xnu-201.tar.gz

[apple/xnu.git] / bsd / kern / uipc_usrreq.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, 1989, 1991, 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: @(#)uipc_usrreq.c 8.3 (Berkeley) 1/4/94
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/domain.h>
#include <sys/fcntl.h>
#include <sys/malloc.h>         /* XXX must be before <sys/file.h> */
#include <sys/file.h>
#include <sys/filedesc.h>
#include <sys/lock.h>
#include <sys/mbuf.h>
#include <sys/namei.h>
#include <sys/proc.h>
#include <sys/protosw.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/stat.h>
#include <sys/sysctl.h>
#include <sys/un.h>
#include <sys/unpcb.h>
#include <sys/vnode.h>

#include <kern/zalloc.h>

struct  zone *unp_zone;
static  unp_gen_t unp_gencnt;
static  u_int unp_count;

static  struct unp_head unp_shead, unp_dhead;

/*
 * Unix communications domain.
 *
 * TODO:
 *      SEQPACKET, RDM
 *      rethink name space problems
 *      need a proper out-of-band
 *      lock pushdown
 */
static struct   sockaddr sun_noname = { sizeof(sun_noname), AF_LOCAL };
static ino_t    unp_ino;                /* prototype for fake inode numbers */

static int     unp_attach __P((struct socket *));
static void    unp_detach __P((struct unpcb *));
static int     unp_bind __P((struct unpcb *,struct sockaddr *, struct proc *));
static int     unp_connect __P((struct socket *,struct sockaddr *,
                                struct proc *));
static void    unp_disconnect __P((struct unpcb *));
static void    unp_shutdown __P((struct unpcb *));
static void    unp_drop __P((struct unpcb *, int));
static void    unp_gc __P((void));
static void    unp_scan __P((struct mbuf *, void (*)(struct file *)));
static void    unp_mark __P((struct file *));
static void    unp_discard __P((struct file *));
static int     unp_internalize __P((struct mbuf *, struct proc *));

static int
uipc_abort(struct socket *so)
{
        struct unpcb *unp = sotounpcb(so);

        if (unp == 0)
                return EINVAL;
        unp_drop(unp, ECONNABORTED);
        return 0;
}

static int
uipc_accept(struct socket *so, struct sockaddr **nam)
{
        struct unpcb *unp = sotounpcb(so);

        if (unp == 0)
                return EINVAL;

        /*
         * Pass back name of connected socket,
         * if it was bound and we are still connected
         * (our peer may have closed already!).
         */
        if (unp->unp_conn && unp->unp_conn->unp_addr) {
                *nam = dup_sockaddr((struct sockaddr *)unp->unp_conn->unp_addr,
                                    1);
        } else {
                *nam = dup_sockaddr((struct sockaddr *)&sun_noname, 1);
        }
        return 0;
}

static int
uipc_attach(struct socket *so, int proto, struct proc *p)
{
        struct unpcb *unp = sotounpcb(so);

        if (unp != 0)
                return EISCONN;
        return unp_attach(so);
}

static int
uipc_bind(struct socket *so, struct sockaddr *nam, struct proc *p)
{
        struct unpcb *unp = sotounpcb(so);

        if (unp == 0)
                return EINVAL;

        return unp_bind(unp, nam, p);
}

static int
uipc_connect(struct socket *so, struct sockaddr *nam, struct proc *p)
{
        struct unpcb *unp = sotounpcb(so);

        if (unp == 0)
                return EINVAL;
        return unp_connect(so, nam, p);
}

static int
uipc_connect2(struct socket *so1, struct socket *so2)
{
        struct unpcb *unp = sotounpcb(so1);

        if (unp == 0)
                return EINVAL;

        return unp_connect2(so1, so2);
}

/* control is EOPNOTSUPP */

static int
uipc_detach(struct socket *so)
{
        struct unpcb *unp = sotounpcb(so);

        if (unp == 0)
                return EINVAL;

        unp_detach(unp);
        return 0;
}

static int
uipc_disconnect(struct socket *so)
{
        struct unpcb *unp = sotounpcb(so);

        if (unp == 0)
                return EINVAL;
        unp_disconnect(unp);
        return 0;
}

static int
uipc_listen(struct socket *so, struct proc *p)
{
        struct unpcb *unp = sotounpcb(so);

        if (unp == 0 || unp->unp_vnode == 0)
                return EINVAL;
        return 0;
}

static int
uipc_peeraddr(struct socket *so, struct sockaddr **nam)
{
        struct unpcb *unp = sotounpcb(so);

        if (unp == 0)
                return EINVAL;
        if (unp->unp_conn && unp->unp_conn->unp_addr)
                *nam = dup_sockaddr((struct sockaddr *)unp->unp_conn->unp_addr,
                                    1);
        return 0;
}

