1 /*- 2 * Copyright (c) 1982, 1986, 1990, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 4. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * @(#)in_pcb.h 8.1 (Berkeley) 6/10/93 30 * $FreeBSD$ 31 */ 32 33 #ifndef _NETINET_IN_PCB_H_ 34 #define _NETINET_IN_PCB_H_ 35 36 #include <sys/queue.h> 37 #include <sys/_lock.h> 38 #include <sys/_mutex.h> 39 #include <sys/_rwlock.h> 40 41 #include <net/route.h> 42 43 #ifdef _KERNEL 44 #include <sys/rwlock.h> 45 #endif 46 47 #define in6pcb inpcb /* for KAME src sync over BSD*'s */ 48 #define in6p_sp inp_sp /* for KAME src sync over BSD*'s */ 49 struct inpcbpolicy; 50 51 /* 52 * Struct inpcb is the ommon structure pcb for the Internet Protocol 53 * implementation. 54 * 55 * Pointers to local and foreign host table entries, local and foreign socket 56 * numbers, and pointers up (to a socket structure) and down (to a 57 * protocol-specific control block) are stored here. 58 */ 59 LIST_HEAD(inpcbhead, inpcb); 60 LIST_HEAD(inpcbporthead, inpcbport); 61 typedef u_quad_t inp_gen_t; 62 63 /* 64 * PCB with AF_INET6 null bind'ed laddr can receive AF_INET input packet. 65 * So, AF_INET6 null laddr is also used as AF_INET null laddr, by utilizing 66 * the following structure. 67 */ 68 struct in_addr_4in6 { 69 u_int32_t ia46_pad32[3]; 70 struct in_addr ia46_addr4; 71 }; 72 73 /* 74 * NOTE: ipv6 addrs should be 64-bit aligned, per RFC 2553. in_conninfo has 75 * some extra padding to accomplish this. 76 */ 77 struct in_endpoints { 78 u_int16_t ie_fport; /* foreign port */ 79 u_int16_t ie_lport; /* local port */ 80 /* protocol dependent part, local and foreign addr */ 81 union { 82 /* foreign host table entry */ 83 struct in_addr_4in6 ie46_foreign; 84 struct in6_addr ie6_foreign; 85 } ie_dependfaddr; 86 union { 87 /* local host table entry */ 88 struct in_addr_4in6 ie46_local; 89 struct in6_addr ie6_local; 90 } ie_dependladdr; 91 #define ie_faddr ie_dependfaddr.ie46_foreign.ia46_addr4 92 #define ie_laddr ie_dependladdr.ie46_local.ia46_addr4 93 #define ie6_faddr ie_dependfaddr.ie6_foreign 94 #define ie6_laddr ie_dependladdr.ie6_local 95 }; 96 97 /* 98 * XXX The defines for inc_* are hacks and should be changed to direct 99 * references. 100 */ 101 struct in_conninfo { 102 u_int8_t inc_flags; 103 u_int8_t inc_len; 104 u_int16_t inc_fibnum; /* XXX was pad, 16 bits is plenty */ 105 /* protocol dependent part */ 106 struct in_endpoints inc_ie; 107 }; 108 #define inc_isipv6 inc_flags /* temp compatability */ 109 #define inc_fport inc_ie.ie_fport 110 #define inc_lport inc_ie.ie_lport 111 #define inc_faddr inc_ie.ie_faddr 112 #define inc_laddr inc_ie.ie_laddr 113 #define inc6_faddr inc_ie.ie6_faddr 114 #define inc6_laddr inc_ie.ie6_laddr 115 116 struct icmp6_filter; 117 118 /*- 119 * struct inpcb captures the network layer state for TCP, UDP, and raw IPv4 120 * and IPv6 sockets. In the case of TCP, further per-connection state is 121 * hung off of inp_ppcb most of the time. Almost all fields of