->t_mpflags & TMPF_RESET)) {
                        flags = (TH_RST | TH_ACK);
                } else
#endif
                flags = TH_ACK;
        } else {
                m_freem(m->m_next);
                m->m_next = 0;
                m->m_data = (caddr_t)ipgen;
                /* m_len is set later */
                tlen = 0;
#define xchg(a, b, type) { type t; t = a; a = b; b = t; }
#if INET6
                if (isipv6) {
                        /* Expect 32-bit aligned IP on strict-align platforms */
                        IP6_HDR_STRICT_ALIGNMENT_CHECK(ip6);
                        xchg(ip6->ip6_dst, ip6->ip6_src, struct in6_addr);
                        nth = (struct tcphdr *)(void *)(ip6 + 1);
                } else
#endif /* INET6 */
                {
                        /* Expect 32-bit aligned IP on strict-align platforms */
                        IP_HDR_STRICT_ALIGNMENT_CHECK(ip);
                        xchg(ip->ip_dst.s_addr, ip->ip_src.s_addr, n_long);
                        nth = (struct tcphdr *)(void *)(ip + 1);
                }
                if (th != nth) {
                        /*
                         * this is usually a case when an extension header
                         * exists between the IPv6 header and the
                         * TCP header.
                         */
                        nth->th_sport = th->th_sport;
                        nth->th_dport = th->th_dport;
                }
                xchg(nth->th_dport, nth->th_sport, n_short);
#undef xchg
        }
#if INET6
        if (isipv6) {
                ip6->ip6_plen = htons((u_short)(sizeof(struct tcphdr) +
                    tlen));
                tlen += sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
        } else
#endif
        {
                tlen += sizeof(struct tcpiphdr);
                ip->ip_len = tlen;
                ip->ip_ttl = ip_defttl;
        }
        m->m_len = tlen;
        m->m_pkthdr.len = tlen;
        m->m_pkthdr.rcvif = 0;
        if (tra->keep_alive) {
                m->m_pkthdr.pkt_flags |= PKTF_KEEPALIVE;
        }
#if CONFIG_MACF_NET
        if (tp != NULL && tp->t_inpcb != NULL) {
                /*
                 * Packet is associated with a socket, so allow the
                 * label of the response to reflect the socket label.
                 */
                mac_mbuf_label_associate_inpcb(tp->t_inpcb, m);
        } else {
                /*
                 * Packet is not associated with a socket, so possibly
                 * update the label in place.
                 */
                mac_netinet_tcp_reply(m);
        }
#endif

        nth->th_seq = htonl(seq);
        nth->th_ack = htonl(ack);
        nth->th_x2 = 0;
        nth->th_off = sizeof(struct tcphdr) >> 2;
        nth->th_flags = flags;
        if (tp) {
                nth->th_win = htons((u_short) (win >> tp->rcv_scale));
        } else {
                nth->th_win = htons((u_short)win);
        }
        nth->th_urp = 0;
#if INET6
        if (isipv6) {
                nth->th_sum = 0;
                nth->th_sum = in6_pseudo(&ip6->ip6_src, &ip6->ip6_dst,
                    htonl((tlen - sizeof(struct ip6_hdr)) + IPPROTO_TCP));
                m->m_pkthdr.csum_flags = CSUM_TCPIPV6;
                m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
                ip6->ip6_hlim = in6_selecthlim(tp ? tp->t_inpcb : NULL,
                    ro6 && ro6->ro_rt ? ro6->ro_rt->rt_ifp : NULL);
        } else
#endif /* INET6 */
        {
                nth->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
                    htons((u_short)(tlen - sizeof(struct ip) + ip->ip_p)));
                m->m_pkthdr.csum_flags = CSUM_TCP;
                m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
        }
#if TCPDEBUG
        if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) {
                tcp_trace(TA_OUTPUT, 0, tp, mtod(m, void *), th, 0);
        }
#endif

#if NECP
        necp_mark_packet_from_socket(m, tp ? tp->t_inpcb : NULL, 0, 0, 0);
#endif /* NECP */

#if IPSEC
        if (tp != NULL && tp->t_inpcb->inp_sp != NULL &&
            ipsec_setsocket(m, tp ? tp->t_inpcb->inp_socket : NULL) != 0) {
                m_freem(m);
                return;
        }
#endif

        if (tp != NULL) {
                u_int32_t svc_flags = 0;
                if (isipv6) {
                        svc_flags |= PKT_SCF_IPV6;
                }
                sotc = tp->t_inpcb->inp_socket->so_traffic_class;
                set_packet_service_class(m, tp->t_inpcb->inp_socket,
                    sotc, svc_flags);

                /* Embed flowhash and flow control flags */
                m->m_pkthdr.pkt_flowsrc = FLOWSRC_INPCB;
                m->m_pkthdr.pkt_flowid = tp->t_inpcb->inp_flowhash;
                m->m_pkthdr.pkt_flags |= (PKTF_FLOW_ID | PKTF_FLOW_LOCALSRC | PKTF_FLOW_ADV);
                m->m_pkthdr.pkt_proto = IPPROTO_TCP;
                m->m_pkthdr.tx_tcp_pid = tp->t_inpcb->inp_socket->last_pid;
                m->m_pkthdr.tx_tcp_e_pid = tp->t_inpcb->inp_socket->e_pid;
        }

#if INET6
        if (isipv6) {
                struct ip6_out_args ip6oa;
                bzero(&ip6oa, sizeof(ip6oa));
                ip6oa.ip6oa_boundif = tra->ifscope;
                ip6oa.ip6oa_flags = IP6OAF_SELECT_SRCIF | IP6OAF_BOUND_SRCADDR;
                ip6oa.ip6oa_sotc = SO_TC_UNSPEC;
                ip6oa.ip6oa_netsvctype = _NET_SERVICE_TYPE_UNSPEC;

                if (tra->ifscope != IFSCOPE_NONE) {
                        ip6oa.ip6oa_flags |= IP6OAF_BOUND_IF;
                }
                if (tra->nocell) {
                        ip6oa.ip6oa_flags |= IP6OAF_NO_CELLULAR;
                }
                if (tra->noexpensive) {
                        ip6oa.ip6oa_flags |= IP6OAF_NO_EXPENSIVE;
                }
                if (tra->noconstrained) {
                        ip6oa.ip6oa_flags |= IP6OAF_NO_CONSTRAINED;
                }
                if (tra->awdl_unrestricted) {
                        ip6oa.ip6oa_flags |= IP6OAF_AWDL_UNRESTRICTED;
                }
                if (tra->intcoproc_allowed) {
                        ip6oa.ip6oa_flags |= IP6OAF_INTCOPROC_ALLOWED;
                }
                ip6oa.ip6oa_sotc = sotc;
                if (tp != NULL) {
                        if ((tp->t_inpcb->inp_socket->so_flags1 & SOF1_QOSMARKING_ALLOWED)) {
                                ip6oa.ip6oa_flags |= IP6OAF_QOSMARKING_ALLOWED;
                        }
                        ip6oa.ip6oa_netsvctype = tp->t_inpcb->inp_socket->so_netsvctype;
                }
                (void) ip6_output(m, NULL, ro6, IPV6_OUTARGS, NULL,
                    NULL, &ip6oa);

                if (tp != NULL && ro6 != NULL && ro6->ro_rt != NULL &&
                    (outif = ro6->ro_rt->rt_ifp) !=
                    tp->t_inpcb->in6p_last_outifp) {
                        tp->t_inpcb->in6p_last_outifp = outif;
                }

                if (ro6 == &sro6) {
                        ROUTE_RELEASE(ro6);
                }
        } else
#endif /* INET6 */
        {
                struct ip_out_args ipoa;
                bzero(&ipoa, sizeof(ipoa));
                ipoa.ipoa_boundif = tra->ifscope;
                ipoa.ipoa_flags = IPOAF_SELECT_SRCIF | IPOAF_BOUND_SRCADDR;
                ipoa.ipoa_sotc = SO_TC_UNSPEC;
                ipoa.ipoa_netsvctype = _NET_SERVICE_TYPE_UNSPEC;

                if (tra->ifscope != IFSCOPE_NONE) {
                        ipoa.ipoa_flags |= IPOAF_BOUND_IF;
                }
                if (tra->nocell) {
                        ipoa.ipoa_flags |= IPOAF_NO_CELLULAR;
                }
                if (tra->noexpensive) {
                        ipoa.ipoa_flags |= IPOAF_NO_EXPENSIVE;
                }
                if (tra->noconstrained) {
                        ipoa.ipoa_flags |= IPOAF_NO_CONSTRAINED;
                }
                if (tra->awdl_unrestricted) {
                        ipoa.ipoa_flags |= IPOAF_AWDL_UNRESTRICTED;
                }
                ipoa.ipoa_sotc = sotc;
                if (tp != NULL) {
                        if ((tp->t_inpcb->inp_socket->so_flags1 & SOF1_QOSMARKING_ALLOWED)) {
                                ipoa.ipoa_flags |= IPOAF_QOSMARKING_ALLOWED;
                        }
                        ipoa.ipoa_netsvctype = tp->t_inpcb->inp_socket->so_netsvctype;
                }
                if (ro != &sro) {
                        /* Copy the cached route and take an extra reference */
                        inp_route_copyout(tp->t_inpcb, &sro);
                }
                /*
                 * For consistency, pass a local route copy.
                 */
                (void) ip_output(m, NULL, &sro, IP_OUTARGS, NULL, &ipoa);

                if (tp != NULL && sro.ro_rt != NULL &&
                    (outif = sro.ro_rt->rt_ifp) !=
                    tp->t_inpcb->inp_last_outifp) {
                        tp->t_inpcb->inp_last_outifp = outif;
                }
                if (ro != &sro) {
                        /* Synchronize cached PCB route */
                        inp_route_copyin(tp->t_inpcb, &sro);
                } else {
                        ROUTE_RELEASE(&sro);
                }
        }
}

/*
 * Create a new TCP control block, making an
 * empty reassembly queue and hooking it to the argument
 * protocol control block.  The `inp' parameter must have
 * come from the zone allocator set up in tcp_init().
 */
struct tcpcb *
tcp_newtcpcb(struct inpcb *inp)
{
        struct inp_tp *it;
        struct tcpcb *tp;
        struct socket *so = inp->inp_socket;
#if INET6
        int isipv6 = (inp->inp_vflag & INP_IPV6) != 0;
#endif /* INET6 */

        calculate_tcp_clock();

        if ((so->so_flags1 & SOF1_CACHED_IN_SOCK_LAYER) == 0) {
                it = (struct inp_tp *)(void *)inp;
                tp = &it->tcb;
        } else {
                tp = (struct tcpcb *)(void *)inp->inp_saved_ppcb;
        }

        bzero((char *) tp, sizeof(struct tcpcb));
        LIST_INIT(&tp->t_segq);
        tp->t_maxseg = tp->t_maxopd =
#if INET6
            isipv6 ? tcp_v6mssdflt :
#endif /* INET6 */
            tcp_mssdflt;

        if (tcp_do_rfc1323) {
                tp->t_flags = (TF_REQ_SCALE | TF_REQ_TSTMP);
        }
        if (tcp_do_sack) {
                tp->t_flagsext |= TF_SACK_ENABLE;
        }

        TAILQ_INIT(&tp->snd_holes);
        SLIST_INIT(&tp->t_rxt_segments);
        SLIST_INIT(&tp->t_notify_ack);
        tp->t_inpcb = inp;
        /*
         * Init srtt to TCPTV_SRTTBASE (0), so we can tell that we have no
         * rtt estimate.  Set rttvar so that srtt + 4 * rttvar gives
         * reasonable initial retransmit time.
         */
        tp->t_srtt = TCPTV_SRTTBASE;
        tp->t_rttvar =
            ((TCPTV_RTOBASE - TCPTV_SRTTBASE) << TCP_RTTVAR_SHIFT) / 4;
        tp->t_rttmin = tcp_TCPTV_MIN;
        tp->t_rxtcur = TCPTV_RTOBASE;

        if (tcp_use_newreno) {
                /* use newreno by default */
                tp->tcp_cc_index = TCP_CC_ALGO_NEWRENO_INDEX;
        } else {
                tp->tcp_cc_index = TCP_CC_ALGO_CUBIC_INDEX;
        }

        tcp_cc_allocate_state(tp);

        if (CC_ALGO(tp)->init != NULL) {
                CC_ALGO(tp)->init(tp);
        }

        tp->snd_cwnd = TCP_CC_CWND_INIT_BYTES;
        tp->snd_ssthresh = TCP_MAXWIN << TCP_MAX_WINSHIFT;
        tp->snd_ssthresh_prev = TCP_MAXWIN << TCP_MAX_WINSHIFT;
        tp->t_rcvtime = tcp_now;
        tp->tentry.timer_start = tcp_now;
        tp->rcv_unackwin = tcp_now;
        tp->t_persist_timeout = tcp_max_persist_timeout;
        tp->t_persist_stop = 0;
        tp->t_flagsext |= TF_RCVUNACK_WAITSS;
        tp->t_rexmtthresh = tcprexmtthresh;

        /* Enable bandwidth measurement on this connection */
        tp->t_flagsext |= TF_MEASURESNDBW;
        if (tp->t_bwmeas == NULL) {
                tp->t_bwmeas = tcp_bwmeas_alloc(tp);
                if (tp->t_bwmeas == NULL) {
                        tp->t_flagsext &= ~TF_MEASURESNDBW;
                }
        }

        /* Clear time wait tailq entry */
        tp->t_twentry.tqe_next = NULL;
        tp->t_twentry.tqe_prev = NULL;

        /*
         * IPv4 TTL initialization is necessary for an IPv6 socket as well,
         * because the socket may be bound to an IPv6 wildcard address,
         * which may match an IPv4-mapped IPv6 address.
         */
        inp->inp_ip_ttl = ip_defttl;
        inp->inp_ppcb = (caddr_t)tp;
        return tp;            /* XXX */
}

/*
 * Drop a TCP connection, reporting
 * the specified error.  If connection is synchronized,
 * then send a RST to peer.
 */
struct tcpcb *
tcp_drop(struct tcpcb *tp, int errno)
{
        struct socket *so = tp->t_inpcb->inp_socket;
#if CONFIG_DTRACE
        struct inpcb *inp = tp->t_inpcb;
#endif

        if (TCPS_HAVERCVDSYN(tp->t_state)) {
                DTRACE_TCP4(state__change, void, NULL, struct inpcb *, inp,
                    struct tcpcb *, tp, int32_t, TCPS_CLOSED);
                tp->t_state = TCPS_CLOSED;
                (void) tcp_output(tp);
                tcpstat.tcps_drops++;
        } else {
                tcpstat.tcps_conndrops++;
        }
        if (errno == ETIMEDOUT && tp->t_softerror) {
                errno = tp->t_softerror;
        }
        so->so_error = errno;

        TCP_LOG_CONNECTION_SUMMARY(tp);

        return tcp_close(tp);
}

void
tcp_getrt_rtt(struct tcpcb *tp, struct rtentry *rt)
{
        u_int32_t rtt = rt->rt_rmx.rmx_rtt;
        int isnetlocal = (tp->t_flags & TF_LOCAL);

        TCP_LOG_RTM_RTT(tp, rt);

        if (rtt != 0 && tcp_init_rtt_from_cache != 0) {
                /*
                 * XXX the lock bit for RTT indicates that the value
                 * is also a minimum value; this is subject to time.
                 */
                if (rt->rt_rmx.rmx_locks & RTV_RTT) {
                        tp->t_rttmin = rtt / (RTM_RTTUNIT / TCP_RETRANSHZ);
                } else {
                        tp->t_rttmin = isnetlocal ? tcp_TCPTV_MIN :
                            TCPTV_REXMTMIN;
                }

                tp->t_srtt =
                    rtt / (RTM_RTTUNIT / (TCP_RETRANSHZ * TCP_RTT_SCALE));
                tcpstat.tcps_usedrtt++;

                if (rt->rt_rmx.rmx_rttvar) {
                        tp->t_rttvar = rt->rt_rmx.rmx_rttvar /
                            (RTM_RTTUNIT / (TCP_RETRANSHZ * TCP_RTTVAR_SCALE));
                        tcpstat.tcps_usedrttvar++;
                } else {
                        /* default variation is +- 1 rtt */
                        tp->t_rttvar =
                            tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE;
                }

                /*
                 * The RTO formula in the route metric case is based on:
                 *     4 * srtt + 8 * rttvar
                 * modulo the min, max and slop
                 */
                TCPT_RANGESET(tp->t_rxtcur,
                    ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1,
                    tp->t_rttmin, TCPTV_REXMTMAX,
                    TCP_ADD_REXMTSLOP(tp));
        }

