xnu-1504.15.3.tar.gz

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

/*
 * Copyright (c) 2000-2008 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, 1993
 *      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.
 *
 *      From: @(#)tcp_usrreq.c  8.2 (Berkeley) 1/3/94
 * $FreeBSD: src/sys/netinet/tcp_usrreq.c,v 1.51.2.9 2001/08/22 00:59:12 silby Exp $
 */


#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/sysctl.h>
#include <sys/mbuf.h>
#if INET6
#include <sys/domain.h>
#endif /* INET6 */
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/protosw.h>

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

#include <netinet/in.h>
#include <netinet/in_systm.h>
#if INET6
#include <netinet/ip6.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>
#if INET6
#include <netinet6/ip6_var.h>
#endif
#include <netinet/tcp.h>
#include <netinet/tcp_fsm.h>
#include <netinet/tcp_seq.h>
#include <netinet/tcp_timer.h>
#include <netinet/tcp_var.h>
#include <netinet/tcpip.h>
#if TCPDEBUG
#include <netinet/tcp_debug.h>
#endif

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

/*
 * TCP protocol interface to socket abstraction.
 */
extern  char *tcpstates[];      /* XXX ??? */

static int      tcp_attach(struct socket *, struct proc *);
static int      tcp_connect(struct tcpcb *, struct sockaddr *, struct proc *);
#if INET6
static int      tcp6_connect(struct tcpcb *, struct sockaddr *, struct proc *);
#endif /* INET6 */
static struct tcpcb *
                tcp_disconnect(struct tcpcb *);
static struct tcpcb *
                tcp_usrclosed(struct tcpcb *);

__private_extern__ int  tcp_win_scale = 3;
SYSCTL_INT(_net_inet_tcp, OID_AUTO, win_scale_factor, CTLFLAG_RW,
    &tcp_win_scale, 0, "Window scaling factor");

static u_int32_t tcps_in_sw_cksum;
SYSCTL_UINT(_net_inet_tcp, OID_AUTO, in_sw_cksum, CTLFLAG_RD,
    &tcps_in_sw_cksum, 0,
    "Number of received packets checksummed in software");

static u_int64_t tcps_in_sw_cksum_bytes;
SYSCTL_QUAD(_net_inet_tcp, OID_AUTO, in_sw_cksum_bytes, CTLFLAG_RD,
    &tcps_in_sw_cksum_bytes,
    "Amount of received data checksummed in software");

static u_int32_t tcps_out_sw_cksum;
SYSCTL_UINT(_net_inet_tcp, OID_AUTO, out_sw_cksum, CTLFLAG_RD,
    &tcps_out_sw_cksum, 0,
    "Number of transmitted packets checksummed in software");

static u_int64_t tcps_out_sw_cksum_bytes;
SYSCTL_QUAD(_net_inet_tcp, OID_AUTO, out_sw_cksum_bytes, CTLFLAG_RD,
    &tcps_out_sw_cksum_bytes,
    "Amount of transmitted data checksummed in software");

#if TCPDEBUG
#define TCPDEBUG0       int ostate = 0
#define TCPDEBUG1()     ostate = tp ? tp->t_state : 0
#define TCPDEBUG2(req)  if (tp && (so->so_options & SO_DEBUG)) \
                                tcp_trace(TA_USER, ostate, tp, 0, 0, req)
#else
#define TCPDEBUG0
#define TCPDEBUG1()
#define TCPDEBUG2(req)
#endif

#if CONFIG_USESOCKTHRESHOLD
__private_extern__ unsigned int tcp_sockthreshold = 64;
#else
__private_extern__ unsigned int tcp_sockthreshold = 0;
#endif
SYSCTL_INT(_net_inet_tcp, OID_AUTO, sockthreshold, CTLFLAG_RW, 
    &tcp_sockthreshold , 0, "TCP Socket size increased if less than threshold");

/*
 * TCP attaches to socket via pru_attach(), reserving space,
 * and an internet control block.
 *
 * Returns:     0                       Success
 *              EISCONN
 *      tcp_attach:ENOBUFS
 *      tcp_attach:ENOMEM
 *      tcp_attach:???                  [IPSEC specific]
 */
static int
tcp_usr_attach(struct socket *so, __unused int proto, struct proc *p)
{
        int error;
        struct inpcb *inp = sotoinpcb(so);
        struct tcpcb *tp = 0;
        TCPDEBUG0;

        TCPDEBUG1();
        if (inp) {
                error = EISCONN;
                goto out;
        }

        error = tcp_attach(so, p);
        if (error)
                goto out;

        if ((so->so_options & SO_LINGER) && so->so_linger == 0)
                so->so_linger = TCP_LINGERTIME * hz;
        tp = sototcpcb(so);
out:
        TCPDEBUG2(PRU_ATTACH);
        return error;
}

/*
 * pru_detach() detaches the TCP protocol from the socket.
 * If the protocol state is non-embryonic, then can't
 * do this directly: have to initiate a pru_disconnect(),
 * which may finish later; embryonic TCB's can just
 * be discarded here.
 */
static int
tcp_usr_detach(struct socket *so)
{
        int error = 0;
        struct inpcb *inp = sotoinpcb(so);
        struct tcpcb *tp;
        TCPDEBUG0;

        if (inp == 0 || (inp->inp_state == INPCB_STATE_DEAD)) {
                return EINVAL;  /* XXX */
        }
#if 1
        lck_mtx_assert(((struct inpcb *)so->so_pcb)->inpcb_mtx, LCK_MTX_ASSERT_OWNED);
#endif
        tp = intotcpcb(inp);
        /* In case we got disconnected from the peer */
        if (tp == 0) 
            goto out;
        TCPDEBUG1();
        tp = tcp_disconnect(tp);
out:
        TCPDEBUG2(PRU_DETACH);
        return error;
}

#define COMMON_START()  TCPDEBUG0; \
                        do { \
                                     if (inp == 0 || (inp->inp_state == INPCB_STATE_DEAD)) { \
                                             return EINVAL; \
                                     } \
                                     tp = intotcpcb(inp); \
                                     TCPDEBUG1(); \
                     } while(0)
                             
