bsd/man/man4/ip6.4

   1 .\"     $NetBSD: ip6.4,v 1.20 2005/01/11 06:01:41 itojun Exp $
   2 .\"     $KAME: ip6.4,v 1.23 2005/01/11 05:56:25 itojun Exp $
   3 .\"     $OpenBSD: ip6.4,v 1.21 2005/01/06 03:50:46 itojun Exp $
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  31 .Dd December 29, 2004
  32 .Dt IP6 4
  33 .Os
  34 .Sh NAME
  35 .Nm ip6
  36 .Nd Internet Protocol version 6 (IPv6) network layer
  37 .Sh SYNOPSIS
  38 .In sys/socket.h
  39 .In netinet/in.h
  40 .Ft int
  41 .Fn socket AF_INET6 SOCK_RAW proto
  42 .Sh DESCRIPTION
  43 The IPv6 network layer is used by the IPv6 protocol family for
  44 transporting data.
  45 IPv6 packets contain an IPv6 header that is not provided as part of the
  46 payload contents when passed to an application.
  47 IPv6 header options affect the behavior of this protocol and may be used
  48 by high-level protocols (such as the
  49 .Xr tcp 4
  50 and
  51 .Xr udp 4
  52 protocols) as well as directly by
  53 .Dq raw sockets ,
  54 which process IPv6 messages at a lower-level and may be useful for
  55 developing new protocols and special-purpose applications.
  56 .Ss Header
  57 All IPv6 packets begin with an IPv6 header.
  58 When data received by the kernel are passed to the application, this
  59 header is not included in buffer, even when raw sockets are being used.
  60 Likewise, when data are sent to the kernel for transmit from the
  61 application, the buffer is not examined for an IPv6 header:
  62 the kernel always constructs the header.
  63 To directly access IPv6 headers from received packets and specify them
  64 as part of the buffer passed to the kernel, link-level access
  65 .Po
  66 .Xr bpf 4 ,
  67 for example
  68 .Pc
  69 must instead be utilized.
  70 .Pp
  71 The header has the following definition:
  72 .Bd -literal -offset indent
  73 struct ip6_hdr {
  74      union {
  75           struct ip6_hdrctl {
  76                u_int32_t ip6_un1_flow;  /* 20 bits of flow ID */
  77                u_int16_t ip6_un1_plen;  /* payload length */
  78                u_int8_t  ip6_un1_nxt;   /* next header */
  79                u_int8_t  ip6_un1_hlim;  /* hop limit */
  80           } ip6_un1;
  81           u_int8_t ip6_un2_vfc;   /* version and class */
  82      } ip6_ctlun;
  83      struct in6_addr ip6_src;   /* source address */
  84      struct in6_addr ip6_dst;   /* destination address */
  85 } __packed;
  86
  87 #define ip6_vfc         ip6_ctlun.ip6_un2_vfc
  88 #define ip6_flow        ip6_ctlun.ip6_un1.ip6_un1_flow
  89 #define ip6_plen        ip6_ctlun.ip6_un1.ip6_un1_plen
  90 #define ip6_nxt         ip6_ctlun.ip6_un1.ip6_un1_nxt
  91 #define ip6_hlim        ip6_ctlun.ip6_un1.ip6_un1_hlim
  92 #define ip6_hops        ip6_ctlun.ip6_un1.ip6_un1_hlim
  93 .Ed
  94 .Pp
  95 All fields are in network-byte order.
  96 Any options specified (see
  97 .Sx Options
  98 below) must also be specified in network-byte order.
  99 .Pp
 100 .Va ip6_flow
 101 specifies the flow ID.
 102 .Va ip6_plen
 103 specifies the payload length.
 104 .Va ip6_nxt
 105 specifies the type of the next header.
 106 .Va ip6_hlim
 107 specifies the hop limit.
 108 .Pp
 109 The top 4 bits of
 110 .Va ip6_vfc
 111 specify the class and the bottom 4 bits specify the version.