        TCP_LOG_RTT_INFO(tp);
}

static inline void
tcp_create_ifnet_stats_per_flow(struct tcpcb *tp,
    struct ifnet_stats_per_flow *ifs)
{
        struct inpcb *inp;
        struct socket *so;
        if (tp == NULL || ifs == NULL) {
                return;
        }

        bzero(ifs, sizeof(*ifs));
        inp = tp->t_inpcb;
        so = inp->inp_socket;

        ifs->ipv4 = (inp->inp_vflag & INP_IPV6) ? 0 : 1;
        ifs->local = (tp->t_flags & TF_LOCAL) ? 1 : 0;
        ifs->connreset = (so->so_error == ECONNRESET) ? 1 : 0;
        ifs->conntimeout = (so->so_error == ETIMEDOUT) ? 1 : 0;
        ifs->ecn_flags = tp->ecn_flags;
        ifs->txretransmitbytes = tp->t_stat.txretransmitbytes;
        ifs->rxoutoforderbytes = tp->t_stat.rxoutoforderbytes;
        ifs->rxmitpkts = tp->t_stat.rxmitpkts;
        ifs->rcvoopack = tp->t_rcvoopack;
        ifs->pawsdrop = tp->t_pawsdrop;
        ifs->sack_recovery_episodes = tp->t_sack_recovery_episode;
        ifs->reordered_pkts = tp->t_reordered_pkts;
        ifs->dsack_sent = tp->t_dsack_sent;
        ifs->dsack_recvd = tp->t_dsack_recvd;
        ifs->srtt = tp->t_srtt;
        ifs->rttupdated = tp->t_rttupdated;
        ifs->rttvar = tp->t_rttvar;
        ifs->rttmin = get_base_rtt(tp);
        if (tp->t_bwmeas != NULL && tp->t_bwmeas->bw_sndbw_max > 0) {
                ifs->bw_sndbw_max = tp->t_bwmeas->bw_sndbw_max;
        } else {
                ifs->bw_sndbw_max = 0;
        }
        if (tp->t_bwmeas != NULL && tp->t_bwmeas->bw_rcvbw_max > 0) {
                ifs->bw_rcvbw_max = tp->t_bwmeas->bw_rcvbw_max;
        } else {
                ifs->bw_rcvbw_max = 0;
        }
        ifs->bk_txpackets = so->so_tc_stats[MBUF_TC_BK].txpackets;
        ifs->txpackets = inp->inp_stat->txpackets;
        ifs->rxpackets = inp->inp_stat->rxpackets;
}

static inline void
tcp_flow_ecn_perf_stats(struct ifnet_stats_per_flow *ifs,
    struct if_tcp_ecn_perf_stat *stat)
{
        u_int64_t curval, oldval;
        stat->total_txpkts += ifs->txpackets;
        stat->total_rxpkts += ifs->rxpackets;
        stat->total_rxmitpkts += ifs->rxmitpkts;
        stat->total_oopkts += ifs->rcvoopack;
        stat->total_reorderpkts += (ifs->reordered_pkts +
            ifs->pawsdrop + ifs->dsack_sent + ifs->dsack_recvd);

        /* Average RTT */
        curval = ifs->srtt >> TCP_RTT_SHIFT;
        if (curval > 0 && ifs->rttupdated >= 16) {
                if (stat->rtt_avg == 0) {
                        stat->rtt_avg = curval;
                } else {
                        oldval = stat->rtt_avg;
                        stat->rtt_avg = ((oldval << 4) - oldval + curval) >> 4;
                }
        }

        /* RTT variance */
        curval = ifs->rttvar >> TCP_RTTVAR_SHIFT;
        if (curval > 0 && ifs->rttupdated >= 16) {
                if (stat->rtt_var == 0) {
                        stat->rtt_var = curval;
                } else {
                        oldval = stat->rtt_var;
                        stat->rtt_var =
                            ((oldval << 4) - oldval + curval) >> 4;
                }
        }

        /* SACK episodes */
        stat->sack_episodes += ifs->sack_recovery_episodes;
        if (ifs->connreset) {
                stat->rst_drop++;
        }
}

static inline void
tcp_flow_lim_stats(struct ifnet_stats_per_flow *ifs,
    struct if_lim_perf_stat *stat)
{
        u_int64_t curval, oldval;

        stat->lim_total_txpkts += ifs->txpackets;
        stat->lim_total_rxpkts += ifs->rxpackets;
        stat->lim_total_retxpkts += ifs->rxmitpkts;
        stat->lim_total_oopkts += ifs->rcvoopack;

        if (ifs->bw_sndbw_max > 0) {
                /* convert from bytes per ms to bits per second */
                ifs->bw_sndbw_max *= 8000;
                stat->lim_ul_max_bandwidth = max(stat->lim_ul_max_bandwidth,
                    ifs->bw_sndbw_max);
        }

        if (ifs->bw_rcvbw_max > 0) {
                /* convert from bytes per ms to bits per second */
                ifs->bw_rcvbw_max *= 8000;
                stat->lim_dl_max_bandwidth = max(stat->lim_dl_max_bandwidth,
                    ifs->bw_rcvbw_max);
        }

        /* Average RTT */
        curval = ifs->srtt >> TCP_RTT_SHIFT;
        if (curval > 0 && ifs->rttupdated >= 16) {
                if (stat->lim_rtt_average == 0) {
                        stat->lim_rtt_average = curval;
                } else {
                        oldval = stat->lim_rtt_average;
                        stat->lim_rtt_average =
                            ((oldval << 4) - oldval + curval) >> 4;
                }
        }

        /* RTT variance */
        curval = ifs->rttvar >> TCP_RTTVAR_SHIFT;
        if (curval > 0 && ifs->rttupdated >= 16) {
                if (stat->lim_rtt_variance == 0) {
                        stat->lim_rtt_variance = curval;
                } else {
                        oldval = stat->lim_rtt_variance;
                        stat->lim_rtt_variance =
                            ((oldval << 4) - oldval + curval) >> 4;
                }
        }

        if (stat->lim_rtt_min == 0) {
                stat->lim_rtt_min = ifs->rttmin;
        } else {
                stat->lim_rtt_min = min(stat->lim_rtt_min, ifs->rttmin);
        }

        /* connection timeouts */
        stat->lim_conn_attempts++;
        if (ifs->conntimeout) {
                stat->lim_conn_timeouts++;
        }

        /* bytes sent using background delay-based algorithms */
        stat->lim_bk_txpkts += ifs->bk_txpackets;
}

/*
 * Close a TCP control block:
 *      discard all space held by the tcp
 *      discard internet protocol block
 *      wake up any sleepers
 */
struct tcpcb *
tcp_close(struct tcpcb *tp)
{
        struct inpcb *inp = tp->t_inpcb;
        struct socket *so = inp->inp_socket;
#if INET6
        int isipv6 = (inp->inp_vflag & INP_IPV6) != 0;
#endif /* INET6 */
        struct route *ro;
        struct rtentry *rt;
        int dosavessthresh;
        struct ifnet_stats_per_flow ifs;

        /* tcp_close was called previously, bail */
        if (inp->inp_ppcb == NULL) {
                return NULL;
        }

        tcp_canceltimers(tp);
        KERNEL_DEBUG(DBG_FNC_TCP_CLOSE | DBG_FUNC_START, tp, 0, 0, 0, 0);

        /*
         * If another thread for this tcp is currently in ip (indicated by
         * the TF_SENDINPROG flag), defer the cleanup until after it returns
         * back to tcp.  This is done to serialize the close until after all
         * pending output is finished, in order to avoid having the PCB be
         * detached and the cached route cleaned, only for ip to cache the
         * route back into the PCB again.  Note that we've cleared all the
         * timers at this point.  Set TF_CLOSING to indicate to tcp_output()
         * that is should call us again once it returns from ip; at that
         * point both flags should be cleared and we can proceed further
         * with the cleanup.
         */
        if ((tp->t_flags & TF_CLOSING) ||
            inp->inp_sndinprog_cnt > 0) {
                tp->t_flags |= TF_CLOSING;
                return NULL;
        }

        TCP_LOG_CONNECTION_SUMMARY(tp);

        DTRACE_TCP4(state__change, void, NULL, struct inpcb *, inp,
            struct tcpcb *, tp, int32_t, TCPS_CLOSED);

#if INET6
        ro = (isipv6 ? (struct route *)&inp->in6p_route : &inp->inp_route);
#else
        ro = &inp->inp_route;
#endif
        rt = ro->ro_rt;
        if (rt != NULL) {
                RT_LOCK_SPIN(rt);
        }

        /*
         * If we got enough samples through the srtt filter,
         * save the rtt and rttvar in the routing entry.
         * 'Enough' is arbitrarily defined as the 16 samples.
         * 16 samples is enough for the srtt filter to converge
         * to within 5% of the correct value; fewer samples and
         * we could save a very bogus rtt.
         *
         * Don't update the default route's characteristics and don't
         * update anything that the user "locked".
         */
        if (tp->t_rttupdated >= 16) {
                u_int32_t i = 0;
                bool log_rtt = false;

#if INET6
                if (isipv6) {
                        struct sockaddr_in6 *sin6;

                        if (rt == NULL) {
                                goto no_valid_rt;
                        }
                        sin6 = (struct sockaddr_in6 *)(void *)rt_key(rt);
                        if (IN6_IS_ADDR_UNSPECIFIED(&sin6->sin6_addr)) {
                                goto no_valid_rt;
                        }
                } else
#endif /* INET6 */
                if (ROUTE_UNUSABLE(ro) ||
                    SIN(rt_key(rt))->sin_addr.s_addr == INADDR_ANY) {
                        DTRACE_TCP4(state__change, void, NULL,
                            struct inpcb *, inp, struct tcpcb *, tp,
                            int32_t, TCPS_CLOSED);
                        tp->t_state = TCPS_CLOSED;
                        goto no_valid_rt;
                }

                RT_LOCK_ASSERT_HELD(rt);
                if ((rt->rt_rmx.rmx_locks & RTV_RTT) == 0) {
                        i = tp->t_srtt *
                            (RTM_RTTUNIT / (TCP_RETRANSHZ * TCP_RTT_SCALE));
                        if (rt->rt_rmx.rmx_rtt && i) {
                                /*
                                 * filter this update to half the old & half
                                 * the new values, converting scale.
                                 * See route.h and tcp_var.h for a
                                 * description of the scaling constants.
                                 */
                                rt->rt_rmx.rmx_rtt =
                                    (rt->rt_rmx.rmx_rtt + i) / 2;
                        } else {
                                rt->rt_rmx.rmx_rtt = i;
                        }
                        tcpstat.tcps_cachedrtt++;
                        log_rtt = true;
                }
                if ((rt->rt_rmx.rmx_locks & RTV_RTTVAR) == 0) {
                        i = tp->t_rttvar *
                            (RTM_RTTUNIT / (TCP_RETRANSHZ * TCP_RTTVAR_SCALE));
                        if (rt->rt_rmx.rmx_rttvar && i) {
                                rt->rt_rmx.rmx_rttvar =
                                    (rt->rt_rmx.rmx_rttvar + i) / 2;
                        } else {
                                rt->rt_rmx.rmx_rttvar = i;
                        }
                        tcpstat.tcps_cachedrttvar++;
                        log_rtt = true;
                }
                if (log_rtt) {
                        TCP_LOG_RTM_RTT(tp, rt);
                        TCP_LOG_RTT_INFO(tp);
                }
                /*
                 * The old comment here said:
                 * update the pipelimit (ssthresh) if it has been updated
                 * already or if a pipesize was specified & the threshhold
                 * got below half the pipesize.  I.e., wait for bad news
                 * before we start updating, then update on both good
                 * and bad news.
                 *
                 * But we want to save the ssthresh even if no pipesize is
                 * specified explicitly in the route, because such
                 * connections still have an implicit pipesize specified
                 * by the global tcp_sendspace.  In the absence of a reliable
                 * way to calculate the pipesize, it will have to do.
                 */
                i = tp->snd_ssthresh;
                if (rt->rt_rmx.rmx_sendpipe != 0) {
                        dosavessthresh = (i < rt->rt_rmx.rmx_sendpipe / 2);
                } else {
                        dosavessthresh = (i < so->so_snd.sb_hiwat / 2);
                }
                if (((rt->rt_rmx.rmx_locks & RTV_SSTHRESH) == 0 &&
                    i != 0 && rt->rt_rmx.rmx_ssthresh != 0) ||
                    dosavessthresh) {
                        /*
                         * convert the limit from user data bytes to
                         * packets then to packet data bytes.
                         */
                        i = (i + tp->t_maxseg / 2) / tp->t_maxseg;
                        if (i < 2) {
                                i = 2;
                        }
                        i *= (u_int32_t)(tp->t_maxseg +
#if INET6
                            isipv6 ? sizeof(struct ip6_hdr) +
                            sizeof(struct tcphdr) :
#endif /* INET6 */
                            sizeof(struct tcpiphdr));
                        if (rt->rt_rmx.rmx_ssthresh) {
                                rt->rt_rmx.rmx_ssthresh =
                                    (rt->rt_rmx.rmx_ssthresh + i) / 2;
                        } else {
                                rt->rt_rmx.rmx_ssthresh = i;
                        }
                        tcpstat.tcps_cachedssthresh++;
                }
        }

        /*
         * Mark route for deletion if no information is cached.
         */
        if (rt != NULL && (so->so_flags & SOF_OVERFLOW) && tcp_lq_overflow) {
                if (!(rt->rt_rmx.rmx_locks & RTV_RTT) &&
                    rt->rt_rmx.rmx_rtt == 0) {
                        rt->rt_flags |= RTF_DELCLONE;
                }
        }

no_valid_rt:
        if (rt != NULL) {
                RT_UNLOCK(rt);
        }

        /* free the reassembly queue, if any */
        (void) tcp_freeq(tp);

        /* performance stats per interface */
        tcp_create_ifnet_stats_per_flow(tp, &ifs);
        tcp_update_stats_per_flow(&ifs, inp->inp_last_outifp);

        tcp_free_sackholes(tp);
        tcp_notify_ack_free(tp);

        inp_decr_sndbytes_allunsent(so, tp->snd_una);

        if (tp->t_bwmeas != NULL) {
                tcp_bwmeas_free(tp);
        }
        tcp_rxtseg_clean(tp);
        /* Free the packet list */
        if (tp->t_pktlist_head != NULL) {
                m_freem_list(tp->t_pktlist_head);
        }
        TCP_PKTLIST_CLEAR(tp);

        if (so->so_flags1 & SOF1_CACHED_IN_SOCK_LAYER) {
                inp->inp_saved_ppcb = (caddr_t) tp;
        }

        tp->t_state = TCPS_CLOSED;

        /*
         * Issue a wakeup before detach so that we don't miss
         * a wakeup
         */
        sodisconnectwakeup(so);

        /*
         * Clean up any LRO state
         */
        if (tp->t_flagsext & TF_LRO_OFFLOADED) {
                tcp_lro_remove_state(inp->inp_laddr, inp->inp_faddr,
                    inp->inp_lport, inp->inp_fport);
                tp->t_flagsext &= ~TF_LRO_OFFLOADED;
        }
        /*
         * Make sure to clear the TCP Keep Alive Offload as it is
         * ref counted on the interface
         */
        tcp_clear_keep_alive_offload(so);

        /*
         * If this is a socket that does not want to wakeup the device
         * for it's traffic, the application might need to know that the
         * socket is closed, send a notification.
         */
        if ((so->so_options & SO_NOWAKEFROMSLEEP) &&
            inp->inp_state != INPCB_STATE_DEAD &&
            !(inp->inp_flags2 & INP2_TIMEWAIT)) {
                socket_post_kev_msg_closed(so);
        }

        if (CC_ALGO(tp)->cleanup != NULL) {
                CC_ALGO(tp)->cleanup(tp);
        }

        if (tp->t_ccstate != NULL) {
                zfree(tcp_cc_zone, tp->t_ccstate);
                tp->t_ccstate = NULL;
        }
        tp->tcp_cc_index = TCP_CC_ALGO_NONE;

        /* Can happen if we close the socket before receiving the third ACK */
        if ((tp->t_tfo_flags & TFO_F_COOKIE_VALID)) {
                OSDecrementAtomic(&tcp_tfo_halfcnt);

