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 /* 123 * Prevent packet filtering from starving the modification of 124 * the packet filters. We would prefer a reader/writer locking 125 * mechanism with guaranteed ordering, though. 126 */ 127 if (ph->ph_busy_count == -1 || ph->ph_want_write) { 128 m_freem(*mp); 129 *mp = NULL; 130 return (ENOBUFS); 131 } 132 133 PFIL_RLOCK(ph); 134 for (pfh = pfil_hook_get(dir, ph); pfh != NULL; 135 pfh = TAILQ_NEXT(pfh, pfil_link)) { 136 if (pfh->pfil_func != NULL) { 137 rv = (*pfh->pfil_func)(pfh->pfil_arg, &m, ifp, dir, inp); 138 if (rv != 0 || m == NULL) 139 break; 140 } 141 } 142 PFIL_RUNLOCK(ph); 143 144 *mp = m; 145 return (rv); 146 } 147 148 /* 149 * pfil_head_register() registers a pfil_head with the packet filter 150 * hook mechanism. 151 */ 152 int 153 pfil_head_register(struct pfil_head *ph) 154 { 155 struct pfil_head *lph; 156 157 PFIL_LIST_LOCK(); 158 LIST_FOREACH(lph, &pfil_head_list, ph_list) 159 if (ph->ph_type == lph->ph_type && 160 ph->ph_un.phu_val == lph->ph_un.phu_val) { 161 PFIL_LIST_UNLOCK(); 162 return EEXIST; 163 } 164 PFIL_LIST_UNLOCK(); 165 166 if (mtx_initialized(&ph->ph_mtx)) { /* should not happen */ 167 KASSERT((0), ("%s: allready initialized!", __func__)); 168 return EBUSY; 169 } else { 170 ph->ph_busy_count = -1; 171 ph->ph_want_write = 1; 172 mtx_init(&ph->ph_mtx, "pfil_head_mtx", NULL, MTX_DEF); 173 cv_init(&ph->ph_cv, "pfil_head_cv"); 174 mtx_lock(&ph->ph_mtx); /* XXX: race? */ 175 } 176 177 TAILQ_INIT(&ph->ph_in); 178 TAILQ_INIT(&ph->ph_out); 179 180 PFIL_LIST_LOCK(); 181 LIST_INSERT_HEAD(&pfil_head_list, ph, ph_list); 182 PFIL_LIST_UNLOCK(); 183 184 PFIL_WUNLOCK(ph); 185 186 return (0); 187 } 188 189 /* 190 * pfil_head_unregister() removes a pfil_head from the packet filter 191 * hook mechanism. 192 */ 193 int 194 pfil_head_unregister(struct pfil_head *ph) 195 { 196 struct packet_filter_hook *pfh, *pfnext; 197 198 PFIL_LIST_LOCK(); 199 /* 200 * LIST_REMOVE is safe for unlocked pfil_heads in ph_list. 201 * No need to WLOCK all of them. 202 */ 203 LIST_REMOVE(ph, ph_list); 204 PFIL_LIST_UNLOCK(); 205 206 PFIL_WLOCK(ph); /* XXX: may sleep (cv_wait)! */ 207 208 TAILQ_FOREACH_SAFE(pfh, &ph->ph_in, pfil_link, pfnext) 209 free(pfh, M_IFADDR); 210 TAILQ_FOREACH_SAFE(pfh, &ph->ph_out, pfil_link, pfnext) 211 free(pfh, M_IFADDR); 212 cv_destroy(&ph->ph_cv); 213 mtx_destroy(&ph->ph_mtx); 214 215 return (0); 216 } 217 218 /* 219 * pfil_head_get() returns the pfil_head for a given key/dlt. 220 */ 221 struct pfil_head * 222 pfil_head_get(int type, u_long val) 223 { 224 struct pfil_head *ph; 225 226 PFIL_LIST_LOCK(); 227 LIST_FOREACH(ph, &pfil_head_list, ph_list) 228 if (ph->ph_type == type && ph->ph_un.phu_val == val) 229 break; 230 PFIL_LIST_UNLOCK(); 231 232 return (ph); 233 } 234 235 /* 236 * pfil_add_hook() adds a function to the packet filter hook. the 237 * flags are: 238 * PFIL_IN call me on incoming packets 239 * PFIL_OUT call me on outgoing packets 240 * PFIL_ALL call me on all of the above 241 * PFIL_WAITOK OK to call malloc with M_WAITOK. 