 112 .Pp
 113 .Va ip6_src
 114 and
 115 .Va ip6_dst
 116 specify the source and destination addresses.
 117 .Pp
 118 The IPv6 header may be followed by any number of extension headers that start
 119 with the following generic definition:
 120 .Bd -literal -offset indent
 121 struct ip6_ext {
 122      u_int8_t ip6e_nxt;
 123      u_int8_t ip6e_len;
 124 } __packed;
 125 .Ed
 126 .Ss Options
 127 IPv6 allows header options on packets to manipulate the behavior of the
 128 protocol.
 129 These options and other control requests are accessed with the
 130 .Xr getsockopt 2
 131 and
 132 .Xr setsockopt 2
 133 system calls at level
 134 .Dv IPPROTO_IPV6
 135 and by using ancillary data in
 136 .Xr recvmsg 2
 137 and
 138 .Xr sendmsg 2 .
 139 They can be used to access most of the fields in the IPv6 header and
 140 extension headers.
 141 .Pp
 142 The following socket options are supported:
 143 .Bl -tag -width Ds
 144 .\" .It Dv IPV6_OPTIONS
 145 .It Dv IPV6_UNICAST_HOPS Fa "int *"
 146 Get or set the default hop limit header field for outgoing unicast
 147 datagrams sent on this socket.
 148 A value of \-1 resets to the default value.
 149 .\" .It Dv IPV6_RECVOPTS Fa "int *"
 150 .\" Get or set the status of whether all header options will be
 151 .\" delivered along with the datagram when it is received.
 152 .\" .It Dv IPV6_RECVRETOPTS Fa "int *"
 153 .\" Get or set the status of whether header options will be delivered
 154 .\" for reply.
 155 .\" .It Dv IPV6_RECVDSTADDR Fa "int *"
 156 .\" Get or set the status of whether datagrams are received with
 157 .\" destination addresses.
 158 .\" .It Dv IPV6_RETOPTS
 159 .\" Get or set IPv6 options.
 160 .It Dv IPV6_MULTICAST_IF Fa "u_int *"
 161 Get or set the interface from which multicast packets will be sent.
 162 For hosts with multiple interfaces, each multicast transmission is sent
 163 from the primary network interface.
 164 The interface is specified as its index as provided by
 165 .Xr if_nametoindex 3 .
 166 A value of zero specifies the default interface.
 167 .It Dv IPV6_MULTICAST_HOPS Fa "int *"
 168 Get or set the default hop limit header field for outgoing multicast
 169 datagrams sent on this socket.
 170 This option controls the scope of multicast datagram transmissions.
 171 .Pp
 172 Datagrams with a hop limit of 1 are not forwarded beyond the local
 173 network.
 174 Multicast datagrams with a hop limit of zero will not be transmitted on
 175 any network but may be delivered locally if the sending host belongs to
 176 the destination group and if multicast loopback (see below) has not been
 177 disabled on the sending socket.
 178 Multicast datagrams with a hop limit greater than 1 may be forwarded to
 179 the other networks if a multicast router (such as
 180 .Xr mrouted 8 )
 181 is attached to the local network.
 182 .It Dv IPV6_MULTICAST_LOOP Fa "u_int *"
 183 Get or set the status of whether multicast datagrams will be looped back
 184 for local delivery when a multicast datagram is sent to a group to which
 185 the sending host belongs.
 186 .Pp
 187 This option improves performance for applications that may have no more
 188 than one instance on a single host (such as a router daemon) by
 189 eliminating the overhead of receiving their own transmissions.
 190 It should generally not be used by applications for which there may be
 191 more than one instance on a single host (such as a conferencing program)
 192 or for which the sender does not belong to the destination group
 193 (such as a time-querying program).
 194 .Pp
 195 A multicast datagram sent with an initial hop limit greater than 1 may
 196 be delivered to the sending host on a different interface from that on
 197 which it was sent if the host belongs to the destination group on that
 198 other interface.