static int
uipc_rcvd(struct socket *so, int flags)
{
        struct unpcb *unp = sotounpcb(so);
        struct socket *so2;

        if (unp == 0)
                return EINVAL;
        switch (so->so_type) {
        case SOCK_DGRAM:
                panic("uipc_rcvd DGRAM?");
                /*NOTREACHED*/

        case SOCK_STREAM:
#define rcv (&so->so_rcv)
#define snd (&so2->so_snd)
                if (unp->unp_conn == 0)
                        break;
                so2 = unp->unp_conn->unp_socket;
                /*
                 * Adjust backpressure on sender
                 * and wakeup any waiting to write.
                 */
                snd->sb_mbmax += unp->unp_mbcnt - rcv->sb_mbcnt;
                unp->unp_mbcnt = rcv->sb_mbcnt;
                snd->sb_hiwat += unp->unp_cc - rcv->sb_cc;
                unp->unp_cc = rcv->sb_cc;
                sowwakeup(so2);
#undef snd
#undef rcv
                break;

        default:
                panic("uipc_rcvd unknown socktype");
        }
        return 0;
}

/* pru_rcvoob is EOPNOTSUPP */

static int
uipc_send(struct socket *so, int flags, struct mbuf *m, struct sockaddr *nam,
          struct mbuf *control, struct proc *p)
{
        int error = 0;
        struct unpcb *unp = sotounpcb(so);
        struct socket *so2;

        if (unp == 0) {
                error = EINVAL;
                goto release;
        }
        if (flags & PRUS_OOB) {
                error = EOPNOTSUPP;
                goto release;
        }

        if (control && (error = unp_internalize(control, p)))
                goto release;

        switch (so->so_type) {
        case SOCK_DGRAM: 
        {
                struct sockaddr *from;

                if (nam) {
                        if (unp->unp_conn) {
                                error = EISCONN;
                                break;
                        }
                        error = unp_connect(so, nam, p);
                        if (error)
                                break;
                } else {
                        if (unp->unp_conn == 0) {
                                error = ENOTCONN;
                                break;
                        }
                }
                so2 = unp->unp_conn->unp_socket;
                if (unp->unp_addr)
                        from = (struct sockaddr *)unp->unp_addr;
                else
                        from = &sun_noname;
                if (sbappendaddr(&so2->so_rcv, from, m, control)) {
                        sorwakeup(so2);
                        m = 0;
                        control = 0;
                } else
                        error = ENOBUFS;
                if (nam)
                        unp_disconnect(unp);
                break;
        }

        case SOCK_STREAM:
#define rcv (&so2->so_rcv)
#define snd (&so->so_snd)
                /* Connect if not connected yet. */
                /*
                 * Note: A better implementation would complain
                 * if not equal to the peer's address.
                 */
                if ((so->so_state & SS_ISCONNECTED) == 0) {
                        if (nam) {
                                error = unp_connect(so, nam, p);
                                if (error)
                                        break;  /* XXX */
                        } else {
                                error = ENOTCONN;
                                break;
                        }
                }

                if (so->so_state & SS_CANTSENDMORE) {
                        error = EPIPE;
                        break;
                }
                if (unp->unp_conn == 0)
                        panic("uipc_send connected but no connection?");
                so2 = unp->unp_conn->unp_socket;
                /*
                 * Send to paired receive port, and then reduce
                 * send buffer hiwater marks to maintain backpressure.
                 * Wake up readers.
                 */
                if (control) {
                        if (sbappendcontrol(rcv, m, control))
                                control = 0;
                } else
                        sbappend(rcv, m);
                snd->sb_mbmax -=
                        rcv->sb_mbcnt - unp->unp_conn->unp_mbcnt;
                unp->unp_conn->unp_mbcnt = rcv->sb_mbcnt;
                snd->sb_hiwat -= rcv->sb_cc - unp->unp_conn->unp_cc;
                unp->unp_conn->unp_cc = rcv->sb_cc;
                sorwakeup(so2);
                m = 0;
#undef snd
#undef rcv
                break;

        default:
                panic("uipc_send unknown socktype");
        }

        /*
         * SEND_EOF is equivalent to a SEND followed by
         * a SHUTDOWN.
         */
        if (flags & PRUS_EOF) {
                socantsendmore(so);
                unp_shutdown(unp);
        }

release:
        if (control)
                m_freem(control);
        if (m)
                m_freem(m);
        return error;
}

static int
uipc_sense(struct socket *so, struct stat *sb)
{
        struct unpcb *unp = sotounpcb(so);
        struct socket *so2;