#define COMMON_END(req) out: TCPDEBUG2(req); return error; goto out


/*
 * Give the socket an address.
 *
 * Returns:     0                       Success
 *              EINVAL                  Invalid argument [COMMON_START]
 *              EAFNOSUPPORT            Address family not supported
 *      in_pcbbind:EADDRNOTAVAIL        Address not available.
 *      in_pcbbind:EINVAL               Invalid argument
 *      in_pcbbind:EAFNOSUPPORT         Address family not supported [notdef]
 *      in_pcbbind:EACCES               Permission denied
 *      in_pcbbind:EADDRINUSE           Address in use
 *      in_pcbbind:EAGAIN               Resource unavailable, try again
 *      in_pcbbind:EPERM                Operation not permitted
 */
static int
tcp_usr_bind(struct socket *so, struct sockaddr *nam, struct proc *p)
{
        int error = 0;
        struct inpcb *inp = sotoinpcb(so);
        struct tcpcb *tp;
        struct sockaddr_in *sinp;

        COMMON_START();

        if (nam->sa_family != 0 && nam->sa_family != AF_INET) {
                error = EAFNOSUPPORT;
                goto out;
        }

        /*
         * Must check for multicast addresses and disallow binding
         * to them.
         */
        sinp = (struct sockaddr_in *)nam;
        if (sinp->sin_family == AF_INET &&
            IN_MULTICAST(ntohl(sinp->sin_addr.s_addr))) {
                error = EAFNOSUPPORT;
                goto out;
        }
        error = in_pcbbind(inp, nam, p);
        if (error)
                goto out;
        COMMON_END(PRU_BIND);

}

#if INET6
static int
tcp6_usr_bind(struct socket *so, struct sockaddr *nam, struct proc *p)
{
        int error = 0;
        struct inpcb *inp = sotoinpcb(so);
        struct tcpcb *tp;
        struct sockaddr_in6 *sin6p;

        COMMON_START();

        if (nam->sa_family != 0 && nam->sa_family != AF_INET6) {
                error = EAFNOSUPPORT;
                goto out;
        }

        /*
         * Must check for multicast addresses and disallow binding
         * to them.
         */
        sin6p = (struct sockaddr_in6 *)nam;
        if (sin6p->sin6_family == AF_INET6 &&
            IN6_IS_ADDR_MULTICAST(&sin6p->sin6_addr)) {
                error = EAFNOSUPPORT;
                goto out;
        }
        inp->inp_vflag &= ~INP_IPV4;
        inp->inp_vflag |= INP_IPV6;
        if ((inp->inp_flags & IN6P_IPV6_V6ONLY) == 0) {
                if (IN6_IS_ADDR_UNSPECIFIED(&sin6p->sin6_addr))
                        inp->inp_vflag |= INP_IPV4;
                else if (IN6_IS_ADDR_V4MAPPED(&sin6p->sin6_addr)) {
                        struct sockaddr_in sin;

                        in6_sin6_2_sin(&sin, sin6p);
                        inp->inp_vflag |= INP_IPV4;
                        inp->inp_vflag &= ~INP_IPV6;
                        error = in_pcbbind(inp, (struct sockaddr *)&sin, p);
                        goto out;
                }
        }
        error = in6_pcbbind(inp, nam, p);
        if (error)
                goto out;
        COMMON_END(PRU_BIND);
}
#endif /* INET6 */

/*
 * Prepare to accept connections.
 *
 * Returns:     0                       Success
 *              EINVAL [COMMON_START]
 *      in_pcbbind:EADDRNOTAVAIL        Address not available.
 *      in_pcbbind:EINVAL               Invalid argument
 *      in_pcbbind:EAFNOSUPPORT         Address family not supported [notdef]
 *      in_pcbbind:EACCES               Permission denied
 *      in_pcbbind:EADDRINUSE           Address in use
 *      in_pcbbind:EAGAIN               Resource unavailable, try again
 *      in_pcbbind:EPERM                Operation not permitted
 */
static int
tcp_usr_listen(struct socket *so, struct proc *p)
{
        int error = 0;
        struct inpcb *inp = sotoinpcb(so);
        struct tcpcb *tp;

        COMMON_START();
        if (inp->inp_lport == 0)
                error = in_pcbbind(inp, (struct sockaddr *)0, p);
        if (error == 0)
                tp->t_state = TCPS_LISTEN;
        COMMON_END(PRU_LISTEN);
}

#if INET6
static int
tcp6_usr_listen(struct socket *so, struct proc *p)
{
        int error = 0;
        struct inpcb *inp = sotoinpcb(so);
        struct tcpcb *tp;

        COMMON_START();
        if (inp->inp_lport == 0) {
                inp->inp_vflag &= ~INP_IPV4;
                if ((inp->inp_flags & IN6P_IPV6_V6ONLY) == 0)
                        inp->inp_vflag |= INP_IPV4;
                error = in6_pcbbind(inp, (struct sockaddr *)0, p);
        }
        if (error == 0)
                tp->t_state = TCPS_LISTEN;
        COMMON_END(PRU_LISTEN);
}
#endif /* INET6 */

/*
 * Initiate connection to peer.
 * Create a template for use in transmissions on this connection.
 * Enter SYN_SENT state, and mark socket as connecting.
 * Start keep-alive timer, and seed output sequence space.
 * Send initial segment on connection.
 */
static int
tcp_usr_connect(struct socket *so, struct sockaddr *nam, struct proc *p)
{
        int error = 0;
        struct inpcb *inp = sotoinpcb(so);
        struct tcpcb *tp;
        struct sockaddr_in *sinp;

        TCPDEBUG0;
        if (inp == 0)
                return EINVAL;
        else if (inp->inp_state == INPCB_STATE_DEAD) {
                if (so->so_error) {
                        error = so->so_error;
                        so->so_error = 0;
                        return error;
                } else
                        return EINVAL;
        }
        tp = intotcpcb(inp);
        TCPDEBUG1();

        if (nam->sa_family != 0 && nam->sa_family != AF_INET) {
                error = EAFNOSUPPORT;
                goto out;
        }
        /*
         * Must disallow TCP ``connections'' to multicast addresses.
         */
        sinp = (struct sockaddr_in *)nam;
        if (sinp->sin_family == AF_INET
            && IN_MULTICAST(ntohl(sinp->sin_addr.s_addr))) {
                error = EAFNOSUPPORT;
                goto out;
        }


        if ((error = tcp_connect(tp, nam, p)) != 0)
                goto out;
        error = tcp_output(tp);
        COMMON_END(PRU_CONNECT);
}

