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

/*
 * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * The contents of this file constitute Original Code as defined in and
 * are subject to the Apple Public Source License Version 1.1 (the
 * "License").  You may not use this file except in compliance with the
 * License.  Please obtain a copy of the License at
 * http://www.apple.com/publicsource and read it before using this file.
 * 
 * This 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 OR NON-INFRINGEMENT.  Please see the
 * License for the specific language governing rights and limitations
 * under the License.
 * 
 * @APPLE_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.
 *
 * $FreeBSD: src/sys/netinet/ip_divert.c,v 1.98 2004/08/17 22:05:54 andre Exp $
 */

#ifndef INET
#error "IPDIVERT requires INET."
#endif

#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/socket.h>
#include <sys/domain.h>
#include <sys/protosw.h>
#include <sys/socketvar.h>
#include <sys/sysctl.h>
#include <sys/systm.h>
#include <sys/proc.h>


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

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

#include <kern/zalloc.h>

/*
 * Divert sockets
 */

/*
 * Allocate enough space to hold a full IP packet
 */
#define DIVSNDQ         (65536 + 100)
#define DIVRCVQ         (65536 + 100)

/*
 * Divert sockets work in conjunction with ipfw, see the divert(4)
 * manpage for features.
 * Internally, packets selected by ipfw in ip_input() or ip_output(),
 * and never diverted before, are passed to the input queue of the
 * divert socket with a given 'divert_port' number (as specified in
 * the matching ipfw rule), and they are tagged with a 16 bit cookie
 * (representing the rule number of the matching ipfw rule), which
 * is passed to process reading from the socket.
 *
 * Packets written to the divert socket are again tagged with a cookie
 * (usually the same as above) and a destination address.
 * If the destination address is INADDR_ANY then the packet is
 * treated as outgoing and sent to ip_output(), otherwise it is
 * treated as incoming and sent to ip_input().
 * In both cases, the packet is tagged with the cookie.
 *
 * On reinjection, processing in ip_input() and ip_output()
 * will be exactly the same as for the original packet, except that
 * ipfw processing will start at the rule number after the one
 * written in the cookie (so, tagging a packet with a cookie of 0
 * will cause it to be effectively considered as a standard packet).
 */

/* Internal variables */
static struct inpcbhead divcb;
static struct inpcbinfo divcbinfo;

static u_long   div_sendspace = DIVSNDQ;        /* XXX sysctl ? */
static u_long   div_recvspace = DIVRCVQ;        /* XXX sysctl ? */

/* Optimization: have this preinitialized */
static struct sockaddr_in divsrc = { sizeof(divsrc), AF_INET,  };

/* Internal functions */
static int div_output(struct socket *so,
                struct mbuf *m, struct sockaddr *addr, struct mbuf *control);

extern int load_ipfw(void);
/*
 * Initialize divert connection block queue.
 */
void
div_init(void)
{
        struct inpcbinfo *pcbinfo;
        LIST_INIT(&divcb);
        divcbinfo.listhead = &divcb;
        /*
         * XXX We don't use the hash list for divert IP, but it's easier
         * to allocate a one entry hash list than it is to check all
         * over the place for hashbase == NULL.
         */
        divcbinfo.hashbase = hashinit(1, M_PCB, &divcbinfo.hashmask);
        divcbinfo.porthashbase = hashinit(1, M_PCB, &divcbinfo.porthashmask);
        divcbinfo.ipi_zone = (void *) zinit(sizeof(struct inpcb),(maxsockets * sizeof(struct inpcb)),
                                   4096, "divzone");
        pcbinfo = &divcbinfo;
        /*
         * allocate lock group attribute and group for udp pcb mutexes
         */
        pcbinfo->mtx_grp_attr = lck_grp_attr_alloc_init();

        pcbinfo->mtx_grp = lck_grp_alloc_init("divcb", pcbinfo->mtx_grp_attr);
                
