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_TCLASS Fa "int *"
 314 Get or set the value of the traffic class field used for outgoing
 315 datagrams on this socket. The value must be between -1 and 255.
 316 A value of -1 resets to the default value.
 317 .It Dv IPV6_RECVTCLASS Fa "int *"
 318 Get or set the status of whether the traffic class header field
 319 will be provided as ancillary data along with the payload in subsequent
 320 .Xr recvmsg 2
 321 calls. The header field is stored as a single value of type int.
 322 .It Dv IPV6_RTHDR Fa "int *"
 323 Get or set whether the routing header from subsequent packets will be
 324 provided as ancillary data along with the payload in subsequent
 325 .Xr recvmsg 2
 326 calls.
 327 The header is stored in the following structure in the ancillary data
 328 returned:
 329 .Bd -literal
 330 struct ip6_rthdr {
 331         u_int8_t ip6r_nxt;      /* next header */
 332         u_int8_t ip6r_len;      /* length in units of 8 octets */
 333         u_int8_t ip6r_type;     /* routing type */
 334         u_int8_t ip6r_segleft;  /* segments left */
 335 /* followed by routing-type-specific data */
 336 } __packed;
 337 .Ed
 338 .Pp
 339 The
 340 .Fn inet6_option_space
 341 routine and family of routines may be used to manipulate this data.
 342 .Pp
 343 This option requires superuser privileges.
 344 .It Dv IPV6_PKTOPTIONS Fa "struct cmsghdr *"
 345 Get or set all header options and extension headers at one time on the
 346 last packet sent or received on the socket.
 347 All options must fit within the size of an mbuf (see
 348 .Xr mbuf 9 ) .
 349 Options are specified as a series of
 350 .Vt cmsghdr
 351 structures followed by corresponding values.
 352 .Va cmsg_level
 353 is set to
 354 .Dv IPPROTO_IPV6 ,
 355 .Va cmsg_type
 356 to one of the other values in this list, and trailing data to the option
 357 value.
 358 When setting options, if the length
 359 .Va optlen
 360 to
 361 .Xr setsockopt 2
 362 is zero, all header options will be reset to their default values.
 363 Otherwise, the length should specify the size the series of control
 364 messages consumes.
 365 .Pp
 366 Instead of using
 367 .Xr sendmsg 2
 368 to specify option values, the ancillary data used in these calls that
 369 correspond to the desired header options may be directly specified as
 370 the control message in the series of control messages provided as the
 371 argument to
 372 .Xr setsockopt 2 .
 373 .It Dv IPV6_CHECKSUM Fa "int *"
 374 Get or set the byte offset into a packet where the 16-bit checksum is
 375 located.
 376 When set, this byte offset is where incoming packets will be expected
 377 to have checksums of their data stored and where outgoing packets will
 378 have checksums of their data computed and stored by the kernel.
 379 A value of \-1 specifies that no checksums will be checked on incoming
 380 packets and that no checksums will be computed or stored on outgoing
 381 packets.
 382 The offset of the checksum for ICMPv6 sockets cannot be relocated or
 383 turned off.
 384 .It Dv IPV6_V6ONLY Fa "int *"
 385 Get or set whether only IPv6 connections can be made to this socket.
 386 For wildcard sockets, this can restrict connections to IPv6 only.
 387 .\"With
 388 .\".Ox
 389 .\"IPv6 sockets are always IPv6-only, so the socket option is read-only
 390 .\"(not modifiable).
 391 .\".It Dv IPV6_FAITH Fa "int *"
 392 .\"Get or set the status of whether
 393 .\".Xr faith 4
 394 .\"connections can be made to this socket.
 395 .It Dv IPV6_USE_MIN_MTU Fa "int *"
 396 Get or set whether the minimal IPv6 maximum transmission unit (MTU) size
 397 will be used to avoid fragmentation from occurring for subsequent
 398 outgoing datagrams.
 399 .El
 400 .Pp
 401 The
 402 .Dv IPV6_PKTINFO ,
 403 .\" .Dv IPV6_NEXTHOP ,
 404 .Dv IPV6_HOPLIMIT ,
 405 .Dv IPV6_HOPOPTS ,
 406 .Dv IPV6_DSTOPTS ,
 407 and
 408 .Dv IPV6_RTHDR
 409 options will return ancillary data along with payload contents in subsequent
 410 .Xr recvmsg 2
 411 calls with
 412 .Va cmsg_level
 413 set to
 414 .Dv IPPROTO_IPV6
 415 and
 416 .Va cmsg_type
 417 set to respective option name value (e.g.,
 418 .Dv IPV6_HOPTLIMIT ) .
 419 These options may also be used directly as ancillary
 420 .Va cmsg_type
 421 values in
 422 .Xr sendmsg 2
 423 to set options on the packet being transmitted by the call.
 424 The
 425 .Va cmsg_level
 426 value must be
 427 .Dv IPPROTO_IPV6 .