                /* Panic if something has gone terribly wrong. */
                VERIFY(tcp_tfo_halfcnt >= 0);

                tp->t_tfo_flags &= ~TFO_F_COOKIE_VALID;
        }

#if INET6
        if (SOCK_CHECK_DOM(so, PF_INET6)) {
                in6_pcbdetach(inp);
        } else
#endif /* INET6 */
        in_pcbdetach(inp);

        /*
         * Call soisdisconnected after detach because it might unlock the socket
         */
        soisdisconnected(so);
        tcpstat.tcps_closed++;
        KERNEL_DEBUG(DBG_FNC_TCP_CLOSE | DBG_FUNC_END,
            tcpstat.tcps_closed, 0, 0, 0, 0);
        return NULL;
}

int
tcp_freeq(struct tcpcb *tp)
{
        struct tseg_qent *q;
        int rv = 0;

        while ((q = LIST_FIRST(&tp->t_segq)) != NULL) {
                LIST_REMOVE(q, tqe_q);
                m_freem(q->tqe_m);
                zfree(tcp_reass_zone, q);
                rv = 1;
        }
        tp->t_reassqlen = 0;
        return rv;
}


/*
 * Walk the tcpbs, if existing, and flush the reassembly queue,
 * if there is one when do_tcpdrain is enabled
 * Also defunct the extended background idle socket
 * Do it next time if the pcbinfo lock is in use
 */
void
tcp_drain(void)
{
        struct inpcb *inp;
        struct tcpcb *tp;

        if (!lck_rw_try_lock_exclusive(tcbinfo.ipi_lock)) {
                return;
        }

        LIST_FOREACH(inp, tcbinfo.ipi_listhead, inp_list) {
                if (in_pcb_checkstate(inp, WNT_ACQUIRE, 0) !=
                    WNT_STOPUSING) {
                        socket_lock(inp->inp_socket, 1);
                        if (in_pcb_checkstate(inp, WNT_RELEASE, 1)
                            == WNT_STOPUSING) {
                                /* lost a race, try the next one */
                                socket_unlock(inp->inp_socket, 1);
                                continue;
                        }
                        tp = intotcpcb(inp);

                        if (do_tcpdrain) {
                                tcp_freeq(tp);
                        }

                        so_drain_extended_bk_idle(inp->inp_socket);

                        socket_unlock(inp->inp_socket, 1);
                }
        }
        lck_rw_done(tcbinfo.ipi_lock);
}

/*
 * Notify a tcp user of an asynchronous error;
 * store error as soft error, but wake up user
 * (for now, won't do anything until can select for soft error).
 *
 * Do not wake up user since there currently is no mechanism for
 * reporting soft errors (yet - a kqueue filter may be added).
 */
static void
tcp_notify(struct inpcb *inp, int error)
{
        struct tcpcb *tp;

        if (inp == NULL || (inp->inp_state == INPCB_STATE_DEAD)) {
                return; /* pcb is gone already */
        }
        tp = (struct tcpcb *)inp->inp_ppcb;

        VERIFY(tp != NULL);
        /*
         * Ignore some errors if we are hooked up.
         * If connection hasn't completed, has retransmitted several times,
         * and receives a second error, give up now.  This is better
         * than waiting a long time to establish a connection that
         * can never complete.
         */
        if (tp->t_state == TCPS_ESTABLISHED &&
            (error == EHOSTUNREACH || error == ENETUNREACH ||
            error == EHOSTDOWN)) {
                if (inp->inp_route.ro_rt) {
                        rtfree(inp->inp_route.ro_rt);
                        inp->inp_route.ro_rt = (struct rtentry *)NULL;
                }
        } else if (tp->t_state < TCPS_ESTABLISHED && tp->t_rxtshift > 3 &&
            tp->t_softerror) {
                tcp_drop(tp, error);
        } else {
                tp->t_softerror = error;
        }
}

struct bwmeas *
tcp_bwmeas_alloc(struct tcpcb *tp)
{
        struct bwmeas *elm;
        elm = zalloc(tcp_bwmeas_zone);
        if (elm == NULL) {
                return elm;
        }

        bzero(elm, bwmeas_elm_size);
        elm->bw_minsizepkts = TCP_BWMEAS_BURST_MINSIZE;
        elm->bw_minsize = elm->bw_minsizepkts * tp->t_maxseg;
        return elm;
}

void
tcp_bwmeas_free(struct tcpcb *tp)
{
        zfree(tcp_bwmeas_zone, tp->t_bwmeas);
        tp->t_bwmeas = NULL;
        tp->t_flagsext &= ~(TF_MEASURESNDBW);
}

int
get_tcp_inp_list(struct inpcb **inp_list, int n, inp_gen_t gencnt)
{
        struct tcpcb *tp;
        struct inpcb *inp;
        int i = 0;

        LIST_FOREACH(inp, tcbinfo.ipi_listhead, inp_list) {
                if (inp->inp_gencnt <= gencnt &&
                    inp->inp_state != INPCB_STATE_DEAD) {
                        inp_list[i++] = inp;
                }
                if (i >= n) {
                        break;
                }
        }

        TAILQ_FOREACH(tp, &tcp_tw_tailq, t_twentry) {
                inp = tp->t_inpcb;
                if (inp->inp_gencnt <= gencnt &&
                    inp->inp_state != INPCB_STATE_DEAD) {
                        inp_list[i++] = inp;
                }
                if (i >= n) {
                        break;
                }
        }
        return i;
}

/*
 * tcpcb_to_otcpcb copies specific bits of a tcpcb to a otcpcb format.
 * The otcpcb data structure is passed to user space and must not change.
 */
static void
tcpcb_to_otcpcb(struct tcpcb *tp, struct otcpcb *otp)
{
        otp->t_segq = (uint32_t)VM_KERNEL_ADDRPERM(tp->t_segq.lh_first);
        otp->t_dupacks = tp->t_dupacks;
        otp->t_timer[TCPT_REXMT_EXT] = tp->t_timer[TCPT_REXMT];
        otp->t_timer[TCPT_PERSIST_EXT] = tp->t_timer[TCPT_PERSIST];
        otp->t_timer[TCPT_KEEP_EXT] = tp->t_timer[TCPT_KEEP];
        otp->t_timer[TCPT_2MSL_EXT] = tp->t_timer[TCPT_2MSL];
        otp->t_inpcb =
            (_TCPCB_PTR(struct inpcb *))VM_KERNEL_ADDRPERM(tp->t_inpcb);
        otp->t_state = tp->t_state;
        otp->t_flags = tp->t_flags;
        otp->t_force = (tp->t_flagsext & TF_FORCE) ? 1 : 0;
        otp->snd_una = tp->snd_una;
        otp->snd_max = tp->snd_max;
        otp->snd_nxt = tp->snd_nxt;
        otp->snd_up = tp->snd_up;
        otp->snd_wl1 = tp->snd_wl1;
        otp->snd_wl2 = tp->snd_wl2;
        otp->iss = tp->iss;
        otp->irs = tp->irs;
        otp->rcv_nxt = tp->rcv_nxt;
        otp->rcv_adv = tp->rcv_adv;
        otp->rcv_wnd = tp->rcv_wnd;
        otp->rcv_up = tp->rcv_up;
        otp->snd_wnd = tp->snd_wnd;
        otp->snd_cwnd = tp->snd_cwnd;
        otp->snd_ssthresh = tp->snd_ssthresh;
        otp->t_maxopd = tp->t_maxopd;
        otp->t_rcvtime = tp->t_rcvtime;
        otp->t_starttime = tp->t_starttime;
        otp->t_rtttime = tp->t_rtttime;
        otp->t_rtseq = tp->t_rtseq;
        otp->t_rxtcur = tp->t_rxtcur;
        otp->t_maxseg = tp->t_maxseg;
        otp->t_srtt = tp->t_srtt;
        otp->t_rttvar = tp->t_rttvar;
        otp->t_rxtshift = tp->t_rxtshift;
        otp->t_rttmin = tp->t_rttmin;
        otp->t_rttupdated = tp->t_rttupdated;
        otp->max_sndwnd = tp->max_sndwnd;
        otp->t_softerror = tp->t_softerror;
        otp->t_oobflags = tp->t_oobflags;
        otp->t_iobc = tp->t_iobc;
        otp->snd_scale = tp->snd_scale;
        otp->rcv_scale = tp->rcv_scale;
        otp->request_r_scale = tp->request_r_scale;
        otp->requested_s_scale = tp->requested_s_scale;
        otp->ts_recent = tp->ts_recent;
        otp->ts_recent_age = tp->ts_recent_age;
        otp->last_ack_sent = tp->last_ack_sent;
        otp->cc_send = 0;
        otp->cc_recv = 0;
        otp->snd_recover = tp->snd_recover;
        otp->snd_cwnd_prev = tp->snd_cwnd_prev;
        otp->snd_ssthresh_prev = tp->snd_ssthresh_prev;
        otp->t_badrxtwin = 0;
}

static int
tcp_pcblist SYSCTL_HANDLER_ARGS
{
#pragma unused(oidp, arg1, arg2)
        int error, i = 0, n;
        struct inpcb **inp_list;
        inp_gen_t gencnt;
        struct xinpgen xig;

        /*
         * The process of preparing the TCB list is too time-consuming and
         * resource-intensive to repeat twice on every request.
         */
        lck_rw_lock_shared(tcbinfo.ipi_lock);
        if (req->oldptr == USER_ADDR_NULL) {
                n = tcbinfo.ipi_count;
                req->oldidx = 2 * (sizeof(xig))
                    + (n + n / 8) * sizeof(struct xtcpcb);
                lck_rw_done(tcbinfo.ipi_lock);
                return 0;
        }

        if (req->newptr != USER_ADDR_NULL) {
                lck_rw_done(tcbinfo.ipi_lock);
                return EPERM;
        }

        /*
         * OK, now we're committed to doing something.
         */
        gencnt = tcbinfo.ipi_gencnt;
        n = tcbinfo.ipi_count;

        bzero(&xig, sizeof(xig));
        xig.xig_len = sizeof(xig);
        xig.xig_count = n;
        xig.xig_gen = gencnt;
        xig.xig_sogen = so_gencnt;
        error = SYSCTL_OUT(req, &xig, sizeof(xig));
        if (error) {
                lck_rw_done(tcbinfo.ipi_lock);
                return error;
        }
        /*
         * We are done if there is no pcb
         */
        if (n == 0) {
                lck_rw_done(tcbinfo.ipi_lock);
                return 0;
        }

        inp_list = _MALLOC(n * sizeof(*inp_list), M_TEMP, M_WAITOK);
        if (inp_list == 0) {
                lck_rw_done(tcbinfo.ipi_lock);
                return ENOMEM;
        }

        n = get_tcp_inp_list(inp_list, n, gencnt);

        error = 0;
        for (i = 0; i < n; i++) {
                struct xtcpcb xt;
                caddr_t inp_ppcb;
                struct inpcb *inp;

                inp = inp_list[i];

                if (in_pcb_checkstate(inp, WNT_ACQUIRE, 0) == WNT_STOPUSING) {
                        continue;
                }
                socket_lock(inp->inp_socket, 1);
                if (in_pcb_checkstate(inp, WNT_RELEASE, 1) == WNT_STOPUSING) {
                        socket_unlock(inp->inp_socket, 1);
                        continue;
                }
                if (inp->inp_gencnt > gencnt) {
                        socket_unlock(inp->inp_socket, 1);
                        continue;
                }

                bzero(&xt, sizeof(xt));
                xt.xt_len = sizeof(xt);
                /* XXX should avoid extra copy */
                inpcb_to_compat(inp, &xt.xt_inp);
                inp_ppcb = inp->inp_ppcb;
                if (inp_ppcb != NULL) {
                        tcpcb_to_otcpcb((struct tcpcb *)(void *)inp_ppcb,
                            &xt.xt_tp);
                } else {
                        bzero((char *) &xt.xt_tp, sizeof(xt.xt_tp));
                }
                if (inp->inp_socket) {
                        sotoxsocket(inp->inp_socket, &xt.xt_socket);
                }

                socket_unlock(inp->inp_socket, 1);

                error = SYSCTL_OUT(req, &xt, sizeof(xt));
        }
        if (!error) {
                /*
                 * Give the user an updated idea of our state.
                 * If the generation differs from what we told
                 * her before, she knows that something happened
                 * while we were processing this request, and it
                 * might be necessary to retry.
                 */
                bzero(&xig, sizeof(xig));
                xig.xig_len = sizeof(xig);
                xig.xig_gen = tcbinfo.ipi_gencnt;
                xig.xig_sogen = so_gencnt;
                xig.xig_count = tcbinfo.ipi_count;
                error = SYSCTL_OUT(req, &xig, sizeof(xig));
        }
        FREE(inp_list, M_TEMP);
        lck_rw_done(tcbinfo.ipi_lock);
        return error;
}

SYSCTL_PROC(_net_inet_tcp, TCPCTL_PCBLIST, pcblist,
    CTLTYPE_STRUCT | CTLFLAG_RD | CTLFLAG_LOCKED, 0, 0,
    tcp_pcblist, "S,xtcpcb", "List of active TCP connections");

#if !CONFIG_EMBEDDED

static void
tcpcb_to_xtcpcb64(struct tcpcb *tp, struct xtcpcb64 *otp)
{
        otp->t_segq = (uint32_t)VM_KERNEL_ADDRPERM(tp->t_segq.lh_first);
        otp->t_dupacks = tp->t_dupacks;
        otp->t_timer[TCPT_REXMT_EXT] = tp->t_timer[TCPT_REXMT];
        otp->t_timer[TCPT_PERSIST_EXT] = tp->t_timer[TCPT_PERSIST];
        otp->t_timer[TCPT_KEEP_EXT] = tp->t_timer[TCPT_KEEP];
        otp->t_timer[TCPT_2MSL_EXT] = tp->t_timer[TCPT_2MSL];
        otp->t_state = tp->t_state;
        otp->t_flags = tp->t_flags;
        otp->t_force = (tp->t_flagsext & TF_FORCE) ? 1 : 0;
        otp->snd_una = tp->snd_una;
        otp->snd_max = tp->snd_max;
        otp->snd_nxt = tp->snd_nxt;
        otp->snd_up = tp->snd_up;
        otp->snd_wl1 = tp->snd_wl1;
        otp->snd_wl2 = tp->snd_wl2;
        otp->iss = tp->iss;
        otp->irs = tp->irs;
        otp->rcv_nxt = tp->rcv_nxt;
        otp->rcv_adv = tp->rcv_adv;
        otp->rcv_wnd = tp->rcv_wnd;
        otp->rcv_up = tp->rcv_up;
        otp->snd_wnd = tp->snd_wnd;
        otp->snd_cwnd = tp->snd_cwnd;
        otp->snd_ssthresh = tp->snd_ssthresh;
        otp->t_maxopd = tp->t_maxopd;
        otp->t_rcvtime = tp->t_rcvtime;
        otp->t_starttime = tp->t_starttime;
        otp->t_rtttime = tp->t_rtttime;
        otp->t_rtseq = tp->t_rtseq;
        otp->t_rxtcur = tp->t_rxtcur;
        otp->t_maxseg = tp->t_maxseg;
        otp->t_srtt = tp->t_srtt;
        otp->t_rttvar = tp->t_rttvar;
        otp->t_rxtshift = tp->t_rxtshift;
        otp->t_rttmin = tp->t_rttmin;
        otp->t_rttupdated = tp->t_rttupdated;
        otp->max_sndwnd = tp->max_sndwnd;
        otp->t_softerror = tp->t_softerror;
        otp->t_oobflags = tp->t_oobflags;
        otp->t_iobc = tp->t_iobc;
        otp->snd_scale = tp->snd_scale;
        otp->rcv_scale = tp->rcv_scale;
        otp->request_r_scale = tp->request_r_scale;
        otp->requested_s_scale = tp->requested_s_scale;
        otp->ts_recent = tp->ts_recent;
        otp->ts_recent_age = tp->ts_recent_age;
        otp->last_ack_sent = tp->last_ack_sent;
        otp->cc_send = 0;
        otp->cc_recv = 0;
        otp->snd_recover = tp->snd_recover;
        otp->snd_cwnd_prev = tp->snd_cwnd_prev;
        otp->snd_ssthresh_prev = tp->snd_ssthresh_prev;
        otp->t_badrxtwin = 0;
}


static int
tcp_pcblist64 SYSCTL_HANDLER_ARGS
{
#pragma unused(oidp, arg1, arg2)
        int error, i = 0, n;
        struct inpcb **inp_list;
        inp_gen_t gencnt;
        struct xinpgen xig;