 199 The multicast loopback control option has no effect on such delivery.
 200 .It Dv IPV6_JOIN_GROUP Fa "struct ipv6_mreq *"
 201 Join a multicast group.
 202 A host must become a member of a multicast group before it can receive
 203 datagrams sent to the group.
 204 .Bd -literal
 205 struct ipv6_mreq {
 206         struct in6_addr ipv6mr_multiaddr;
 207         unsigned int    ipv6mr_interface;
 208 };
 209 .Ed
 210 .Pp
 211 .Va ipv6mr_interface
 212 may be set to zeroes to choose the default multicast interface or to the
 213 index of a particular multicast-capable interface if the host is
 214 multihomed.
 215 Membership is associated with a single interface; programs running on
 216 multihomed hosts may need to join the same group on more than one
 217 interface.
 218 .Pp
 219 If the multicast address is unspecified (i.e., all zeroes), messages
 220 from all multicast addresses will be accepted by this group.
 221 Note that setting to this value requires superuser privileges.
 222 .It Dv IPV6_LEAVE_GROUP Fa "struct ipv6_mreq *"
 223 Drop membership from the associated multicast group.
 224 Memberships are automatically dropped when the socket is closed or when
 225 the process exits.
 226 .It Dv IPV6_PORTRANGE Fa "int *"
 227 Get or set the allocation policy of ephemeral ports for when the kernel
 228 automatically binds a local address to this socket.
 229 The following values are available:
 230 .Pp
 231 .Bl -tag -width IPV6_PORTRANGE_DEFAULT -compact
 232 .It Dv IPV6_PORTRANGE_DEFAULT
 233 Use the regular range of non-reserved ports (varies, see
 234 .Xr sysctl 8 ) .
 235 .It Dv IPV6_PORTRANGE_HIGH
 236 Use a high range (varies, see
 237 .Xr sysctl 8 ) .
 238 .It Dv IPV6_PORTRANGE_LOW
 239 Use a low, reserved range (600\-1023).
 240 .El
 241 .It Dv IPV6_PKTINFO Fa "int *"
 242 Get or set whether additional information about subsequent packets will
 243 be provided as ancillary data along with the payload in subsequent
 244 .Xr recvmsg 2
 245 calls.
 246 The information is stored in the following structure in the ancillary
 247 data returned:
 248 .Bd -literal
 249 struct in6_pktinfo {
 250         struct in6_addr ipi6_addr;    /* src/dst IPv6 address */
 251         unsigned int    ipi6_ifindex; /* send/recv if index */
 252 };
 253 .Ed
 254 .It Dv IPV6_HOPLIMIT Fa "int *"
 255 Get or set whether the hop limit header field from subsequent packets
 256 will be provided as ancillary data along with the payload in subsequent
 257 .Xr recvmsg 2
 258 calls.
 259 The value is stored as an
 260 .Vt int
 261 in the ancillary data returned.
 262 .\" .It Dv IPV6_NEXTHOP Fa "int *"
 263 .\" Get or set whether the address of the next hop for subsequent
 264 .\" packets will be provided as ancillary data along with the payload in
 265 .\" subsequent
 266 .\" .Xr recvmsg 2
 267 .\" calls.
 268 .\" The option is stored as a
 269 .\" .Vt sockaddr
 270 .\" structure in the ancillary data returned.
 271 .\" .Pp
 272 .\" This option requires superuser privileges.
 273 .It Dv IPV6_HOPOPTS Fa "int *"
 274 Get or set whether the hop-by-hop options from subsequent packets will be
 275 provided as ancillary data along with the payload in subsequent
 276 .Xr recvmsg 2
 277 calls.
 278 The option is stored in the following structure in the ancillary data
 279 returned:
 280 .Bd -literal
 281 struct ip6_hbh {
 282         u_int8_t ip6h_nxt;      /* next header */
 283         u_int8_t ip6h_len;      /* length in units of 8 octets */
 284 /* followed by options */
 285 } __packed;
 286 .Ed
 287 .Pp
 288 The
 289 .Fn inet6_option_space
 290 routine and family of routines may be used to manipulate this data.