 428 For these options, the ancillary data object value format is the same
 429 as the value returned as explained for each when received with
 430 .Xr recvmsg 2 .
 431 .Pp
 432 Note that using
 433 .Xr sendmsg 2
 434 to specify options on particular packets works only on UDP and raw sockets.
 435 To manipulate header options for packets on TCP sockets, only the socket
 436 options may be used.
 437 .Pp
 438 In some cases, there are multiple APIs defined for manipulating an IPv6
 439 header field.
 440 A good example is the outgoing interface for multicast datagrams, which
 441 can be set by the
 442 .Dv IPV6_MULTICAST_IF
 443 socket option, through the
 444 .Dv IPV6_PKTINFO
 445 option, and through the
 446 .Va sin6_scope_id
 447 field of the socket address passed to the
 448 .Xr sendto 2
 449 system call.
 450 .Pp
 451 Resolving these conflicts is implementation dependent.
 452 This implementation determines the value in the following way:
 453 options specified by using ancillary data (i.e.,
 454 .Xr sendmsg 2 )
 455 are considered first,
 456 options specified by using
 457 .Dv IPV6_PKTOPTIONS
 458 to set
 459 .Dq sticky
 460 options are considered second,
 461 options specified by using the individual, basic, and direct socket
 462 options (e.g.,
 463 .Dv IPV6_UNICAST_HOPS )
 464 are considered third,
 465 and options specified in the socket address supplied to
 466 .Xr sendto 2
 467 are the last choice.
 468 .Ss Multicasting
 469 IPv6 multicasting is supported only on
 470 .Dv AF_INET6
 471 sockets of type
 472 .Dv SOCK_DGRAM
 473 and
 474 .Dv SOCK_RAW ,
 475 and only on networks where the interface driver supports
 476 multicasting.
 477 Socket options (see above) that manipulate membership of
 478 multicast groups and other multicast options include
 479 .Dv IPV6_MULTICAST_IF ,
 480 .Dv IPV6_MULTICAST_HOPS ,
 481 .Dv IPV6_MULTICAST_LOOP ,
 482 .Dv IPV6_LEAVE_GROUP ,
 483 and
 484 .Dv IPV6_JOIN_GROUP .
 485 .Ss Raw Sockets
 486 Raw IPv6 sockets are connectionless and are normally used with the
 487 .Xr sendto 2
 488 and
 489 .Xr recvfrom 2
 490 calls, although the
 491 .Xr connect 2
 492 call may be used to fix the destination address for future outgoing
 493 packets so that
 494 .Xr send 2
 495 may instead be used and the
 496 .Xr bind 2
 497 call may be used to fix the source address for future outgoing
 498 packets instead of having the kernel choose a source address.
 499 .Pp
 500 By using
 501 .Xr connect 2
 502 or
 503 .Xr bind 2 ,
 504 raw socket input is constrained to only packets with their
 505 source address matching the socket destination address if
 506 .Xr connect 2
 507 was used and to packets with their destination address
 508 matching the socket source address if
 509 .Xr bind 2
 510 was used.
 511 .Pp
 512 If the
 513 .Ar proto
 514 argument to
 515 .Xr socket 2
 516 is zero, the default protocol
 517 .Pq Dv IPPROTO_RAW
 518 is used for outgoing packets.
 519 For incoming packets, protocols recognized by kernel are
 520 .Sy not
 521 passed to the application socket (e.g.,
 522 .Xr tcp 4
 523 and
 524 .Xr udp 4 )
 525 except for some ICMPv6 messages.
 526 The ICMPv6 messages not passed to raw sockets include echo, timestamp,
 527 and address mask requests.
 528 If
 529 .Ar proto
 530 is non-zero, only packets with this protocol will be passed to the
 531 socket.
 532 .Pp
 533 IPv6 fragments are also not passed to application sockets until
 534 they have been reassembled.
 535 If reception of all packets is desired, link-level access (such as
 536 .Xr bpf 4 )
 537 must be used instead.
 538 .Pp
 539 Outgoing packets automatically have an IPv6 header prepended to them
 540 (based on the destination address and the protocol number the socket
 541 was created with).
 542 Incoming packets are received by an application without the IPv6 header
 543 or any extension headers.
 544 .Pp
 545 Outgoing packets will be fragmented automatically by the kernel if they
 546 are too large.
 547 Incoming packets will be reassembled before being sent to the raw socket,
 548 so packet fragments or fragment headers will never be seen on a raw socket.
