/*      $NetBSD: pfil.c,v 1.20 2001/11/12 23:49:46 lukem Exp $  */

/*
 * Copyright (c) 1996 Matthew R. Green
 * 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. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
 */

#include <sys/param.h>
#include <sys/errno.h>
#include <sys/malloc.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/systm.h>
#include <sys/proc.h>
#include <sys/queue.h>
#include <sys/sysctl.h>

#include <net/if.h>
#include <net/if_var.h>
#include <net/pfil.h>
#include <net/netmsg2.h>
#include <net/netisr2.h>

#define PFIL_CFGPORT    netisr_cpuport(0)

/*
 * The packet filter hooks are designed for anything to call them to
 * possibly intercept the packet.
 */
struct packet_filter_hook {
        TAILQ_ENTRY(packet_filter_hook) pfil_link;
        pfil_func_t     pfil_func;
        void            *pfil_arg;
        int             pfil_flags;
};

struct netmsg_pfil {
        struct netmsg_base      base;
        pfil_func_t             pfil_func;
        void                    *pfil_arg;
        int                     pfil_flags;
        struct pfil_head        *pfil_ph;
};

static LIST_HEAD(, pfil_head) pfil_head_list =
        LIST_HEAD_INITIALIZER(&pfil_head_list);

static pfil_list_t      *pfil_list_alloc(void);
static void             pfil_list_free(pfil_list_t *);
static void             pfil_list_dup(const pfil_list_t *, pfil_list_t *,
                                      const struct packet_filter_hook *);
static void             pfil_list_add(pfil_list_t *, pfil_func_t, void *, int);
static struct packet_filter_hook *
                        pfil_list_find(const pfil_list_t *, pfil_func_t,
                                       const void *);

static void             pfil_remove_hook_dispatch(netmsg_t);
static void             pfil_add_hook_dispatch(netmsg_t);

int filters_default_to_accept = 0;
SYSCTL_INT(_net, OID_AUTO, filters_default_to_accept, CTLFLAG_RW,
    &filters_default_to_accept, 0,
    "cause ipfw* modules to not block by default");
TUNABLE_INT("net.filters_default_to_accept", &filters_default_to_accept);

/*
 * pfil_run_hooks() runs the specified packet filter hooks.
 */
int
pfil_run_hooks(struct pfil_head *ph, struct mbuf **mp, struct ifnet *ifp,
    int dir)
{
        struct packet_filter_hook *pfh;
        struct mbuf *m = *mp;
        pfil_list_t *list;
        int rv = 0;

        if (dir == PFIL_IN)
                list = ph->ph_in;
        else if (dir == PFIL_OUT)
                list = ph->ph_out;
        else
                return 0; /* XXX panic? */

        /* Make sure 'list' is really used. */
        cpu_ccfence();
        TAILQ_FOREACH(pfh, list, pfil_link) {
                if (pfh->pfil_func != NULL) {
                        rv = pfh->pfil_func(pfh->pfil_arg, &m, ifp, dir);
                        if (rv != 0 || m == NULL)
                                break;
                }
        }

        *mp = m;
        return (rv);
}

/*
 * pfil_head_register() registers a pfil_head with the packet filter
 * hook mechanism.
 */
int
pfil_head_register(struct pfil_head *ph)
{
        struct pfil_head *lph;

        LIST_FOREACH(lph, &pfil_head_list, ph_list) {
                if (ph->ph_type == lph->ph_type &&
                    ph->ph_un.phu_val == lph->ph_un.phu_val)
                        return EEXIST;
        }

        ph->ph_in = pfil_list_alloc();
        ph->ph_out = pfil_list_alloc();
        ph->ph_hashooks = 0;

        LIST_INSERT_HEAD(&pfil_head_list, ph, ph_list);

        return (0);
}

/*
 * pfil_head_unregister() removes a pfil_head from the packet filter
 * hook mechanism.
 */
int
pfil_head_unregister(struct pfil_head *pfh)
{
        LIST_REMOVE(pfh, ph_list);
        return (0);
}

/*
 * pfil_head_get() returns the pfil_head for a given key/dlt.
 */
struct pfil_head *
pfil_head_get(int type, u_long val)
{
        struct pfil_head *ph;