#if INET6
static int
tcp6_usr_connect(struct socket *so, struct sockaddr *nam, struct proc *p)
{
        int error = 0;
        struct inpcb *inp = sotoinpcb(so);
        struct tcpcb *tp;
        struct sockaddr_in6 *sin6p;

        COMMON_START();

        if (nam->sa_family != 0 && nam->sa_family != AF_INET6) {
                error = EAFNOSUPPORT;
                goto out;
        }

        /*
         * Must disallow TCP ``connections'' to multicast addresses.
         */
        sin6p = (struct sockaddr_in6 *)nam;
        if (sin6p->sin6_family == AF_INET6
            && IN6_IS_ADDR_MULTICAST(&sin6p->sin6_addr)) {
                error = EAFNOSUPPORT;
                goto out;
        }

        if (IN6_IS_ADDR_V4MAPPED(&sin6p->sin6_addr)) {
                struct sockaddr_in sin;

                if ((inp->inp_flags & IN6P_IPV6_V6ONLY) != 0)
                        return (EINVAL);

                in6_sin6_2_sin(&sin, sin6p);
                inp->inp_vflag |= INP_IPV4;
                inp->inp_vflag &= ~INP_IPV6;
                if ((error = tcp_connect(tp, (struct sockaddr *)&sin, p)) != 0)
                        goto out;
                error = tcp_output(tp);
                goto out;
        }
        inp->inp_vflag &= ~INP_IPV4;
        inp->inp_vflag |= INP_IPV6;
        if ((error = tcp6_connect(tp, nam, p)) != 0)
                goto out;
        error = tcp_output(tp);
        if (error)
                goto out;
        COMMON_END(PRU_CONNECT);
}
#endif /* INET6 */

/*
 * Initiate disconnect from peer.
 * If connection never passed embryonic stage, just drop;
 * else if don't need to let data drain, then can just drop anyways,
 * else have to begin TCP shutdown process: mark socket disconnecting,
 * drain unread data, state switch to reflect user close, and
 * send segment (e.g. FIN) to peer.  Socket will be really disconnected
 * when peer sends FIN and acks ours.
 *
 * SHOULD IMPLEMENT LATER PRU_CONNECT VIA REALLOC TCPCB.
 */
static int
tcp_usr_disconnect(struct socket *so)
{
        int error = 0;
        struct inpcb *inp = sotoinpcb(so);
        struct tcpcb *tp;
        
#if 1
        lck_mtx_assert(((struct inpcb *)so->so_pcb)->inpcb_mtx, LCK_MTX_ASSERT_OWNED);
#endif
        COMMON_START();
        /* In case we got disconnected from the peer */
        if (tp == 0)
            goto out;
        tp = tcp_disconnect(tp);
        COMMON_END(PRU_DISCONNECT);
}

/*
 * Accept a connection.  Essentially all the work is
 * done at higher levels; just return the address
 * of the peer, storing through addr.
 */
static int
tcp_usr_accept(struct socket *so, struct sockaddr **nam)
{
        int error = 0;
        struct inpcb *inp = sotoinpcb(so);
        struct tcpcb *tp = NULL;
        TCPDEBUG0;

        if (so->so_state & SS_ISDISCONNECTED) {
                error = ECONNABORTED;
                goto out;
        }
        if (inp == 0 || (inp->inp_state == INPCB_STATE_DEAD)) {
                return (EINVAL);
        }
        tp = intotcpcb(inp);
        TCPDEBUG1();
        in_setpeeraddr(so, nam);
        COMMON_END(PRU_ACCEPT);
}

#if INET6
static int
tcp6_usr_accept(struct socket *so, struct sockaddr **nam)
{
        int error = 0;
        struct inpcb *inp = sotoinpcb(so);
        struct tcpcb *tp = NULL;
        TCPDEBUG0;

        if (so->so_state & SS_ISDISCONNECTED) {
                error = ECONNABORTED;
                goto out;
        }
        if (inp == 0 || (inp->inp_state == INPCB_STATE_DEAD)) {
                return (EINVAL);
        }
        tp = intotcpcb(inp);
        TCPDEBUG1();
        in6_mapped_peeraddr(so, nam);
        COMMON_END(PRU_ACCEPT);
}
#endif /* INET6 */

/*
 * Mark the connection as being incapable of further output.
 *
 * Returns:     0                       Success
 *              EINVAL [COMMON_START]
 *      tcp_output:EADDRNOTAVAIL
 *      tcp_output:ENOBUFS
 *      tcp_output:EMSGSIZE
 *      tcp_output:EHOSTUNREACH
 *      tcp_output:ENETUNREACH
 *      tcp_output:ENETDOWN
 *      tcp_output:ENOMEM
 *      tcp_output:EACCES
 *      tcp_output:EMSGSIZE
 *      tcp_output:ENOBUFS
 *      tcp_output:???                  [ignorable: mostly IPSEC/firewall/DLIL]
 */
static int
tcp_usr_shutdown(struct socket *so)
{
        int error = 0;
        struct inpcb *inp = sotoinpcb(so);
        struct tcpcb *tp;

        COMMON_START();
        socantsendmore(so);
        /* In case we got disconnected from the peer */
        if (tp == 0)
            goto out;
        tp = tcp_usrclosed(tp);
        if (tp)
                error = tcp_output(tp);
        COMMON_END(PRU_SHUTDOWN);
}

/*
 * After a receive, possibly send window update to peer.
 */
static int
tcp_usr_rcvd(struct socket *so, __unused int flags)
{
        int error = 0;
        struct inpcb *inp = sotoinpcb(so);
        struct tcpcb *tp;

        COMMON_START();
        /* In case we got disconnected from the peer */
        if (tp == 0)
            goto out;
        tcp_output(tp);
        COMMON_END(PRU_RCVD);
}