242 */ 243 int 244 pfil_add_hook(int (*func)(void *, struct mbuf **, struct ifnet *, int, struct inpcb *), 245 void *arg, int flags, struct pfil_head *ph) 246 { 247 struct packet_filter_hook *pfh1 = NULL; 248 struct packet_filter_hook *pfh2 = NULL; 249 int err; 250 251 /* Get memory */ 252 if (flags & PFIL_IN) { 253 pfh1 = (struct packet_filter_hook *)malloc(sizeof(*pfh1), 254 M_IFADDR, (flags & PFIL_WAITOK) ? M_WAITOK : M_NOWAIT); 255 if (pfh1 == NULL) { 256 err = ENOMEM; 257 goto error; 258 } 259 } 260 if (flags & PFIL_OUT) { 261 pfh2 = (struct packet_filter_hook *)malloc(sizeof(*pfh1), 262 M_IFADDR, (flags & PFIL_WAITOK) ? M_WAITOK : M_NOWAIT); 263 if (pfh2 == NULL) { 264 err = ENOMEM; 265 goto error; 266 } 267 } 268 269 /* Lock */ 270 if (flags & PFIL_WAITOK) 271 PFIL_WLOCK(ph); 272 else { 273 err = PFIL_TRY_WLOCK(ph); 274 if (err) 275 goto error; 276 } 277 278 /* Add */ 279 if (flags & PFIL_IN) { 280 pfh1->pfil_func = func; 281 pfh1->pfil_arg = arg; 282 err = pfil_list_add(&ph->ph_in, pfh1, flags & ~PFIL_OUT); 283 if (err) 284 goto done; 285 } 286 if (flags & PFIL_OUT) { 287 pfh2->pfil_func = func; 288 pfh2->pfil_arg = arg; 289 err = pfil_list_add(&ph->ph_out, pfh2, flags & ~PFIL_IN); 290 if (err) { 291 if (flags & PFIL_IN) 292 pfil_list_remove(&ph->ph_in, func, arg); 293 goto done; 294 } 295 } 296 297 ph->ph_busy_count = 0; 298 PFIL_WUNLOCK(ph); 299 300 return 0; 301 done: 302 PFIL_WUNLOCK(ph); 303 error: 304 if (pfh1 != NULL) 305 free(pfh1, M_IFADDR); 306 if (pfh2 != NULL) 307 free(pfh2, M_IFADDR); 308 return err; 309 } 310 311 /* 312 * pfil_remove_hook removes a specific function from the packet filter 313 * hook list. 314 */ 315 int 316 pfil_remove_hook(int (*func)(void *, struct mbuf **, struct ifnet *, int, struct inpcb *), 317 void *arg, int flags, struct pfil_head *ph) 318 { 319 int err = 0; 320 321 if (flags & PFIL_WAITOK) 322 PFIL_WLOCK(ph); 323 else { 324 err = PFIL_TRY_WLOCK(ph); 325 if (err) 326 return err; 327 } 328 329 if (flags & PFIL_IN) 330 err = pfil_list_remove(&ph->ph_in, func, arg); 331 if ((err == 0) && (flags & PFIL_OUT)) 332 err = pfil_list_remove(&ph->ph_out, func, arg); 333 334 if (TAILQ_EMPTY(&ph->ph_in) && TAILQ_EMPTY(&ph->ph_out)) 335 ph->ph_busy_count = -1; 336 337 PFIL_WUNLOCK(ph); 338 339 return err; 340 } 341 342 static int 343 pfil_list_add(pfil_list_t *list, struct packet_filter_hook *pfh1, int flags) 344 { 345 struct packet_filter_hook *pfh; 346 347 /* 348 * First make sure the hook is not already there. 349 */ 350 TAILQ_FOREACH(pfh, list, pfil_link) 351 if (pfh->pfil_func == pfh1->pfil_func && 352 pfh->pfil_arg == pfh1->pfil_arg) 353 return EEXIST; 354 /* 355 * insert the input list in reverse order of the output list 356 * so that the same path is followed in or out of the kernel. 357 */ 358 if (flags & PFIL_IN) 359 TAILQ_INSERT_HEAD(list, pfh1, pfil_link); 360 else 361 TAILQ_INSERT_TAIL(list, pfh1, pfil_link); 362 363 return 0; 364 } 365 366 /* 367 * pfil_list_remove is an internal function that takes a function off the 368 * specified list. 369 */ 370 static int 371 pfil_list_remove(pfil_list_t *list, 372 int (*func)(void *, struct mbuf **, struct ifnet *, int, struct inpcb *), void *arg) 373 { 374 struct packet_filter_hook *pfh; 375 376 TAILQ_FOREACH(pfh, list, pfil_link) 377 if (pfh->pfil_func == func && pfh->pfil_arg == arg) { 378 TAILQ_REMOVE(list, pfh, pfil_link); 379 free(pfh, M_IFADDR); 380 return 0; 381 } 382 return ENOENT; 383 } 384