1.\" $NetBSD: ip6.4,v 1.27 2007/08/20 16:08:55 perry 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 $ 4.\" 5.\" Copyright (c) 1983, 1991, 1993 6.\" The Regents of the University of California. 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. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.Dd December 5, 2006 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 43The IPv6 network layer is used by the IPv6 protocol family for 44transporting data. 45IPv6 packets contain an IPv6 header that is not provided as part of the 46payload contents when passed to an application. 47IPv6 header options affect the behavior of this protocol and may be used 48by high-level protocols (such as the 49.Xr tcp 4 50and 51.Xr udp 4 52protocols) as well as directly by 53.Dq raw sockets , 54which process IPv6 messages at a lower-level and may be useful for 55developing new protocols and special-purpose applications. 56.Ss Header 57All IPv6 packets begin with an IPv6 header. 58When data received by the kernel are passed to the application, this 59header is not included in buffer, even when raw sockets are being used. 60Likewise, when data are sent to the kernel for transmit from the 61application, the buffer is not examined for an IPv6 header: 62the kernel always constructs the header. 63To directly access IPv6 headers from received packets and specify them 64as part of the buffer passed to the kernel, link-level access 65.Po 66.Xr bpf 4 , 67for example 68.Pc 69must be used instead. 70.Pp 71The header has the following definition: 72.Bd -literal -offset indent 73struct ip6_hdr { 74 union { 75 struct ip6_hdrctl { 76 uint32_t ip6_un1_flow; /* 20 bits of flow ID */ 77 uint16_t ip6_un1_plen; /* payload length */ 78 uint8_t ip6_un1_nxt; /* next header */ 79 uint8_t ip6_un1_hlim; /* hop limit */ 80 } ip6_un1; 81 uint8_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 95All fields are in network-byte order. 96Any options specified (see 97.Sx Options 98below) must also be specified in network-byte order. 99.Pp 100.Va ip6_flow 101specifies the flow ID. 102.Va ip6_plen 103specifies the payload length. 104.Va ip6_nxt 105specifies the type of the next header. 106.Va ip6_hlim 107specifies the hop limit. 108.Pp 109The top 4 bits of 110.Va ip6_vfc 111specify the class and the bottom 4 bits specify the version. 112.Pp 113.Va ip6_src 114and 115.Va ip6_dst 116specify the source and destination addresses. 117.Pp 118The IPv6 header may be followed by any number of extension headers that start 119with the following generic definition: 120.Bd -literal -offset indent 121struct ip6_ext { 122 uint8_t ip6e_nxt; 123 uint8_t ip6e_len; 124} __packed; 125.Ed 126.Ss Options 127IPv6 allows header options on packets to manipulate the behavior of the 128protocol. 129These options and other control requests are accessed with the 130.Xr getsockopt 2 131and 132.Xr setsockopt 2 133system calls at level 134.Dv IPPROTO_IPV6 135and by using ancillary data in 136.Xr recvmsg 2 137and 138.Xr sendmsg 2 . 139They can be used to access most of the fields in the IPv6 header and 140extension headers. 141.Pp 142The following socket options are supported: 143.Bl -tag -width Ds 144.\" .It Dv IPV6_OPTIONS 145.It Dv IPV6_UNICAST_HOPS Fa "int *" 146Get or set the default hop limit header field for outgoing unicast 147datagrams sent on this socket. 148A 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 *" 161Get or set the interface from which multicast packets will be sent. 162For hosts with multiple interfaces, each multicast transmission is sent 163from the primary network interface. 164The interface is specified as its index as provided by 165.Xr if_nametoindex 3 . 166A value of zero specifies the default interface. 167.It Dv IPV6_MULTICAST_HOPS Fa "int *" 168Get or set the default hop limit header field for outgoing multicast 169datagrams sent on this socket. 170This option controls the scope of multicast datagram transmissions. 171.Pp 172Datagrams with a hop limit of 1 are not forwarded beyond the local 173network. 174Multicast datagrams with a hop limit of zero will not be transmitted on 175any network but may be delivered locally if the sending host belongs to 176the destination group and if multicast loopback (see below) has not been 177disabled on the sending socket. 