/*
 * Do a send by putting data in output queue and updating urgent
 * marker if URG set.  Possibly send more data.  Unlike the other
 * pru_*() routines, the mbuf chains are our responsibility.  We
 * must either enqueue them or free them.  The other pru_* routines
 * generally are caller-frees.
 *
 * Returns:     0                       Success
 *              ECONNRESET
 *              EINVAL
 *              ENOBUFS
 *      tcp_connect:EADDRINUSE          Address in use
 *      tcp_connect:EADDRNOTAVAIL       Address not available.
 *      tcp_connect:EINVAL              Invalid argument
 *      tcp_connect:EAFNOSUPPORT        Address family not supported [notdef]
 *      tcp_connect:EACCES              Permission denied
 *      tcp_connect:EAGAIN              Resource unavailable, try again
 *      tcp_connect:EPERM               Operation not permitted
 *      tcp_output:EADDRNOTAVAIL
 *      tcp_output:ENOBUFS
 *      tcp_output:EMSGSIZE
 *      tcp_output:EHOSTUNREACH
 *      tcp_output:ENETUNREACH
 *      tcp_output:ENETDOWN
 *      tcp_output:ENOMEM
 *      tcp_output:EACCES
 *      tcp_output:EMSGSIZE
 *      tcp_output:ENOBUFS
 *      tcp_output:???                  [ignorable: mostly IPSEC/firewall/DLIL]
 *      tcp6_connect:???                [IPV6 only]
 */
static int
tcp_usr_send(struct socket *so, int flags, struct mbuf *m, 
             struct sockaddr *nam, struct mbuf *control, struct proc *p)
{
        int error = 0;
        struct inpcb *inp = sotoinpcb(so);
        struct tcpcb *tp;
#if INET6
        int isipv6;
#endif
        TCPDEBUG0;

        if (inp == NULL || inp->inp_state == INPCB_STATE_DEAD) {
                /*
                 * OOPS! we lost a race, the TCP session got reset after
                 * we checked SS_CANTSENDMORE, eg: while doing uiomove or a
                 * network interrupt in the non-splnet() section of sosend().
                 */
                if (m)
                        m_freem(m);
                if (control)
                        m_freem(control);
                error = ECONNRESET;     /* XXX EPIPE? */
                tp = NULL;
                TCPDEBUG1();
                goto out;
        }
#if INET6
        isipv6 = nam && nam->sa_family == AF_INET6;
#endif /* INET6 */
        tp = intotcpcb(inp);
        TCPDEBUG1();
        if (control) {
                /* TCP doesn't do control messages (rights, creds, etc) */
                if (control->m_len) {
                        m_freem(control);
                        if (m)
                                m_freem(m);
                        error = EINVAL;
                        goto out;
                }
                m_freem(control);       /* empty control, just free it */
        }
        if(!(flags & PRUS_OOB)) {
                sbappendstream(&so->so_snd, m);
                if (nam && tp->t_state < TCPS_SYN_SENT) {
                        /*
                         * Do implied connect if not yet connected,
                         * initialize window to default value, and
                         * initialize maxseg/maxopd using peer's cached
                         * MSS.
                         */
#if INET6
                        if (isipv6)
                                error = tcp6_connect(tp, nam, p);
                        else
#endif /* INET6 */
                        error = tcp_connect(tp, nam, p);
                        if (error)
                                goto out;
                        tp->snd_wnd = TTCP_CLIENT_SND_WND;
                        tcp_mss(tp, -1, IFSCOPE_NONE);
                }

                if (flags & PRUS_EOF) {
                        /*
                         * Close the send side of the connection after
                         * the data is sent.
                         */
                        socantsendmore(so);
                        tp = tcp_usrclosed(tp);
                }
                if (tp != NULL) {
                        if (flags & PRUS_MORETOCOME)
                                tp->t_flags |= TF_MORETOCOME;
                        error = tcp_output(tp);
                        if (flags & PRUS_MORETOCOME)
                                tp->t_flags &= ~TF_MORETOCOME;
                }
        } else {
                if (sbspace(&so->so_snd) == 0) { 
                        /* if no space is left in sockbuf, 
                         * do not try to squeeze in OOB traffic */
                        m_freem(m);
                        error = ENOBUFS;
                        goto out;
                }
                /*
                 * According to RFC961 (Assigned Protocols),
                 * the urgent pointer points to the last octet
                 * of urgent data.  We continue, however,
                 * to consider it to indicate the first octet
                 * of data past the urgent section.
                 * Otherwise, snd_up should be one lower.
                 */
                sbappendstream(&so->so_snd, m);
                if (nam && tp->t_state < TCPS_SYN_SENT) {
                        /*
                         * Do implied connect if not yet connected,
                         * initialize window to default value, and
                         * initialize maxseg/maxopd using peer's cached
                         * MSS.
                         */
#if INET6
                        if (isipv6)
                                error = tcp6_connect(tp, nam, p);
                        else
#endif /* INET6 */
                        error = tcp_connect(tp, nam, p);
                        if (error)
                                goto out;
                        tp->snd_wnd = TTCP_CLIENT_SND_WND;
                        tcp_mss(tp, -1, IFSCOPE_NONE);
                }
                tp->snd_up = tp->snd_una + so->so_snd.sb_cc;
                tp->t_force = 1;
                error = tcp_output(tp);
                tp->t_force = 0;
        }
        COMMON_END((flags & PRUS_OOB) ? PRU_SENDOOB : 
                   ((flags & PRUS_EOF) ? PRU_SEND_EOF : PRU_SEND));
}

/*
 * Abort the TCP.
 */
static int
tcp_usr_abort(struct socket *so)
{
        int error = 0;
        struct inpcb *inp = sotoinpcb(so);
        struct tcpcb *tp;

        COMMON_START();
        /* In case we got disconnected from the peer */
        if (tp == 0)
            goto out;
        tp = tcp_drop(tp, ECONNABORTED);
        so->so_usecount--;
        COMMON_END(PRU_ABORT);
}

