pfil.c

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    1 /*      $FreeBSD$ */
    2 /*      $NetBSD: pfil.c,v 1.20 2001/11/12 23:49:46 lukem Exp $  */
    3 
    4 /*-
    5  * Copyright (c) 1996 Matthew R. Green
    6  * All rights reserved.
    7  *
    8  * Redistribution and use in source and binary forms, with or without
    9  * modification, are permitted provided that the following conditions
   10  * are met:
   11  * 1. Redistributions of source code must retain the above copyright
   12  *    notice, this list of conditions and the following disclaimer.
   13  * 2. Redistributions in binary form must reproduce the above copyright
   14  *    notice, this list of conditions and the following disclaimer in the
   15  *    documentation and/or other materials provided with the distribution.
   16  * 3. The name of the author may not be used to endorse or promote products
   17  *    derived from this software without specific prior written permission.
   18  *
   19  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
   20  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   21  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   22  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
   23  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
   24  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   25  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
   26  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   27  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   29  * SUCH DAMAGE.
   30  */
   31 
   32 #include <sys/param.h>
   33 #include <sys/kernel.h>
   34 #include <sys/errno.h>
   35 #include <sys/malloc.h>
   36 #include <sys/socket.h>
   37 #include <sys/socketvar.h>
   38 #include <sys/systm.h>
   39 #include <sys/condvar.h>
   40 #include <sys/lock.h>
   41 #include <sys/mutex.h>
   42 #include <sys/proc.h>
   43 #include <sys/queue.h>
   44 
   45 #include <net/if.h>
   46 #include <net/pfil.h>
   47 
   48 static struct mtx pfil_global_lock;
   49 
   50 MTX_SYSINIT(pfil_heads_lock, &pfil_global_lock, "pfil_head_list lock", MTX_DEF);
   51 
   52 static int pfil_list_add(pfil_list_t *, struct packet_filter_hook *, int);
   53 
   54 static int pfil_list_remove(pfil_list_t *,
   55     int (*)(void *, struct mbuf **, struct ifnet *, int, struct inpcb *), void *);
   56 
   57 LIST_HEAD(, pfil_head) pfil_head_list =
   58     LIST_HEAD_INITIALIZER(&pfil_head_list);
   59 
   60 static __inline void
   61 PFIL_RLOCK(struct pfil_head *ph)
   62 {
   63         mtx_lock(&ph->ph_mtx);
   64         ph->ph_busy_count++;
   65         mtx_unlock(&ph->ph_mtx);
   66 }
   67 
   68 static __inline void
   69 PFIL_RUNLOCK(struct pfil_head *ph)
   70 {
   71         mtx_lock(&ph->ph_mtx);
   72         ph->ph_busy_count--;
   73         if (ph->ph_busy_count == 0 && ph->ph_want_write)
   74                 cv_signal(&ph->ph_cv);
   75         mtx_unlock(&ph->ph_mtx);
   76 }
   77 
   78 static __inline void
   79 PFIL_WLOCK(struct pfil_head *ph)
   80 {
   81         mtx_lock(&ph->ph_mtx);
   82         ph->ph_want_write = 1;
   83         while (ph->ph_busy_count > 0)
   84                 cv_wait(&ph->ph_cv, &ph->ph_mtx);
   85 }
   86 
   87 static __inline int
   88 PFIL_TRY_WLOCK(struct pfil_head *ph)
   89 {
   90         mtx_lock(&ph->ph_mtx);
   91         ph->ph_want_write = 1;
   92         if (ph->ph_busy_count > 0) {
   93                 ph->ph_want_write = 0;
   94                 mtx_unlock(&ph->ph_mtx);
   95                 return EBUSY;
   96         }
   97         return 0;
   98 }
   99 
  100 static __inline void
  101 PFIL_WUNLOCK(struct pfil_head *ph)
  102 {
  103         ph->ph_want_write = 0;
  104         cv_signal(&ph->ph_cv);
  105         mtx_unlock(&ph->ph_mtx);
  106 }
  107 
  108 #define PFIL_LIST_LOCK() mtx_lock(&pfil_global_lock)
  109 #define PFIL_LIST_UNLOCK() mtx_unlock(&pfil_global_lock)
  110 
  111 /*
  112  * pfil_run_hooks() runs the specified packet filter hooks.
  113  */
  114 int
  115 pfil_run_hooks(struct pfil_head *ph, struct mbuf **mp, struct ifnet *ifp,
  116     int dir, struct inpcb *inp)
  117 {
  118         struct packet_filter_hook *pfh;
  119         struct mbuf *m = *mp;
  120         int rv = 0;
  121 
  122         if (ph->ph_busy_count == -1)
  123                 return (0);
  124         /*
  125          * Prevent packet filtering from starving the modification of
  126          * the packet filters. We would prefer a reader/writer locking
  127          * mechanism with guaranteed ordering, though.