struct inpcb 122 * are static after creation or protected by a per-inpcb rwlock, inp_lock. A 123 * few fields also require the global pcbinfo lock for the inpcb to be held, 124 * when modified, such as the global connection lists and hashes, as well as 125 * binding information (which affects which hash a connection is on). This 126 * model means that connections can be looked up without holding the 127 * per-connection lock, which is important for performance when attempting to 128 * find the connection for a packet given its IP and port tuple. Writing to 129 * these fields that write locks be held on both the inpcb and global locks. 130 * 131 * Key: 132 * (c) - Constant after initialization 133 * (i) - Protected by the inpcb lock 134 * (p) - Protected by the pcbinfo lock for the inpcb 135 * (s) - Protected by another subsystem's locks 136 * (x) - Undefined locking 137 * 138 * A few other notes: 139 * 140 * When a read lock is held, stability of the field is guaranteed; to write 141 * to a field, a write lock must generally be held. 142 * 143 * netinet/netinet6-layer code should not assume that the inp_socket pointer 144 * is safe to dereference without inp_lock being held, even for protocols 145 * other than TCP (where the inpcb persists during TIMEWAIT even after the 146 * socket has been freed), or there may be close(2)-related races. 147 * 148 * The inp_vflag field is overloaded, and would otherwise ideally be (c). 149 */ 150 struct inpcb { 151 LIST_ENTRY(inpcb) inp_hash; /* (i/p) hash list */ 152 LIST_ENTRY(inpcb) inp_list; /* (i/p) list for all PCBs for proto */ 153 void *inp_ppcb; /* (i) pointer to per-protocol pcb */ 154 struct inpcbinfo *inp_pcbinfo; /* (c) PCB list info */ 155 struct socket *inp_socket; /* (i) back pointer to socket */ 156 157 u_int32_t inp_flow; /* (i) IPv6 flow information */ 158 int inp_flags; /* (i) generic IP/datagram flags */ 159 160 u_char inp_vflag; /* (i) IP version flag (v4/v6) */ 161 #define INP_IPV4 0x1 162 #define INP_IPV6 0x2 163 #define INP_IPV6PROTO 0x4 /* opened under IPv6 protocol */ 164 #define INP_TIMEWAIT 0x8 /* .. probably doesn't go here */ 165 #define INP_ONESBCAST 0x10 /* send all-ones broadcast */ 166 #define INP_DROPPED 0x20 /* protocol drop flag */ 167 #define INP_SOCKREF 0x40 /* strong socket reference */ 168 u_char inp_ip_ttl; /* (i) time to live proto */ 169 u_char inp_ip_p; /* (c) protocol proto */ 170 u_char inp_ip_minttl; /* (i) minimum TTL or drop */ 171 uint32_t inp_ispare1; /* (x) connection id / queue id */ 172 void *inp_pspare[2]; /* (x) rtentry / general use */ 173 174 /* Local and foreign ports, local and foreign addr. */ 175 struct in_conninfo inp_inc; 176 177 /* (i/p) list for PCB's local port */ 178 struct label *inp_label; /* (i) MAC label */ 179 struct inpcbpolicy *inp_sp; /* (s) for IPSEC */ 180 181 /* Protocol-dependent part; options. */ 182 struct { 183 u_char inp4_ip_tos; /* (i) type of service proto */ 184 struct mbuf *inp4_options; /* (i) IP