 291 .Pp
 292 This option requires superuser privileges.
 293 .It Dv IPV6_DSTOPTS Fa "int *"
 294 Get or set whether the destination options from subsequent packets will
 295 be provided as ancillary data along with the payload in subsequent
 296 .Xr recvmsg 2
 297 calls.
 298 The option is stored in the following structure in the ancillary data
 299 returned:
 300 .Bd -literal
 301 struct ip6_dest {
 302         u_int8_t ip6d_nxt;      /* next header */
 303         u_int8_t ip6d_len;      /* length in units of 8 octets */
 304 /* followed by options */
 305 } __packed;
 306 .Ed
 307 .Pp
 308 The
 309 .Fn inet6_option_space
 310 routine and family of routines may be used to manipulate this data.
 311 .Pp
 312 This option requires superuser privileges.
 313 .It Dv IPV6_RTHDR Fa "int *"
 314 Get or set whether the routing header from subsequent packets will be
 315 provided as ancillary data along with the payload in subsequent
 316 .Xr recvmsg 2
 317 calls.
 318 The header is stored in the following structure in the ancillary data
 319 returned:
 320 .Bd -literal
 321 struct ip6_rthdr {
 322         u_int8_t ip6r_nxt;      /* next header */
 323         u_int8_t ip6r_len;      /* length in units of 8 octets */
 324         u_int8_t ip6r_type;     /* routing type */
 325         u_int8_t ip6r_segleft;  /* segments left */
 326 /* followed by routing-type-specific data */
 327 } __packed;
 328 .Ed
 329 .Pp
 330 The
 331 .Fn inet6_option_space
 332 routine and family of routines may be used to manipulate this data.
 333 .Pp
 334 This option requires superuser privileges.
 335 .It Dv IPV6_PKTOPTIONS Fa "struct cmsghdr *"
 336 Get or set all header options and extension headers at one time on the
 337 last packet sent or received on the socket.
 338 All options must fit within the size of an mbuf (see
 339 .Xr mbuf 9 ) .
 340 Options are specified as a series of
 341 .Vt cmsghdr
 342 structures followed by corresponding values.
 343 .Va cmsg_level
 344 is set to
 345 .Dv IPPROTO_IPV6 ,
 346 .Va cmsg_type
 347 to one of the other values in this list, and trailing data to the option
 348 value.
 349 When setting options, if the length
 350 .Va optlen
 351 to
 352 .Xr setsockopt 2
 353 is zero, all header options will be reset to their default values.
 354 Otherwise, the length should specify the size the series of control
 355 messages consumes.
 356 .Pp
 357 Instead of using
 358 .Xr sendmsg 2
 359 to specify option values, the ancillary data used in these calls that
 360 correspond to the desired header options may be directly specified as
 361 the control message in the series of control messages provided as the
 362 argument to
 363 .Xr setsockopt 2 .
 364 .It Dv IPV6_CHECKSUM Fa "int *"
 365 Get or set the byte offset into a packet where the 16-bit checksum is
 366 located.
 367 When set, this byte offset is where incoming packets will be expected
 368 to have checksums of their data stored and where outgoing packets will
 369 have checksums of their data computed and stored by the kernel.
 370 A value of \-1 specifies that no checksums will be checked on incoming
 371 packets and that no checksums will be computed or stored on outgoing
 372 packets.
 373 The offset of the checksum for ICMPv6 sockets cannot be relocated or
 374 turned off.
 375 .It Dv IPV6_V6ONLY Fa "int *"
 376 Get or set whether only IPv6 connections can be made to this socket.
 377 For wildcard sockets, this can restrict connections to IPv6 only.
 378 .\"With
 379 .\".Ox
 380 .\"IPv6 sockets are always IPv6-only, so the socket option is read-only
 381 .\"(not modifiable).