178Multicast datagrams with a hop limit greater than 1 may be forwarded to 179the other networks if a multicast router (such as 180.Xr mrouted 8 ) 181is attached to the local network. 182.It Dv IPV6_MULTICAST_LOOP Fa "u_int *" 183Get or set the status of whether multicast datagrams will be looped back 184for local delivery when a multicast datagram is sent to a group to which 185the sending host belongs. 186.Pp 187This option improves performance for applications that may have no more 188than one instance on a single host (such as a router daemon) by 189eliminating the overhead of receiving their own transmissions. 190It should generally not be used by applications for which there may be 191more than one instance on a single host (such as a conferencing program) 192or for which the sender does not belong to the destination group 193(such as a time-querying program). 194.Pp 195A multicast datagram sent with an initial hop limit greater than 1 may 196be delivered to the sending host on a different interface from that on 197which it was sent if the host belongs to the destination group on that 198other interface. 199The multicast loopback control option has no effect on such delivery. 200.It Dv IPV6_JOIN_GROUP Fa "struct ipv6_mreq *" 201Join a multicast group. 202A host must become a member of a multicast group before it can receive 203datagrams sent to the group. 204.Bd -literal 205struct ipv6_mreq { 206 struct in6_addr ipv6mr_multiaddr; 207 unsigned int ipv6mr_interface; 208}; 209.Ed 210.Pp 211.Va ipv6mr_interface 212may be set to zeroes to choose the default multicast interface or to the 213index of a particular multicast-capable interface if the host is 214multihomed. 215Membership is associated with a single interface; programs running on 216multihomed hosts may need to join the same group on more than one 217interface. 218.Pp 219If the multicast address is unspecified (i.e., all zeroes), messages 220from all multicast addresses will be accepted by this group. 221Note that setting to this value requires superuser privileges. 222.It Dv IPV6_LEAVE_GROUP Fa "struct ipv6_mreq *" 223Drop membership from the associated multicast group. 224Memberships are automatically dropped when the socket is closed or when 225the process exits. 226.It Dv IPV6_IPSEC_POLICY Fa "struct sadb_x_policy *" 227Get or set IPSec policy for sockets. 228For example, 229.Bd -literal 230const char *policy = "in ipsec ah/transport//require"; 231char *buf = ipsec_set_policy(policy, strlen(policy)); 232setsockopt(s, IPPROTO_IPV6, IPV6_IPSEC_POLICY, buf, ipsec_get_policylen(buf)); 233.Ed 234.It Dv IPV6_PORTRANGE Fa "int *" 235Get or set the allocation policy of ephemeral ports for when the kernel 236automatically binds a local address to this socket. 237The following values are available: 238.Pp 239.Bl -tag -width IPV6_PORTRANGE_DEFAULT -compact 240.It Dv IPV6_PORTRANGE_DEFAULT 241Use the regular range of non-reserved ports (varies, see 242.Xr sysctl 8 ) . 243.It Dv IPV6_PORTRANGE_HIGH 244Use a high range (varies, see 245.Xr sysctl 8 ) . 246.It Dv IPV6_PORTRANGE_LOW 247Use a low, reserved range (600\-1023). 248.El 249.It Dv IPV6_PKTINFO Fa "int *" 250Get or set whether additional information about subsequent packets will 251be provided as ancillary data along with the payload in subsequent 252.Xr recvmsg 2 253calls. 254The information is stored in the following structure in the ancillary 255data returned: 256.Bd -literal 257struct in6_pktinfo { 258 struct in6_addr ipi6_addr; /* src/dst IPv6 address */ 259 unsigned int ipi6_ifindex; /* send/recv if index */ 260}; 261.Ed 262.It Dv IPV6_HOPLIMIT Fa "int *" 263Get or set whether the hop limit header field from subsequent packets 264will be provided as ancillary data along with the payload in subsequent 265.Xr recvmsg 2 266calls. 267The value is stored as an 268.Vt int 269in the ancillary data returned. 270.\" .It Dv IPV6_NEXTHOP Fa "int *" 271.\" Get or set whether the address of the next hop for subsequent 272.\" packets will be provided as ancillary data along with the payload in 273.\" subsequent 274.\" .Xr recvmsg 2 275.\" calls. 276.\" The option is stored as a 277.\" .Vt sockaddr 278.\" structure in the ancillary data returned. 279.\" .Pp 280.\" This option requires superuser privileges. 