1 /* $NetBSD: npf_handler.c,v 1.29 2014/03/14 11:29:44 rmind Exp $ */ 2 3 /*- 4 * Copyright (c) 2009-2013 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This material is based upon work partially supported by The 8 * NetBSD Foundation under a contract with Mindaugas Rasiukevicius. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 29 * POSSIBILITY OF SUCH DAMAGE. 30 */ 31 32 /* 33 * NPF packet handler. 34 * 35 * Note: pfil(9) hooks are currently locked by softnet_lock and kernel-lock. 36 */ 37 38 #include <sys/cdefs.h> 39 __KERNEL_RCSID(0, "$NetBSD: npf_handler.c,v 1.29 2014/03/14 11:29:44 rmind Exp $"); 40 41 #include <sys/types.h> 42 #include <sys/param.h> 43 44 #include <sys/mbuf.h> 45 #include <sys/mutex.h> 46 #include <net/if.h> 47 #include <net/pfil.h> 48 #include <sys/socketvar.h> 49 50 #include <netinet/in_systm.h> 51 #include <netinet/in.h> 52 #include <netinet/ip_var.h> 53 #include <netinet/ip6.h> 54 #include <netinet6/ip6_var.h> 55 56 #include "npf_impl.h" 57 58 static bool pfil_registered = false; 59 static pfil_head_t * npf_ph_if = NULL; 60 static pfil_head_t * npf_ph_inet = NULL; 61 static pfil_head_t * npf_ph_inet6 = NULL; 62 63 #ifndef INET6 64 #define ip6_reass_packet(x, y) ENOTSUP 65 #endif 66 67 /* 68 * npf_ifhook: hook handling interface changes. 69 */ 70 static int 71 npf_ifhook(void *arg, struct mbuf **mp, ifnet_t *ifp, int di) 72 { 73 u_long cmd = (u_long)mp; 74 75 if (di == PFIL_IFNET) { 76 switch (cmd) { 77 case PFIL_IFNET_ATTACH: 78 npf_ifmap_attach(ifp); 79 break; 80 case PFIL_IFNET_DETACH: 81 npf_ifmap_detach(ifp); 82 break; 83 } 84 } 85 return 0; 86 } 87 88 static int 89 npf_reassembly(npf_cache_t *npc, nbuf_t *nbuf, struct mbuf **mp) 90 { 91 int error = EINVAL; 92 93 /* Reset the mbuf as it may have changed. */ 94 *mp = nbuf_head_mbuf(nbuf); 95 nbuf_reset(nbuf); 96 97 if (npf_iscached(npc, NPC_IP4)) { 98 struct ip *ip = nbuf_dataptr(nbuf); 99 error = ip_reass_packet(mp, ip); 100 } else if (npf_iscached(npc, NPC_IP6)) { 101 /* 102 * Note: ip6_reass_packet() offset is the start of 103 * the fragment header. 104 */ 105 error = ip6_reass_packet(mp, npc->npc_hlen); 106 if (error && *mp == NULL) { 107 memset(nbuf, 0, sizeof(nbuf_t)); 108 } 109 } 110 if (error) { 111 npf_stats_inc(NPF_STAT_REASSFAIL); 112 return error; 113 } 114 if (*mp == NULL) { 115 /* More fragments should come. */ 116 npf_stats_inc(NPF_STAT_FRAGMENTS); 117 return 0; 118 } 119 120 /* 121 * Reassembly is complete, we have the final packet. 122 * Cache again, since layer 4 data is accessible now. 123 */ 124 nbuf_init(nbuf, *mp, nbuf->nb_ifp); 125 npc->npc_info = 0; 126 127 if (npf_cache_all(npc, nbuf) & NPC_IPFRAG) { 128 return EINVAL; 129 } 130 npf_stats_inc(NPF_STAT_REASSEMBLY); 131 return 0; 132 } 133 134 /* 135 * npf_packet_handler: main packet handling routine for layer 3. 136 * 137 * Note: packet flow and inspection logic is in strict order. 138 */ 139 int 140 npf_packet_handler(void *arg, struct mbuf **mp, ifnet_t *ifp, int di) 141 { 142 nbuf_t nbuf; 143 npf_cache_t npc; 144 npf_session_t *se; 145 npf_rule_t *rl; 146 npf_rproc_t *rp; 147 int error, retfl; 148 int decision; 149 150 /* 151 * Initialise packet information cache. 