 382 .\".It Dv IPV6_FAITH Fa "int *"
 383 .\"Get or set the status of whether
 384 .\".Xr faith 4
 385 .\"connections can be made to this socket.
 386 .It Dv IPV6_USE_MIN_MTU Fa "int *"
 387 Get or set whether the minimal IPv6 maximum transmission unit (MTU) size
 388 will be used to avoid fragmentation from occurring for subsequent
 389 outgoing datagrams.
 390 .It Dv IPV6_AUTH_LEVEL Fa "int *"
 391 Get or set the
 392 .Xr ipsec 4
 393 authentication level.
 394 .It Dv IPV6_ESP_TRANS_LEVEL Fa "int *"
 395 Get or set the ESP transport level.
 396 .It Dv IPV6_ESP_NETWORK_LEVEL Fa "int *"
 397 Get or set the ESP encapsulation level.
 398 .It Dv IPV6_IPCOMP_LEVEL Fa "int *"
 399 Get or set the
 400 .Xr ipcomp 4
 401 level.
 402 .El
 403 .Pp
 404 The
 405 .Dv IPV6_PKTINFO ,
 406 .\" .Dv IPV6_NEXTHOP ,
 407 .Dv IPV6_HOPLIMIT ,
 408 .Dv IPV6_HOPOPTS ,
 409 .Dv IPV6_DSTOPTS ,
 410 and
 411 .Dv IPV6_RTHDR
 412 options will return ancillary data along with payload contents in subsequent
 413 .Xr recvmsg 2
 414 calls with
 415 .Va cmsg_level
 416 set to
 417 .Dv IPPROTO_IPV6
 418 and
 419 .Va cmsg_type
 420 set to respective option name value (e.g.,
 421 .Dv IPV6_HOPTLIMIT ) .
 422 These options may also be used directly as ancillary
 423 .Va cmsg_type
 424 values in
 425 .Xr sendmsg 2
 426 to set options on the packet being transmitted by the call.
 427 The
 428 .Va cmsg_level
 429 value must be
 430 .Dv IPPROTO_IPV6 .
 431 For these options, the ancillary data object value format is the same
 432 as the value returned as explained for each when received with
 433 .Xr recvmsg 2 .
 434 .Pp
 435 Note that using
 436 .Xr sendmsg 2
 437 to specify options on particular packets works only on UDP and raw sockets.
 438 To manipulate header options for packets on TCP sockets, only the socket
 439 options may be used.
 440 .Pp
 441 In some cases, there are multiple APIs defined for manipulating an IPv6
 442 header field.
 443 A good example is the outgoing interface for multicast datagrams, which
 444 can be set by the
 445 .Dv IPV6_MULTICAST_IF
 446 socket option, through the
 447 .Dv IPV6_PKTINFO
 448 option, and through the
 449 .Va sin6_scope_id
 450 field of the socket address passed to the
 451 .Xr sendto 2
 452 system call.
 453 .Pp
 454 Resolving these conflicts is implementation dependent.
 455 This implementation determines the value in the following way:
 456 options specified by using ancillary data (i.e.,
 457 .Xr sendmsg 2 )
 458 are considered first,
 459 options specified by using
 460 .Dv IPV6_PKTOPTIONS
 461 to set
 462 .Dq sticky
 463 options are considered second,
 464 options specified by using the individual, basic, and direct socket
 465 options (e.g.,
 466 .Dv IPV6_UNICAST_HOPS )
 467 are considered third,
 468 and options specified in the socket address supplied to
 469 .Xr sendto 2
 470 are the last choice.
 471 .Ss Multicasting
 472 IPv6 multicasting is supported only on
 473 .Dv AF_INET6
 474 sockets of type
 475 .Dv SOCK_DGRAM
 476 and
 477 .Dv SOCK_RAW ,
 478 and only on networks where the interface driver supports
 479 multicasting.