        /*
         * allocate the lock attribute for divert pcb mutexes
         */
        pcbinfo->mtx_attr = lck_attr_alloc_init();

        if ((pcbinfo->mtx = lck_rw_alloc_init(pcbinfo->mtx_grp, pcbinfo->mtx_attr)) == NULL)
                return; /* pretty much dead if this fails... */

        if (!IPFW_LOADED) {
                load_ipfw();
        }
}

/*
 * IPPROTO_DIVERT is not a real IP protocol; don't allow any packets
 * with that protocol number to enter the system from the outside.
 */
void
div_input(struct mbuf *m, __unused int off)
{
        ipstat.ips_noproto++;
        m_freem(m);
}

/*
 * Divert a packet by passing it up to the divert socket at port 'port'.
 *
 * Setup generic address and protocol structures for div_input routine,
 * then pass them along with mbuf chain.
 * ###LOCK  called in ip_mutex from ip_output/ip_input
 */
void
divert_packet(struct mbuf *m, int incoming, int port, int rule)
{
        struct ip *ip;
        struct inpcb *inp;
        struct socket *sa;
        u_int16_t nport;

        /* Sanity check */
        KASSERT(port != 0, ("%s: port=0", __FUNCTION__));

        divsrc.sin_port = rule;         /* record matching rule */

        /* Assure header */
        if (m->m_len < sizeof(struct ip) &&
            (m = m_pullup(m, sizeof(struct ip))) == 0) {
                return;
        }
        ip = mtod(m, struct ip *);

        /*
         * Record receive interface address, if any.
         * But only for incoming packets.
         */
        divsrc.sin_addr.s_addr = 0;
        if (incoming) {
                struct ifaddr *ifa;

                /* Sanity check */
                KASSERT((m->m_flags & M_PKTHDR), ("%s: !PKTHDR", __FUNCTION__));

                /* Find IP address for receive interface */
                ifnet_lock_shared(m->m_pkthdr.rcvif);
                TAILQ_FOREACH(ifa, &m->m_pkthdr.rcvif->if_addrhead, ifa_link) {
                        if (ifa->ifa_addr == NULL)
                                continue;
                        if (ifa->ifa_addr->sa_family != AF_INET)
                                continue;
                        divsrc.sin_addr =
                            ((struct sockaddr_in *) ifa->ifa_addr)->sin_addr;
                        break;
                }
                ifnet_lock_done(m->m_pkthdr.rcvif);
        }
        /*
         * Record the incoming interface name whenever we have one.
         */
        bzero(&divsrc.sin_zero, sizeof(divsrc.sin_zero));
        if (m->m_pkthdr.rcvif) {
                /*
                 * Hide the actual interface name in there in the 
                 * sin_zero array. XXX This needs to be moved to a
                 * different sockaddr type for divert, e.g.
                 * sockaddr_div with multiple fields like 
                 * sockaddr_dl. Presently we have only 7 bytes
                 * but that will do for now as most interfaces
                 * are 4 or less + 2 or less bytes for unit.
                 * There is probably a faster way of doing this,
                 * possibly taking it from the sockaddr_dl on the iface.
                 * This solves the problem of a P2P link and a LAN interface
                 * having the same address, which can result in the wrong
                 * interface being assigned to the packet when fed back
                 * into the divert socket. Theoretically if the daemon saves
                 * and re-uses the sockaddr_in as suggested in the man pages,
                 * this iface name will come along for the ride.
                 * (see div_output for the other half of this.)
                 */ 
                snprintf(divsrc.sin_zero, sizeof(divsrc.sin_zero),
                        "%s%d", m->m_pkthdr.rcvif->if_name,
                        m->m_pkthdr.rcvif->if_unit);
        }