        LIST_FOREACH(ph, &pfil_head_list, ph_list) {
                if (ph->ph_type == type && ph->ph_un.phu_val == val)
                        break;
        }
        return (ph);
}

static void
pfil_add_hook_dispatch(netmsg_t nmsg)
{
        struct netmsg_pfil *pfilmsg = (struct netmsg_pfil *)nmsg;
        pfil_func_t func = pfilmsg->pfil_func;
        void *arg = pfilmsg->pfil_arg;
        int flags = pfilmsg->pfil_flags;
        struct pfil_head *ph = pfilmsg->pfil_ph;
        const struct packet_filter_hook *pfh;
        pfil_list_t *list_in = NULL, *list_out = NULL;
        pfil_list_t *old_list_in = NULL, *old_list_out = NULL;
        int err = 0;

        /* This probably should not happen ... */
        if ((flags & (PFIL_IN | PFIL_OUT)) == 0)
                goto reply; /* XXX panic? */

        /*
         * If pfil hooks exist on any of the requested lists,
         * then bail out.
         */
        if (flags & PFIL_IN) {
                pfh = pfil_list_find(ph->ph_in, func, arg);
                if (pfh != NULL) {
                        err = EEXIST;
                        goto reply;
                }
        }
        if (flags & PFIL_OUT) {
                pfh = pfil_list_find(ph->ph_out, func, arg);
                if (pfh != NULL) {
                        err = EEXIST;
                        goto reply;
                }
        }

        /*
         * Duplicate the requested lists, install new hooks
         * on the duplication
         */
        if (flags & PFIL_IN) {
                list_in = pfil_list_alloc();
                pfil_list_dup(ph->ph_in, list_in, NULL);
                pfil_list_add(list_in, func, arg, flags & ~PFIL_OUT);
        }
        if (flags & PFIL_OUT) {
                list_out = pfil_list_alloc();
                pfil_list_dup(ph->ph_out, list_out, NULL);
                pfil_list_add(list_out, func, arg, flags & ~PFIL_IN);
        }

        /*
         * Switch list pointers, but keep the old ones
         */
        if (list_in != NULL) {
                old_list_in = ph->ph_in;
                ph->ph_in = list_in;
        }
        if (list_out != NULL) {
                old_list_out = ph->ph_out;
                ph->ph_out = list_out;
        }

        /*
         * Wait until everyone has finished the old lists iteration
         */
        netmsg_service_sync();
        ph->ph_hashooks = 1;

        /*
         * Now it is safe to free the old lists, since no one sees it
         */
        if (old_list_in != NULL)
                pfil_list_free(old_list_in);
        if (old_list_out != NULL)
                pfil_list_free(old_list_out);
reply:
        lwkt_replymsg(&nmsg->base.lmsg, err);
}

/*
 * pfil_add_hook() adds a function to the packet filter hook.  the
 * flags are:
 *      PFIL_IN         call me on incoming packets
 *      PFIL_OUT        call me on outgoing packets
 *      PFIL_ALL        call me on all of the above
 */
int
pfil_add_hook(pfil_func_t func, void *arg, int flags, struct pfil_head *ph)
{
        struct netmsg_pfil pfilmsg;
        netmsg_base_t nmsg;
        int error;

        nmsg = &pfilmsg.base;
        netmsg_init(nmsg, NULL, &curthread->td_msgport,
                    0, pfil_add_hook_dispatch);
        pfilmsg.pfil_func = func;
        pfilmsg.pfil_arg = arg;
        pfilmsg.pfil_flags = flags;
        pfilmsg.pfil_ph = ph;

        error = lwkt_domsg(PFIL_CFGPORT, &nmsg->lmsg, 0);
        return error;
}

static void
pfil_remove_hook_dispatch(netmsg_t nmsg)
{
        struct netmsg_pfil *pfilmsg = (struct netmsg_pfil *)nmsg;
        pfil_func_t func = pfilmsg->pfil_func;
        void *arg = pfilmsg->pfil_arg;
        int flags = pfilmsg->pfil_flags;
        struct pfil_head *ph = pfilmsg->pfil_ph;
        struct packet_filter_hook *skip_in = NULL, *skip_out = NULL;
        pfil_list_t *list_in = NULL, *list_out = NULL;
        pfil_list_t *old_list_in = NULL, *old_list_out = NULL;
        int err = 0;

        /* This probably should not happen ... */
        if ((flags & (PFIL_IN | PFIL_OUT)) == 0)
                goto reply; /* XXX panic? */

        /*
         * The pfil hook should exist on all requested lists,
         * if not just bail out
         */
        if (flags & PFIL_IN) {
                skip_in = pfil_list_find(ph->ph_in, func, arg);
                if (!skip_in) {
                        err = ENOENT;
                        goto reply;
                }
        }
        if (flags & PFIL_OUT) {
                skip_out = pfil_list_find(ph->ph_out, func, arg);
                if (!skip_out) {
                        err = ENOENT;
                        goto reply;
                }
        }

