1.\" $KAME: ip6.4,v 1.23 2005/01/11 05:56:25 itojun Exp $ 2.\" $OpenBSD: ip6.4,v 1.21 2005/01/06 03:50:46 itojun Exp $ 3.\" 4.\" Copyright (c) 1983, 1991, 1993 5.\" The Regents of the University of California. All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 3. Neither the name of the University nor the names of its contributors 16.\" may be used to endorse or promote products derived from this software 17.\" without specific prior written permission. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29.\" SUCH DAMAGE. 30.\" 31.\" $FreeBSD$ 32.\" 33.Dd July 24, 2022 34.Dt IP6 4 35.Os 36.Sh NAME 37.Nm ip6 38.Nd Internet Protocol version 6 (IPv6) network layer 39.Sh SYNOPSIS 40.In sys/socket.h 41.In netinet/in.h 42.Ft int 43.Fn socket AF_INET6 SOCK_RAW proto 44.Sh DESCRIPTION 45The IPv6 network layer is used by the IPv6 protocol family for 46transporting data. 47IPv6 packets contain an IPv6 header that is not provided as part of the 48payload contents when passed to an application. 49IPv6 header options affect the behavior of this protocol and may be used 50by high-level protocols (such as the 51.Xr tcp 4 52and 53.Xr udp 4 54protocols) as well as directly by 55.Dq raw sockets , 56which process IPv6 messages at a lower-level and may be useful for 57developing new protocols and special-purpose applications. 58.Ss Header 59All IPv6 packets begin with an IPv6 header. 60When data received by the kernel are passed to the application, this 61header is not included in buffer, even when raw sockets are being used. 62Likewise, when data are sent to the kernel for transmit from the 63application, the buffer is not examined for an IPv6 header: 64the kernel always constructs the header. 65To directly access IPv6 headers from received packets and specify them 66as part of the buffer passed to the kernel, link-level access 67.Po 68.Xr bpf 4 , 69for example 70.Pc 71must instead be utilized. 72.Pp 73The header has the following definition: 74.Bd -literal -offset indent 75struct ip6_hdr { 76 union { 77 struct ip6_hdrctl { 78 uint32_t ip6_un1_flow; /* 20 bits of flow ID */ 79 uint16_t ip6_un1_plen; /* payload length */ 80 uint8_t ip6_un1_nxt; /* next header */ 81 uint8_t ip6_un1_hlim; /* hop limit */ 82 } ip6_un1; 83 uint8_t ip6_un2_vfc; /* version and class */ 84 } ip6_ctlun; 85 struct in6_addr ip6_src; /* source address */ 86 struct in6_addr ip6_dst; /* destination address */ 87} __packed; 88 89#define ip6_vfc ip6_ctlun.ip6_un2_vfc 90#define ip6_flow ip6_ctlun.ip6_un1.ip6_un1_flow 91#define ip6_plen ip6_ctlun.ip6_un1.ip6_un1_plen 92#define ip6_nxt ip6_ctlun.ip6_un1.ip6_un1_nxt 93#define ip6_hlim ip6_ctlun.ip6_un1.ip6_un1_hlim 94#define ip6_hops ip6_ctlun.ip6_un1.ip6_un1_hlim 95.Ed 96.Pp 97All fields are in network-byte order. 98Any options specified (see 99.Sx Options 100below) must also be specified in network-byte order. 101.Pp 102.Va ip6_flow 103specifies the flow ID. 104.Va ip6_plen 105specifies the payload length. 106.Va ip6_nxt 107specifies the type of the next header. 108.Va ip6_hlim 109specifies the hop limit. 110.Pp 111The top 4 bits of 112.Va ip6_vfc 113specify the class and the bottom 4 bits specify the version. 114.Pp 115.Va ip6_src 116and 117.Va ip6_dst 118specify the source and destination addresses. 119.Pp 120The IPv6 header may be followed by any number of extension headers that start 121with the following generic definition: 122.Bd -literal -offset indent 123struct ip6_ext { 124 uint8_t ip6e_nxt; 125 uint8_t ip6e_len; 126} __packed; 127.Ed 128.Ss Options 129IPv6 allows header options on packets to manipulate the behavior of the 130protocol. 131These options and other control requests are accessed with the 132.Xr getsockopt 2 133and 134.Xr setsockopt 2 135system calls at level 136.Dv IPPROTO_IPV6 137and by using ancillary data in 138.Xr recvmsg 2 139and 140.Xr sendmsg 2 . 141They can be used to access most of the fields in the IPv6 header and 142extension headers. 