/*
 * Receive out-of-band data.
 *
 * Returns:     0                       Success
 *              EINVAL [COMMON_START]
 *              EINVAL
 *              EWOULDBLOCK
 */
static int
tcp_usr_rcvoob(struct socket *so, struct mbuf *m, int flags)
{
        int error = 0;
        struct inpcb *inp = sotoinpcb(so);
        struct tcpcb *tp;

        COMMON_START();
        if ((so->so_oobmark == 0 &&
             (so->so_state & SS_RCVATMARK) == 0) ||
            so->so_options & SO_OOBINLINE ||
            tp->t_oobflags & TCPOOB_HADDATA) {
                error = EINVAL;
                goto out;
        }
        if ((tp->t_oobflags & TCPOOB_HAVEDATA) == 0) {
                error = EWOULDBLOCK;
                goto out;
        }
        m->m_len = 1;
        *mtod(m, caddr_t) = tp->t_iobc;
        if ((flags & MSG_PEEK) == 0)
                tp->t_oobflags ^= (TCPOOB_HAVEDATA | TCPOOB_HADDATA);
        COMMON_END(PRU_RCVOOB);
}

/* xxx - should be const */
struct pr_usrreqs tcp_usrreqs = {
        tcp_usr_abort, tcp_usr_accept, tcp_usr_attach, tcp_usr_bind,
        tcp_usr_connect, pru_connect2_notsupp, in_control, tcp_usr_detach,
        tcp_usr_disconnect, tcp_usr_listen, in_setpeeraddr, tcp_usr_rcvd,
        tcp_usr_rcvoob, tcp_usr_send, pru_sense_null, tcp_usr_shutdown,
        in_setsockaddr, sosend, soreceive, pru_sopoll_notsupp
};

#if INET6
struct pr_usrreqs tcp6_usrreqs = {
        tcp_usr_abort, tcp6_usr_accept, tcp_usr_attach, tcp6_usr_bind,
        tcp6_usr_connect, pru_connect2_notsupp, in6_control, tcp_usr_detach,
        tcp_usr_disconnect, tcp6_usr_listen, in6_mapped_peeraddr, tcp_usr_rcvd,
        tcp_usr_rcvoob, tcp_usr_send, pru_sense_null, tcp_usr_shutdown,
        in6_mapped_sockaddr, sosend, soreceive, pru_sopoll_notsupp
};
#endif /* INET6 */

/*
 * Common subroutine to open a TCP connection to remote host specified
 * by struct sockaddr_in in mbuf *nam.  Call in_pcbbind to assign a local
 * port number if needed.  Call in_pcbladdr to do the routing and to choose
 * a local host address (interface).  If there is an existing incarnation
 * of the same connection in TIME-WAIT state and if the remote host was
 * sending CC options and if the connection duration was < MSL, then
 * truncate the previous TIME-WAIT state and proceed.
 * Initialize connection parameters and enter SYN-SENT state.
 *
 * Returns:     0                       Success
 *              EADDRINUSE
 *              EINVAL
 *      in_pcbbind:EADDRNOTAVAIL        Address not available.
 *      in_pcbbind:EINVAL               Invalid argument
 *      in_pcbbind:EAFNOSUPPORT         Address family not supported [notdef]
 *      in_pcbbind:EACCES               Permission denied
 *      in_pcbbind:EADDRINUSE           Address in use
 *      in_pcbbind:EAGAIN               Resource unavailable, try again
 *      in_pcbbind:EPERM                Operation not permitted
 *      in_pcbladdr:EINVAL              Invalid argument
 *      in_pcbladdr:EAFNOSUPPORT        Address family not supported
 *      in_pcbladdr:EADDRNOTAVAIL       Address not available
 */
static int
tcp_connect(tp, nam, p)
        register struct tcpcb *tp;
        struct sockaddr *nam;
        struct proc *p;
{
        struct inpcb *inp = tp->t_inpcb, *oinp;
        struct socket *so = inp->inp_socket;
        struct tcpcb *otp;
        struct sockaddr_in *sin = (struct sockaddr_in *)nam;
        struct sockaddr_in *ifaddr;
        struct rmxp_tao *taop;
        struct rmxp_tao tao_noncached;
        int error;

        if (inp->inp_lport == 0) {
                error = in_pcbbind(inp, (struct sockaddr *)0, p);
                if (error)
                        return error;
        }

        /*
         * Cannot simply call in_pcbconnect, because there might be an
         * earlier incarnation of this same connection still in
         * TIME_WAIT state, creating an ADDRINUSE error.
         */
        error = in_pcbladdr(inp, nam, &ifaddr);
        if (error)
                return error;

        tcp_unlock(inp->inp_socket, 0, 0);
        oinp = in_pcblookup_hash(inp->inp_pcbinfo,
            sin->sin_addr, sin->sin_port,
            inp->inp_laddr.s_addr != INADDR_ANY ? inp->inp_laddr
                                                : ifaddr->sin_addr,
            inp->inp_lport,  0, NULL);

        tcp_lock(inp->inp_socket, 0, 0);
        if (oinp) {
                if (oinp != inp) /* 4143933: avoid deadlock if inp == oinp */
                        tcp_lock(oinp->inp_socket, 1, 0);
                if (in_pcb_checkstate(oinp, WNT_RELEASE, 1) == WNT_STOPUSING) {
                        if (oinp != inp)
                                tcp_unlock(oinp->inp_socket, 1, 0);
                        goto skip_oinp;
                }

                if (oinp != inp && (otp = intotcpcb(oinp)) != NULL &&
                otp->t_state == TCPS_TIME_WAIT &&
                    otp->t_starttime < (u_int32_t)tcp_msl &&
                    (otp->t_flags & TF_RCVD_CC))
                        otp = tcp_close(otp);
                else {
                        printf("tcp_connect: inp=%p err=EADDRINUSE\n", inp);
                        if (oinp != inp)
                                tcp_unlock(oinp->inp_socket, 1, 0);
                        return EADDRINUSE;
                }
                if (oinp != inp)
                        tcp_unlock(oinp->inp_socket, 1, 0);
        }
skip_oinp:
        if ((inp->inp_laddr.s_addr == INADDR_ANY ? ifaddr->sin_addr.s_addr :
                 inp->inp_laddr.s_addr) == sin->sin_addr.s_addr &&
            inp->inp_lport == sin->sin_port)
                        return EINVAL;
        if (!lck_rw_try_lock_exclusive(inp->inp_pcbinfo->mtx)) {
                /*lock inversion issue, mostly with udp multicast packets */
                socket_unlock(inp->inp_socket, 0);
                lck_rw_lock_exclusive(inp->inp_pcbinfo->mtx);
                socket_lock(inp->inp_socket, 0);
        }
        if (inp->inp_laddr.s_addr == INADDR_ANY)
                inp->inp_laddr = ifaddr->sin_addr;
        inp->inp_faddr = sin->sin_addr;
        inp->inp_fport = sin->sin_port;
        in_pcbrehash(inp);
        lck_rw_done(inp->inp_pcbinfo->mtx);