options */ 185 struct ip_moptions *inp4_moptions; /* (i) IP multicast options */ 186 } inp_depend4; 187 #define inp_fport inp_inc.inc_fport 188 #define inp_lport inp_inc.inc_lport 189 #define inp_faddr inp_inc.inc_faddr 190 #define inp_laddr inp_inc.inc_laddr 191 #define inp_ip_tos inp_depend4.inp4_ip_tos 192 #define inp_options inp_depend4.inp4_options 193 #define inp_moptions inp_depend4.inp4_moptions 194 struct { 195 /* (i) IP options */ 196 struct mbuf *inp6_options; 197 /* (i) IP6 options for outgoing packets */ 198 struct ip6_pktopts *inp6_outputopts; 199 /* (i) IP multicast options */ 200 struct ip6_moptions *inp6_moptions; 201 /* (i) ICMPv6 code type filter */ 202 struct icmp6_filter *inp6_icmp6filt; 203 /* (i) IPV6_CHECKSUM setsockopt */ 204 int inp6_cksum; 205 short inp6_hops; 206 } inp_depend6; 207 LIST_ENTRY(inpcb) inp_portlist; /* (i/p) */ 208 struct inpcbport *inp_phd; /* (i/p) head of this list */ 209 #define inp_zero_size offsetof(struct inpcb, inp_gencnt) 210 inp_gen_t inp_gencnt; /* (c) generation count of this instance */ 211 struct rwlock inp_lock; 212 213 #define in6p_faddr inp_inc.inc6_faddr 214 #define in6p_laddr inp_inc.inc6_laddr 215 #define in6p_hops inp_depend6.inp6_hops /* default hop limit */ 216 #define in6p_ip6_nxt inp_ip_p 217 #define in6p_flowinfo inp_flow 218 #define in6p_vflag inp_vflag 219 #define in6p_options inp_depend6.inp6_options 220 #define in6p_outputopts inp_depend6.inp6_outputopts 221 #define in6p_moptions inp_depend6.inp6_moptions 222 #define in6p_icmp6filt inp_depend6.inp6_icmp6filt 223 #define in6p_cksum inp_depend6.inp6_cksum 224 #define in6p_flags inp_flags /* for KAME src sync over BSD*'s */ 225 #define in6p_socket inp_socket /* for KAME src sync over BSD*'s */ 226 #define in6p_lport inp_lport /* for KAME src sync over BSD*'s */ 227 #define in6p_fport inp_fport /* for KAME src sync over BSD*'s */ 228 #define in6p_ppcb inp_ppcb /* for KAME src sync over BSD*'s */ 229 }; 230 /* 231 * The range of the generation count, as used in this implementation, is 9e19. 232 * We would have to create 300 billion connections per second for this number 233 * to roll over in a year. This seems sufficiently unlikely that we simply 234 * don't concern ourselves with that possibility. 235 */ 236 237 /* 238 * Interface exported to userland by various protocols which use inpcbs. Hack 239 * alert -- only define if struct xsocket is in scope. 240 */ 241 #ifdef _SYS_SOCKETVAR_H_ 242 struct xinpcb { 243 size_t xi_len; /* length of this structure */ 244 struct inpcb xi_inp; 245 struct xsocket xi_socket; 246 u_quad_t xi_alignment_hack; 247 }; 248 249 struct xinpgen { 250 size_t xig_len; /* length of this structure */ 251 u_int xig_count; /* number of PCBs at this time */ 252 inp_gen_t xig_gen; /* generation count at this time */ 253 so_gen_t xig_sogen; /* socket generation count at this time */ 254 }; 255 #endif /* _SYS_SOCKETVAR_H_ */ 256 257 struct inpcbport { 258 LIST_ENTRY(inpcbport) phd_hash; 259 struct inpcbhead phd_pcblist; 260 u_short phd_port; 261 }; 262 263 /* 264 * Global data structure for each high-level protocol (UDP, TCP, ...) in both 265 * IPv4 and IPv6. Holds inpcb lists and information for managing them. 266 */ 267 struct inpcbinfo { 268 /* 269 * Global list of inpcbs on the protocol. 