  128          */
  129         if (ph->ph_want_write) {
  130                 m_freem(*mp);
  131                 *mp = NULL;
  132                 return (ENOBUFS);
  133         }
  134 
  135         PFIL_RLOCK(ph);
  136         for (pfh = pfil_hook_get(dir, ph); pfh != NULL;
  137              pfh = TAILQ_NEXT(pfh, pfil_link)) {
  138                 if (pfh->pfil_func != NULL) {
  139                         rv = (*pfh->pfil_func)(pfh->pfil_arg, &m, ifp, dir, inp);
  140                         if (rv != 0 || m == NULL)
  141                                 break;
  142                 }
  143         }
  144         PFIL_RUNLOCK(ph);
  145         
  146         *mp = m;
  147         return (rv);
  148 }
  149 
  150 /*
  151  * pfil_head_register() registers a pfil_head with the packet filter
  152  * hook mechanism.
  153  */
  154 int
  155 pfil_head_register(struct pfil_head *ph)
  156 {
  157         struct pfil_head *lph;
  158 
  159         PFIL_LIST_LOCK();
  160         LIST_FOREACH(lph, &pfil_head_list, ph_list)
  161                 if (ph->ph_type == lph->ph_type &&
  162                     ph->ph_un.phu_val == lph->ph_un.phu_val) {
  163                         PFIL_LIST_UNLOCK();
  164                         return EEXIST;
  165                 }
  166         PFIL_LIST_UNLOCK();
  167 
  168         if (mtx_initialized(&ph->ph_mtx)) {     /* should not happen */
  169                 KASSERT((0), ("%s: allready initialized!", __func__));
  170                 return EBUSY;
  171         } else {
  172                 ph->ph_busy_count = -1;
  173                 ph->ph_want_write = 1;
  174                 mtx_init(&ph->ph_mtx, "pfil_head_mtx", NULL, MTX_DEF);
  175                 cv_init(&ph->ph_cv, "pfil_head_cv");
  176                 mtx_lock(&ph->ph_mtx);                  /* XXX: race? */
  177         }
  178 
  179         TAILQ_INIT(&ph->ph_in);
  180         TAILQ_INIT(&ph->ph_out);
  181 
  182         PFIL_LIST_LOCK();
  183         LIST_INSERT_HEAD(&pfil_head_list, ph, ph_list);
  184         PFIL_LIST_UNLOCK();
  185         
  186         PFIL_WUNLOCK(ph);
  187         
  188         return (0);
  189 }
  190 
  191 /*
  192  * pfil_head_unregister() removes a pfil_head from the packet filter
  193  * hook mechanism.
  194  */
  195 int
  196 pfil_head_unregister(struct pfil_head *ph)
  197 {
  198         struct packet_filter_hook *pfh, *pfnext;
  199                 
  200         PFIL_LIST_LOCK();
  201         /* 
  202          * LIST_REMOVE is safe for unlocked pfil_heads in ph_list.
  203          * No need to WLOCK all of them.
  204          */
  205         LIST_REMOVE(ph, ph_list);
  206         PFIL_LIST_UNLOCK();
  207 
  208         PFIL_WLOCK(ph);                 /* XXX: may sleep (cv_wait)! */
  209         
  210         TAILQ_FOREACH_SAFE(pfh, &ph->ph_in, pfil_link, pfnext)
  211                 free(pfh, M_IFADDR);
  212         TAILQ_FOREACH_SAFE(pfh, &ph->ph_out, pfil_link, pfnext)
  213                 free(pfh, M_IFADDR);
  214         cv_destroy(&ph->ph_cv);
  215         mtx_destroy(&ph->ph_mtx);
  216         
  217         return (0);
  218 }
  219 
  220 /*
  221  * pfil_head_get() returns the pfil_head for a given key/dlt.
  222  */
  223 struct pfil_head *
  224 pfil_head_get(int type, u_long val)
  225 {
  226         struct pfil_head *ph;
  227 
  228         PFIL_LIST_LOCK();
  229         LIST_FOREACH(ph, &pfil_head_list, ph_list)
  230                 if (ph->ph_type == type && ph->ph_un.phu_val == val)
  231                         break;
  232         PFIL_LIST_UNLOCK();
  233         
  234         return (ph);
  235 }
  236 
  237 /*
  238  * pfil_add_hook() adds a function to the packet filter hook.  the
  239  * flags are:
  240  *      PFIL_IN         call me on incoming packets
  241  *      PFIL_OUT        call me on outgoing packets
  242  *      PFIL_ALL        call me on all of the above
  243  *      PFIL_WAITOK     OK to call malloc with M_WAITOK.