        /*
         * The process of preparing the TCB list is too time-consuming and
         * resource-intensive to repeat twice on every request.
         */
        lck_rw_lock_shared(tcbinfo.ipi_lock);
        if (req->oldptr == USER_ADDR_NULL) {
                n = tcbinfo.ipi_count;
                req->oldidx = 2 * (sizeof(xig))
                    + (n + n / 8) * sizeof(struct xtcpcb64);
                lck_rw_done(tcbinfo.ipi_lock);
                return 0;
        }

        if (req->newptr != USER_ADDR_NULL) {
                lck_rw_done(tcbinfo.ipi_lock);
                return EPERM;
        }

        /*
         * OK, now we're committed to doing something.
         */
        gencnt = tcbinfo.ipi_gencnt;
        n = tcbinfo.ipi_count;

        bzero(&xig, sizeof(xig));
        xig.xig_len = sizeof(xig);
        xig.xig_count = n;
        xig.xig_gen = gencnt;
        xig.xig_sogen = so_gencnt;
        error = SYSCTL_OUT(req, &xig, sizeof(xig));
        if (error) {
                lck_rw_done(tcbinfo.ipi_lock);
                return error;
        }
        /*
         * We are done if there is no pcb
         */
        if (n == 0) {
                lck_rw_done(tcbinfo.ipi_lock);
                return 0;
        }

        inp_list = _MALLOC(n * sizeof(*inp_list), M_TEMP, M_WAITOK);
        if (inp_list == 0) {
                lck_rw_done(tcbinfo.ipi_lock);
                return ENOMEM;
        }

        n = get_tcp_inp_list(inp_list, n, gencnt);

        error = 0;
        for (i = 0; i < n; i++) {
                struct xtcpcb64 xt;
                struct inpcb *inp;

                inp = inp_list[i];

                if (in_pcb_checkstate(inp, WNT_ACQUIRE, 0) == WNT_STOPUSING) {
                        continue;
                }
                socket_lock(inp->inp_socket, 1);
                if (in_pcb_checkstate(inp, WNT_RELEASE, 1) == WNT_STOPUSING) {
                        socket_unlock(inp->inp_socket, 1);
                        continue;
                }
                if (inp->inp_gencnt > gencnt) {
                        socket_unlock(inp->inp_socket, 1);
                        continue;
                }

                bzero(&xt, sizeof(xt));
                xt.xt_len = sizeof(xt);
                inpcb_to_xinpcb64(inp, &xt.xt_inpcb);
                xt.xt_inpcb.inp_ppcb =
                    (uint64_t)VM_KERNEL_ADDRPERM(inp->inp_ppcb);
                if (inp->inp_ppcb != NULL) {
                        tcpcb_to_xtcpcb64((struct tcpcb *)inp->inp_ppcb,
                            &xt);
                }
                if (inp->inp_socket) {
                        sotoxsocket64(inp->inp_socket,
                            &xt.xt_inpcb.xi_socket);
                }

                socket_unlock(inp->inp_socket, 1);

                error = SYSCTL_OUT(req, &xt, sizeof(xt));
        }
        if (!error) {
                /*
                 * Give the user an updated idea of our state.
                 * If the generation differs from what we told
                 * her before, she knows that something happened
                 * while we were processing this request, and it
                 * might be necessary to retry.
                 */
                bzero(&xig, sizeof(xig));
                xig.xig_len = sizeof(xig);
                xig.xig_gen = tcbinfo.ipi_gencnt;
                xig.xig_sogen = so_gencnt;
                xig.xig_count = tcbinfo.ipi_count;
                error = SYSCTL_OUT(req, &xig, sizeof(xig));
        }
        FREE(inp_list, M_TEMP);
        lck_rw_done(tcbinfo.ipi_lock);
        return error;
}

SYSCTL_PROC(_net_inet_tcp, OID_AUTO, pcblist64,
    CTLTYPE_STRUCT | CTLFLAG_RD | CTLFLAG_LOCKED, 0, 0,
    tcp_pcblist64, "S,xtcpcb64", "List of active TCP connections");

#endif /* !CONFIG_EMBEDDED */

static int
tcp_pcblist_n SYSCTL_HANDLER_ARGS
{
#pragma unused(oidp, arg1, arg2)
        int error = 0;

        error = get_pcblist_n(IPPROTO_TCP, req, &tcbinfo);

        return error;
}


SYSCTL_PROC(_net_inet_tcp, OID_AUTO, pcblist_n,
    CTLTYPE_STRUCT | CTLFLAG_RD | CTLFLAG_LOCKED, 0, 0,
    tcp_pcblist_n, "S,xtcpcb_n", "List of active TCP connections");

static int
tcp_progress_indicators SYSCTL_HANDLER_ARGS
{
#pragma unused(oidp, arg1, arg2)

        return ntstat_tcp_progress_indicators(req);
}

SYSCTL_PROC(_net_inet_tcp, OID_AUTO, progress,
    CTLTYPE_STRUCT | CTLFLAG_RW | CTLFLAG_LOCKED | CTLFLAG_ANYBODY, 0, 0,
    tcp_progress_indicators, "S", "Various items that indicate the current state of progress on the link");


__private_extern__ void
tcp_get_ports_used(uint32_t ifindex, int protocol, uint32_t flags,
    bitstr_t *bitfield)
{
        inpcb_get_ports_used(ifindex, protocol, flags, bitfield,
            &tcbinfo);
}

__private_extern__ uint32_t
tcp_count_opportunistic(unsigned int ifindex, u_int32_t flags)
{
        return inpcb_count_opportunistic(ifindex, &tcbinfo, flags);
}

__private_extern__ uint32_t
tcp_find_anypcb_byaddr(struct ifaddr *ifa)
{
        return inpcb_find_anypcb_byaddr(ifa, &tcbinfo);
}

static void
tcp_handle_msgsize(struct ip *ip, struct inpcb *inp)
{
        struct rtentry *rt = NULL;
        u_short ifscope = IFSCOPE_NONE;
        int mtu;
        struct sockaddr_in icmpsrc = {
                .sin_len = sizeof(struct sockaddr_in),
                .sin_family = AF_INET, .sin_port = 0, .sin_addr = { .s_addr = 0 },
                .sin_zero = { 0, 0, 0, 0, 0, 0, 0, 0 }
        };
        struct icmp *icp = NULL;

        icp = (struct icmp *)(void *)
            ((caddr_t)ip - offsetof(struct icmp, icmp_ip));

        icmpsrc.sin_addr = icp->icmp_ip.ip_dst;

        /*
         * MTU discovery:
         * If we got a needfrag and there is a host route to the
         * original destination, and the MTU is not locked, then
         * set the MTU in the route to the suggested new value
         * (if given) and then notify as usual.  The ULPs will
         * notice that the MTU has changed and adapt accordingly.
         * If no new MTU was suggested, then we guess a new one
         * less than the current value.  If the new MTU is
         * unreasonably small (defined by sysctl tcp_minmss), then
         * we reset the MTU to the interface value and enable the
         * lock bit, indicating that we are no longer doing MTU
         * discovery.
         */
        if (ROUTE_UNUSABLE(&(inp->inp_route)) == false) {
                rt = inp->inp_route.ro_rt;
        }

        /*
         * icmp6_mtudisc_update scopes the routing lookup
         * to the incoming interface (delivered from mbuf
         * packet header.
         * That is mostly ok but for asymmetric networks
         * that may be an issue.
         * Frag needed OR Packet too big really communicates
         * MTU for the out data path.
         * Take the interface scope from cached route or
         * the last outgoing interface from inp
         */
        if (rt != NULL) {
                ifscope = (rt->rt_ifp != NULL) ?
                    rt->rt_ifp->if_index : IFSCOPE_NONE;
        } else {
                ifscope = (inp->inp_last_outifp != NULL) ?
                    inp->inp_last_outifp->if_index : IFSCOPE_NONE;
        }

        if ((rt == NULL) ||
            !(rt->rt_flags & RTF_HOST) ||
            (rt->rt_flags & (RTF_CLONING | RTF_PRCLONING))) {
                rt = rtalloc1_scoped((struct sockaddr *)&icmpsrc, 0,
                    RTF_CLONING | RTF_PRCLONING, ifscope);
        } else if (rt) {
                RT_LOCK(rt);
                rtref(rt);
                RT_UNLOCK(rt);
        }

        if (rt != NULL) {
                RT_LOCK(rt);
                if ((rt->rt_flags & RTF_HOST) &&
                    !(rt->rt_rmx.rmx_locks & RTV_MTU)) {
                        mtu = ntohs(icp->icmp_nextmtu);
                        /*
                         * XXX Stock BSD has changed the following
                         * to compare with icp->icmp_ip.ip_len
                         * to converge faster when sent packet
                         * < route's MTU. We may want to adopt
                         * that change.
                         */
                        if (mtu == 0) {
                                mtu = ip_next_mtu(rt->rt_rmx.
                                    rmx_mtu, 1);
                        }
#if DEBUG_MTUDISC
                        printf("MTU for %s reduced to %d\n",
                            inet_ntop(AF_INET,
                            &icmpsrc.sin_addr, ipv4str,
                            sizeof(ipv4str)), mtu);
#endif
                        if (mtu < max(296, (tcp_minmss +
                            sizeof(struct tcpiphdr)))) {
                                rt->rt_rmx.rmx_locks |= RTV_MTU;
                        } else if (rt->rt_rmx.rmx_mtu > mtu) {
                                rt->rt_rmx.rmx_mtu = mtu;
                        }
                }
                RT_UNLOCK(rt);
                rtfree(rt);
        }
}

void
tcp_ctlinput(int cmd, struct sockaddr *sa, void *vip, __unused struct ifnet *ifp)
{
        tcp_seq icmp_tcp_seq;
        struct ip *ip = vip;
        struct in_addr faddr;
        struct inpcb *inp;
        struct tcpcb *tp;
        struct tcphdr *th;
        struct icmp *icp;
        void (*notify)(struct inpcb *, int) = tcp_notify;

        faddr = ((struct sockaddr_in *)(void *)sa)->sin_addr;
        if (sa->sa_family != AF_INET || faddr.s_addr == INADDR_ANY) {
                return;
        }

        if ((unsigned)cmd >= PRC_NCMDS) {
                return;
        }

        /* Source quench is deprecated */
        if (cmd == PRC_QUENCH) {
                return;
        }

        if (cmd == PRC_MSGSIZE) {
                notify = tcp_mtudisc;
        } else if (icmp_may_rst && (cmd == PRC_UNREACH_ADMIN_PROHIB ||
            cmd == PRC_UNREACH_PORT || cmd == PRC_UNREACH_PROTOCOL ||
            cmd == PRC_TIMXCEED_INTRANS) && ip) {
                notify = tcp_drop_syn_sent;
        }
        /*
         * Hostdead is ugly because it goes linearly through all PCBs.
         * XXX: We never get this from ICMP, otherwise it makes an
         * excellent DoS attack on machines with many connections.
         */
        else if (cmd == PRC_HOSTDEAD) {
                ip = NULL;
        } else if (inetctlerrmap[cmd] == 0 && !PRC_IS_REDIRECT(cmd)) {
                return;
        }


        if (ip == NULL) {
                in_pcbnotifyall(&tcbinfo, faddr, inetctlerrmap[cmd], notify);
                return;
        }

        icp = (struct icmp *)(void *)
            ((caddr_t)ip - offsetof(struct icmp, icmp_ip));
        th = (struct tcphdr *)(void *)((caddr_t)ip + (IP_VHL_HL(ip->ip_vhl) << 2));
        icmp_tcp_seq = ntohl(th->th_seq);

        inp = in_pcblookup_hash(&tcbinfo, faddr, th->th_dport,
            ip->ip_src, th->th_sport, 0, NULL);

        if (inp == NULL ||
            inp->inp_socket == NULL) {
                return;
        }

        socket_lock(inp->inp_socket, 1);
        if (in_pcb_checkstate(inp, WNT_RELEASE, 1) ==
            WNT_STOPUSING) {
                socket_unlock(inp->inp_socket, 1);
                return;
        }

        if (PRC_IS_REDIRECT(cmd)) {
                /* signal EHOSTDOWN, as it flushes the cached route */
                (*notify)(inp, EHOSTDOWN);
        } else {
                tp = intotcpcb(inp);
                if (SEQ_GEQ(icmp_tcp_seq, tp->snd_una) &&
                    SEQ_LT(icmp_tcp_seq, tp->snd_max)) {
                        if (cmd == PRC_MSGSIZE) {
                                tcp_handle_msgsize(ip, inp);
                        }

                        (*notify)(inp, inetctlerrmap[cmd]);
                }
        }
        socket_unlock(inp->inp_socket, 1);
}

#if INET6
void
tcp6_ctlinput(int cmd, struct sockaddr *sa, void *d, __unused struct ifnet *ifp)
{
        tcp_seq icmp_tcp_seq;
        struct in6_addr *dst;
        void (*notify)(struct inpcb *, int) = tcp_notify;
        struct ip6_hdr *ip6;
        struct mbuf *m;
        struct inpcb *inp;
        struct tcpcb *tp;
        struct icmp6_hdr *icmp6;
        struct ip6ctlparam *ip6cp = NULL;
        const struct sockaddr_in6 *sa6_src = NULL;
        unsigned int mtu;
        unsigned int off;

        struct tcp_ports {
                uint16_t th_sport;
                uint16_t th_dport;
        } t_ports;

        if (sa->sa_family != AF_INET6 ||
            sa->sa_len != sizeof(struct sockaddr_in6)) {
                return;
        }

        /* Source quench is deprecated */
        if (cmd == PRC_QUENCH) {
                return;
        }

        if ((unsigned)cmd >= PRC_NCMDS) {
                return;
        }

        /* if the parameter is from icmp6, decode it. */
        if (d != NULL) {
                ip6cp = (struct ip6ctlparam *)d;
                icmp6 = ip6cp->ip6c_icmp6;
                m = ip6cp->ip6c_m;
                ip6 = ip6cp->ip6c_ip6;
                off = ip6cp->ip6c_off;
                sa6_src = ip6cp->ip6c_src;
                dst = ip6cp->ip6c_finaldst;
        } else {
                m = NULL;
                ip6 = NULL;
                off = 0;        /* fool gcc */
                sa6_src = &sa6_any;
                dst = NULL;
        }

        if (cmd == PRC_MSGSIZE) {
                notify = tcp_mtudisc;
        } else if (icmp_may_rst && (cmd == PRC_UNREACH_ADMIN_PROHIB ||
            cmd == PRC_UNREACH_PORT || cmd == PRC_TIMXCEED_INTRANS) &&
            ip6 != NULL) {
                notify = tcp_drop_syn_sent;
        }
        /*
         * Hostdead is ugly because it goes linearly through all PCBs.
         * XXX: We never get this from ICMP, otherwise it makes an
         * excellent DoS attack on machines with many connections.
         */
        else if (cmd == PRC_HOSTDEAD) {
                ip6 = NULL;
        } else if (inet6ctlerrmap[cmd] == 0 && !PRC_IS_REDIRECT(cmd)) {
                return;
        }


        if (ip6 == NULL) {
                in6_pcbnotify(&tcbinfo, sa, 0, (struct sockaddr *)(size_t)sa6_src,
                    0, cmd, NULL, notify);
                return;
        }

        /* Check if we can safely get the ports from the tcp hdr */
        if (m == NULL ||
            (m->m_pkthdr.len <
            (int32_t) (off + sizeof(struct tcp_ports)))) {
                return;
        }
        bzero(&t_ports, sizeof(struct tcp_ports));
        m_copydata(m, off, sizeof(struct tcp_ports), (caddr_t)&t_ports);

        off += sizeof(struct tcp_ports);
        if (m->m_pkthdr.len < (int32_t) (off + sizeof(tcp_seq))) {
                return;
        }
        m_copydata(m, off, sizeof(tcp_seq), (caddr_t)&icmp_tcp_seq);
        icmp_tcp_seq = ntohl(icmp_tcp_seq);

        if (cmd == PRC_MSGSIZE) {
                mtu = ntohl(icmp6->icmp6_mtu);
                /*
                 * If no alternative MTU was proposed, or the proposed
                 * MTU was too small, set to the min.
                 */
                if (mtu < IPV6_MMTU) {
                        mtu = IPV6_MMTU - 8;
                }
        }

        inp = in6_pcblookup_hash(&tcbinfo, &ip6->ip6_dst, t_ports.th_dport,
            &ip6->ip6_src, t_ports.th_sport, 0, NULL);

        if (inp == NULL ||
            inp->inp_socket == NULL) {
                return;
        }

        socket_lock(inp->inp_socket, 1);
        if (in_pcb_checkstate(inp, WNT_RELEASE, 1) ==
            WNT_STOPUSING) {
                socket_unlock(inp->inp_socket, 1);
                return;
        }

        if (PRC_IS_REDIRECT(cmd)) {
                /* signal EHOSTDOWN, as it flushes the cached route */
                (*notify)(inp, EHOSTDOWN);
        } else {
                tp = intotcpcb(inp);
                if (SEQ_GEQ(icmp_tcp_seq, tp->snd_una) &&
                    SEQ_LT(icmp_tcp_seq, tp->snd_max)) {
                        if (cmd == PRC_MSGSIZE) {
                                /*
                                 * Only process the offered MTU if it
                                 * is smaller than the current one.
                                 */
                                if (mtu < tp->t_maxseg +
                                    (sizeof(struct tcphdr) + sizeof(struct ip6_hdr))) {
                                        (*notify)(inp, inetctlerrmap[cmd]);
                                }
                        } else {
                                (*notify)(inp, inetctlerrmap[cmd]);
                        }
                }
        }
        socket_unlock(inp->inp_socket, 1);
}
#endif /* INET6 */