270 */ 271 struct inpcbhead *ipi_listhead; 272 u_int ipi_count; 273 274 /* 275 * Global hash of inpcbs, hashed by local and foreign addresses and 276 * port numbers. 277 */ 278 struct inpcbhead *ipi_hashbase; 279 u_long ipi_hashmask; 280 281 /* 282 * Global hash of inpcbs, hashed by only local port number. 283 */ 284 struct inpcbporthead *ipi_porthashbase; 285 u_long ipi_porthashmask; 286 287 /* 288 * Fields associated with port lookup and allocation. 289 */ 290 u_short ipi_lastport; 291 u_short ipi_lastlow; 292 u_short ipi_lasthi; 293 294 /* 295 * UMA zone from which inpcbs are allocated for this protocol. 296 */ 297 struct uma_zone *ipi_zone; 298 299 /* 300 * Generation count--incremented each time a connection is allocated 301 * or freed. 302 */ 303 u_quad_t ipi_gencnt; 304 struct rwlock ipi_lock; 305 306 /* 307 * vimage 1 308 * general use 1 309 */ 310 void *ipi_pspare[2]; 311 }; 312 313 #define INP_LOCK_INIT(inp, d, t) \ 314 rw_init_flags(&(inp)->inp_lock, (t), RW_RECURSE | RW_DUPOK) 315 #define INP_LOCK_DESTROY(inp) rw_destroy(&(inp)->inp_lock) 316 #define INP_RLOCK(inp) rw_rlock(&(inp)->inp_lock) 317 #define INP_WLOCK(inp) rw_wlock(&(inp)->inp_lock) 318 #define INP_TRY_RLOCK(inp) rw_try_rlock(&(inp)->inp_lock) 319 #define INP_TRY_WLOCK(inp) rw_try_wlock(&(inp)->inp_lock) 320 #define INP_RUNLOCK(inp) rw_runlock(&(inp)->inp_lock) 321 #define INP_WUNLOCK(inp) rw_wunlock(&(inp)->inp_lock) 322 #define INP_LOCK_ASSERT(inp) rw_assert(&(inp)->inp_lock, RA_LOCKED) 323 #define INP_RLOCK_ASSERT(inp) rw_assert(&(inp)->inp_lock, RA_RLOCKED) 324 #define INP_WLOCK_ASSERT(inp) rw_assert(&(inp)->inp_lock, RA_WLOCKED) 325 #define INP_UNLOCK_ASSERT(inp) rw_assert(&(inp)->inp_lock, RA_UNLOCKED) 326 327 #ifdef _KERNEL 328 /* 329 * These locking functions are for inpcb consumers outside of sys/netinet, 330 * more specifically, they were added for the benefit of TOE drivers. The 331 * macros are reserved for use by the stack. 332 */ 333 void inp_wlock(struct inpcb *); 334 void inp_wunlock(struct inpcb *); 335 void inp_rlock(struct inpcb *); 336 void inp_runlock(struct inpcb *); 337 338 #ifdef INVARIANTS 339 void inp_lock_assert(struct inpcb *); 340 void inp_unlock_assert(struct inpcb *); 341 #else 342 static __inline void 343 inp_lock_assert(struct inpcb *inp __unused) 344 { 345 } 346 347 static __inline void 348 inp_unlock_assert(struct inpcb *inp __unused) 349 { 350 } 351 352 #endif 353 354 void inp_apply_all(void (*func)(struct inpcb *, void *), void *arg); 355 int inp_ip_tos_get(const struct inpcb *inp); 356 void inp_ip_tos_set(struct inpcb *inp, int val); 357 struct socket * 358 inp_inpcbtosocket(struct inpcb *inp); 359 struct