        if (unp == 0)
                return EINVAL;
        sb->st_blksize = so->so_snd.sb_hiwat;
        if (so->so_type == SOCK_STREAM && unp->unp_conn != 0) {
                so2 = unp->unp_conn->unp_socket;
                sb->st_blksize += so2->so_rcv.sb_cc;
        }
        sb->st_dev = NODEV;
        if (unp->unp_ino == 0)
                unp->unp_ino = unp_ino++;
        sb->st_ino = unp->unp_ino;
        return (0);
}

static int
uipc_shutdown(struct socket *so)
{
        struct unpcb *unp = sotounpcb(so);

        if (unp == 0)
                return EINVAL;
        socantsendmore(so);
        unp_shutdown(unp);
        return 0;
}

static int
uipc_sockaddr(struct socket *so, struct sockaddr **nam)
{
        struct unpcb *unp = sotounpcb(so);

        if (unp == 0)
                return EINVAL;
        if (unp->unp_addr)
                *nam = dup_sockaddr((struct sockaddr *)unp->unp_addr, 1);
        return 0;
}

struct pr_usrreqs uipc_usrreqs = {
        uipc_abort, uipc_accept, uipc_attach, uipc_bind, uipc_connect,
        uipc_connect2, pru_control_notsupp, uipc_detach, uipc_disconnect,
        uipc_listen, uipc_peeraddr, uipc_rcvd, pru_rcvoob_notsupp,
        uipc_send, uipc_sense, uipc_shutdown, uipc_sockaddr,
        sosend, soreceive, sopoll
};
        
/*
 * Both send and receive buffers are allocated PIPSIZ bytes of buffering
 * for stream sockets, although the total for sender and receiver is
 * actually only PIPSIZ.
 * Datagram sockets really use the sendspace as the maximum datagram size,
 * and don't really want to reserve the sendspace.  Their recvspace should
 * be large enough for at least one max-size datagram plus address.
 */
#ifndef PIPSIZ
#define PIPSIZ  8192
#endif
static u_long   unpst_sendspace = PIPSIZ;
static u_long   unpst_recvspace = PIPSIZ;
static u_long   unpdg_sendspace = 2*1024;       /* really max datagram size */
static u_long   unpdg_recvspace = 4*1024;

static int      unp_rights;                     /* file descriptors in flight */

SYSCTL_DECL(_net_local_stream);
SYSCTL_INT(_net_local_stream, OID_AUTO, sendspace, CTLFLAG_RW, 
           &unpst_sendspace, 0, "");
SYSCTL_INT(_net_local_stream, OID_AUTO, recvspace, CTLFLAG_RW,
           &unpst_recvspace, 0, "");
SYSCTL_DECL(_net_local_dgram);
SYSCTL_INT(_net_local_dgram, OID_AUTO, maxdgram, CTLFLAG_RW,
           &unpdg_sendspace, 0, "");
SYSCTL_INT(_net_local_dgram, OID_AUTO, recvspace, CTLFLAG_RW,
           &unpdg_recvspace, 0, "");
SYSCTL_DECL(_net_local);
SYSCTL_INT(_net_local, OID_AUTO, inflight, CTLFLAG_RD, &unp_rights, 0, "");

static int
unp_attach(so)
        struct socket *so;
{
        register struct unpcb *unp;
        int error;

        if (so->so_snd.sb_hiwat == 0 || so->so_rcv.sb_hiwat == 0) {
                switch (so->so_type) {

                case SOCK_STREAM:
                        error = soreserve(so, unpst_sendspace, unpst_recvspace);
                        break;

                case SOCK_DGRAM:
                        error = soreserve(so, unpdg_sendspace, unpdg_recvspace);
                        break;

                default:
                        panic("unp_attach");
                }
                if (error)
                        return (error);
        }
        unp = zalloc(unp_zone);
        if (unp == NULL)
                return (ENOBUFS);
        bzero(unp, sizeof *unp);
        unp->unp_gencnt = ++unp_gencnt;
        unp_count++;
        LIST_INIT(&unp->unp_refs);
        unp->unp_socket = so;
        LIST_INSERT_HEAD(so->so_type == SOCK_DGRAM ? &unp_dhead
                         : &unp_shead, unp, unp_link);
        so->so_pcb = (caddr_t)unp;
        return (0);
}