        /* Put packet on socket queue, if any */
        sa = NULL;
        nport = htons((u_int16_t)port);
        lck_rw_lock_shared(divcbinfo.mtx);      
        LIST_FOREACH(inp, &divcb, inp_list) {
                if (inp->inp_lport == nport)
                        sa = inp->inp_socket;
        }
        if (sa) {
                int error = 0;
                
                socket_lock(sa, 1);
                if (sbappendaddr(&sa->so_rcv, (struct sockaddr *)&divsrc,
                                m, (struct mbuf *)0, &error) != 0)
                        sorwakeup(sa);
                socket_unlock(sa, 1);
        } else {
                m_freem(m);
                ipstat.ips_noproto++;
                ipstat.ips_delivered--;
        }
        lck_rw_done(divcbinfo.mtx);     
}

/*
 * Deliver packet back into the IP processing machinery.
 *
 * If no address specified, or address is 0.0.0.0, send to ip_output();
 * otherwise, send to ip_input() and mark as having been received on
 * the interface with that address.
 * ###LOCK  called in inet_proto mutex when from div_send. 
 */
static int
div_output(so, m, addr, control)
        struct socket *so;
        register struct mbuf *m;
        struct sockaddr *addr;
        struct mbuf *control;
{
        register struct inpcb *const inp = sotoinpcb(so);
        register struct ip *const ip = mtod(m, struct ip *);
        struct sockaddr_in *sin = (struct sockaddr_in *)addr;
        int error = 0;

        if (control)
                m_freem(control);               /* XXX */

        /* Loopback avoidance and state recovery */
        if (sin) {
                struct m_tag *mtag;
                struct divert_tag *dt;
                int     len = 0;
                char    *c = sin->sin_zero;

                mtag = m_tag_alloc(KERNEL_MODULE_TAG_ID, KERNEL_TAG_TYPE_DIVERT,
                                sizeof(struct divert_tag), M_NOWAIT);
                if (mtag == NULL) {
                        error = ENOBUFS;
                        goto cantsend;
                }
                dt = (struct divert_tag *)(mtag+1);
                dt->info = 0;
                dt->cookie = sin->sin_port;
                m_tag_prepend(m, mtag);

                /*
                 * Find receive interface with the given name or IP address.
                 * The name is user supplied data so don't trust it's size or 
                 * that it is zero terminated. The name has priority.
                 * We are presently assuming that the sockaddr_in 
                 * has not been replaced by a sockaddr_div, so we limit it
                 * to 16 bytes in total. the name is stuffed (if it exists)
                 * in the sin_zero[] field.
                 */
                while (*c++ && (len++ < sizeof(sin->sin_zero)));
                if ((len > 0) && (len < sizeof(sin->sin_zero)))
                        m->m_pkthdr.rcvif = ifunit(sin->sin_zero);
        }

        /* Reinject packet into the system as incoming or outgoing */
        if (!sin || sin->sin_addr.s_addr == 0) {
                /*
                 * Don't allow both user specified and setsockopt options,
                 * and don't allow packet length sizes that will crash
                 */
                if (((ip->ip_hl != (sizeof (*ip) >> 2)) && inp->inp_options) ||
                     ((u_short)ntohs(ip->ip_len) > m->m_pkthdr.len)) {
                        error = EINVAL;
                        goto cantsend;
                }

                /* Convert fields to host order for ip_output() */
                NTOHS(ip->ip_len);
                NTOHS(ip->ip_off);

                /* Send packet to output processing */
                ipstat.ips_rawout++;                    /* XXX */
                socket_unlock(so, 0);
                error = ip_output(m,
                            inp->inp_options, &inp->inp_route,
                        (so->so_options & SO_DONTROUTE) |
                        IP_ALLOWBROADCAST | IP_RAWOUTPUT,
                        inp->inp_moptions);
                socket_lock(so, 0);
        } else {
                struct  ifaddr *ifa;