281.It Dv IPV6_HOPOPTS Fa "int *" 282Get or set whether the hop-by-hop options from subsequent packets will be 283provided as ancillary data along with the payload in subsequent 284.Xr recvmsg 2 285calls. 286The option is stored in the following structure in the ancillary data 287returned: 288.Bd -literal 289struct ip6_hbh { 290 uint8_t ip6h_nxt; /* next header */ 291 uint8_t ip6h_len; /* length in units of 8 octets */ 292/* followed by options */ 293} __packed; 294.Ed 295.Pp 296The 297.Fn inet6_option_space 298routine and family of routines may be used to manipulate this data. 299.Pp 300This option requires superuser privileges. 301.It Dv IPV6_DSTOPTS Fa "int *" 302Get or set whether the destination options from subsequent packets will 303be provided as ancillary data along with the payload in subsequent 304.Xr recvmsg 2 305calls. 306The option is stored in the following structure in the ancillary data 307returned: 308.Bd -literal 309struct ip6_dest { 310 uint8_t ip6d_nxt; /* next header */ 311 uint8_t ip6d_len; /* length in units of 8 octets */ 312/* followed by options */ 313} __packed; 314.Ed 315.Pp 316The 317.Fn inet6_option_space 318routine and family of routines may be used to manipulate this data. 319.Pp 320This option requires superuser privileges. 321.It Dv IPV6_RTHDR Fa "int *" 322Get or set whether the routing header from subsequent packets will be 323provided as ancillary data along with the payload in subsequent 324.Xr recvmsg 2 325calls. 326The header is stored in the following structure in the ancillary data 327returned: 328.Bd -literal 329struct ip6_rthdr { 330 uint8_t ip6r_nxt; /* next header */ 331 uint8_t ip6r_len; /* length in units of 8 octets */ 332 uint8_t ip6r_type; /* routing type */ 333 uint8_t ip6r_segleft; /* segments left */ 334/* followed by routing-type-specific data */ 335} __packed; 336.Ed 337.Pp 338The 339.Fn inet6_option_space 340routine and family of routines may be used to manipulate this data. 341.Pp 342This option requires superuser privileges. 343.It Dv IPV6_PKTOPTIONS Fa "struct cmsghdr *" 344Get or set all header options and extension headers at one time on the 345last packet sent or received on the socket. 346All options must fit within the size of an mbuf (see 347.Xr mbuf 9 ) . 348Options are specified as a series of 349.Vt cmsghdr 350structures followed by corresponding values. 351.Va cmsg_level 352is set to 353.Dv IPPROTO_IPV6 , 354.Va cmsg_type 355to one of the other values in this list, and trailing data to the option 356value. 357When setting options, if the length 358.Va optlen 359to 360.Xr setsockopt 2 361is zero, all header options will be reset to their default values. 362Otherwise, the length should specify the size the series of control 363messages consumes. 364.Pp 365Instead of using 366.Xr sendmsg 2 367to specify option values, the ancillary data used in these calls that 368correspond to the desired header options may be directly specified as 369the control message in the series of control messages provided as the 370argument to 371.Xr setsockopt 2 . 372.It Dv IPV6_CHECKSUM Fa "int *" 373Get or set the byte offset into a packet where the 16-bit checksum is 374located. 375When set, this byte offset is where incoming packets will be expected 376to have checksums of their data stored and where outgoing packets will 377have checksums of their data computed and stored by the kernel. 378A value of \-1 specifies that no checksums will be checked on incoming 379packets and that no checksums will be computed or stored on outgoing 380packets. 381The offset of the checksum for ICMPv6 sockets cannot be relocated or 382turned off. 383.It Dv IPV6_V6ONLY Fa "int *" 384Get or set whether only IPv6 connections can be made to this socket. 385For wildcard sockets, this can restrict connections to IPv6 only. 386.\"With 387.\".Ox 388.\"IPv6 sockets are always IPv6-only, so the socket option is read-only 389.\"(not modifiable). 390.It Dv IPV6_FAITH Fa "int *" 391Get or set the status of whether 392.Xr faith 4 393connections can be made to this socket. 394.It Dv IPV6_USE_MIN_MTU Fa "int *" 395Get or set whether the minimal IPv6 maximum transmission unit (MTU) size 396will be used to avoid fragmentation from occurring for subsequent 397outgoing datagrams. 