/*
 * Following is where TCP initial sequence number generation occurs.
 *
 * There are two places where we must use initial sequence numbers:
 * 1.  In SYN-ACK packets.
 * 2.  In SYN packets.
 *
 * The ISNs in SYN-ACK packets have no monotonicity requirement,
 * and should be as unpredictable as possible to avoid the possibility
 * of spoofing and/or connection hijacking.  To satisfy this
 * requirement, SYN-ACK ISNs are generated via the arc4random()
 * function.  If exact RFC 1948 compliance is requested via sysctl,
 * these ISNs will be generated just like those in SYN packets.
 *
 * The ISNs in SYN packets must be monotonic; TIME_WAIT recycling
 * depends on this property.  In addition, these ISNs should be
 * unguessable so as to prevent connection hijacking.  To satisfy
 * the requirements of this situation, the algorithm outlined in
 * RFC 1948 is used to generate sequence numbers.
 *
 * For more information on the theory of operation, please see
 * RFC 1948.
 *
 * Implementation details:
 *
 * Time is based off the system timer, and is corrected so that it
 * increases by one megabyte per second.  This allows for proper
 * recycling on high speed LANs while still leaving over an hour
 * before rollover.
 *
 * Two sysctls control the generation of ISNs:
 *
 * net.inet.tcp.isn_reseed_interval controls the number of seconds
 * between seeding of isn_secret.  This is normally set to zero,
 * as reseeding should not be necessary.
 *
 * net.inet.tcp.strict_rfc1948 controls whether RFC 1948 is followed
 * strictly.  When strict compliance is requested, reseeding is
 * disabled and SYN-ACKs will be generated in the same manner as
 * SYNs.  Strict mode is disabled by default.
 *
 */

#define ISN_BYTES_PER_SECOND 1048576

tcp_seq
tcp_new_isn(struct tcpcb *tp)
{
        u_int32_t md5_buffer[4];
        tcp_seq new_isn;
        struct timeval timenow;
        u_char isn_secret[32];
        int isn_last_reseed = 0;
        MD5_CTX isn_ctx;

        /* Use arc4random for SYN-ACKs when not in exact RFC1948 mode. */
        if (((tp->t_state == TCPS_LISTEN) || (tp->t_state == TCPS_TIME_WAIT)) &&
            tcp_strict_rfc1948 == 0)
#ifdef __APPLE__
        { return RandomULong(); }
#else
        { return arc4random(); }
#endif
        getmicrotime(&timenow);

        /* Seed if this is the first use, reseed if requested. */
        if ((isn_last_reseed == 0) ||
            ((tcp_strict_rfc1948 == 0) && (tcp_isn_reseed_interval > 0) &&
            (((u_int)isn_last_reseed + (u_int)tcp_isn_reseed_interval * hz)
            < (u_int)timenow.tv_sec))) {
#ifdef __APPLE__
                read_frandom(&isn_secret, sizeof(isn_secret));
#else
                read_random_unlimited(&isn_secret, sizeof(isn_secret));
#endif
                isn_last_reseed = timenow.tv_sec;
        }

        /* Compute the md5 hash and return the ISN. */
        MD5Init(&isn_ctx);
        MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_fport,
            sizeof(u_short));
        MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_lport,
            sizeof(u_short));
#if INET6
        if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) {
                MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->in6p_faddr,
                    sizeof(struct in6_addr));
                MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->in6p_laddr,
                    sizeof(struct in6_addr));
        } else
#endif
        {
                MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_faddr,
                    sizeof(struct in_addr));
                MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_laddr,
                    sizeof(struct in_addr));
        }
        MD5Update(&isn_ctx, (u_char *) &isn_secret, sizeof(isn_secret));
        MD5Final((u_char *) &md5_buffer, &isn_ctx);
        new_isn = (tcp_seq) md5_buffer[0];
        new_isn += timenow.tv_sec * (ISN_BYTES_PER_SECOND / hz);
        return new_isn;
}


/*
 * When a specific ICMP unreachable message is received and the
 * connection state is SYN-SENT, drop the connection.  This behavior
 * is controlled by the icmp_may_rst sysctl.
 */
void
tcp_drop_syn_sent(struct inpcb *inp, int errno)
{
        struct tcpcb *tp = intotcpcb(inp);

        if (tp && tp->t_state == TCPS_SYN_SENT) {
                tcp_drop(tp, errno);
        }
}

/*
 * When `need fragmentation' ICMP is received, update our idea of the MSS
 * based on the new value in the route.  Also nudge TCP to send something,
 * since we know the packet we just sent was dropped.
 * This duplicates some code in the tcp_mss() function in tcp_input.c.
 */
void
tcp_mtudisc(
        struct inpcb *inp,
        __unused int errno
        )
{
        struct tcpcb *tp = intotcpcb(inp);
        struct rtentry *rt;
        struct rmxp_tao *taop;
        struct socket *so = inp->inp_socket;
        int offered;
        int mss;
        u_int32_t mtu;
        u_int32_t protoHdrOverhead = sizeof(struct tcpiphdr);
#if INET6
        int isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0;

        /*
         * Nothing left to send after the socket is defunct or TCP is in the closed state
         */
        if ((so->so_state & SS_DEFUNCT) || (tp != NULL && tp->t_state == TCPS_CLOSED)) {
                return;
        }

        if (isipv6) {
                protoHdrOverhead = sizeof(struct ip6_hdr) +
                    sizeof(struct tcphdr);
        }
#endif /* INET6 */

        if (tp != NULL) {
#if INET6
                if (isipv6) {
                        rt = tcp_rtlookup6(inp, IFSCOPE_NONE);
                } else
#endif /* INET6 */
                rt = tcp_rtlookup(inp, IFSCOPE_NONE);
                if (!rt || !rt->rt_rmx.rmx_mtu) {
                        tp->t_maxopd = tp->t_maxseg =
#if INET6
                            isipv6 ? tcp_v6mssdflt :
#endif /* INET6 */
                            tcp_mssdflt;

                        /* Route locked during lookup above */
                        if (rt != NULL) {
                                RT_UNLOCK(rt);
                        }
                        return;
                }
                taop = rmx_taop(rt->rt_rmx);
                offered = taop->tao_mssopt;
                mtu = rt->rt_rmx.rmx_mtu;

                /* Route locked during lookup above */
                RT_UNLOCK(rt);

#if NECP
                // Adjust MTU if necessary.
                mtu = necp_socket_get_effective_mtu(inp, mtu);
#endif /* NECP */
                mss = mtu - protoHdrOverhead;

                if (offered) {
                        mss = min(mss, offered);
                }
                /*
                 * XXX - The above conditional probably violates the TCP
                 * spec.  The problem is that, since we don't know the
                 * other end's MSS, we are supposed to use a conservative
                 * default.  But, if we do that, then MTU discovery will
                 * never actually take place, because the conservative
                 * default is much less than the MTUs typically seen
                 * on the Internet today.  For the moment, we'll sweep
                 * this under the carpet.
                 *
                 * The conservative default might not actually be a problem
                 * if the only case this occurs is when sending an initial
                 * SYN with options and data to a host we've never talked
                 * to before.  Then, they will reply with an MSS value which
                 * will get recorded and the new parameters should get
                 * recomputed.  For Further Study.
                 */
                if (tp->t_maxopd <= mss) {
                        return;
                }
                tp->t_maxopd = mss;

                if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP &&
                    (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP) {
                        mss -= TCPOLEN_TSTAMP_APPA;
                }

#if MPTCP
                mss -= mptcp_adj_mss(tp, TRUE);
#endif
                if (so->so_snd.sb_hiwat < mss) {
                        mss = so->so_snd.sb_hiwat;
                }

                tp->t_maxseg = mss;

                ASSERT(tp->t_maxseg);

                /*
                 * Reset the slow-start flight size as it may depends on the
                 * new MSS
                 */
                if (CC_ALGO(tp)->cwnd_init != NULL) {
                        CC_ALGO(tp)->cwnd_init(tp);
                }
                tcpstat.tcps_mturesent++;
                tp->t_rtttime = 0;
                tp->snd_nxt = tp->snd_una;
                tcp_output(tp);
        }
}

/*
 * Look-up the routing entry to the peer of this inpcb.  If no route
 * is found and it cannot be allocated the return NULL.  This routine
 * is called by TCP routines that access the rmx structure and by tcp_mss
 * to get the interface MTU.  If a route is found, this routine will
 * hold the rtentry lock; the caller is responsible for unlocking.
 */
struct rtentry *
tcp_rtlookup(struct inpcb *inp, unsigned int input_ifscope)
{
        struct route *ro;
        struct rtentry *rt;
        struct tcpcb *tp;

        LCK_MTX_ASSERT(rnh_lock, LCK_MTX_ASSERT_NOTOWNED);

        ro = &inp->inp_route;
        if ((rt = ro->ro_rt) != NULL) {
                RT_LOCK(rt);
        }

        if (ROUTE_UNUSABLE(ro)) {
                if (rt != NULL) {
                        RT_UNLOCK(rt);
                        rt = NULL;
                }
                ROUTE_RELEASE(ro);
                /* No route yet, so try to acquire one */
                if (inp->inp_faddr.s_addr != INADDR_ANY) {
                        unsigned int ifscope;

                        ro->ro_dst.sa_family = AF_INET;
                        ro->ro_dst.sa_len = sizeof(struct sockaddr_in);
                        ((struct sockaddr_in *)(void *)&ro->ro_dst)->sin_addr =
                            inp->inp_faddr;

                        /*
                         * If the socket was bound to an interface, then
                         * the bound-to-interface takes precedence over
                         * the inbound interface passed in by the caller
                         * (if we get here as part of the output path then
                         * input_ifscope is IFSCOPE_NONE).
                         */
                        ifscope = (inp->inp_flags & INP_BOUND_IF) ?
                            inp->inp_boundifp->if_index : input_ifscope;

                        rtalloc_scoped(ro, ifscope);
                        if ((rt = ro->ro_rt) != NULL) {
                                RT_LOCK(rt);
                        }
                }
        }
        if (rt != NULL) {
                RT_LOCK_ASSERT_HELD(rt);
        }

        /*
         * Update MTU discovery determination. Don't do it if:
         *      1) it is disabled via the sysctl
         *      2) the route isn't up
         *      3) the MTU is locked (if it is, then discovery has been
         *         disabled)
         */

        tp = intotcpcb(inp);

        if (!path_mtu_discovery || ((rt != NULL) &&
            (!(rt->rt_flags & RTF_UP) || (rt->rt_rmx.rmx_locks & RTV_MTU)))) {
                tp->t_flags &= ~TF_PMTUD;
        } else {
                tp->t_flags |= TF_PMTUD;
        }

        if (rt != NULL && rt->rt_ifp != NULL) {
                somultipages(inp->inp_socket,
                    (rt->rt_ifp->if_hwassist & IFNET_MULTIPAGES));
                tcp_set_tso(tp, rt->rt_ifp);
                soif2kcl(inp->inp_socket,
                    (rt->rt_ifp->if_eflags & IFEF_2KCL));
                tcp_set_ecn(tp, rt->rt_ifp);
                if (inp->inp_last_outifp == NULL) {
                        inp->inp_last_outifp = rt->rt_ifp;
                }
        }

        /* Note if the peer is local */
        if (rt != NULL && !(rt->rt_ifp->if_flags & IFF_POINTOPOINT) &&
            (rt->rt_gateway->sa_family == AF_LINK ||
            rt->rt_ifp->if_flags & IFF_LOOPBACK ||
            in_localaddr(inp->inp_faddr))) {
                tp->t_flags |= TF_LOCAL;
        }

        /*
         * Caller needs to call RT_UNLOCK(rt).
         */
        return rt;
}

#if INET6
struct rtentry *
tcp_rtlookup6(struct inpcb *inp, unsigned int input_ifscope)
{
        struct route_in6 *ro6;
        struct rtentry *rt;
        struct tcpcb *tp;

        LCK_MTX_ASSERT(rnh_lock, LCK_MTX_ASSERT_NOTOWNED);

        ro6 = &inp->in6p_route;
        if ((rt = ro6->ro_rt) != NULL) {
                RT_LOCK(rt);
        }

        if (ROUTE_UNUSABLE(ro6)) {
                if (rt != NULL) {
                        RT_UNLOCK(rt);
                        rt = NULL;
                }
                ROUTE_RELEASE(ro6);
                /* No route yet, so try to acquire one */
                if (!IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_faddr)) {
                        struct sockaddr_in6 *dst6;
                        unsigned int ifscope;

                        dst6 = (struct sockaddr_in6 *)&ro6->ro_dst;
                        dst6->sin6_family = AF_INET6;
                        dst6->sin6_len = sizeof(*dst6);
                        dst6->sin6_addr = inp->in6p_faddr;

                        /*
                         * If the socket was bound to an interface, then
                         * the bound-to-interface takes precedence over
                         * the inbound interface passed in by the caller
                         * (if we get here as part of the output path then
                         * input_ifscope is IFSCOPE_NONE).
                         */
                        ifscope = (inp->inp_flags & INP_BOUND_IF) ?
                            inp->inp_boundifp->if_index : input_ifscope;

                        rtalloc_scoped((struct route *)ro6, ifscope);
                        if ((rt = ro6->ro_rt) != NULL) {
                                RT_LOCK(rt);
                        }
                }
        }
        if (rt != NULL) {
                RT_LOCK_ASSERT_HELD(rt);
        }

        /*
         * Update path MTU Discovery determination
         * while looking up the route:
         *  1) we have a valid route to the destination
         *  2) the MTU is not locked (if it is, then discovery has been
         *    disabled)
         */


        tp = intotcpcb(inp);

        /*
         * Update MTU discovery determination. Don't do it if:
         *      1) it is disabled via the sysctl
         *      2) the route isn't up
         *      3) the MTU is locked (if it is, then discovery has been
         *         disabled)
         */

        if (!path_mtu_discovery || ((rt != NULL) &&
            (!(rt->rt_flags & RTF_UP) || (rt->rt_rmx.rmx_locks & RTV_MTU)))) {
                tp->t_flags &= ~TF_PMTUD;
        } else {
                tp->t_flags |= TF_PMTUD;
        }

        if (rt != NULL && rt->rt_ifp != NULL) {
                somultipages(inp->inp_socket,
                    (rt->rt_ifp->if_hwassist & IFNET_MULTIPAGES));
                tcp_set_tso(tp, rt->rt_ifp);
                soif2kcl(inp->inp_socket,
                    (rt->rt_ifp->if_eflags & IFEF_2KCL));
                tcp_set_ecn(tp, rt->rt_ifp);
                if (inp->inp_last_outifp == NULL) {
                        inp->inp_last_outifp = rt->rt_ifp;
                }

                /* Note if the peer is local */
                if (!(rt->rt_ifp->if_flags & IFF_POINTOPOINT) &&
                    (IN6_IS_ADDR_LOOPBACK(&inp->in6p_faddr) ||
                    IN6_IS_ADDR_LINKLOCAL(&inp->in6p_faddr) ||
                    rt->rt_gateway->sa_family == AF_LINK ||
                    in6_localaddr(&inp->in6p_faddr))) {
                        tp->t_flags |= TF_LOCAL;
                }
        }

        /*
         * Caller needs to call RT_UNLOCK(rt).
         */
        return rt;
}
#endif /* INET6 */