static void
unp_detach(unp)
        register struct unpcb *unp;
{
        LIST_REMOVE(unp, unp_link);
        unp->unp_gencnt = ++unp_gencnt;
        --unp_count;
        if (unp->unp_vnode) {
                unp->unp_vnode->v_socket = 0;
                thread_funnel_switch(NETWORK_FUNNEL, KERNEL_FUNNEL);
                vrele(unp->unp_vnode);
                thread_funnel_switch(KERNEL_FUNNEL, NETWORK_FUNNEL);
                unp->unp_vnode = 0;
        }
        if (unp->unp_conn)
                unp_disconnect(unp);
        while (unp->unp_refs.lh_first)
                unp_drop(unp->unp_refs.lh_first, ECONNRESET);
        soisdisconnected(unp->unp_socket);
        unp->unp_socket->so_pcb = 0;
        if (unp_rights) {
                /*
                 * Normally the receive buffer is flushed later,
                 * in sofree, but if our receive buffer holds references
                 * to descriptors that are now garbage, we will dispose
                 * of those descriptor references after the garbage collector
                 * gets them (resulting in a "panic: closef: count < 0").
                 */
                sorflush(unp->unp_socket);
                unp_gc();
        }
        if (unp->unp_addr)
                FREE(unp->unp_addr, M_SONAME);
        zfree(unp_zone, unp);
}

static int
unp_bind(unp, nam, p)
        struct unpcb *unp;
        struct sockaddr *nam;
        struct proc *p;
{
        struct sockaddr_un *soun = (struct sockaddr_un *)nam;
        register struct vnode *vp;
        struct vattr vattr;
        int error, namelen;
        struct nameidata nd;
        char buf[SOCK_MAXADDRLEN];

        if (unp->unp_vnode != NULL)
                return (EINVAL);
#define offsetof(s, e) ((char *)&((s *)0)->e - (char *)((s *)0))
        namelen = soun->sun_len - offsetof(struct sockaddr_un, sun_path);
        if (namelen <= 0)
                return EINVAL;
        strncpy(buf, soun->sun_path, namelen);
        buf[namelen] = 0;       /* null-terminate the string */
        thread_funnel_switch(NETWORK_FUNNEL, KERNEL_FUNNEL);
        NDINIT(&nd, CREATE, FOLLOW | LOCKPARENT, UIO_SYSSPACE,
            buf, p);
/* SHOULD BE ABLE TO ADOPT EXISTING AND wakeup() ALA FIFO's */
        error = namei(&nd);
        if (error) {
                thread_funnel_switch(KERNEL_FUNNEL, NETWORK_FUNNEL);
                return (error);
        }
        vp = nd.ni_vp;
        if (vp != NULL) {
                VOP_ABORTOP(nd.ni_dvp, &nd.ni_cnd);
                if (nd.ni_dvp == vp)
                        vrele(nd.ni_dvp);
                else
                        vput(nd.ni_dvp);
                vrele(vp);
                thread_funnel_switch(KERNEL_FUNNEL, NETWORK_FUNNEL);
                return (EADDRINUSE);
        }
        VATTR_NULL(&vattr);
        vattr.va_type = VSOCK;
        vattr.va_mode = (ACCESSPERMS & ~p->p_fd->fd_cmask);
        VOP_LEASE(nd.ni_dvp, p, p->p_ucred, LEASE_WRITE);
        error = VOP_CREATE(nd.ni_dvp, &nd.ni_vp, &nd.ni_cnd, &vattr);
#if 0
        /* In FreeBSD create leave s parent held ; not here */
        vput(nd.ni_dvp);
#endif
        if (error) {
                thread_funnel_switch(KERNEL_FUNNEL, NETWORK_FUNNEL);
                return (error);
        }
        vp = nd.ni_vp;
        vp->v_socket = unp->unp_socket;
        unp->unp_vnode = vp;
        unp->unp_addr = (struct sockaddr_un *)dup_sockaddr(nam, 1);
        VOP_UNLOCK(vp, 0, p);
        thread_funnel_switch(KERNEL_FUNNEL, NETWORK_FUNNEL);
        return (0);
}

static int
unp_connect(so, nam, p)
        struct socket *so;
        struct sockaddr *nam;
        struct proc *p;
{
        register struct sockaddr_un *soun = (struct sockaddr_un *)nam;
        register struct vnode *vp;
        register struct socket *so2, *so3;
        struct unpcb *unp2, *unp3;
        int error, len;
        struct nameidata nd;
        char buf[SOCK_MAXADDRLEN];

        len = nam->sa_len - offsetof(struct sockaddr_un, sun_path);
        if (len <= 0)
                return EINVAL;
        strncpy(buf, soun->sun_path, len);
        buf[len] = 0;