398.It Dv IPV6_AUTH_LEVEL Fa "int *" 399Get or set the 400.Xr ipsec 4 401authentication level. 402.It Dv IPV6_ESP_TRANS_LEVEL Fa "int *" 403Get or set the ESP transport level. 404.It Dv IPV6_ESP_NETWORK_LEVEL Fa "int *" 405Get or set the ESP encapsulation level. 406.It Dv IPV6_IPCOMP_LEVEL Fa "int *" 407Get or set the 408.Xr ipcomp 4 409level. 410.El 411.Pp 412The 413.Dv IPV6_PKTINFO , 414.\" .Dv IPV6_NEXTHOP , 415.Dv IPV6_HOPLIMIT , 416.Dv IPV6_HOPOPTS , 417.Dv IPV6_DSTOPTS , 418and 419.Dv IPV6_RTHDR 420options will return ancillary data along with payload contents in subsequent 421.Xr recvmsg 2 422calls with 423.Va cmsg_level 424set to 425.Dv IPPROTO_IPV6 426and 427.Va cmsg_type 428set to respective option name value (e.g., 429.Dv IPV6_HOPTLIMIT ) . 430These options may also be used directly as ancillary 431.Va cmsg_type 432values in 433.Xr sendmsg 2 434to set options on the packet being transmitted by the call. 435The 436.Va cmsg_level 437value must be 438.Dv IPPROTO_IPV6 . 439For these options, the ancillary data object value format is the same 440as the value returned as explained for each when received with 441.Xr recvmsg 2 . 442.Pp 443Note that using 444.Xr sendmsg 2 445to specify options on particular packets works only on UDP and raw sockets. 446To manipulate header options for packets on TCP sockets, only the socket 447options may be used. 448.Pp 449In some cases, there are multiple APIs defined for manipulating an IPv6 450header field. 451A good example is the outgoing interface for multicast datagrams, which 452can be set by the 453.Dv IPV6_MULTICAST_IF 454socket option, through the 455.Dv IPV6_PKTINFO 456option, and through the 457.Va sin6_scope_id 458field of the socket address passed to the 459.Xr sendto 2 460system call. 461.Pp 462Resolving these conflicts is implementation dependent. 463This implementation determines the value in the following way: 464options specified by using ancillary data (i.e., 465.Xr sendmsg 2 ) 466are considered first, 467options specified by using 468.Dv IPV6_PKTOPTIONS 469to set 470.Dq sticky 471options are considered second, 472options specified by using the individual, basic, and direct socket 473options (e.g., 474.Dv IPV6_UNICAST_HOPS ) 475are considered third, 476and options specified in the socket address supplied to 477.Xr sendto 2 478are the last choice. 479.Ss Multicasting 480IPv6 multicasting is supported only on 481.Dv AF_INET6 482sockets of type 483.Dv SOCK_DGRAM 484and 485.Dv SOCK_RAW , 486and only on networks where the interface driver supports 487multicasting. 488Socket options (see above) that manipulate membership of 489multicast groups and other multicast options include 490.Dv IPV6_MULTICAST_IF , 491.Dv IPV6_MULTICAST_HOPS , 492.Dv IPV6_MULTICAST_LOOP , 493.Dv IPV6_LEAVE_GROUP , 494and 495.Dv IPV6_JOIN_GROUP . 496.Ss Raw Sockets 497Raw IPv6 sockets are connectionless and are normally used with the 498.Xr sendto 2 499and 500.Xr recvfrom 2 501calls, although the 502.Xr connect 2 503call may be used to fix the destination address for future outgoing 504packets so that 505.Xr send 2 506may instead be used and the 507.Xr bind 2 508call may be used to fix the source address for future outgoing 509packets instead of having the kernel choose a source address. 510.Pp 511By using 512.Xr connect 2 513or 514.Xr bind 2 , 515raw socket input is constrained to only packets with their 516source address matching the socket destination address if 517.Xr connect 2 518was used and to packets with their destination address 519matching the socket source address if 520.Xr bind 2 521was used. 522.Pp 523If the 524.Ar proto 525argument to 526.Xr socket 2 527is zero, the default protocol 528.Pq Dv IPPROTO_RAW 529is used for outgoing packets. 530For incoming packets, protocols recognized by kernel are 531.Sy not 532passed to the application socket (e.g., 533.Xr tcp 4 534and 535.Xr udp 4 ) 536except for some ICMPv6 messages. 537The ICMPv6 messages not passed to raw sockets include echo, timestamp, 538and address mask requests. 539If 540.Ar proto 541is non-zero, only packets with this protocol will be passed to the 542socket. 543.Pp 544IPv6 fragments are also not passed to application sockets until 545they have been reassembled. 