 480 Socket options (see above) that manipulate membership of
 481 multicast groups and other multicast options include
 482 .Dv IPV6_MULTICAST_IF ,
 483 .Dv IPV6_MULTICAST_HOPS ,
 484 .Dv IPV6_MULTICAST_LOOP ,
 485 .Dv IPV6_LEAVE_GROUP ,
 486 and
 487 .Dv IPV6_JOIN_GROUP .
 488 .Ss Raw Sockets
 489 Raw IPv6 sockets are connectionless and are normally used with the
 490 .Xr sendto 2
 491 and
 492 .Xr recvfrom 2
 493 calls, although the
 494 .Xr connect 2
 495 call may be used to fix the destination address for future outgoing
 496 packets so that
 497 .Xr send 2
 498 may instead be used and the
 499 .Xr bind 2
 500 call may be used to fix the source address for future outgoing
 501 packets instead of having the kernel choose a source address.
 502 .Pp
 503 By using
 504 .Xr connect 2
 505 or
 506 .Xr bind 2 ,
 507 raw socket input is constrained to only packets with their
 508 source address matching the socket destination address if
 509 .Xr connect 2
 510 was used and to packets with their destination address
 511 matching the socket source address if
 512 .Xr bind 2
 513 was used.
 514 .Pp
 515 If the
 516 .Ar proto
 517 argument to
 518 .Xr socket 2
 519 is zero, the default protocol
 520 .Pq Dv IPPROTO_RAW
 521 is used for outgoing packets.
 522 For incoming packets, protocols recognized by kernel are
 523 .Sy not
 524 passed to the application socket (e.g.,
 525 .Xr tcp 4
 526 and
 527 .Xr udp 4 )
 528 except for some ICMPv6 messages.
 529 The ICMPv6 messages not passed to raw sockets include echo, timestamp,
 530 and address mask requests.
 531 If
 532 .Ar proto
 533 is non-zero, only packets with this protocol will be passed to the
 534 socket.
 535 .Pp
 536 IPv6 fragments are also not passed to application sockets until
 537 they have been reassembled.
 538 If reception of all packets is desired, link-level access (such as
 539 .Xr bpf 4 )
 540 must be used instead.
 541 .Pp
 542 Outgoing packets automatically have an IPv6 header prepended to them
 543 (based on the destination address and the protocol number the socket
 544 was created with).
 545 Incoming packets are received by an application without the IPv6 header
 546 or any extension headers.
 547 .Pp
 548 Outgoing packets will be fragmented automatically by the kernel if they
 549 are too large.
 550 Incoming packets will be reassembled before being sent to the raw socket,
 551 so packet fragments or fragment headers will never be seen on a raw socket.
 552 .Sh EXAMPLES
 553 The following determines the hop limit on the next packet received:
 554 .Bd -literal
 555 struct iovec iov[2];
 556 u_char buf[BUFSIZ];
 557 struct cmsghdr *cm;
 558 struct msghdr m;
 559 int found, optval;
 560 u_char data[2048];
 561
 562 /* Create socket. */
 563
 564 (void)memset(&m, 0, sizeof(m));
 565 (void)memset(&iov, 0, sizeof(iov));
 566
 567 iov[0].iov_base = data;         /* buffer for packet payload */
 568 iov[0].iov_len = sizeof(data);  /* expected packet length */
 569
 570 m.msg_name = &from;             /* sockaddr_in6 of peer */
 571 m.msg_namelen = sizeof(from);
 572 m.msg_iov = iov;
 573 m.msg_iovlen = 1;
 574 m.msg_control = (caddr_t)buf;   /* buffer for control messages */
 575 m.msg_controllen = sizeof(buf);
 576
 577 /*
 578  * Enable the hop limit value from received packets to be
 579  * returned along with the payload.