152 * Note: it is enough to clear the info bits. 153 */ 154 KASSERT(ifp != NULL); 155 nbuf_init(&nbuf, *mp, ifp); 156 npc.npc_info = 0; 157 decision = NPF_DECISION_BLOCK; 158 error = 0; 159 retfl = 0; 160 rp = NULL; 161 162 /* Cache everything. Determine whether it is an IP fragment. */ 163 if (npf_cache_all(&npc, &nbuf) & NPC_IPFRAG) { 164 /* 165 * Pass to IPv4 or IPv6 reassembly mechanism. 166 */ 167 error = npf_reassembly(&npc, &nbuf, mp); 168 if (error) { 169 se = NULL; 170 goto out; 171 } 172 if (*mp == NULL) { 173 /* More fragments should come; return. */ 174 return 0; 175 } 176 } 177 178 /* Inspect the list of sessions (if found, acquires a reference). */ 179 se = npf_session_inspect(&npc, &nbuf, di, &error); 180 181 /* If "passing" session found - skip the ruleset inspection. */ 182 if (se && npf_session_pass(se, &rp)) { 183 npf_stats_inc(NPF_STAT_PASS_SESSION); 184 KASSERT(error == 0); 185 goto pass; 186 } 187 if (error) { 188 if (error == ENETUNREACH) 189 goto block; 190 goto out; 191 } 192 193 /* Acquire the lock, inspect the ruleset using this packet. */ 194 int slock = npf_config_read_enter(); 195 npf_ruleset_t *rlset = npf_config_ruleset(); 196 197 rl = npf_ruleset_inspect(&npc, &nbuf, rlset, di, NPF_LAYER_3); 198 if (rl == NULL) { 199 const bool pass = npf_default_pass(); 200 npf_config_read_exit(slock); 201 202 if (pass) { 203 npf_stats_inc(NPF_STAT_PASS_DEFAULT); 204 goto pass; 205 } 206 npf_stats_inc(NPF_STAT_BLOCK_DEFAULT); 207 goto block; 208 } 209 210 /* 211 * Get the rule procedure (acquires a reference) for association 212 * with a session (if any) and execution. 213 */ 214 KASSERT(rp == NULL); 215 rp = npf_rule_getrproc(rl); 216 217 /* Conclude with the rule and release the lock. */ 218 error = npf_rule_conclude(rl, &retfl); 219 npf_config_read_exit(slock); 220 221 if (error) { 222 npf_stats_inc(NPF_STAT_BLOCK_RULESET); 223 goto block; 224 } 225 npf_stats_inc(NPF_STAT_PASS_RULESET); 226 227 /* 228 * Establish a "pass" session, if required. Just proceed, 229 * if session creation fails (e.g. due to unsupported protocol). 230 */ 231 if ((retfl & NPF_RULE_STATEFUL) != 0 && !se) { 232 se = npf_session_establish(&npc, &nbuf, di, 233 (retfl & NPF_RULE_MULTIENDS) == 0); 234 if (se) { 235 /* 236 * Note: the reference on the rule procedure is 237 * transfered to the session. It will be released 238 * on session destruction. 239 */ 240 npf_session_setpass(se, rp); 241 } 242 } 243 pass: 244 decision = NPF_DECISION_PASS; 245 KASSERT(error == 0); 246 /* 247 * Perform NAT. 248 */ 249 error = npf_do_nat(&npc, se, &nbuf, di); 250 block: 251 /* 252 * Execute the rule procedure, if any is associated. 253 * It may reverse the decision from pass to block. 254 */ 255 if (rp) { 256 npf_rproc_run(&npc, &nbuf, rp, &decision); 257 } 258 out: 259 /* 260 * Release the reference on a session. Release the reference on a 261 * rule procedure only if there was no association. 