        /*
         * Duplicate the requested lists, but the pfil hook to
         * be deleted is not copied
         */
        if (flags & PFIL_IN) {
                KKASSERT(skip_in != NULL);
                list_in = pfil_list_alloc();
                pfil_list_dup(ph->ph_in, list_in, skip_in);
        }
        if (flags & PFIL_OUT) {
                KKASSERT(skip_out != NULL);
                list_out = pfil_list_alloc();
                pfil_list_dup(ph->ph_out, list_out, skip_out);
        }

        /*
         * Switch list pointers, but keep the old ones
         */
        if (list_in != NULL) {
                old_list_in = ph->ph_in;
                ph->ph_in = list_in;
        }
        if (list_out != NULL) {
                old_list_out = ph->ph_out;
                ph->ph_out = list_out;
        }

        /*
         * Wait until everyone has finished the old lists iteration
         */
        if (TAILQ_EMPTY(ph->ph_in) && TAILQ_EMPTY(ph->ph_out))
                ph->ph_hashooks = 0;
        netmsg_service_sync();

        /*
         * Now it is safe to free the old lists, since no one sees it
         */
        if (old_list_in != NULL)
                pfil_list_free(old_list_in);
        if (old_list_out != NULL)
                pfil_list_free(old_list_out);
reply:
        lwkt_replymsg(&nmsg->base.lmsg, err);
}

/*
 * pfil_remove_hook removes a specific function from the packet filter
 * hook list.
 */
int
pfil_remove_hook(pfil_func_t func, void *arg, int flags, struct pfil_head *ph)
{
        struct netmsg_pfil pfilmsg;
        netmsg_base_t nmsg;

        nmsg = &pfilmsg.base;
        netmsg_init(nmsg, NULL, &curthread->td_msgport,
                    0, pfil_remove_hook_dispatch);
        pfilmsg.pfil_func = func;
        pfilmsg.pfil_arg = arg;
        pfilmsg.pfil_flags = flags;
        pfilmsg.pfil_ph = ph;

        return lwkt_domsg(PFIL_CFGPORT, &nmsg->lmsg, 0);
}

static void
pfil_list_add(pfil_list_t *list, pfil_func_t func, void *arg, int flags)
{
        struct packet_filter_hook *pfh;

        KKASSERT(&curthread->td_msgport == PFIL_CFGPORT);

        pfh = kmalloc(sizeof(*pfh), M_IFADDR, M_WAITOK);

        pfh->pfil_func = func;
        pfh->pfil_arg  = arg;
        pfh->pfil_flags = flags;

        /*
         * Insert the input list in reverse order of the output list
         * so that the same path is followed in or out of the kernel.
         */
        if (flags & PFIL_IN)
                TAILQ_INSERT_HEAD(list, pfh, pfil_link);
        else
                TAILQ_INSERT_TAIL(list, pfh, pfil_link);
}

static void
pfil_list_dup(const pfil_list_t *from, pfil_list_t *to,
              const struct packet_filter_hook *skip)
{
        struct packet_filter_hook *pfh_to, *pfh_from;

        KKASSERT(&curthread->td_msgport == PFIL_CFGPORT);
        KKASSERT(TAILQ_EMPTY(to));

        TAILQ_FOREACH(pfh_from, from, pfil_link) {
                if (pfh_from == skip)
                        continue;

                pfh_to = kmalloc(sizeof(*pfh_to), M_IFADDR, M_WAITOK);
                bcopy(pfh_from, pfh_to, sizeof(*pfh_to));

                TAILQ_INSERT_TAIL(to, pfh_to, pfil_link);
        }
}

static pfil_list_t *
pfil_list_alloc(void)
{
        pfil_list_t *list;

        list = kmalloc(sizeof(*list), M_IFADDR, M_WAITOK);
        TAILQ_INIT(list);
        return list;
}

static void
pfil_list_free(pfil_list_t *list)
{
        struct packet_filter_hook *pfh;

        while ((pfh = TAILQ_FIRST(list)) != NULL) {
                TAILQ_REMOVE(list, pfh, pfil_link);
                kfree(pfh, M_IFADDR);
        }
        kfree(list, M_IFADDR);
}

static struct packet_filter_hook *
pfil_list_find(const pfil_list_t *list, pfil_func_t func, const void *arg)
{
        struct packet_filter_hook *pfh;

        KKASSERT(&curthread->td_msgport == PFIL_CFGPORT);

        TAILQ_FOREACH(pfh, list, pfil_link) {
                if (pfh->pfil_func == func && pfh->pfil_arg == arg)
                        return pfh;
        }
        return NULL;
}