        thread_funnel_switch(NETWORK_FUNNEL, KERNEL_FUNNEL);
        NDINIT(&nd, LOOKUP, FOLLOW | LOCKLEAF, UIO_SYSSPACE, buf, p);
        error = namei(&nd);
        if (error) {
                thread_funnel_switch(KERNEL_FUNNEL, NETWORK_FUNNEL);
                return (error);
        }
        vp = nd.ni_vp;
        if (vp->v_type != VSOCK) {
                error = ENOTSOCK;
                goto bad;
        }
        error = VOP_ACCESS(vp, VWRITE, p->p_ucred, p);
        if (error)
                goto bad;
        so2 = vp->v_socket;
        if (so2 == 0) {
                error = ECONNREFUSED;
                goto bad;
        }
        if (so->so_type != so2->so_type) {
                error = EPROTOTYPE;
                goto bad;
        }
        thread_funnel_switch(KERNEL_FUNNEL, NETWORK_FUNNEL);
        if (so->so_proto->pr_flags & PR_CONNREQUIRED) {
                if ((so2->so_options & SO_ACCEPTCONN) == 0 ||
                    (so3 = sonewconn(so2, 0)) == 0) {
                        error = ECONNREFUSED;
                        thread_funnel_switch(NETWORK_FUNNEL, KERNEL_FUNNEL);
                        goto bad;
                }
                unp2 = sotounpcb(so2);
                unp3 = sotounpcb(so3);
                if (unp2->unp_addr)
                        unp3->unp_addr = (struct sockaddr_un *)
                                dup_sockaddr((struct sockaddr *)
                                             unp2->unp_addr, 1);
                so2 = so3;
        }
        error = unp_connect2(so, so2);
        thread_funnel_switch(NETWORK_FUNNEL, KERNEL_FUNNEL);
bad:
        vput(vp);
        thread_funnel_switch(KERNEL_FUNNEL, NETWORK_FUNNEL);
        return (error);
}

int
unp_connect2(so, so2)
        register struct socket *so;
        register struct socket *so2;
{
        register struct unpcb *unp = sotounpcb(so);
        register struct unpcb *unp2;

        if (so2->so_type != so->so_type)
                return (EPROTOTYPE);
        unp2 = sotounpcb(so2);

        /* Verify both sockets are still opened */
        if (unp == 0 || unp2 == 0)
                return (EINVAL);

        unp->unp_conn = unp2;
        switch (so->so_type) {

        case SOCK_DGRAM:
                LIST_INSERT_HEAD(&unp2->unp_refs, unp, unp_reflink);
                soisconnected(so);
                break;

        case SOCK_STREAM:
                unp2->unp_conn = unp;
                soisconnected(so);
                soisconnected(so2);
                break;

        default:
                panic("unp_connect2");
        }
        return (0);
}

static void
unp_disconnect(unp)
        struct unpcb *unp;
{
        register struct unpcb *unp2 = unp->unp_conn;

        if (unp2 == 0)
                return;
        unp->unp_conn = 0;
        switch (unp->unp_socket->so_type) {

        case SOCK_DGRAM:
                LIST_REMOVE(unp, unp_reflink);
                unp->unp_socket->so_state &= ~SS_ISCONNECTED;
                break;

        case SOCK_STREAM:
                soisdisconnected(unp->unp_socket);
                unp2->unp_conn = 0;
                soisdisconnected(unp2->unp_socket);
                break;
        }
}

#ifdef notdef
void
unp_abort(unp)
        struct unpcb *unp;
{

        unp_detach(unp);
}
#endif

static int
unp_pcblist SYSCTL_HANDLER_ARGS
{
        int error, i, n;
        struct unpcb *unp, **unp_list;
        unp_gen_t gencnt;
        struct xunpgen xug;
        struct unp_head *head;

        head = ((intptr_t)arg1 == SOCK_DGRAM ? &unp_dhead : &unp_shead);

        /*
         * The process of preparing the PCB list is too time-consuming and
         * resource-intensive to repeat twice on every request.
         */
        if (req->oldptr == 0) {
                n = unp_count;
                req->oldidx = 2 * (sizeof xug)
                        + (n + n/8) * sizeof(struct xunpcb);
                return 0;
        }

        if (req->newptr != 0)
                return EPERM;

        /*
         * OK, now we're committed to doing something.
         */
        gencnt = unp_gencnt;
        n = unp_count;

        xug.xug_len = sizeof xug;
        xug.xug_count = n;
        xug.xug_gen = gencnt;
        xug.xug_sogen = so_gencnt;
        error = SYSCTL_OUT(req, &xug, sizeof xug);
        if (error)
                return error;

        /*
         * We are done if there is no pcb
         */
        if (n == 0) 
            return 0;

        unp_list = _MALLOC(n * sizeof *unp_list, M_TEMP, M_WAITOK);
        if (unp_list == 0)
                return ENOMEM;
        
        for (unp = head->lh_first, i = 0; unp && i < n;
             unp = unp->unp_link.le_next) {
                if (unp->unp_gencnt <= gencnt)
                        unp_list[i++] = unp;
        }
        n = i;                  /* in case we lost some during malloc */