#if IPSEC
/* compute ESP/AH header size for TCP, including outer IP header. */
size_t
ipsec_hdrsiz_tcp(struct tcpcb *tp)
{
        struct inpcb *inp;
        struct mbuf *m;
        size_t hdrsiz;
        struct ip *ip;
#if INET6
        struct ip6_hdr *ip6 = NULL;
#endif /* INET6 */
        struct tcphdr *th;

        if ((tp == NULL) || ((inp = tp->t_inpcb) == NULL)) {
                return 0;
        }
        MGETHDR(m, M_DONTWAIT, MT_DATA);        /* MAC-OK */
        if (!m) {
                return 0;
        }

#if INET6
        if ((inp->inp_vflag & INP_IPV6) != 0) {
                ip6 = mtod(m, struct ip6_hdr *);
                th = (struct tcphdr *)(void *)(ip6 + 1);
                m->m_pkthdr.len = m->m_len =
                    sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
                tcp_fillheaders(tp, ip6, th);
                hdrsiz = ipsec6_hdrsiz(m, IPSEC_DIR_OUTBOUND, inp);
        } else
#endif /* INET6 */
        {
                ip = mtod(m, struct ip *);
                th = (struct tcphdr *)(ip + 1);
                m->m_pkthdr.len = m->m_len = sizeof(struct tcpiphdr);
                tcp_fillheaders(tp, ip, th);
                hdrsiz = ipsec4_hdrsiz(m, IPSEC_DIR_OUTBOUND, inp);
        }
        m_free(m);
        return hdrsiz;
}
#endif /* IPSEC */

/*
 * Return a pointer to the cached information about the remote host.
 * The cached information is stored in the protocol specific part of
 * the route metrics.
 */
struct rmxp_tao *
tcp_gettaocache(struct inpcb *inp)
{
        struct rtentry *rt;
        struct rmxp_tao *taop;

#if INET6
        if ((inp->inp_vflag & INP_IPV6) != 0) {
                rt = tcp_rtlookup6(inp, IFSCOPE_NONE);
        } else
#endif /* INET6 */
        rt = tcp_rtlookup(inp, IFSCOPE_NONE);

        /* Make sure this is a host route and is up. */
        if (rt == NULL ||
            (rt->rt_flags & (RTF_UP | RTF_HOST)) != (RTF_UP | RTF_HOST)) {
                /* Route locked during lookup above */
                if (rt != NULL) {
                        RT_UNLOCK(rt);
                }
                return NULL;
        }

        taop = rmx_taop(rt->rt_rmx);
        /* Route locked during lookup above */
        RT_UNLOCK(rt);
        return taop;
}

/*
 * Clear all the TAO cache entries, called from tcp_init.
 *
 * XXX
 * This routine is just an empty one, because we assume that the routing
 * routing tables are initialized at the same time when TCP, so there is
 * nothing in the cache left over.
 */
static void
tcp_cleartaocache(void)
{
}

int
tcp_lock(struct socket *so, int refcount, void *lr)
{
        void *lr_saved;

        if (lr == NULL) {
                lr_saved = __builtin_return_address(0);
        } else {
                lr_saved = lr;
        }

retry:
        if (so->so_pcb != NULL) {
                if (so->so_flags & SOF_MP_SUBFLOW) {
                        struct mptcb *mp_tp = tptomptp(sototcpcb(so));
                        struct socket *mp_so = mptetoso(mp_tp->mpt_mpte);

                        socket_lock(mp_so, refcount);

                        /*
                         * Check if we became non-MPTCP while waiting for the lock.
                         * If yes, we have to retry to grab the right lock.
                         */
                        if (!(so->so_flags & SOF_MP_SUBFLOW)) {
                                socket_unlock(mp_so, refcount);
                                goto retry;
                        }
                } else {
                        lck_mtx_lock(&((struct inpcb *)so->so_pcb)->inpcb_mtx);

                        if (so->so_flags & SOF_MP_SUBFLOW) {
                                /*
                                 * While waiting for the lock, we might have
                                 * become MPTCP-enabled (see mptcp_subflow_socreate).
                                 */
                                lck_mtx_unlock(&((struct inpcb *)so->so_pcb)->inpcb_mtx);
                                goto retry;
                        }
                }
        } else {
                panic("tcp_lock: so=%p NO PCB! lr=%p lrh= %s\n",
                    so, lr_saved, solockhistory_nr(so));
                /* NOTREACHED */
        }

        if (so->so_usecount < 0) {
                panic("tcp_lock: so=%p so_pcb=%p lr=%p ref=%x lrh= %s\n",
                    so, so->so_pcb, lr_saved, so->so_usecount,
                    solockhistory_nr(so));
                /* NOTREACHED */
        }
        if (refcount) {
                so->so_usecount++;
        }
        so->lock_lr[so->next_lock_lr] = lr_saved;
        so->next_lock_lr = (so->next_lock_lr + 1) % SO_LCKDBG_MAX;
        return 0;
}

int
tcp_unlock(struct socket *so, int refcount, void *lr)
{
        void *lr_saved;

        if (lr == NULL) {
                lr_saved = __builtin_return_address(0);
        } else {
                lr_saved = lr;
        }

#ifdef MORE_TCPLOCK_DEBUG
        printf("tcp_unlock: so=0x%llx sopcb=0x%llx lock=0x%llx ref=%x "
            "lr=0x%llx\n", (uint64_t)VM_KERNEL_ADDRPERM(so),
            (uint64_t)VM_KERNEL_ADDRPERM(so->so_pcb),
            (uint64_t)VM_KERNEL_ADDRPERM(&(sotoinpcb(so)->inpcb_mtx)),
            so->so_usecount, (uint64_t)VM_KERNEL_ADDRPERM(lr_saved));
#endif
        if (refcount) {
                so->so_usecount--;
        }

        if (so->so_usecount < 0) {
                panic("tcp_unlock: so=%p usecount=%x lrh= %s\n",
                    so, so->so_usecount, solockhistory_nr(so));
                /* NOTREACHED */
        }
        if (so->so_pcb == NULL) {
                panic("tcp_unlock: so=%p NO PCB usecount=%x lr=%p lrh= %s\n",
                    so, so->so_usecount, lr_saved, solockhistory_nr(so));
                /* NOTREACHED */
        } else {
                so->unlock_lr[so->next_unlock_lr] = lr_saved;
                so->next_unlock_lr = (so->next_unlock_lr + 1) % SO_LCKDBG_MAX;

                if (so->so_flags & SOF_MP_SUBFLOW) {
                        struct mptcb *mp_tp = tptomptp(sototcpcb(so));
                        struct socket *mp_so = mptetoso(mp_tp->mpt_mpte);

                        socket_lock_assert_owned(mp_so);

                        socket_unlock(mp_so, refcount);
                } else {
                        LCK_MTX_ASSERT(&((struct inpcb *)so->so_pcb)->inpcb_mtx,
                            LCK_MTX_ASSERT_OWNED);
                        lck_mtx_unlock(&((struct inpcb *)so->so_pcb)->inpcb_mtx);
                }
        }
        return 0;
}

lck_mtx_t *
tcp_getlock(struct socket *so, int flags)
{
        struct inpcb *inp = sotoinpcb(so);

        if (so->so_pcb) {
                if (so->so_usecount < 0) {
                        panic("tcp_getlock: so=%p usecount=%x lrh= %s\n",
                            so, so->so_usecount, solockhistory_nr(so));
                }

                if (so->so_flags & SOF_MP_SUBFLOW) {
                        struct mptcb *mp_tp = tptomptp(sototcpcb(so));
                        struct socket *mp_so = mptetoso(mp_tp->mpt_mpte);

                        return mp_so->so_proto->pr_getlock(mp_so, flags);
                } else {
                        return &inp->inpcb_mtx;
                }
        } else {
                panic("tcp_getlock: so=%p NULL so_pcb %s\n",
                    so, solockhistory_nr(so));
                return so->so_proto->pr_domain->dom_mtx;
        }
}

/*
 * Determine if we can grow the recieve socket buffer to avoid sending
 * a zero window update to the peer. We allow even socket buffers that
 * have fixed size (set by the application) to grow if the resource
 * constraints are met. They will also be trimmed after the application
 * reads data.
 */
static void
tcp_sbrcv_grow_rwin(struct tcpcb *tp, struct sockbuf *sb)
{
        u_int32_t rcvbufinc = tp->t_maxseg << 4;
        u_int32_t rcvbuf = sb->sb_hiwat;
        struct socket *so = tp->t_inpcb->inp_socket;

        if (tcp_recv_bg == 1 || IS_TCP_RECV_BG(so)) {
                return;
        }
        /*
         * If message delivery is enabled, do not count
         * unordered bytes in receive buffer towards hiwat
         */
        if (so->so_flags & SOF_ENABLE_MSGS) {
                rcvbuf = rcvbuf - so->so_msg_state->msg_uno_bytes;
        }

        if (tcp_do_autorcvbuf == 1 &&
            tcp_cansbgrow(sb) &&
            (tp->t_flags & TF_SLOWLINK) == 0 &&
            (so->so_flags1 & SOF1_EXTEND_BK_IDLE_WANTED) == 0 &&
            (rcvbuf - sb->sb_cc) < rcvbufinc &&
            rcvbuf < tcp_autorcvbuf_max &&
            (sb->sb_idealsize > 0 &&
            sb->sb_hiwat <= (sb->sb_idealsize + rcvbufinc))) {
                sbreserve(sb,
                    min((sb->sb_hiwat + rcvbufinc), tcp_autorcvbuf_max));
        }
}

int32_t
tcp_sbspace(struct tcpcb *tp)
{
        struct socket *so = tp->t_inpcb->inp_socket;
        struct sockbuf *sb = &so->so_rcv;
        u_int32_t rcvbuf;
        int32_t space;
        int32_t pending = 0;

        if (so->so_flags & SOF_MP_SUBFLOW) {
                /* We still need to grow TCP's buffer to have a BDP-estimate */
                tcp_sbrcv_grow_rwin(tp, sb);

                return mptcp_sbspace(tptomptp(tp));
        }

        tcp_sbrcv_grow_rwin(tp, sb);

        /* hiwat might have changed */
        rcvbuf = sb->sb_hiwat;

        /*
         * If message delivery is enabled, do not count
         * unordered bytes in receive buffer towards hiwat mark.
         * This value is used to return correct rwnd that does
         * not reflect the extra unordered bytes added to the
         * receive socket buffer.
         */
        if (so->so_flags & SOF_ENABLE_MSGS) {
                rcvbuf = rcvbuf - so->so_msg_state->msg_uno_bytes;
        }

        space =  ((int32_t) imin((rcvbuf - sb->sb_cc),
            (sb->sb_mbmax - sb->sb_mbcnt)));
        if (space < 0) {
                space = 0;
        }

#if CONTENT_FILTER
        /* Compensate for data being processed by content filters */
        pending = cfil_sock_data_space(sb);
#endif /* CONTENT_FILTER */
        if (pending > space) {
                space = 0;
        } else {
                space -= pending;
        }

        /*
         * Avoid increasing window size if the current window
         * is already very low, we could be in "persist" mode and
         * we could break some apps (see rdar://5409343)
         */

        if (space < tp->t_maxseg) {
                return space;
        }

        /* Clip window size for slower link */

        if (((tp->t_flags & TF_SLOWLINK) != 0) && slowlink_wsize > 0) {
                return imin(space, slowlink_wsize);
        }

        return space;
}
/*
 * Checks TCP Segment Offloading capability for a given connection
 * and interface pair.
 */
void
tcp_set_tso(struct tcpcb *tp, struct ifnet *ifp)
{
#if INET6
        struct inpcb *inp;
        int isipv6;
#endif /* INET6 */
#if MPTCP
        /*
         * We can't use TSO if this tcpcb belongs to an MPTCP session.
         */
        if (tp->t_mpflags & TMPF_MPTCP_TRUE) {
                tp->t_flags &= ~TF_TSO;
                return;
        }
#endif
#if INET6
        inp = tp->t_inpcb;
        isipv6 = (inp->inp_vflag & INP_IPV6) != 0;

        if (isipv6) {
                if (ifp && (ifp->if_hwassist & IFNET_TSO_IPV6)) {
                        tp->t_flags |= TF_TSO;
                        if (ifp->if_tso_v6_mtu != 0) {
                                tp->tso_max_segment_size = ifp->if_tso_v6_mtu;
                        } else {
                                tp->tso_max_segment_size = TCP_MAXWIN;
                        }
                } else {
                        tp->t_flags &= ~TF_TSO;
                }
        } else
#endif /* INET6 */

        {
                if (ifp && (ifp->if_hwassist & IFNET_TSO_IPV4)) {
                        tp->t_flags |= TF_TSO;
                        if (ifp->if_tso_v4_mtu != 0) {
                                tp->tso_max_segment_size = ifp->if_tso_v4_mtu;
                        } else {
                                tp->tso_max_segment_size = TCP_MAXWIN;
                        }
                } else {
                        tp->t_flags &= ~TF_TSO;
                }
        }
}

#define TIMEVAL_TO_TCPHZ(_tv_) ((_tv_).tv_sec * TCP_RETRANSHZ + \
        (_tv_).tv_usec / TCP_RETRANSHZ_TO_USEC)

/*
 * Function to calculate the tcp clock. The tcp clock will get updated
 * at the boundaries of the tcp layer. This is done at 3 places:
 * 1. Right before processing an input tcp packet
 * 2. Whenever a connection wants to access the network using tcp_usrreqs
 * 3. When a tcp timer fires or before tcp slow timeout
 *
 */

void
calculate_tcp_clock(void)
{
        struct timeval tv = tcp_uptime;
        struct timeval interval = {.tv_sec = 0, .tv_usec = TCP_RETRANSHZ_TO_USEC};
        struct timeval now, hold_now;
        uint32_t incr = 0;

        microuptime(&now);

        /*
         * Update coarse-grained networking timestamp (in sec.); the idea
         * is to update the counter returnable via net_uptime() when
         * we read time.
         */
        net_update_uptime_with_time(&now);

        timevaladd(&tv, &interval);
        if (timevalcmp(&now, &tv, >)) {
                /* time to update the clock */
                lck_spin_lock(tcp_uptime_lock);
                if (timevalcmp(&tcp_uptime, &now, >=)) {
                        /* clock got updated while waiting for the lock */
                        lck_spin_unlock(tcp_uptime_lock);
                        return;
                }

                microuptime(&now);
                hold_now = now;
                tv = tcp_uptime;
                timevalsub(&now, &tv);

                incr = TIMEVAL_TO_TCPHZ(now);
                if (incr > 0) {
                        tcp_uptime = hold_now;
                        tcp_now += incr;
                }

                lck_spin_unlock(tcp_uptime_lock);
        }
}

/*
 * Compute receive window scaling that we are going to request
 * for this connection based on  sb_hiwat. Try to leave some
 * room to potentially increase the window size upto a maximum
 * defined by the constant tcp_autorcvbuf_max.
 */
void
tcp_set_max_rwinscale(struct tcpcb *tp, struct socket *so, struct ifnet *ifp)
{
        uint32_t maxsockbufsize;
        uint32_t rcvbuf_max;

        if (!tcp_do_rfc1323) {
                tp->request_r_scale = 0;
                return;
        }

        /*
         * When we start a connection and don't know about the interface, set
         * the scaling factor simply to the max - we can always announce less.
         */
        if (!ifp || (IFNET_IS_CELLULAR(ifp) && (ifp->if_eflags & IFEF_3CA))) {
                rcvbuf_max = (tcp_autorcvbuf_max << 1);
        } else {
                rcvbuf_max = tcp_autorcvbuf_max;
        }

        tp->request_r_scale = max(tcp_win_scale, tp->request_r_scale);
        maxsockbufsize = ((so->so_rcv.sb_flags & SB_USRSIZE) != 0) ?
            so->so_rcv.sb_hiwat : rcvbuf_max;

        while (tp->request_r_scale < TCP_MAX_WINSHIFT &&
            (TCP_MAXWIN << tp->request_r_scale) < maxsockbufsize) {
                tp->request_r_scale++;
        }
        tp->request_r_scale = min(tp->request_r_scale, TCP_MAX_WINSHIFT);
}

int
tcp_notsent_lowat_check(struct socket *so)
{
        struct inpcb *inp = sotoinpcb(so);
        struct tcpcb *tp = NULL;
        int notsent = 0;

        if (inp != NULL) {
                tp = intotcpcb(inp);
        }

        if (tp == NULL) {
                return 0;
        }

        notsent = so->so_snd.sb_cc -
            (tp->snd_nxt - tp->snd_una);