 580  */
 581 optval = 1;
 582 if (setsockopt(s, IPPROTO_IPV6, IPV6_HOPLIMIT, &optval,
 583     sizeof(optval)) == -1)
 584         err(1, "setsockopt");
 585
 586 found = 0;
 587 while (!found) {
 588         if (recvmsg(s, &m, 0) == -1)
 589                 err(1, "recvmsg");
 590         for (cm = CMSG_FIRSTHDR(&m); cm != NULL;
 591              cm = CMSG_NXTHDR(&m, cm)) {
 592                 if (cm->cmsg_level == IPPROTO_IPV6 &&
 593                     cm->cmsg_type == IPV6_HOPLIMIT &&
 594                     cm->cmsg_len == CMSG_LEN(sizeof(int))) {
 595                         found = 1;
 596                         (void)printf("hop limit: %d\en",
 597                             *(int *)CMSG_DATA(cm));
 598                         break;
 599                 }
 600         }
 601 }
 602 .Ed
 603 .Sh DIAGNOSTICS
 604 A socket operation may fail with one of the following errors returned:
 605 .Bl -tag -width EADDRNOTAVAILxx
 606 .It Bq Er EISCONN
 607 when trying to establish a connection on a socket which
 608 already has one or when trying to send a datagram with the destination
 609 address specified and the socket is already connected.
 610 .It Bq Er ENOTCONN
 611 when trying to send a datagram, but
 612 no destination address is specified, and the socket hasn't been
 613 connected.
 614 .It Bq Er ENOBUFS
 615 when the system runs out of memory for
 616 an internal data structure.
 617 .It Bq Er EADDRNOTAVAIL
 618 when an attempt is made to create a
 619 socket with a network address for which no network interface
 620 exists.
 621 .It Bq Er EACCES
 622 when an attempt is made to create
 623 a raw IPv6 socket by a non-privileged process.
 624 .El
 625 .Pp
 626 The following errors specific to IPv6 may occur when setting or getting
 627 header options:
 628 .Bl -tag -width EADDRNOTAVAILxx
 629 .It Bq Er EINVAL
 630 An unknown socket option name was given.
 631 .It Bq Er EINVAL
 632 An ancillary data object was improperly formed.
 633 .El
 634 .Sh SEE ALSO
 635 .Xr getsockopt 2 ,
 636 .Xr recv 2 ,
 637 .Xr send 2 ,
 638 .Xr setsockopt 2 ,
 639 .Xr socket 2 ,
 640 .\" .Xr inet6_option_space 3 ,
 641 .\" .Xr inet6_rthdr_space 3 ,
 642 .Xr if_nametoindex 3 ,
 643 .Xr bpf 4 ,
 644 .Xr icmp6 4 ,
 645 .Xr inet6 4 ,
 646 .Xr netintro 4 ,
 647 .Xr tcp 4 ,
 648 .Xr udp 4
 649 .Rs
 650 .%A W. Stevens
 651 .%A M. Thomas
 652 .%T Advanced Sockets API for IPv6
 653 .%R RFC 2292
 654 .%D February 1998
 655 .Re
 656 .Rs
 657 .%A S. Deering
 658 .%A R. Hinden
 659 .%T Internet Protocol, Version 6 (IPv6) Specification
 660 .%R RFC 2460
 661 .%D December 1998
 662 .Re
 663 .Rs
 664 .%A R. Gilligan
 665 .%A S. Thomson
 666 .%A J. Bound
 667 .%A W. Stevens
 668 .%T Basic Socket Interface Extensions for IPv6
 669 .%R RFC 2553
 670 .%D March 1999
 671 .Re
 672 .Rs
 673 .%A W. Stevens
 674 .%A B. Fenner
 675 .%A A. Rudoff
 676 .%T UNIX Network Programming, third edition
 677 .Re
 678 .Sh STANDARDS
 679 Most of the socket options are defined in RFC 2292 or RFC 2553.
 680 The
 681 .Dv IPV6_V6ONLY
 682 socket option is defined in RFC 3542.
 683 The
 684 .Dv IPV6_PORTRANGE
 685 socket option and the conflict resolution rule are not defined in the
 686 RFCs and should be considered implementation dependent.