                /* If no luck with the name above. check by IP address.  */
                if (m->m_pkthdr.rcvif == NULL) {
                        /*
                         * Make sure there are no distractions
                         * for ifa_ifwithaddr. Clear the port and the ifname.
                         * Maybe zap all 8 bytes at once using a 64bit write?
                         */
                        bzero(sin->sin_zero, sizeof(sin->sin_zero));
                        /* *((u_int64_t *)sin->sin_zero) = 0; */ /* XXX ?? */
                        sin->sin_port = 0;
                        if (!(ifa = ifa_ifwithaddr((struct sockaddr *) sin))) {
                                error = EADDRNOTAVAIL;
                                goto cantsend;
                        }
                        m->m_pkthdr.rcvif = ifa->ifa_ifp;
                        ifafree(ifa);
                }
                
                if ((~IF_HWASSIST_CSUM_FLAGS(m->m_pkthdr.rcvif->if_hwassist) & 
                                m->m_pkthdr.csum_flags) == 0) {
                        if (m->m_pkthdr.csum_flags & CSUM_DELAY_DATA) {
                                m->m_pkthdr.csum_flags &= ~CSUM_DELAY_DATA;
                        }
                        m->m_pkthdr.csum_flags |=
                                CSUM_DATA_VALID | CSUM_PSEUDO_HDR |
                                CSUM_IP_CHECKED | CSUM_IP_VALID;
                        m->m_pkthdr.csum_data = 0xffff;
                }
                else if (m->m_pkthdr.csum_flags & CSUM_DELAY_DATA) {
                        int     hlen;
                        
#ifdef _IP_VHL
                        hlen = IP_VHL_HL(ip->ip_vhl) << 2;
#else
                        hlen = ip->ip_hl << 2;
#endif
                        in_delayed_cksum(m);
                        m->m_pkthdr.csum_flags &= ~CSUM_DELAY_DATA;
                        ip->ip_sum = in_cksum(m, hlen);
                }

                /* Send packet to input processing */
                proto_inject(PF_INET, m);
        }

        return error;

cantsend:
        m_freem(m);
        return error;
}

static int
div_attach(struct socket *so, int proto, struct proc *p)
{
        struct inpcb *inp;
        int error;


        inp  = sotoinpcb(so);
        if (inp)
                panic("div_attach");
        if (p && (error = proc_suser(p)) != 0)
                return error;

        error = soreserve(so, div_sendspace, div_recvspace);
        if (error)
                return error;
        error = in_pcballoc(so, &divcbinfo, p);
        if (error)
                return error;
        inp = (struct inpcb *)so->so_pcb;
        inp->inp_ip_p = proto;
        inp->inp_vflag |= INP_IPV4;
        inp->inp_flags |= INP_HDRINCL;
        /* The socket is always "connected" because
           we always know "where" to send the packet */
        so->so_state |= SS_ISCONNECTED;

#ifdef MORE_DICVLOCK_DEBUG
        printf("div_attach: so=%x sopcb=%x lock=%x ref=%x\n",
                        so, so->so_pcb, ((struct inpcb *)so->so_pcb)->inpcb_mtx, so->so_usecount);
#endif
        return 0;
}

static int
div_detach(struct socket *so)
{
        struct inpcb *inp;

#ifdef MORE_DICVLOCK_DEBUG
        printf("div_detach: so=%x sopcb=%x lock=%x ref=%x\n",
                        so, so->so_pcb, ((struct inpcb *)so->so_pcb)->inpcb_mtx, so->so_usecount);
#endif
        inp = sotoinpcb(so);
        if (inp == 0)
                panic("div_detach: so=%x null inp\n", so);
        in_pcbdetach(inp);
        inp->inp_state = INPCB_STATE_DEAD;
        return 0;
}

static int
div_abort(struct socket *so)
{
        soisdisconnected(so);
        return div_detach(so);
}

static int
div_disconnect(struct socket *so)
{
        if ((so->so_state & SS_ISCONNECTED) == 0)
                return ENOTCONN;
        return div_abort(so);
}

static int
div_bind(struct socket *so, struct sockaddr *nam, struct proc *p)
{
        struct inpcb *inp;
        int error;

