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 } 386