        /*
         * When we send a FIN or SYN, not_sent can be negative.
         * In that case also we need to send a write event to the
         * process if it is waiting. In the FIN case, it will
         * get an error from send because cantsendmore will be set.
         */
        if (notsent <= tp->t_notsent_lowat) {
                return 1;
        }

        /*
         * When Nagle's algorithm is not disabled, it is better
         * to wakeup the client until there is atleast one
         * maxseg of data to write.
         */
        if ((tp->t_flags & TF_NODELAY) == 0 &&
            notsent > 0 && notsent < tp->t_maxseg) {
                return 1;
        }
        return 0;
}

void
tcp_rxtseg_insert(struct tcpcb *tp, tcp_seq start, tcp_seq end)
{
        struct tcp_rxt_seg *rxseg = NULL, *prev = NULL, *next = NULL;
        u_int32_t rxcount = 0;

        if (SLIST_EMPTY(&tp->t_rxt_segments)) {
                tp->t_dsack_lastuna = tp->snd_una;
        }
        /*
         * First check if there is a segment already existing for this
         * sequence space.
         */

        SLIST_FOREACH(rxseg, &tp->t_rxt_segments, rx_link) {
                if (SEQ_GT(rxseg->rx_start, start)) {
                        break;
                }
                prev = rxseg;
        }
        next = rxseg;

        /* check if prev seg is for this sequence */
        if (prev != NULL && SEQ_LEQ(prev->rx_start, start) &&
            SEQ_GEQ(prev->rx_end, end)) {
                prev->rx_count++;
                return;
        }

        /*
         * There are a couple of possibilities at this point.
         * 1. prev overlaps with the beginning of this sequence
         * 2. next overlaps with the end of this sequence
         * 3. there is no overlap.
         */

        if (prev != NULL && SEQ_GT(prev->rx_end, start)) {
                if (prev->rx_start == start && SEQ_GT(end, prev->rx_end)) {
                        start = prev->rx_end + 1;
                        prev->rx_count++;
                } else {
                        prev->rx_end = (start - 1);
                        rxcount = prev->rx_count;
                }
        }

        if (next != NULL && SEQ_LT(next->rx_start, end)) {
                if (SEQ_LEQ(next->rx_end, end)) {
                        end = next->rx_start - 1;
                        next->rx_count++;
                } else {
                        next->rx_start = end + 1;
                        rxcount = next->rx_count;
                }
        }
        if (!SEQ_LT(start, end)) {
                return;
        }

        rxseg = (struct tcp_rxt_seg *) zalloc(tcp_rxt_seg_zone);
        if (rxseg == NULL) {
                return;
        }
        bzero(rxseg, sizeof(*rxseg));
        rxseg->rx_start = start;
        rxseg->rx_end = end;
        rxseg->rx_count = rxcount + 1;

        if (prev != NULL) {
                SLIST_INSERT_AFTER(prev, rxseg, rx_link);
        } else {
                SLIST_INSERT_HEAD(&tp->t_rxt_segments, rxseg, rx_link);
        }
}

struct tcp_rxt_seg *
tcp_rxtseg_find(struct tcpcb *tp, tcp_seq start, tcp_seq end)
{
        struct tcp_rxt_seg *rxseg;
        if (SLIST_EMPTY(&tp->t_rxt_segments)) {
                return NULL;
        }

        SLIST_FOREACH(rxseg, &tp->t_rxt_segments, rx_link) {
                if (SEQ_LEQ(rxseg->rx_start, start) &&
                    SEQ_GEQ(rxseg->rx_end, end)) {
                        return rxseg;
                }
                if (SEQ_GT(rxseg->rx_start, start)) {
                        break;
                }
        }
        return NULL;
}

void
tcp_rxtseg_clean(struct tcpcb *tp)
{
        struct tcp_rxt_seg *rxseg, *next;

        SLIST_FOREACH_SAFE(rxseg, &tp->t_rxt_segments, rx_link, next) {
                SLIST_REMOVE(&tp->t_rxt_segments, rxseg,
                    tcp_rxt_seg, rx_link);
                zfree(tcp_rxt_seg_zone, rxseg);
        }
        tp->t_dsack_lastuna = tp->snd_max;
}

boolean_t
tcp_rxtseg_detect_bad_rexmt(struct tcpcb *tp, tcp_seq th_ack)
{
        boolean_t bad_rexmt;
        struct tcp_rxt_seg *rxseg;

        if (SLIST_EMPTY(&tp->t_rxt_segments)) {
                return FALSE;
        }

        /*
         * If all of the segments in this window are not cumulatively
         * acknowledged, then there can still be undetected packet loss.
         * Do not restore congestion window in that case.
         */
        if (SEQ_LT(th_ack, tp->snd_recover)) {
                return FALSE;
        }

        bad_rexmt = TRUE;
        SLIST_FOREACH(rxseg, &tp->t_rxt_segments, rx_link) {
                if (rxseg->rx_count > 1 ||
                    !(rxseg->rx_flags & TCP_RXT_SPURIOUS)) {
                        bad_rexmt = FALSE;
                        break;
                }
        }
        return bad_rexmt;
}

boolean_t
tcp_rxtseg_dsack_for_tlp(struct tcpcb *tp)
{
        boolean_t dsack_for_tlp = FALSE;
        struct tcp_rxt_seg *rxseg;
        if (SLIST_EMPTY(&tp->t_rxt_segments)) {
                return FALSE;
        }

        SLIST_FOREACH(rxseg, &tp->t_rxt_segments, rx_link) {
                if (rxseg->rx_count == 1 &&
                    SLIST_NEXT(rxseg, rx_link) == NULL &&
                    (rxseg->rx_flags & TCP_RXT_DSACK_FOR_TLP)) {
                        dsack_for_tlp = TRUE;
                        break;
                }
        }
        return dsack_for_tlp;
}

u_int32_t
tcp_rxtseg_total_size(struct tcpcb *tp)
{
        struct tcp_rxt_seg *rxseg;
        u_int32_t total_size = 0;

        SLIST_FOREACH(rxseg, &tp->t_rxt_segments, rx_link) {
                total_size += (rxseg->rx_end - rxseg->rx_start) + 1;
        }
        return total_size;
}

void
tcp_get_connectivity_status(struct tcpcb *tp,
    struct tcp_conn_status *connstatus)
{
        if (tp == NULL || connstatus == NULL) {
                return;
        }
        bzero(connstatus, sizeof(*connstatus));
        if (tp->t_rxtshift >= TCP_CONNECTIVITY_PROBES_MAX) {
                if (TCPS_HAVEESTABLISHED(tp->t_state)) {
                        connstatus->write_probe_failed = 1;
                } else {
                        connstatus->conn_probe_failed = 1;
                }
        }
        if (tp->t_rtimo_probes >= TCP_CONNECTIVITY_PROBES_MAX) {
                connstatus->read_probe_failed = 1;
        }
        if (tp->t_inpcb != NULL && tp->t_inpcb->inp_last_outifp != NULL &&
            (tp->t_inpcb->inp_last_outifp->if_eflags & IFEF_PROBE_CONNECTIVITY)) {
                connstatus->probe_activated = 1;
        }
}

boolean_t
tfo_enabled(const struct tcpcb *tp)
{
        return (tp->t_flagsext & TF_FASTOPEN)? TRUE : FALSE;
}

void
tcp_disable_tfo(struct tcpcb *tp)
{
        tp->t_flagsext &= ~TF_FASTOPEN;
}

static struct mbuf *
tcp_make_keepalive_frame(struct tcpcb *tp, struct ifnet *ifp,
    boolean_t is_probe)
{
        struct inpcb *inp = tp->t_inpcb;
        struct tcphdr *th;
        u_int8_t *data;
        int win = 0;
        struct mbuf *m;

        /*
         * The code assumes the IP + TCP headers fit in an mbuf packet header
         */
        _CASSERT(sizeof(struct ip) + sizeof(struct tcphdr) <= _MHLEN);
        _CASSERT(sizeof(struct ip6_hdr) + sizeof(struct tcphdr) <= _MHLEN);

        MGETHDR(m, M_WAIT, MT_HEADER);
        if (m == NULL) {
                return NULL;
        }
        m->m_pkthdr.pkt_proto = IPPROTO_TCP;

        data = mbuf_datastart(m);

        if (inp->inp_vflag & INP_IPV4) {
                bzero(data, sizeof(struct ip) + sizeof(struct tcphdr));
                th = (struct tcphdr *)(void *) (data + sizeof(struct ip));
                m->m_len = sizeof(struct ip) + sizeof(struct tcphdr);
                m->m_pkthdr.len = m->m_len;
        } else {
                VERIFY(inp->inp_vflag & INP_IPV6);

                bzero(data, sizeof(struct ip6_hdr)
                    + sizeof(struct tcphdr));
                th = (struct tcphdr *)(void *)(data + sizeof(struct ip6_hdr));
                m->m_len = sizeof(struct ip6_hdr) +
                    sizeof(struct tcphdr);
                m->m_pkthdr.len = m->m_len;
        }

        tcp_fillheaders(tp, data, th);

        if (inp->inp_vflag & INP_IPV4) {
                struct ip *ip;

                ip = (__typeof__(ip))(void *)data;

                ip->ip_id = rfc6864 ? 0 : ip_randomid();
                ip->ip_off = htons(IP_DF);
                ip->ip_len = htons(sizeof(struct ip) + sizeof(struct tcphdr));
                ip->ip_ttl = inp->inp_ip_ttl;
                ip->ip_tos |= (inp->inp_ip_tos & ~IPTOS_ECN_MASK);
                ip->ip_sum = in_cksum_hdr(ip);
        } else {
                struct ip6_hdr *ip6;

                ip6 = (__typeof__(ip6))(void *)data;

                ip6->ip6_plen = htons(sizeof(struct tcphdr));
                ip6->ip6_hlim = in6_selecthlim(inp, ifp);
                ip6->ip6_flow = ip6->ip6_flow & ~IPV6_FLOW_ECN_MASK;

                if (IN6_IS_SCOPE_EMBED(&ip6->ip6_src)) {
                        ip6->ip6_src.s6_addr16[1] = 0;
                }
                if (IN6_IS_SCOPE_EMBED(&ip6->ip6_dst)) {
                        ip6->ip6_dst.s6_addr16[1] = 0;
                }
        }
        th->th_flags = TH_ACK;

        win = tcp_sbspace(tp);
        if (win > ((int32_t)TCP_MAXWIN << tp->rcv_scale)) {
                win = (int32_t)TCP_MAXWIN << tp->rcv_scale;
        }
        th->th_win = htons((u_short) (win >> tp->rcv_scale));

        if (is_probe) {
                th->th_seq = htonl(tp->snd_una - 1);
        } else {
                th->th_seq = htonl(tp->snd_una);
        }
        th->th_ack = htonl(tp->rcv_nxt);

        /* Force recompute TCP checksum to be the final value */
        th->th_sum = 0;
        if (inp->inp_vflag & INP_IPV4) {
                th->th_sum = inet_cksum(m, IPPROTO_TCP,
                    sizeof(struct ip), sizeof(struct tcphdr));
        } else {
                th->th_sum = inet6_cksum(m, IPPROTO_TCP,
                    sizeof(struct ip6_hdr), sizeof(struct tcphdr));
        }

        return m;
}

void
tcp_fill_keepalive_offload_frames(ifnet_t ifp,
    struct ifnet_keepalive_offload_frame *frames_array,
    u_int32_t frames_array_count, size_t frame_data_offset,
    u_int32_t *used_frames_count)
{
        struct inpcb *inp;
        inp_gen_t gencnt;
        u_int32_t frame_index = *used_frames_count;

        if (ifp == NULL || frames_array == NULL ||
            frames_array_count == 0 ||
            frame_index >= frames_array_count ||
            frame_data_offset >= IFNET_KEEPALIVE_OFFLOAD_FRAME_DATA_SIZE) {
                return;
        }

        /*
         * This function is called outside the regular TCP processing
         * so we need to update the TCP clock.
         */
        calculate_tcp_clock();

        lck_rw_lock_shared(tcbinfo.ipi_lock);
        gencnt = tcbinfo.ipi_gencnt;
        LIST_FOREACH(inp, tcbinfo.ipi_listhead, inp_list) {
                struct socket *so;
                struct ifnet_keepalive_offload_frame *frame;
                struct mbuf *m = NULL;
                struct tcpcb *tp = intotcpcb(inp);

                if (frame_index >= frames_array_count) {
                        break;
                }

                if (inp->inp_gencnt > gencnt ||
                    inp->inp_state == INPCB_STATE_DEAD) {
                        continue;
                }

                if ((so = inp->inp_socket) == NULL ||
                    (so->so_state & SS_DEFUNCT)) {
                        continue;
                }
                /*
                 * check for keepalive offload flag without socket
                 * lock to avoid a deadlock
                 */
                if (!(inp->inp_flags2 & INP2_KEEPALIVE_OFFLOAD)) {
                        continue;
                }

                if (!(inp->inp_vflag & (INP_IPV4 | INP_IPV6))) {
                        continue;
                }
                if (inp->inp_ppcb == NULL ||
                    in_pcb_checkstate(inp, WNT_ACQUIRE, 0) == WNT_STOPUSING) {
                        continue;
                }
                socket_lock(so, 1);
                /* Release the want count */
                if (inp->inp_ppcb == NULL ||
                    (in_pcb_checkstate(inp, WNT_RELEASE, 1) == WNT_STOPUSING)) {
                        socket_unlock(so, 1);
                        continue;
                }
                if ((inp->inp_vflag & INP_IPV4) &&
                    (inp->inp_laddr.s_addr == INADDR_ANY ||
                    inp->inp_faddr.s_addr == INADDR_ANY)) {
                        socket_unlock(so, 1);
                        continue;
                }
                if ((inp->inp_vflag & INP_IPV6) &&
                    (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr) ||
                    IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_faddr))) {
                        socket_unlock(so, 1);
                        continue;
                }
                if (inp->inp_lport == 0 || inp->inp_fport == 0) {
                        socket_unlock(so, 1);
                        continue;
                }
                if (inp->inp_last_outifp == NULL ||
                    inp->inp_last_outifp->if_index != ifp->if_index) {
                        socket_unlock(so, 1);
                        continue;
                }
                if ((inp->inp_vflag & INP_IPV4) && frame_data_offset +
                    sizeof(struct ip) + sizeof(struct tcphdr) >
                    IFNET_KEEPALIVE_OFFLOAD_FRAME_DATA_SIZE) {
                        socket_unlock(so, 1);
                        continue;
                } else if (!(inp->inp_vflag & INP_IPV4) && frame_data_offset +
                    sizeof(struct ip6_hdr) + sizeof(struct tcphdr) >
                    IFNET_KEEPALIVE_OFFLOAD_FRAME_DATA_SIZE) {
                        socket_unlock(so, 1);
                        continue;
                }
                /*
                 * There is no point in waking up the device for connections
                 * that are not established. Long lived connection are meant
                 * for processes that will sent and receive data
                 */
                if (tp->t_state != TCPS_ESTABLISHED) {
                        socket_unlock(so, 1);
                        continue;
                }
                /*
                 * This inp has all the information that is needed to
                 * generate an offload frame.
                 */
                frame = &frames_array[frame_index];
                frame->type = IFNET_KEEPALIVE_OFFLOAD_FRAME_TCP;
                frame->ether_type = (inp->inp_vflag & INP_IPV4) ?
                    IFNET_KEEPALIVE_OFFLOAD_FRAME_ETHERTYPE_IPV4 :
                    IFNET_KEEPALIVE_OFFLOAD_FRAME_ETHERTYPE_IPV6;
                frame->interval = tp->t_keepidle > 0 ? tp->t_keepidle :
                    tcp_keepidle;
                frame->keep_cnt = TCP_CONN_KEEPCNT(tp);
                frame->keep_retry = TCP_CONN_KEEPINTVL(tp);
                if (so->so_options & SO_NOWAKEFROMSLEEP) {
                        frame->flags |=
                            IFNET_KEEPALIVE_OFFLOAD_FLAG_NOWAKEFROMSLEEP;
                }
                frame->local_port = ntohs(inp->inp_lport);
                frame->remote_port = ntohs(inp->inp_fport);
                frame->local_seq = tp->snd_nxt;
                frame->remote_seq = tp->rcv_nxt;
                if (inp->inp_vflag & INP_IPV4) {
                        frame->length = frame_data_offset +
                            sizeof(struct ip) + sizeof(struct tcphdr);
                        frame->reply_length =  frame->length;

                        frame->addr_length = sizeof(struct in_addr);
                        bcopy(&inp->inp_laddr, frame->local_addr,
                            sizeof(struct in_addr));
                        bcopy(&inp->inp_faddr, frame->remote_addr,
                            sizeof(struct in_addr));
                } else {
                        struct in6_addr *ip6;