        error = 0;
        for (i = 0; i < n; i++) {
                unp = unp_list[i];
                if (unp->unp_gencnt <= gencnt) {
                        struct xunpcb xu;
                        xu.xu_len = sizeof xu;
                        xu.xu_unpp = unp;
                        /*
                         * XXX - need more locking here to protect against
                         * connect/disconnect races for SMP.
                         */
                        if (unp->unp_addr)
                                bcopy(unp->unp_addr, &xu.xu_addr, 
                                      unp->unp_addr->sun_len);
                        if (unp->unp_conn && unp->unp_conn->unp_addr)
                                bcopy(unp->unp_conn->unp_addr,
                                      &xu.xu_caddr,
                                      unp->unp_conn->unp_addr->sun_len);
                        bcopy(unp, &xu.xu_unp, sizeof *unp);
                        sotoxsocket(unp->unp_socket, &xu.xu_socket);
                        error = SYSCTL_OUT(req, &xu, sizeof xu);
                }
        }
        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.
                 */
                xug.xug_gen = unp_gencnt;
                xug.xug_sogen = so_gencnt;
                xug.xug_count = unp_count;
                error = SYSCTL_OUT(req, &xug, sizeof xug);
        }
        FREE(unp_list, M_TEMP);
        return error;
}

SYSCTL_PROC(_net_local_dgram, OID_AUTO, pcblist, CTLFLAG_RD, 
            (caddr_t)(long)SOCK_DGRAM, 0, unp_pcblist, "S,xunpcb",
            "List of active local datagram sockets");
SYSCTL_PROC(_net_local_stream, OID_AUTO, pcblist, CTLFLAG_RD, 
            (caddr_t)(long)SOCK_STREAM, 0, unp_pcblist, "S,xunpcb",
            "List of active local stream sockets");

static void
unp_shutdown(unp)
        struct unpcb *unp;
{
        struct socket *so;

        if (unp->unp_socket->so_type == SOCK_STREAM && unp->unp_conn &&
            (so = unp->unp_conn->unp_socket))
                socantrcvmore(so);
}

static void
unp_drop(unp, errno)
        struct unpcb *unp;
        int errno;
{
        struct socket *so = unp->unp_socket;

        so->so_error = errno;
        unp_disconnect(unp);
        if (so->so_head) {
                LIST_REMOVE(unp, unp_link);
                unp->unp_gencnt = ++unp_gencnt;
                unp_count--;
                so->so_pcb = (caddr_t) 0;
                if (unp->unp_addr)
                        FREE(unp->unp_addr, M_SONAME);
                zfree(unp_zone, unp);
                sofree(so);
        }
}

#ifdef notdef
void
unp_drain()
{

}
#endif

int
unp_externalize(rights)
        struct mbuf *rights;
{
        struct proc *p = current_proc();                /* XXX */
        register int i;
        register struct cmsghdr *cm = mtod(rights, struct cmsghdr *);
        register struct file **rp = (struct file **)(cm + 1);
        register struct file *fp;
        int newfds = (cm->cmsg_len - sizeof(*cm)) / sizeof (int);
        int f;


        thread_funnel_switch(NETWORK_FUNNEL, KERNEL_FUNNEL);

        /*
         * if the new FD's will not fit, then we free them all
         */
        if (!fdavail(p, newfds)) {
                for (i = 0; i < newfds; i++) {
                        fp = *rp;
                        unp_discard(fp);
                        *rp++ = 0;
                }

                thread_funnel_switch(KERNEL_FUNNEL, NETWORK_FUNNEL);
                return (EMSGSIZE);
        }
        /*
         * now change each pointer to an fd in the global table to 
         * an integer that is the index to the local fd table entry
         * that we set up to point to the global one we are transferring.
         * XXX this assumes a pointer and int are the same size...!
         */
        for (i = 0; i < newfds; i++) {
                if (fdalloc(p, 0, &f))
                        panic("unp_externalize");
                fp = *rp;
                p->p_fd->fd_ofiles[f] = fp;
                *fdflags(p, f) &= ~UF_RESERVED;
                fp->f_msgcount--;
                unp_rights--;
                *(int *)rp++ = f;
        }

        thread_funnel_switch(KERNEL_FUNNEL, NETWORK_FUNNEL);
        return (0);
}

void
unp_init(void)
{
        unp_zone = zinit(sizeof(struct unpcb), 
                         (nmbclusters * sizeof(struct unpcb)), 
                          4096, "unpzone");
        if (unp_zone == 0)
                panic("unp_init");
        LIST_INIT(&unp_dhead);
        LIST_INIT(&unp_shead);
}