  244  */
  245 int
  246 pfil_add_hook(int (*func)(void *, struct mbuf **, struct ifnet *, int, struct inpcb *),
  247     void *arg, int flags, struct pfil_head *ph)
  248 {
  249         struct packet_filter_hook *pfh1 = NULL;
  250         struct packet_filter_hook *pfh2 = NULL;
  251         int err;
  252 
  253         /* Get memory */
  254         if (flags & PFIL_IN) {
  255                 pfh1 = (struct packet_filter_hook *)malloc(sizeof(*pfh1), 
  256                     M_IFADDR, (flags & PFIL_WAITOK) ? M_WAITOK : M_NOWAIT);
  257                 if (pfh1 == NULL) {
  258                         err = ENOMEM;
  259                         goto error;
  260                 }
  261         }
  262         if (flags & PFIL_OUT) {
  263                 pfh2 = (struct packet_filter_hook *)malloc(sizeof(*pfh1),
  264                     M_IFADDR, (flags & PFIL_WAITOK) ? M_WAITOK : M_NOWAIT);
  265                 if (pfh2 == NULL) {
  266                         err = ENOMEM;
  267                         goto error;
  268                 }
  269         }
  270 
  271         /* Lock */
  272         if (flags & PFIL_WAITOK)
  273                 PFIL_WLOCK(ph);
  274         else {
  275                 err = PFIL_TRY_WLOCK(ph);
  276                 if (err)
  277                         goto error;
  278         }
  279 
  280         /* Add */
  281         if (flags & PFIL_IN) {
  282                 pfh1->pfil_func = func;
  283                 pfh1->pfil_arg = arg;
  284                 err = pfil_list_add(&ph->ph_in, pfh1, flags & ~PFIL_OUT);
  285                 if (err)
  286                         goto done;
  287         }
  288         if (flags & PFIL_OUT) {
  289                 pfh2->pfil_func = func;
  290                 pfh2->pfil_arg = arg;
  291                 err = pfil_list_add(&ph->ph_out, pfh2, flags & ~PFIL_IN);
  292                 if (err) {
  293                         if (flags & PFIL_IN)
  294                                 pfil_list_remove(&ph->ph_in, func, arg);
  295                         goto done;
  296                 }
  297         }
  298 
  299         ph->ph_busy_count = 0;
  300         PFIL_WUNLOCK(ph);
  301 
  302         return 0;
  303 done:
  304         PFIL_WUNLOCK(ph);
  305 error:
  306         if (pfh1 != NULL)
  307                 free(pfh1, M_IFADDR);
  308         if (pfh2 != NULL)
  309                 free(pfh2, M_IFADDR);
  310         return err;
  311 }
  312 
  313 /*
  314  * pfil_remove_hook removes a specific function from the packet filter
  315  * hook list.
  316  */
  317 int
  318 pfil_remove_hook(int (*func)(void *, struct mbuf **, struct ifnet *, int, struct inpcb *),
  319     void *arg, int flags, struct pfil_head *ph)
  320 {
  321         int err = 0;
  322 
  323         if (flags & PFIL_WAITOK)
  324                 PFIL_WLOCK(ph);
  325         else {
  326                 err = PFIL_TRY_WLOCK(ph);
  327                 if (err)
  328                         return err;
  329         }
  330 
  331         if (flags & PFIL_IN)
  332                 err = pfil_list_remove(&ph->ph_in, func, arg);
  333         if ((err == 0) && (flags & PFIL_OUT))
  334                 err = pfil_list_remove(&ph->ph_out, func, arg);
  335 
  336         if (TAILQ_EMPTY(&ph->ph_in) && TAILQ_EMPTY(&ph->ph_out))
  337                 ph->ph_busy_count = -1;
  338 
  339         PFIL_WUNLOCK(ph);
  340         
  341         return err;
  342 }
  343 
  344 static int
  345 pfil_list_add(pfil_list_t *list, struct packet_filter_hook *pfh1, int flags)
  346 {
  347         struct packet_filter_hook *pfh;
  348 
  349         /*
  350          * First make sure the hook is not already there.
  351          */
  352         TAILQ_FOREACH(pfh, list, pfil_link)
  353                 if (pfh->pfil_func == pfh1->pfil_func &&
  354                     pfh->pfil_arg == pfh1->pfil_arg)
  355                         return EEXIST;
  356         /*
  357          * insert the input list in reverse order of the output list
  358          * so that the same path is followed in or out of the kernel.
  359          */
  360         if (flags & PFIL_IN)
  361                 TAILQ_INSERT_HEAD(list, pfh1, pfil_link);
  362         else
  363                 TAILQ_INSERT_TAIL(list, pfh1, pfil_link);
  364 
  365         return 0;
  366 }
  367 
  368 /*
  369  * pfil_list_remove is an internal function that takes a function off the
  370  * specified list.
  371  */
  372 static int
  373 pfil_list_remove(pfil_list_t *list,
  374     int (*func)(void *, struct mbuf **, struct ifnet *, int, struct inpcb *), void *arg)
  375 {
  376         struct packet_filter_hook *pfh;
  377 
  378         TAILQ_FOREACH(pfh, list, pfil_link)
  379                 if (pfh->pfil_func == func && pfh->pfil_arg == arg) {
  380                         TAILQ_REMOVE(list, pfh, pfil_link);
  381                         free(pfh, M_IFADDR);
  382                         return 0;
  383                 }
  384         return ENOENT;
  385 }
Cache object: d3e35c45dc63837862edca54b5ba5141
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FreeBSD/Linux Kernel Cross Reference sys/net/pfil.c

FreeBSD/Linux Kernel Cross Reference
sys/net/pfil.c