tcpcb * 360 inp_inpcbtotcpcb(struct inpcb *inp); 361 void inp_4tuple_get(struct inpcb *inp, uint32_t *laddr, uint16_t *lp, 362 uint32_t *faddr, uint16_t *fp); 363 364 #endif /* _KERNEL */ 365 366 #define INP_INFO_LOCK_INIT(ipi, d) \ 367 rw_init_flags(&(ipi)->ipi_lock, (d), RW_RECURSE) 368 #define INP_INFO_LOCK_DESTROY(ipi) rw_destroy(&(ipi)->ipi_lock) 369 #define INP_INFO_RLOCK(ipi) rw_rlock(&(ipi)->ipi_lock) 370 #define INP_INFO_WLOCK(ipi) rw_wlock(&(ipi)->ipi_lock) 371 #define INP_INFO_TRY_RLOCK(ipi) rw_try_rlock(&(ipi)->ipi_lock) 372 #define INP_INFO_TRY_WLOCK(ipi) rw_try_wlock(&(ipi)->ipi_lock) 373 #define INP_INFO_RUNLOCK(ipi) rw_runlock(&(ipi)->ipi_lock) 374 #define INP_INFO_WUNLOCK(ipi) rw_wunlock(&(ipi)->ipi_lock) 375 #define INP_INFO_LOCK_ASSERT(ipi) rw_assert(&(ipi)->ipi_lock, RA_LOCKED) 376 #define INP_INFO_RLOCK_ASSERT(ipi) rw_assert(&(ipi)->ipi_lock, RA_RLOCKED) 377 #define INP_INFO_WLOCK_ASSERT(ipi) rw_assert(&(ipi)->ipi_lock, RA_WLOCKED) 378 #define INP_INFO_UNLOCK_ASSERT(ipi) rw_assert(&(ipi)->ipi_lock, RA_UNLOCKED) 379 380 #define INP_PCBHASH(faddr, lport, fport, mask) \ 381 (((faddr) ^ ((faddr) >> 16) ^ ntohs((lport) ^ (fport))) & (mask)) 382 #define INP_PCBPORTHASH(lport, mask) \ 383 (ntohs((lport)) & (mask)) 384 385 /* flags in inp_flags: */ 386 #define INP_RECVOPTS 0x01 /* receive incoming IP options */ 387 #define INP_RECVRETOPTS 0x02 /* receive IP options for reply */ 388 #define INP_RECVDSTADDR 0x04 /* receive IP dst address */ 389 #define INP_HDRINCL 0x08 /* user supplies entire IP header */ 390 #define INP_HIGHPORT 0x10 /* user wants "high" port binding */ 391 #define INP_LOWPORT 0x20 /* user wants "low" port binding */ 392 #define INP_ANONPORT 0x40 /* port chosen for user */ 393 #define INP_RECVIF 0x80 /* receive incoming interface */ 394 #define INP_MTUDISC 0x100 /* user can do MTU discovery */ 395 #define INP_FAITH 0x200 /* accept FAITH'ed connections */ 396 #define INP_RECVTTL 0x400 /* receive incoming IP TTL */ 397 #define INP_DONTFRAG 0x800 /* don't fragment packet */ 398 399 #define IN6P_IPV6_V6ONLY 0x008000 /* restrict AF_INET6 socket for v6 */ 400 401 #define IN6P_PKTINFO 0x010000 /* receive IP6 dst and I/F */ 402 #define IN6P_HOPLIMIT 0x020000 /* receive hoplimit */ 403 #define IN6P_HOPOPTS 0x040000 /* receive hop-by-hop options */ 404 #define IN6P_DSTOPTS 0x080000 /* receive dst options after rthdr */ 405 #define IN6P_RTHDR 0x100000 /* receive routing header */ 406 #define IN6P_RTHDRDSTOPTS 0x200000 /* receive dstoptions before rthdr */ 407 #define IN6P_TCLASS 0x400000 /* receive traffic class value */ 408 #define IN6P_AUTOFLOWLABEL 0x800000 /* attach flowlabel automatically */ 409 #define IN6P_RFC2292 0x40000000 /* used RFC2292 API on the socket */ 410 #define IN6P_MTU 0x80000000 /* receive path MTU */ 411 412 #define INP_CONTROLOPTS (INP_RECVOPTS|INP_RECVRETOPTS|INP_RECVDSTADDR|\ 413 INP_RECVIF|INP_RECVTTL|\ 414 IN6P_PKTINFO|IN6P_HOPLIMIT|IN6P_HOPOPTS|\ 415 IN6P_DSTOPTS|IN6P_RTHDR|IN6P_RTHDRDSTOPTS|\ 