#ifndef MIN
#define MIN(a,b) (((a)<(b))?(a):(b))
#endif

static int
unp_internalize(control, p)
        struct mbuf *control;
        struct proc *p;
{
        register struct cmsghdr *cm = mtod(control, struct cmsghdr *);
        register struct file **rp;
        struct file *fp;
        register int i, error;
        int oldfds;

        thread_funnel_switch(NETWORK_FUNNEL, KERNEL_FUNNEL);
        if (cm->cmsg_type != SCM_RIGHTS || cm->cmsg_level != SOL_SOCKET ||
            cm->cmsg_len != control->m_len) {
             thread_funnel_switch(KERNEL_FUNNEL, NETWORK_FUNNEL);
             return (EINVAL);
        }

        oldfds = (cm->cmsg_len - sizeof (*cm)) / sizeof (int);
        rp = (struct file **)(cm + 1);
        for (i = 0; i < oldfds; i++)
             if (error = fdgetf(p, *(int *)rp++, 0)) {

                  thread_funnel_switch(KERNEL_FUNNEL, NETWORK_FUNNEL);
                  return (error);
             }

        rp = (struct file **)(cm + 1);
        for (i = 0; i < oldfds; i++) {
                (void) fdgetf(p, *(int *)rp, &fp);
                *rp++ = fp;
                fref(fp);
                fp->f_msgcount++;
                unp_rights++;
        }

        thread_funnel_switch(KERNEL_FUNNEL, NETWORK_FUNNEL);
        return (0);
}

static int      unp_defer, unp_gcing;

static void
unp_gc()
{
        register struct file *fp, *nextfp;
        register struct socket *so;
        struct file **extra_ref, **fpp;
        int nunref, i;

        if (unp_gcing)
                return;
        unp_gcing = 1;
        unp_defer = 0;
        /* 
         * before going through all this, set all FDs to 
         * be NOT defered and NOT externally accessible
         */
        thread_funnel_switch(NETWORK_FUNNEL, KERNEL_FUNNEL);
        for (fp = filehead.lh_first; fp != 0; fp = fp->f_list.le_next)
                fp->f_flag &= ~(FMARK|FDEFER);
        do {
                for (fp = filehead.lh_first; fp != 0; fp = fp->f_list.le_next) {
                        /*
                         * If the file is not open, skip it
                         */
                        if (fcount(fp) == 0)
                                continue;
                        /*
                         * If we already marked it as 'defer'  in a
                         * previous pass, then try process it this time
                         * and un-mark it
                         */
                        if (fp->f_flag & FDEFER) {
                                fp->f_flag &= ~FDEFER;
                                unp_defer--;
                        } else {
                                /*
                                 * if it's not defered, then check if it's
                                 * already marked.. if so skip it
                                 */
                                if (fp->f_flag & FMARK)
                                        continue;
                                /* 
                                 * If all references are from messages
                                 * in transit, then skip it. it's not 
                                 * externally accessible.
                                 */ 
                                if (fcount(fp) == fp->f_msgcount)
                                        continue;
                                /* 
                                 * If it got this far then it must be
                                 * externally accessible.
                                 */
                                fp->f_flag |= FMARK;
                        }
                        /*
                         * either it was defered, or it is externally 
                         * accessible and not already marked so.
                         * Now check if it is possibly one of OUR sockets.
                         */ 
                        if (fp->f_type != DTYPE_SOCKET ||
                            (so = (struct socket *)fp->f_data) == 0)
                                continue;
                        if (so->so_proto->pr_domain != &localdomain ||
                            (so->so_proto->pr_flags&PR_RIGHTS) == 0)
                                continue;
#ifdef notdef
                        /* if this code is enabled need to run under network funnel */
                        if (so->so_rcv.sb_flags & SB_LOCK) {
                                /*
                                 * This is problematical; it's not clear
                                 * we need to wait for the sockbuf to be
                                 * unlocked (on a uniprocessor, at least),
                                 * and it's also not clear what to do
                                 * if sbwait returns an error due to receipt
                                 * of a signal.  If sbwait does return
                                 * an error, we'll go into an infinite
                                 * loop.  Delete all of this for now.
                                 */
                                (void) sbwait(&so->so_rcv);
                                goto restart;
                        }
#endif
                        /*
                         * So, Ok, it's one of our sockets and it IS externally
                         * accessible (or was defered). Now we look
                         * to see if we hold any file descriptors in its
                         * message buffers. Follow those links and mark them 
                         * as accessible too.
                         */
                        unp_scan(so->so_rcv.sb_mb, unp_mark);
                }
        } while (unp_defer);
        /*
         * We grab an extra reference to each of the file table entries
         * that are not otherwise accessible and then free the rights
         * that are stored in messages on them.
         *
         * The bug in the orginal code is a little tricky, so I'll describe
         * what's wrong with it here.
         *
         * It is incorrect to simply unp_discard each entry for f_msgcount
         * times -- consider the case of sockets A and B that contain
         * references to each other.  On a last close of some other socket,
         * we trigger a gc since the number of outstanding rights (unp_rights)
         * is non-zero.  If during the sweep phase the gc code un_discards,
         * we end up doing a (full) closef on the descriptor.  A closef on A
         * results in the following chain.  Closef calls soo_close, which
         * calls soclose.   Soclose calls first (through the switch
         * uipc_usrreq) unp_detach, which re-invokes unp_gc.  Unp_gc simply
         * returns because the previous instance had set unp_gcing, and
         * we return all the way back to soclose, which marks the socket
         * with SS_NOFDREF, and then calls sofree.  Sofree calls sorflush
         * to free up the rights that are queued in messages on the socket A,
         * i.e., the reference on B.  The sorflush calls via the dom_dispose
         * switch unp_dispose, which unp_scans with unp_discard.  This second
         * instance of unp_discard just calls closef on B.
         *
         * Well, a similar chain occurs on B, resulting in a sorflush on B,
         * which results in another closef on A.  Unfortunately, A is already
         * being closed, and the descriptor has already been marked with
         * SS_NOFDREF, and soclose panics at this point.
         *
         * Here, we first take an extra reference to each inaccessible
         * descriptor.  Then, we call sorflush ourself, since we know
         * it is a Unix domain socket anyhow.  After we destroy all the
         * rights carried in messages, we do a last closef to get rid
         * of our extra reference.  This is the last close, and the
         * unp_detach etc will shut down the socket.
         *
         * 91/09/19, bsy@cs.cmu.edu
         */
        extra_ref = _MALLOC(nfiles * sizeof(struct file *), M_FILE, M_WAITOK);
        for (nunref = 0, fp = filehead.lh_first, fpp = extra_ref; fp != 0;
            fp = nextfp) {
                nextfp = fp->f_list.le_next;
                /* 
                 * If it's not open, skip it
                 */
                if (fcount(fp) == 0)
                        continue;
                /* 
                 * If all refs are from msgs, and it's not marked accessible
                 * then it must be referenced from some unreachable cycle
                 * of (shut-down) FDs, so include it in our
                 * list of FDs to remove
                 */
                if (fcount(fp) == fp->f_msgcount && !(fp->f_flag & FMARK)) {
                        *fpp++ = fp;
                        nunref++;
                        fref(fp);
                }
        }
        /* 
         * for each FD on our hit list, do the following two things
         */
        for (i = nunref, fpp = extra_ref; --i >= 0; ++fpp) {
                struct file *tfp = *fpp;
                if (tfp->f_type == DTYPE_SOCKET && tfp->f_data != NULL) {
                        thread_funnel_switch(KERNEL_FUNNEL, NETWORK_FUNNEL);
                        sorflush((struct socket *)(tfp->f_data));
                        thread_funnel_switch(NETWORK_FUNNEL, KERNEL_FUNNEL);
                }
        }