        /* Compute window scaling to requesti according to sb_hiwat
         * or leave us some room to increase potentially increase the window size depending
         * on the default win scale
         */
        while (tp->request_r_scale < TCP_MAX_WINSHIFT &&
         (TCP_MAXWIN << tp->request_r_scale) < so->so_rcv.sb_hiwat)
                tp->request_r_scale++;

        /*
         * Inflate window size only if no setsockopt was performed on the recv sockbuf and
         * if we're not over our number of active pcbs.
         */

        if (((so->so_rcv.sb_flags & SB_USRSIZE) == 0) && (inp->inp_pcbinfo->ipi_count < tcp_sockthreshold)) {
                tp->request_r_scale = max(tcp_win_scale, tp->request_r_scale);
                so->so_rcv.sb_hiwat = min(TCP_MAXWIN << tp->request_r_scale, (sb_max / (MSIZE+MCLBYTES)) * MCLBYTES);  
        }

        soisconnecting(so);
        tcpstat.tcps_connattempt++;
        tp->t_state = TCPS_SYN_SENT;
        tp->t_timer[TCPT_KEEP] = tp->t_keepinit ? tp->t_keepinit : tcp_keepinit;
        tp->iss = tcp_new_isn(tp);
        tcp_sendseqinit(tp);

        /*
         * Generate a CC value for this connection and
         * check whether CC or CCnew should be used.
         */
        if ((taop = tcp_gettaocache(tp->t_inpcb)) == NULL) {
                taop = &tao_noncached;
                bzero(taop, sizeof(*taop));
        }

        tp->cc_send = CC_INC(tcp_ccgen);
        if (taop->tao_ccsent != 0 &&
            CC_GEQ(tp->cc_send, taop->tao_ccsent)) {
                taop->tao_ccsent = tp->cc_send;
        } else {
                taop->tao_ccsent = 0;
                tp->t_flags |= TF_SENDCCNEW;
        }

        return 0;
}

#if INET6
static int
tcp6_connect(tp, nam, p)
        register struct tcpcb *tp;
        struct sockaddr *nam;
        struct proc *p;
{
        struct inpcb *inp = tp->t_inpcb, *oinp;
        struct socket *so = inp->inp_socket;
        struct tcpcb *otp;
        struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)nam;
        struct in6_addr addr6;
        struct rmxp_tao *taop;
        struct rmxp_tao tao_noncached;
        int error;

        if (inp->inp_lport == 0) {
                error = in6_pcbbind(inp, (struct sockaddr *)0, p);
                if (error)
                        return error;
        }

        /*
         * Cannot simply call in_pcbconnect, because there might be an
         * earlier incarnation of this same connection still in
         * TIME_WAIT state, creating an ADDRINUSE error.
         */
        error = in6_pcbladdr(inp, nam, &addr6);
        if (error)
                return error;
        tcp_unlock(inp->inp_socket, 0, 0);
        oinp = in6_pcblookup_hash(inp->inp_pcbinfo,
                                  &sin6->sin6_addr, sin6->sin6_port,
                                  IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)
                                  ? &addr6
                                  : &inp->in6p_laddr,
                                  inp->inp_lport,  0, NULL);
        tcp_lock(inp->inp_socket, 0, 0);
        if (oinp) {
                if (oinp != inp && (otp = intotcpcb(oinp)) != NULL &&
                    otp->t_state == TCPS_TIME_WAIT &&
                    otp->t_starttime < (u_int32_t)tcp_msl &&
                    (otp->t_flags & TF_RCVD_CC))
                        otp = tcp_close(otp);
                else
                        return EADDRINUSE;
        }
        if (!lck_rw_try_lock_exclusive(inp->inp_pcbinfo->mtx)) {
                /*lock inversion issue, mostly with udp multicast packets */
                socket_unlock(inp->inp_socket, 0);
                lck_rw_lock_exclusive(inp->inp_pcbinfo->mtx);
                socket_lock(inp->inp_socket, 0);
        }
        if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr))
                inp->in6p_laddr = addr6;
        inp->in6p_faddr = sin6->sin6_addr;
        inp->inp_fport = sin6->sin6_port;
        if ((sin6->sin6_flowinfo & IPV6_FLOWINFO_MASK) != 0)
                inp->in6p_flowinfo = sin6->sin6_flowinfo;
        in_pcbrehash(inp);
        lck_rw_done(inp->inp_pcbinfo->mtx);

        /* Compute window scaling to request.  */
        while (tp->request_r_scale < TCP_MAX_WINSHIFT &&
            (TCP_MAXWIN << tp->request_r_scale) < so->so_rcv.sb_hiwat)
                tp->request_r_scale++;

        soisconnecting(so);
        tcpstat.tcps_connattempt++;
        tp->t_state = TCPS_SYN_SENT;
        tp->t_timer[TCPT_KEEP] = tp->t_keepinit ? tp->t_keepinit : tcp_keepinit;
        tp->iss = tcp_new_isn(tp);
        tcp_sendseqinit(tp);