 549 .Sh EXAMPLES
 550 The following determines the hop limit on the next packet received:
 551 .Bd -literal
 552 struct iovec iov[2];
 553 u_char buf[BUFSIZ];
 554 struct cmsghdr *cm;
 555 struct msghdr m;
 556 int found, optval;
 557 u_char data[2048];
 558
 559 /* Create socket. */
 560
 561 (void)memset(&m, 0, sizeof(m));
 562 (void)memset(&iov, 0, sizeof(iov));
 563
 564 iov[0].iov_base = data;         /* buffer for packet payload */
 565 iov[0].iov_len = sizeof(data);  /* expected packet length */
 566
 567 m.msg_name = &from;             /* sockaddr_in6 of peer */
 568 m.msg_namelen = sizeof(from);
 569 m.msg_iov = iov;
 570 m.msg_iovlen = 1;
 571 m.msg_control = (caddr_t)buf;   /* buffer for control messages */
 572 m.msg_controllen = sizeof(buf);
 573
 574 /*
 575  * Enable the hop limit value from received packets to be
 576  * returned along with the payload.
 577  */
 578 optval = 1;
 579 if (setsockopt(s, IPPROTO_IPV6, IPV6_HOPLIMIT, &optval,
 580     sizeof(optval)) == -1)
 581         err(1, "setsockopt");
 582
 583 found = 0;
 584 while (!found) {
 585         if (recvmsg(s, &m, 0) == -1)
 586                 err(1, "recvmsg");
 587         for (cm = CMSG_FIRSTHDR(&m); cm != NULL;
 588              cm = CMSG_NXTHDR(&m, cm)) {
 589                 if (cm->cmsg_level == IPPROTO_IPV6 &&
 590                     cm->cmsg_type == IPV6_HOPLIMIT &&
 591                     cm->cmsg_len == CMSG_LEN(sizeof(int))) {
 592                         found = 1;
 593                         (void)printf("hop limit: %d\en",
 594                             *(int *)CMSG_DATA(cm));
 595                         break;
 596                 }
 597         }
 598 }
 599 .Ed
 600 .Sh DIAGNOSTICS
 601 A socket operation may fail with one of the following errors returned:
 602 .Bl -tag -width EADDRNOTAVAILxx
 603 .It Bq Er EISCONN
 604 when trying to establish a connection on a socket which
 605 already has one or when trying to send a datagram with the destination
 606 address specified and the socket is already connected.
 607 .It Bq Er ENOTCONN
 608 when trying to send a datagram, but
 609 no destination address is specified, and the socket hasn't been
 610 connected.
 611 .It Bq Er ENOBUFS
 612 when the system runs out of memory for
 613 an internal data structure.
 614 .It Bq Er EADDRNOTAVAIL
 615 when an attempt is made to create a
 616 socket with a network address for which no network interface
 617 exists.
 618 .It Bq Er EACCES
 619 when an attempt is made to create
 620 a raw IPv6 socket by a non-privileged process.
 621 .El
 622 .Pp
 623 The following errors specific to IPv6 may occur when setting or getting
 624 header options:
 625 .Bl -tag -width EADDRNOTAVAILxx
 626 .It Bq Er EINVAL
 627 An unknown socket option name was given.
 628 .It Bq Er EINVAL
 629 An ancillary data object was improperly formed.
 630 .El
 631 .Sh SEE ALSO
 632 .Xr getsockopt 2 ,
 633 .Xr recv 2 ,
 634 .Xr send 2 ,
 635 .Xr setsockopt 2 ,
 636 .Xr socket 2 ,
 637 .\" .Xr inet6_option_space 3 ,
 638 .\" .Xr inet6_rthdr_space 3 ,
 639 .Xr if_nametoindex 3 ,
 640 .Xr bpf 4 ,
 641 .Xr icmp6 4 ,
 642 .Xr inet6 4 ,
 643 .Xr netintro 4 ,
 644 .Xr tcp 4 ,
 645 .Xr udp 4
 646 .Rs
 647 .%A W. Stevens
 648 .%A M. Thomas
 649 .%T Advanced Sockets API for IPv6
 650 .%R RFC 2292
 651 .%D February 1998
 652 .Re
 653 .Rs
 654 .%A S. Deering
 655 .%A R. Hinden
 656 .%T Internet Protocol, Version 6 (IPv6) Specification
 657 .%R RFC 2460
 658 .%D December 1998
 659 .Re
 660 .Rs
 661 .%A R. Gilligan
 662 .%A S. Thomson
 663 .%A J. Bound
 664 .%A W. Stevens
 665 .%T Basic Socket Interface Extensions for IPv6
 666 .%R RFC 2553
 667 .%D March 1999
 668 .Re
 669 .Rs
 670 .%A W. Stevens
 671 .%A B. Fenner
 672 .%A A. Rudoff
 673 .%T UNIX Network Programming, third edition
 674 .Re
 675 .Sh STANDARDS
 676 Most of the socket options are defined in RFC 2292 or RFC 2553.
 677 The
 678 .Dv IPV6_V6ONLY
 679 socket option is defined in RFC 3542.
 680 The
 681 .Dv IPV6_PORTRANGE
 682 socket option and the conflict resolution rule are not defined in the
 683 RFCs and should be considered implementation dependent.