546If reception of all packets is desired, link-level access (such as 547.Xr bpf 4 ) 548must be used instead. 549.Pp 550Outgoing packets automatically have an IPv6 header prepended to them 551(based on the destination address and the protocol number the socket 552was created with). 553Incoming packets are received by an application without the IPv6 header 554or any extension headers. 555.Pp 556Outgoing packets will be fragmented automatically by the kernel if they 557are too large. 558Incoming packets will be reassembled before being sent to the raw socket, 559so packet fragments or fragment headers will never be seen on a raw socket. 560.Sh EXAMPLES 561The following determines the hop limit on the next packet received: 562.Bd -literal 563struct iovec iov[2]; 564u_char buf[BUFSIZ]; 565struct cmsghdr *cm; 566struct msghdr m; 567int found, optval; 568u_char data[2048]; 569 570/* Create socket. */ 571 572(void)memset(\*[Am]m, 0, sizeof(m)); 573(void)memset(\*[Am]iov, 0, sizeof(iov)); 574 575iov[0].iov_base = data; /* buffer for packet payload */ 576iov[0].iov_len = sizeof(data); /* expected packet length */ 577 578m.msg_name = \*[Am]from; /* sockaddr_in6 of peer */ 579m.msg_namelen = sizeof(from); 580m.msg_iov = iov; 581m.msg_iovlen = 1; 582m.msg_control = buf; /* buffer for control messages */ 583m.msg_controllen = sizeof(buf); 584 585/* 586 * Enable the hop limit value from received packets to be 587 * returned along with the payload. 588 */ 589optval = 1; 590if (setsockopt(s, IPPROTO_IPV6, IPV6_HOPLIMIT, \*[Am]optval, 591 sizeof(optval)) == -1) 592 err(1, "setsockopt"); 593 594found = 0; 595while (!found) { 596 if (recvmsg(s, \*[Am]m, 0) == -1) 597 err(1, "recvmsg"); 598 for (cm = CMSG_FIRSTHDR(\*[Am]m); cm != NULL; 599 cm = CMSG_NXTHDR(\*[Am]m, cm)) { 600 if (cm-\*[Gt]cmsg_level == IPPROTO_IPV6 \*[Am]\*[Am] 601 cm-\*[Gt]cmsg_type == IPV6_HOPLIMIT \*[Am]\*[Am] 602 cm-\*[Gt]cmsg_len == CMSG_LEN(sizeof(int))) { 603 found = 1; 604 (void)printf("hop limit: %d\en", 605 *(int *)CMSG_DATA(cm)); 606 break; 607 } 608 } 609} 610.Ed 611.Sh DIAGNOSTICS 612A socket operation may fail with one of the following errors returned: 613.Bl -tag -width EADDRNOTAVAILxx 614.It Bq Er EISCONN 615when trying to establish a connection on a socket which 616already has one or when trying to send a datagram with the destination 617address specified and the socket is already connected. 618.It Bq Er ENOTCONN 619when trying to send a datagram, but 620no destination address is specified, and the socket hasn't been 621connected. 622.It Bq Er ENOBUFS 623when the system runs out of memory for 624an internal data structure. 625.It Bq Er EADDRNOTAVAIL 626when an attempt is made to create a 627socket with a network address for which no network interface 628exists. 629.It Bq Er EACCES 630when an attempt is made to create 631a raw IPv6 socket by a non-privileged process. 632.El 633.Pp 634The following errors specific to IPv6 may occur when setting or getting 635header options: 636.Bl -tag -width EADDRNOTAVAILxx 637.It Bq Er EINVAL 638An unknown socket option name was given. 639.It Bq Er EINVAL 640An ancillary data object was improperly formed. 641.El 642.Sh SEE ALSO 643.Xr getsockopt 2 , 644.Xr recv 2 , 645.Xr send 2 , 646.Xr setsockopt 2 , 647.Xr socket 2 , 648.\" .Xr inet6_option_space 3 , 649.\" .Xr inet6_rthdr_space 3 , 650.Xr if_nametoindex 3 , 651.Xr bpf 4 , 652.Xr icmp6 4 , 653.Xr inet6 4 , 654.Xr netintro 4 , 655.Xr tcp 4 , 656.Xr udp 4 657.Rs 658.%A W. Stevens 659.%A M. Thomas 660.%T Advanced Sockets API for IPv6 661.%R RFC 2292 662.%D February 1998 663.Re 664.Rs 665.%A S. Deering 666.%A R. Hinden 667.%T Internet Protocol, Version 6 (IPv6) Specification 668.%R RFC 2460 669.%D December 1998 670.Re 671.Rs 672.%A R. Gilligan 673.%A S. Thomson 674.%A J. Bound 675.%A W. Stevens 676.%T Basic Socket Interface Extensions for IPv6 677.%R RFC 2553 678.%D March 1999 679.Re 680.Rs 681.%A W. Stevens 682.%A B. Fenner 683.%A A. Rudoff 684.%T UNIX Network Programming, third edition 685.Re 686.Sh STANDARDS 687Most of the socket options are defined in RFC 2292 or RFC 2553. 688The 689.Dv IPV6_V6ONLY 690socket option is defined in RFC 3542. 691The 692.Dv IPV6_PORTRANGE 693socket option and the conflict resolution rule are not defined in the 694RFCs and should be considered implementation dependent. 695