        /*
         * Generate a CC value for this connection and
         * check whether CC or CCnew should be used.
         */
        if ((taop = tcp_gettaocache(tp->t_inpcb)) == NULL) {
                taop = &tao_noncached;
                bzero(taop, sizeof(*taop));
        }

        tp->cc_send = CC_INC(tcp_ccgen);
        if (taop->tao_ccsent != 0 &&
            CC_GEQ(tp->cc_send, taop->tao_ccsent)) {
                taop->tao_ccsent = tp->cc_send;
        } else {
                taop->tao_ccsent = 0;
                tp->t_flags |= TF_SENDCCNEW;
        }

        return 0;
}
#endif /* INET6 */

/*
 * The new sockopt interface makes it possible for us to block in the
 * copyin/out step (if we take a page fault).  Taking a page fault at
 * splnet() is probably a Bad Thing.  (Since sockets and pcbs both now
 * use TSM, there probably isn't any need for this function to run at
 * splnet() any more.  This needs more examination.)
 */
int
tcp_ctloutput(so, sopt)
        struct socket *so;
        struct sockopt *sopt;
{
        int     error, opt, optval;
        struct  inpcb *inp;
        struct  tcpcb *tp;

        error = 0;
        inp = sotoinpcb(so);
        if (inp == NULL) {
                return (ECONNRESET);
        }
        if (sopt->sopt_level != IPPROTO_TCP) {
#if INET6
                if (INP_CHECK_SOCKAF(so, AF_INET6))
                        error = ip6_ctloutput(so, sopt);
                else
#endif /* INET6 */
                error = ip_ctloutput(so, sopt);
                return (error);
        }
        tp = intotcpcb(inp);
        if (tp == NULL) {
                return (ECONNRESET);
        }

        switch (sopt->sopt_dir) {
        case SOPT_SET:
                switch (sopt->sopt_name) {
                case TCP_NODELAY:
                case TCP_NOOPT:
                case TCP_NOPUSH:
                        error = sooptcopyin(sopt, &optval, sizeof optval,
                                            sizeof optval);
                        if (error)
                                break;

                        switch (sopt->sopt_name) {
                        case TCP_NODELAY:
                                opt = TF_NODELAY;
                                break;
                        case TCP_NOOPT:
                                opt = TF_NOOPT;
                                break;
                        case TCP_NOPUSH:
                                opt = TF_NOPUSH;
                                break;
                        default:
                                opt = 0; /* dead code to fool gcc */
                                break;
                        }

                        if (optval)
                                tp->t_flags |= opt;
                        else
                                tp->t_flags &= ~opt;
                        break;

                case TCP_MAXSEG:
                        error = sooptcopyin(sopt, &optval, sizeof optval,
                                            sizeof optval);
                        if (error)
                                break;

                        if (optval > 0 && optval <= tp->t_maxseg &&
                            optval + 40 >= tcp_minmss)
                                tp->t_maxseg = optval;
                        else
                                error = EINVAL;
                        break;

                case TCP_KEEPALIVE:
                        error = sooptcopyin(sopt, &optval, sizeof optval,
                                                sizeof optval);
                        if (error)
                                break;
                        if (optval < 0)
                                error = EINVAL;
                        else {
                                tp->t_keepidle = optval * TCP_RETRANSHZ;
                                tp->t_timer[TCPT_KEEP] = TCP_KEEPIDLE(tp); /* reset the timer to new value */
                        }
                        break;

                case TCP_CONNECTIONTIMEOUT:
                        error = sooptcopyin(sopt, &optval, sizeof optval,
                                                sizeof optval);
                        if (error)
                                break;
                        if (optval < 0)
                                error = EINVAL;
                        else 
                                tp->t_keepinit = optval * TCP_RETRANSHZ;
                        break;
                
                default:
                        error = ENOPROTOOPT;
                        break;
                }
                break;

        case SOPT_GET:
                switch (sopt->sopt_name) {
                case TCP_NODELAY:
                        optval = tp->t_flags & TF_NODELAY;
                        break;
                case TCP_MAXSEG:
                        optval = tp->t_maxseg;
                        break;
                case TCP_KEEPALIVE:
                        optval = tp->t_keepidle / TCP_RETRANSHZ;
                        break;
                case TCP_NOOPT:
                        optval = tp->t_flags & TF_NOOPT;
                        break;
                case TCP_NOPUSH:
                        optval = tp->t_flags & TF_NOPUSH;
                        break;
                case TCP_CONNECTIONTIMEOUT:
                        optval = tp->t_keepinit / TCP_RETRANSHZ;
                        break;
                default:
                        error = ENOPROTOOPT;
                        break;
                }
                if (error == 0)
                        error = sooptcopyout(sopt, &optval, sizeof optval);
                break;
        }
        return (error);
}

/*
 * tcp_sendspace and tcp_recvspace are the default send and receive window
 * sizes, respectively.  These are obsolescent (this information should
 * be set by the route).
 */
u_int32_t       tcp_sendspace = 1448*256;
u_int32_t       tcp_recvspace = 1448*384;

/* During attach, the size of socket buffer allocated is limited to
 * sb_max in sbreserve. Disallow setting the tcp send and recv space
 * to be more than sb_max because that will cause tcp_attach to fail
 * (see radar 5713060)
 */  
static int
sysctl_tcp_sospace(struct sysctl_oid *oidp, __unused void *arg1,
        __unused int arg2, struct sysctl_req *req) {
        u_int32_t new_value = 0, *space_p = NULL;
        int changed = 0, error = 0;
        u_quad_t sb_effective_max = (sb_max / (MSIZE+MCLBYTES)) * MCLBYTES;

        switch (oidp->oid_number) {
                case TCPCTL_SENDSPACE:
                        space_p = &tcp_sendspace;
                        break;
                case TCPCTL_RECVSPACE:
                        space_p = &tcp_recvspace;
                        break;
                default:
                        return EINVAL;
        }
        error = sysctl_io_number(req, *space_p, sizeof(u_int32_t),
                &new_value, &changed);
        if (changed) {
                if (new_value > 0 && new_value <= sb_effective_max) {
                        *space_p = new_value;
                } else {
                        error = ERANGE;
                }
        }
        return error;
}