        for (i = nunref, fpp = extra_ref; --i >= 0; ++fpp)
                closef(*fpp, (struct proc *) NULL);
        FREE((caddr_t)extra_ref, M_FILE);
        thread_funnel_switch(KERNEL_FUNNEL, NETWORK_FUNNEL);

        unp_gcing = 0;
}

void
unp_dispose(m)
        struct mbuf *m;
{

        if (m) {
                thread_funnel_switch(NETWORK_FUNNEL, KERNEL_FUNNEL);
                unp_scan(m, unp_discard);
                thread_funnel_switch(KERNEL_FUNNEL, NETWORK_FUNNEL);
        }
}

/* should run under kernel funnel */
static void
unp_scan(m0, op)
        register struct mbuf *m0;
        void (*op) __P((struct file *));
{
        register struct mbuf *m;
        register struct file **rp;
        register struct cmsghdr *cm;
        register int i;
        int qfds;

        while (m0) {
                for (m = m0; m; m = m->m_next)
                        if (m->m_type == MT_CONTROL &&
                            m->m_len >= sizeof(*cm)) {
                                cm = mtod(m, struct cmsghdr *);
                                if (cm->cmsg_level != SOL_SOCKET ||
                                    cm->cmsg_type != SCM_RIGHTS)
                                        continue;
                                qfds = (cm->cmsg_len - sizeof *cm)
                                                / sizeof (struct file *);
                                rp = (struct file **)(cm + 1);
                                for (i = 0; i < qfds; i++)
                                        (*op)(*rp++);
                                break;          /* XXX, but saves time */
                        }
                m0 = m0->m_act;
        }
}

/* should run under kernel funnel */
static void
unp_mark(fp)
        struct file *fp;
{

        if (fp->f_flag & FMARK)
                return;
        unp_defer++;
        fp->f_flag |= (FMARK|FDEFER);
}

/* should run under kernel funnel */
static void
unp_discard(fp)
        struct file *fp;
{

        fp->f_msgcount--;
        unp_rights--;
        (void) closef(fp, (struct proc *)NULL);
}