                        frame->length = frame_data_offset +
                            sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
                        frame->reply_length =  frame->length;

                        frame->addr_length = sizeof(struct in6_addr);
                        ip6 = (struct in6_addr *)(void *)frame->local_addr;
                        bcopy(&inp->in6p_laddr, ip6, sizeof(struct in6_addr));
                        if (IN6_IS_SCOPE_EMBED(ip6)) {
                                ip6->s6_addr16[1] = 0;
                        }

                        ip6 = (struct in6_addr *)(void *)frame->remote_addr;
                        bcopy(&inp->in6p_faddr, ip6, sizeof(struct in6_addr));
                        if (IN6_IS_SCOPE_EMBED(ip6)) {
                                ip6->s6_addr16[1] = 0;
                        }
                }

                /*
                 * First the probe
                 */
                m = tcp_make_keepalive_frame(tp, ifp, TRUE);
                if (m == NULL) {
                        socket_unlock(so, 1);
                        continue;
                }
                bcopy(m->m_data, frame->data + frame_data_offset,
                    m->m_len);
                m_freem(m);

                /*
                 * Now the response packet to incoming probes
                 */
                m = tcp_make_keepalive_frame(tp, ifp, FALSE);
                if (m == NULL) {
                        socket_unlock(so, 1);
                        continue;
                }
                bcopy(m->m_data, frame->reply_data + frame_data_offset,
                    m->m_len);
                m_freem(m);

                frame_index++;
                socket_unlock(so, 1);
        }
        lck_rw_done(tcbinfo.ipi_lock);
        *used_frames_count = frame_index;
}

static bool
inp_matches_kao_frame(ifnet_t ifp, struct ifnet_keepalive_offload_frame *frame,
    struct inpcb *inp)
{
        if (inp->inp_ppcb == NULL) {
                return false;
        }
        /* Release the want count */
        if (in_pcb_checkstate(inp, WNT_RELEASE, 1) == WNT_STOPUSING) {
                return false;
        }
        if (inp->inp_last_outifp == NULL ||
            inp->inp_last_outifp->if_index != ifp->if_index) {
                return false;
        }
        if (frame->local_port != ntohs(inp->inp_lport) ||
            frame->remote_port != ntohs(inp->inp_fport)) {
                return false;
        }
        if (inp->inp_vflag & INP_IPV4) {
                if (memcmp(&inp->inp_laddr, frame->local_addr,
                    sizeof(struct in_addr)) != 0 ||
                    memcmp(&inp->inp_faddr, frame->remote_addr,
                    sizeof(struct in_addr)) != 0) {
                        return false;
                }
        } else if (inp->inp_vflag & INP_IPV6) {
                if (memcmp(&inp->inp_laddr, frame->local_addr,
                    sizeof(struct in6_addr)) != 0 ||
                    memcmp(&inp->inp_faddr, frame->remote_addr,
                    sizeof(struct in6_addr)) != 0) {
                        return false;
                }
        } else {
                return false;
        }
        return true;
}

int
tcp_notify_kao_timeout(ifnet_t ifp,
    struct ifnet_keepalive_offload_frame *frame)
{
        struct inpcb *inp = NULL;
        struct socket *so = NULL;
        bool found = false;

        /*
         *  Unlock the list before posting event on the matching socket
         */
        lck_rw_lock_shared(tcbinfo.ipi_lock);

        LIST_FOREACH(inp, tcbinfo.ipi_listhead, inp_list) {
                if ((so = inp->inp_socket) == NULL ||
                    (so->so_state & SS_DEFUNCT)) {
                        continue;
                }
                if (!(inp->inp_flags2 & INP2_KEEPALIVE_OFFLOAD)) {
                        continue;
                }
                if (!(inp->inp_vflag & (INP_IPV4 | INP_IPV6))) {
                        continue;
                }
                if (inp->inp_ppcb == NULL ||
                    in_pcb_checkstate(inp, WNT_ACQUIRE, 0) == WNT_STOPUSING) {
                        continue;
                }
                socket_lock(so, 1);
                if (inp_matches_kao_frame(ifp, frame, inp)) {
                        /*
                         * Keep the matching socket locked
                         */
                        found = true;
                        break;
                }
                socket_unlock(so, 1);
        }
        lck_rw_done(tcbinfo.ipi_lock);

        if (found) {
                ASSERT(inp != NULL);
                ASSERT(so != NULL);
                ASSERT(so == inp->inp_socket);
                /*
                 * Drop the TCP connection like tcptimers() does
                 */
                struct tcpcb *tp = inp->inp_ppcb;

                tcpstat.tcps_keepdrops++;
                postevent(so, 0, EV_TIMEOUT);
                soevent(so,
                    (SO_FILT_HINT_LOCKED | SO_FILT_HINT_TIMEOUT));
                tp = tcp_drop(tp, ETIMEDOUT);

                tcpstat.tcps_ka_offload_drops++;
                os_log_info(OS_LOG_DEFAULT, "%s: dropped lport %u fport %u\n",
                    __func__, frame->local_port, frame->remote_port);

                socket_unlock(so, 1);
        }

        return 0;
}

errno_t
tcp_notify_ack_id_valid(struct tcpcb *tp, struct socket *so,
    u_int32_t notify_id)
{
        struct tcp_notify_ack_marker *elm;

        if (so->so_snd.sb_cc == 0) {
                return ENOBUFS;
        }

        SLIST_FOREACH(elm, &tp->t_notify_ack, notify_next) {
                /* Duplicate id is not allowed */
                if (elm->notify_id == notify_id) {
                        return EINVAL;
                }
                /* Duplicate position is not allowed */
                if (elm->notify_snd_una == tp->snd_una + so->so_snd.sb_cc) {
                        return EINVAL;
                }
        }
        return 0;
}

errno_t
tcp_add_notify_ack_marker(struct tcpcb *tp, u_int32_t notify_id)
{
        struct tcp_notify_ack_marker *nm, *elm = NULL;
        struct socket *so = tp->t_inpcb->inp_socket;

        MALLOC(nm, struct tcp_notify_ack_marker *, sizeof(*nm),
            M_TEMP, M_WAIT | M_ZERO);
        if (nm == NULL) {
                return ENOMEM;
        }
        nm->notify_id = notify_id;
        nm->notify_snd_una = tp->snd_una + so->so_snd.sb_cc;

        SLIST_FOREACH(elm, &tp->t_notify_ack, notify_next) {
                if (SEQ_GT(nm->notify_snd_una, elm->notify_snd_una)) {
                        break;
                }
        }

        if (elm == NULL) {
                VERIFY(SLIST_EMPTY(&tp->t_notify_ack));
                SLIST_INSERT_HEAD(&tp->t_notify_ack, nm, notify_next);
        } else {
                SLIST_INSERT_AFTER(elm, nm, notify_next);
        }
        tp->t_notify_ack_count++;
        return 0;
}

void
tcp_notify_ack_free(struct tcpcb *tp)
{
        struct tcp_notify_ack_marker *elm, *next;
        if (SLIST_EMPTY(&tp->t_notify_ack)) {
                return;
        }

        SLIST_FOREACH_SAFE(elm, &tp->t_notify_ack, notify_next, next) {
                SLIST_REMOVE(&tp->t_notify_ack, elm, tcp_notify_ack_marker,
                    notify_next);
                FREE(elm, M_TEMP);
        }
        SLIST_INIT(&tp->t_notify_ack);
        tp->t_notify_ack_count = 0;
}

inline void
tcp_notify_acknowledgement(struct tcpcb *tp, struct socket *so)
{
        struct tcp_notify_ack_marker *elm;

        elm = SLIST_FIRST(&tp->t_notify_ack);
        if (SEQ_GEQ(tp->snd_una, elm->notify_snd_una)) {
                soevent(so, SO_FILT_HINT_LOCKED | SO_FILT_HINT_NOTIFY_ACK);
        }
}

void
tcp_get_notify_ack_count(struct tcpcb *tp,
    struct tcp_notify_ack_complete *retid)
{
        struct tcp_notify_ack_marker *elm;
        size_t  complete = 0;

        SLIST_FOREACH(elm, &tp->t_notify_ack, notify_next) {
                if (SEQ_GEQ(tp->snd_una, elm->notify_snd_una)) {
                        complete++;
                } else {
                        break;
                }
        }
        retid->notify_pending = tp->t_notify_ack_count - complete;
        retid->notify_complete_count = min(TCP_MAX_NOTIFY_ACK, complete);
}

void
tcp_get_notify_ack_ids(struct tcpcb *tp,
    struct tcp_notify_ack_complete *retid)
{
        size_t i = 0;
        struct tcp_notify_ack_marker *elm, *next;

        SLIST_FOREACH_SAFE(elm, &tp->t_notify_ack, notify_next, next) {
                if (i >= retid->notify_complete_count) {
                        break;
                }
                if (SEQ_GEQ(tp->snd_una, elm->notify_snd_una)) {
                        retid->notify_complete_id[i++] = elm->notify_id;
                        SLIST_REMOVE(&tp->t_notify_ack, elm,
                            tcp_notify_ack_marker, notify_next);
                        FREE(elm, M_TEMP);
                        tp->t_notify_ack_count--;
                } else {
                        break;
                }
        }
}

bool
tcp_notify_ack_active(struct socket *so)
{
        if ((SOCK_DOM(so) == PF_INET || SOCK_DOM(so) == PF_INET6) &&
            SOCK_TYPE(so) == SOCK_STREAM) {
                struct tcpcb *tp = intotcpcb(sotoinpcb(so));

                if (!SLIST_EMPTY(&tp->t_notify_ack)) {
                        struct tcp_notify_ack_marker *elm;
                        elm = SLIST_FIRST(&tp->t_notify_ack);
                        if (SEQ_GEQ(tp->snd_una, elm->notify_snd_una)) {
                                return true;
                        }
                }
        }
        return false;
}

inline int32_t
inp_get_sndbytes_allunsent(struct socket *so, u_int32_t th_ack)
{
        struct inpcb *inp = sotoinpcb(so);
        struct tcpcb *tp = intotcpcb(inp);

        if ((so->so_snd.sb_flags & SB_SNDBYTE_CNT) &&
            so->so_snd.sb_cc > 0) {
                int32_t unsent, sent;
                sent = tp->snd_max - th_ack;
                if (tp->t_flags & TF_SENTFIN) {
                        sent--;
                }
                unsent = so->so_snd.sb_cc - sent;
                return unsent;
        }
        return 0;
}

#define IFP_PER_FLOW_STAT(_ipv4_, _stat_) { \
        if (_ipv4_) { \
                ifp->if_ipv4_stat->_stat_++; \
        } else { \
                ifp->if_ipv6_stat->_stat_++; \
        } \
}

#define FLOW_ECN_ENABLED(_flags_) \
    ((_flags_ & (TE_ECN_ON)) == (TE_ECN_ON))

void
tcp_update_stats_per_flow(struct ifnet_stats_per_flow *ifs,
    struct ifnet *ifp)
{
        if (ifp == NULL || !IF_FULLY_ATTACHED(ifp)) {
                return;
        }

        ifnet_lock_shared(ifp);
        if (ifs->ecn_flags & TE_SETUPSENT) {
                if (ifs->ecn_flags & TE_CLIENT_SETUP) {
                        IFP_PER_FLOW_STAT(ifs->ipv4, ecn_client_setup);
                        if (FLOW_ECN_ENABLED(ifs->ecn_flags)) {
                                IFP_PER_FLOW_STAT(ifs->ipv4,
                                    ecn_client_success);
                        } else if (ifs->ecn_flags & TE_LOST_SYN) {
                                IFP_PER_FLOW_STAT(ifs->ipv4,
                                    ecn_syn_lost);
                        } else {
                                IFP_PER_FLOW_STAT(ifs->ipv4,
                                    ecn_peer_nosupport);
                        }
                } else {
                        IFP_PER_FLOW_STAT(ifs->ipv4, ecn_server_setup);
                        if (FLOW_ECN_ENABLED(ifs->ecn_flags)) {
                                IFP_PER_FLOW_STAT(ifs->ipv4,
                                    ecn_server_success);
                        } else if (ifs->ecn_flags & TE_LOST_SYN) {
                                IFP_PER_FLOW_STAT(ifs->ipv4,
                                    ecn_synack_lost);
                        } else {
                                IFP_PER_FLOW_STAT(ifs->ipv4,
                                    ecn_peer_nosupport);
                        }
                }
        } else {
                IFP_PER_FLOW_STAT(ifs->ipv4, ecn_off_conn);
        }
        if (FLOW_ECN_ENABLED(ifs->ecn_flags)) {
                if (ifs->ecn_flags & TE_RECV_ECN_CE) {
                        tcpstat.tcps_ecn_conn_recv_ce++;
                        IFP_PER_FLOW_STAT(ifs->ipv4, ecn_conn_recv_ce);
                }
                if (ifs->ecn_flags & TE_RECV_ECN_ECE) {
                        tcpstat.tcps_ecn_conn_recv_ece++;
                        IFP_PER_FLOW_STAT(ifs->ipv4, ecn_conn_recv_ece);
                }
                if (ifs->ecn_flags & (TE_RECV_ECN_CE | TE_RECV_ECN_ECE)) {
                        if (ifs->txretransmitbytes > 0 ||
                            ifs->rxoutoforderbytes > 0) {
                                tcpstat.tcps_ecn_conn_pl_ce++;
                                IFP_PER_FLOW_STAT(ifs->ipv4, ecn_conn_plce);
                        } else {
                                tcpstat.tcps_ecn_conn_nopl_ce++;
                                IFP_PER_FLOW_STAT(ifs->ipv4, ecn_conn_noplce);
                        }
                } else {
                        if (ifs->txretransmitbytes > 0 ||
                            ifs->rxoutoforderbytes > 0) {
                                tcpstat.tcps_ecn_conn_plnoce++;
                                IFP_PER_FLOW_STAT(ifs->ipv4, ecn_conn_plnoce);
                        }
                }
        }

        /* Other stats are interesting for non-local connections only */
        if (ifs->local) {
                ifnet_lock_done(ifp);
                return;
        }

        if (ifs->ipv4) {
                ifp->if_ipv4_stat->timestamp = net_uptime();
                if (FLOW_ECN_ENABLED(ifs->ecn_flags)) {
                        tcp_flow_ecn_perf_stats(ifs, &ifp->if_ipv4_stat->ecn_on);
                } else {
                        tcp_flow_ecn_perf_stats(ifs, &ifp->if_ipv4_stat->ecn_off);
                }
        } else {
                ifp->if_ipv6_stat->timestamp = net_uptime();
                if (FLOW_ECN_ENABLED(ifs->ecn_flags)) {
                        tcp_flow_ecn_perf_stats(ifs, &ifp->if_ipv6_stat->ecn_on);
                } else {
                        tcp_flow_ecn_perf_stats(ifs, &ifp->if_ipv6_stat->ecn_off);
                }
        }

        if (ifs->rxmit_drop) {
                if (FLOW_ECN_ENABLED(ifs->ecn_flags)) {
                        IFP_PER_FLOW_STAT(ifs->ipv4, ecn_on.rxmit_drop);
                } else {
                        IFP_PER_FLOW_STAT(ifs->ipv4, ecn_off.rxmit_drop);
                }
        }
        if (ifs->ecn_fallback_synloss) {
                IFP_PER_FLOW_STAT(ifs->ipv4, ecn_fallback_synloss);
        }
        if (ifs->ecn_fallback_droprst) {
                IFP_PER_FLOW_STAT(ifs->ipv4, ecn_fallback_droprst);
        }
        if (ifs->ecn_fallback_droprxmt) {
                IFP_PER_FLOW_STAT(ifs->ipv4, ecn_fallback_droprxmt);
        }
        if (ifs->ecn_fallback_ce) {
                IFP_PER_FLOW_STAT(ifs->ipv4, ecn_fallback_ce);
        }
        if (ifs->ecn_fallback_reorder) {
                IFP_PER_FLOW_STAT(ifs->ipv4, ecn_fallback_reorder);
        }
        if (ifs->ecn_recv_ce > 0) {
                IFP_PER_FLOW_STAT(ifs->ipv4, ecn_recv_ce);
        }
        if (ifs->ecn_recv_ece > 0) {
                IFP_PER_FLOW_STAT(ifs->ipv4, ecn_recv_ece);
        }

        tcp_flow_lim_stats(ifs, &ifp->if_lim_stat);
        ifnet_lock_done(ifp);
}