SYSCTL_PROC(_net_inet_tcp, TCPCTL_SENDSPACE, sendspace, CTLTYPE_INT | CTLFLAG_RW, 
    &tcp_sendspace , 0, &sysctl_tcp_sospace, "IU", "Maximum outgoing TCP datagram size");
SYSCTL_PROC(_net_inet_tcp, TCPCTL_RECVSPACE, recvspace, CTLTYPE_INT | CTLFLAG_RW, 
    &tcp_recvspace , 0, &sysctl_tcp_sospace, "IU", "Maximum incoming TCP datagram size");


/*
 * Attach TCP protocol to socket, allocating
 * internet protocol control block, tcp control block,
 * bufer space, and entering LISTEN state if to accept connections.
 *
 * Returns:     0                       Success
 *      in_pcballoc:ENOBUFS
 *      in_pcballoc:ENOMEM
 *      in_pcballoc:???                 [IPSEC specific]
 *      soreserve:ENOBUFS
 */
static int
tcp_attach(so, p)
        struct socket *so;
        struct proc *p;
{
        register struct tcpcb *tp;
        struct inpcb *inp;
        int error;
        u_long sb_effective_max;
#if INET6
        int isipv6 = INP_CHECK_SOCKAF(so, AF_INET6) != 0;
#endif

        error = in_pcballoc(so, &tcbinfo, p);
        if (error)
                return (error);

        inp = sotoinpcb(so);

        if (so->so_snd.sb_hiwat == 0 || so->so_rcv.sb_hiwat == 0) {
                /*
                 * The goal is to let clients machines use large send/rcv default windows to compensate for link
                 * latency and make sure the receiver is not constraining the sender window.
                 * But we doon't want to have a few connections use all our mbuf space for servers.
                 * This is done by watching a threshold of tcpcbs in use and bumping the default send and rcvspace
                 * only if that threshold isn't reached.
                 * We're also advertising a much bigger window size (tuneable by sysctl) in correlation with                             * the max socket buffer size if 
                 * we consider that we have enough ressources for it. This window will be adjusted depending on the
                 * global socket layer buffer use with the use of tcp_sbpace
                 */

                if (inp->inp_pcbinfo->ipi_count < tcp_sockthreshold) {
                        sb_effective_max = (sb_max / (MSIZE+MCLBYTES)) * MCLBYTES;  
                        error = soreserve(so, max(min((TCP_MAXWIN << tcp_win_scale)/4, sb_effective_max), tcp_sendspace),
                                        max(min((TCP_MAXWIN << tcp_win_scale)/2, sb_effective_max), tcp_recvspace));
                }
                else    
                        error = soreserve(so, tcp_sendspace, tcp_recvspace);
                if (error)
                        return (error);
        }

#if INET6
        if (isipv6) {
                inp->inp_vflag |= INP_IPV6;
                inp->in6p_hops = -1;    /* use kernel default */
        }
        else
#endif /* INET6 */
        inp->inp_vflag |= INP_IPV4;
        tp = tcp_newtcpcb(inp);
        if (tp == 0) {
                int nofd = so->so_state & SS_NOFDREF;   /* XXX */

                so->so_state &= ~SS_NOFDREF;    /* don't free the socket yet */
#if INET6
                if (isipv6)
                        in6_pcbdetach(inp);
                else
#endif /* INET6 */
                in_pcbdetach(inp);
                so->so_state |= nofd;
                return (ENOBUFS);
        }
        tp->t_state = TCPS_CLOSED;
        return (0);
}

/*
 * Initiate (or continue) disconnect.
 * If embryonic state, just send reset (once).
 * If in ``let data drain'' option and linger null, just drop.
 * Otherwise (hard), mark socket disconnecting and drop
 * current input data; switch states based on user close, and
 * send segment to peer (with FIN).
 */
static struct tcpcb *
tcp_disconnect(tp)
        register struct tcpcb *tp;
{
        struct socket *so = tp->t_inpcb->inp_socket;

        if (tp->t_state < TCPS_ESTABLISHED)
                tp = tcp_close(tp);
        else if ((so->so_options & SO_LINGER) && so->so_linger == 0)
                tp = tcp_drop(tp, 0);
        else {
                soisdisconnecting(so);
                sbflush(&so->so_rcv);
                tp = tcp_usrclosed(tp);
                if (tp)
                        (void) tcp_output(tp);
        }
        return (tp);
}

/*
 * User issued close, and wish to trail through shutdown states:
 * if never received SYN, just forget it.  If got a SYN from peer,
 * but haven't sent FIN, then go to FIN_WAIT_1 state to send peer a FIN.
 * If already got a FIN from peer, then almost done; go to LAST_ACK
 * state.  In all other cases, have already sent FIN to peer (e.g.
 * after PRU_SHUTDOWN), and just have to play tedious game waiting
 * for peer to send FIN or not respond to keep-alives, etc.
 * We can let the user exit from the close as soon as the FIN is acked.
 */
static struct tcpcb *
tcp_usrclosed(tp)
        register struct tcpcb *tp;
{

        switch (tp->t_state) {

        case TCPS_CLOSED:
        case TCPS_LISTEN:
                tp->t_state = TCPS_CLOSED;
                tp = tcp_close(tp);
                break;

        case TCPS_SYN_SENT:
        case TCPS_SYN_RECEIVED:
                tp->t_flags |= TF_NEEDFIN;
                break;

        case TCPS_ESTABLISHED:
                tp->t_state = TCPS_FIN_WAIT_1;
                break;

        case TCPS_CLOSE_WAIT:
                tp->t_state = TCPS_LAST_ACK;
                break;
        }
        if (tp && tp->t_state >= TCPS_FIN_WAIT_2) {
                soisdisconnected(tp->t_inpcb->inp_socket);
                /* To prevent the connection hanging in FIN_WAIT_2 forever. */
                if (tp->t_state == TCPS_FIN_WAIT_2)
                        tp->t_timer[TCPT_2MSL] = tcp_maxidle;
        }
        return (tp);
}

void
tcp_in_cksum_stats(u_int32_t len)
{
        tcps_in_sw_cksum++;
        tcps_in_sw_cksum_bytes += len;
}

void
tcp_out_cksum_stats(u_int32_t len)
{
        tcps_out_sw_cksum++;
        tcps_out_sw_cksum_bytes += len;
}