        inp = sotoinpcb(so);
        /* in_pcbbind assumes that the socket is a sockaddr_in
        * and in_pcbbind requires a valid address. Since divert
        * sockets don't we need to make sure the address is
        * filled in properly.
        * XXX -- divert should not be abusing in_pcbind
        * and should probably have its own family.
        */
        if (nam->sa_family != AF_INET) {
                error = EAFNOSUPPORT;
        } else {
               ((struct sockaddr_in *)nam)->sin_addr.s_addr = INADDR_ANY;
                error = in_pcbbind(inp, nam, p);
        }
        return error;
}

static int
div_shutdown(struct socket *so)
{
        socantsendmore(so);
        return 0;
}

static int
div_send(struct socket *so, __unused int flags, struct mbuf *m, struct sockaddr *nam,
         struct mbuf *control, __unused struct proc *p)
{
        /* Packet must have a header (but that's about it) */
        if (m->m_len < sizeof (struct ip) &&
            (m = m_pullup(m, sizeof (struct ip))) == 0) {
                ipstat.ips_toosmall++;
                m_freem(m);
                return EINVAL;
        }

        /* Send packet */
        return div_output(so, m, nam, control);
}

static int
div_pcblist SYSCTL_HANDLER_ARGS
{
        int error, i, n;
        struct inpcb *inp, **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_exclusive(divcbinfo.mtx);
        if (req->oldptr == USER_ADDR_NULL) {
                n = divcbinfo.ipi_count;
                req->oldidx = 2 * (sizeof xig)
                        + (n + n/8) * sizeof(struct xinpcb);
                lck_rw_done(divcbinfo.mtx);
                return 0;
        }

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

        /*
         * OK, now we're committed to doing something.
         */
        gencnt = divcbinfo.ipi_gencnt;
        n = divcbinfo.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(divcbinfo.mtx);
                return error;
        }

        inp_list = _MALLOC(n * sizeof *inp_list, M_TEMP, M_WAITOK);
        if (inp_list == 0) {
                lck_rw_done(divcbinfo.mtx);
                return ENOMEM;
        }
        
        for (inp = LIST_FIRST(divcbinfo.listhead), i = 0; inp && i < n;
             inp = LIST_NEXT(inp, inp_list)) {
#ifdef __APPLE__
                if (inp->inp_gencnt <= gencnt && inp->inp_state != INPCB_STATE_DEAD)
#else
                if (inp->inp_gencnt <= gencnt && !prison_xinpcb(req->p, inp))
#endif
                        inp_list[i++] = inp;
        }
        n = i;

        error = 0;
        for (i = 0; i < n; i++) {
                inp = inp_list[i];
                if (inp->inp_gencnt <= gencnt && inp->inp_state != INPCB_STATE_DEAD) {
                        struct xinpcb xi;

                        bzero(&xi, sizeof(xi));
                        xi.xi_len = sizeof xi;
                        /* XXX should avoid extra copy */
                        inpcb_to_compat(inp, &xi.xi_inp);
                        if (inp->inp_socket)
                                sotoxsocket(inp->inp_socket, &xi.xi_socket);
                        error = SYSCTL_OUT(req, &xi, sizeof xi);
                }
        }
        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 = divcbinfo.ipi_gencnt;
                xig.xig_sogen = so_gencnt;
                xig.xig_count = divcbinfo.ipi_count;
                error = SYSCTL_OUT(req, &xig, sizeof xig);
        }
        FREE(inp_list, M_TEMP);
        lck_rw_done(divcbinfo.mtx);
        return error;
}

__private_extern__ int
div_lock(struct socket *so, int refcount, int lr)
 {
        int lr_saved;
        if (lr == 0) 
                lr_saved = (unsigned int) __builtin_return_address(0);
        else lr_saved = lr;
        