262 */ 263 if (se) { 264 npf_session_release(se); 265 } else if (rp) { 266 npf_rproc_release(rp); 267 } 268 269 /* Reset mbuf pointer before returning to the caller. */ 270 if ((*mp = nbuf_head_mbuf(&nbuf)) == NULL) { 271 return error ? error : ENOMEM; 272 } 273 274 /* Pass the packet if decided and there is no error. */ 275 if (decision == NPF_DECISION_PASS && !error) { 276 /* 277 * XXX: Disable for now, it will be set accordingly later, 278 * for optimisations (to reduce inspection). 279 */ 280 (*mp)->m_flags &= ~M_CANFASTFWD; 281 return 0; 282 } 283 284 /* 285 * Block the packet. ENETUNREACH is used to indicate blocking. 286 * Depending on the flags and protocol, return TCP reset (RST) or 287 * ICMP destination unreachable. 288 */ 289 if (retfl && npf_return_block(&npc, &nbuf, retfl)) { 290 *mp = NULL; 291 } 292 293 if (!error) { 294 error = ENETUNREACH; 295 } 296 297 if (*mp) { 298 m_freem(*mp); 299 *mp = NULL; 300 } 301 return error; 302 } 303 304 /* 305 * npf_pfil_register: register pfil(9) hooks. 306 */ 307 int 308 npf_pfil_register(bool init) 309 { 310 int error = 0; 311 312 mutex_enter(softnet_lock); 313 KERNEL_LOCK(1, NULL); 314 315 /* Init: interface re-config and attach/detach hook. */ 316 if (!npf_ph_if) { 317 npf_ph_if = pfil_head_get(PFIL_TYPE_IFNET, 0); 318 if (!npf_ph_if) { 319 error = ENOENT; 320 goto out; 321 } 322 error = pfil_add_hook(npf_ifhook, NULL, 323 PFIL_IFADDR | PFIL_IFNET, npf_ph_if); 324 KASSERT(error == 0); 325 } 326 if (init) { 327 goto out; 328 } 329 330 /* Check if pfil hooks are not already registered. */ 331 if (pfil_registered) { 332 error = EEXIST; 333 goto out; 334 } 335 336 /* Capture points of the activity in the IP layer. */ 337 npf_ph_inet = pfil_head_get(PFIL_TYPE_AF, (void *)AF_INET); 338 npf_ph_inet6 = pfil_head_get(PFIL_TYPE_AF, (void *)AF_INET6); 339 if (!npf_ph_inet && !npf_ph_inet6) { 340 error = ENOENT; 341 goto out; 342 } 343 344 /* Packet IN/OUT handlers for IP layer. */ 345 if (npf_ph_inet) { 346 error = pfil_add_hook(npf_packet_handler, NULL, 347 PFIL_ALL, npf_ph_inet); 348 KASSERT(error == 0); 349 } 350 if (npf_ph_inet6) { 351 error = pfil_add_hook(npf_packet_handler, NULL, 352 PFIL_ALL, npf_ph_inet6); 353 KASSERT(error == 0); 354 } 355 pfil_registered = true; 356 out: 357 KERNEL_UNLOCK_ONE(NULL); 358 mutex_exit(softnet_lock); 359 360 return error; 361 } 362 363 /* 364 * npf_pfil_unregister: unregister pfil(9) hooks. 365 */ 366 void 367 npf_pfil_unregister(bool fini) 368 { 369 mutex_enter(softnet_lock); 370 KERNEL_LOCK(1, NULL); 371 372 if (fini && npf_ph_if) { 373 (void)pfil_remove_hook(npf_ifhook, NULL, 374 PFIL_IFADDR | PFIL_IFNET, npf_ph_if); 375 } 376 if (npf_ph_inet) { 377 (void)pfil_remove_hook(npf_packet_handler, NULL, 378 PFIL_ALL, npf_ph_inet); 379 } 380 if (npf_ph_inet6) { 381 (void)pfil_remove_hook(npf_packet_handler, NULL, 382 PFIL_ALL, npf_ph_inet6); 383 } 384 pfil_registered = false; 385 386 KERNEL_UNLOCK_ONE(NULL); 387 mutex_exit(softnet_lock); 388 } 389 390 bool 391 npf_pfil_registered_p(void) 392 { 393 return pfil_registered; 394 } 395