416 IN6P_TCLASS|IN6P_AUTOFLOWLABEL|IN6P_RFC2292|\ 417 IN6P_MTU) 418 #define INP_UNMAPPABLEOPTS (IN6P_HOPOPTS|IN6P_DSTOPTS|IN6P_RTHDR|\ 419 IN6P_TCLASS|IN6P_AUTOFLOWLABEL) 420 421 /* for KAME src sync over BSD*'s */ 422 #define IN6P_HIGHPORT INP_HIGHPORT 423 #define IN6P_LOWPORT INP_LOWPORT 424 #define IN6P_ANONPORT INP_ANONPORT 425 #define IN6P_RECVIF INP_RECVIF 426 #define IN6P_MTUDISC INP_MTUDISC 427 #define IN6P_FAITH INP_FAITH 428 #define IN6P_CONTROLOPTS INP_CONTROLOPTS 429 /* 430 * socket AF version is {newer than,or include} 431 * actual datagram AF version 432 */ 433 434 #define INPLOOKUP_WILDCARD 1 435 #define sotoinpcb(so) ((struct inpcb *)(so)->so_pcb) 436 #define sotoin6pcb(so) sotoinpcb(so) /* for KAME src sync over BSD*'s */ 437 438 #define INP_SOCKAF(so) so->so_proto->pr_domain->dom_family 439 440 #define INP_CHECK_SOCKAF(so, af) (INP_SOCKAF(so) == af) 441 442 #ifdef _KERNEL 443 extern int ipport_reservedhigh; 444 extern int ipport_reservedlow; 445 extern int ipport_lowfirstauto; 446 extern int ipport_lowlastauto; 447 extern int ipport_firstauto; 448 extern int ipport_lastauto; 449 extern int ipport_hifirstauto; 450 extern int ipport_hilastauto; 451 extern struct callout ipport_tick_callout; 452 453 void in_pcbpurgeif0(struct inpcbinfo *, struct ifnet *); 454 int in_pcballoc(struct socket *, struct inpcbinfo *); 455 int in_pcbbind(struct inpcb *, struct sockaddr *, struct ucred *); 456 int in_pcbbind_setup(struct inpcb *, struct sockaddr *, in_addr_t *, 457 u_short *, struct ucred *); 458 int in_pcbconnect(struct inpcb *, struct sockaddr *, struct ucred *); 459 int in_pcbconnect_setup(struct inpcb *, struct sockaddr *, in_addr_t *, 460 u_short *, in_addr_t *, u_short *, struct inpcb **, 461 struct ucred *); 462 void in_pcbdetach(struct inpcb *); 463 void in_pcbdisconnect(struct inpcb *); 464 void in_pcbdrop(struct inpcb *); 465 void in_pcbfree(struct inpcb *); 466 int in_pcbinshash(struct inpcb *); 467 struct inpcb * 468 in_pcblookup_local(struct inpcbinfo *, 469 struct in_addr, u_short, int, struct ucred *); 470 struct inpcb * 471 in_pcblookup_hash(struct inpcbinfo *, struct in_addr, u_int, 472 struct in_addr, u_int, int, struct ifnet *); 473 void in_pcbnotifyall(struct inpcbinfo *pcbinfo, struct in_addr, 474 int, struct inpcb *(*)(struct inpcb *, int)); 475 void in_pcbrehash(struct inpcb *); 476 void in_pcbsetsolabel(struct socket *so); 477 int in_getpeeraddr(struct socket *so, struct sockaddr **nam); 478 int in_getsockaddr(struct socket *so, struct sockaddr **nam); 479 struct sockaddr * 480 in_sockaddr(in_port_t port, struct in_addr *addr); 481 void in_pcbsosetlabel(struct socket *so); 482 void in_pcbremlists(struct inpcb *inp); 483 void ipport_tick(void *xtp); 484 485 /* 486 * Debugging routines compiled in when DDB is present. 487 */ 488 void db_print_inpcb(struct inpcb *inp, const char *name, int indent); 489 490 #endif /* _KERNEL */ 491 492 #endif /* !_NETINET_IN_PCB_H_ */ 493