#ifdef MORE_DICVLOCK_DEBUG
        printf("div_lock: so=%x sopcb=%x lock=%x ref=%x lr=%x\n",
                        so, 
                        so->so_pcb, 
                        so->so_pcb ? ((struct inpcb *)so->so_pcb)->inpcb_mtx : 0, 
                        so->so_usecount, 
                        lr_saved);
#endif
        if (so->so_pcb) {
                lck_mtx_lock(((struct inpcb *)so->so_pcb)->inpcb_mtx);
        } else  {
                panic("div_lock: so=%x NO PCB! lr=%x\n", so, lr_saved);
                lck_mtx_lock(so->so_proto->pr_domain->dom_mtx);
        }
        
        if (so->so_usecount < 0)
                panic("div_lock: so=%x so_pcb=%x lr=%x ref=%x\n",
                so, so->so_pcb, lr_saved, so->so_usecount);
        
        if (refcount)
                so->so_usecount++;
        so->lock_lr[so->next_lock_lr] = (u_int32_t *)lr_saved;
        so->next_lock_lr = (so->next_lock_lr+1) % SO_LCKDBG_MAX;

        return (0);
}

__private_extern__ int
div_unlock(struct socket *so, int refcount, int lr)
{
        int lr_saved;
        lck_mtx_t * mutex_held;
        struct inpcb *inp = sotoinpcb(so);      

        if (lr == 0) 
                lr_saved = (unsigned int) __builtin_return_address(0);
        else lr_saved = lr;

        
#ifdef MORE_DICVLOCK_DEBUG
        printf("div_unlock: so=%x sopcb=%x lock=%x ref=%x lr=%x\n",
                        so, 
                        so->so_pcb, 
                        so->so_pcb ? ((struct inpcb *)so->so_pcb)->inpcb_mtx : 0, 
                        so->so_usecount, 
                        lr_saved);
#endif
        if (refcount)
                so->so_usecount--;
        
        if (so->so_usecount < 0)
                panic("div_unlock: so=%x usecount=%x\n", so, so->so_usecount);
        if (so->so_pcb == NULL) {
                panic("div_unlock: so=%x NO PCB usecount=%x lr=%x\n", so, so->so_usecount, lr_saved);
                mutex_held = so->so_proto->pr_domain->dom_mtx;
        } else {
                mutex_held = ((struct inpcb *)so->so_pcb)->inpcb_mtx;
        }

        if (so->so_usecount == 0 && (inp->inp_wantcnt == WNT_STOPUSING)) {
                lck_rw_lock_exclusive(divcbinfo.mtx);
                in_pcbdispose(inp);
                lck_rw_done(divcbinfo.mtx);
                return (0);
        }
        lck_mtx_assert(mutex_held, LCK_MTX_ASSERT_OWNED);
        so->unlock_lr[so->next_unlock_lr] = (u_int *)lr_saved;
        so->next_unlock_lr = (so->next_unlock_lr+1) % SO_LCKDBG_MAX;
        lck_mtx_unlock(mutex_held);
        return (0);
}

__private_extern__ lck_mtx_t *
div_getlock(struct socket *so, __unused int locktype)
{
        struct inpcb *inpcb = (struct inpcb *)so->so_pcb;
        
        if (so->so_pcb)  {
                if (so->so_usecount < 0)
                        panic("div_getlock: so=%x usecount=%x\n", so, so->so_usecount);
                return(inpcb->inpcb_mtx);
        } else {
                panic("div_getlock: so=%x NULL so_pcb\n", so);
                return (so->so_proto->pr_domain->dom_mtx);
        }
}


struct pr_usrreqs div_usrreqs = {
        div_abort, pru_accept_notsupp, div_attach, div_bind,
        pru_connect_notsupp, pru_connect2_notsupp, in_control, div_detach,
        div_disconnect, pru_listen_notsupp, in_setpeeraddr, pru_rcvd_notsupp,
        pru_rcvoob_notsupp, div_send, pru_sense_null, div_shutdown,
        in_setsockaddr, sosend, soreceive, pru_sopoll_notsupp
};