143.Pp 144The following socket options are supported: 145.Bl -tag -width Ds 146.\" .It Dv IPV6_OPTIONS 147.It Dv IPV6_UNICAST_HOPS Fa "int *" 148Get or set the default hop limit header field for outgoing unicast 149datagrams sent on this socket. 150.\" .It Dv IPV6_RECVOPTS Fa "int *" 151.\" Get or set the status of whether all header options will be 152.\" delivered along with the datagram when it is received. 153.\" .It Dv IPV6_RECVRETOPTS Fa "int *" 154.\" Get or set the status of whether header options will be delivered 155.\" for reply. 156.\" .It Dv IPV6_RECVDSTADDR Fa "int *" 157.\" Get or set the status of whether datagrams are received with 158.\" destination addresses. 159.\" .It Dv IPV6_RETOPTS 160.\" Get or set IPv6 options. 161.It Dv IPV6_MULTICAST_IF Fa "u_int *" 162Get or set the interface from which multicast packets will be sent. 163For hosts with multiple interfaces, each multicast transmission is sent 164from the primary network interface. 165The interface is specified as its index as provided by 166.Xr if_nametoindex 3 . 167A value of zero specifies the default interface. 168.It Dv IPV6_MULTICAST_HOPS Fa "int *" 169Get or set the default hop limit header field for outgoing multicast 170datagrams sent on this socket. 171This option controls the scope of multicast datagram transmissions. 172.Pp 173Datagrams with a hop limit of 1 are not forwarded beyond the local 174network. 175Multicast datagrams with a hop limit of zero will not be transmitted on 176any network but may be delivered locally if the sending host belongs to 177the destination group and if multicast loopback (see below) has not been 178disabled on the sending socket. 179Multicast datagrams with a hop limit greater than 1 may be forwarded to 180the other networks if a multicast router (such as 181.Xr mrouted 8 Pq Pa ports/net/mrouted ) 182is attached to the local network. 183.It Dv IPV6_MULTICAST_LOOP Fa "u_int *" 184Get or set the status of whether multicast datagrams will be looped back 185for local delivery when a multicast datagram is sent to a group to which 186the sending host belongs. 187.Pp 188This option improves performance for applications that may have no more 189than one instance on a single host (such as a router daemon) by 190eliminating the overhead of receiving their own transmissions. 191It should generally not be used by applications for which there may be 192more than one instance on a single host (such as a conferencing program) 193or for which the sender does not belong to the destination group 194(such as a time-querying program). 195.Pp 196A multicast datagram sent with an initial hop limit greater than 1 may 197be delivered to the sending host on a different interface from that on 198which it was sent if the host belongs to the destination group on that 199other interface. 200The multicast loopback control option has no effect on such delivery. 201.It Dv IPV6_JOIN_GROUP Fa "struct ipv6_mreq *" 202Join a multicast group. 203A host must become a member of a multicast group before it can receive 204datagrams sent to the group. 205.Bd -literal 206struct ipv6_mreq { 207 struct in6_addr ipv6mr_multiaddr; 208 unsigned int ipv6mr_interface; 209}; 210.Ed 211.Pp 212.Va ipv6mr_interface 213may be set to zeroes to choose the default multicast interface or to the 214index of a particular multicast-capable interface if the host is 215multihomed. 216Membership is associated with a single interface; programs running on 217multihomed hosts may need to join the same group on more than one 218interface. 219.Pp 220If the multicast address is unspecified (i.e., all zeroes), messages 221from all multicast addresses will be accepted by this group. 222Note that setting to this value requires superuser privileges. 223.It Dv IPV6_LEAVE_GROUP Fa "struct ipv6_mreq *" 224Drop membership from the associated multicast group. 225Memberships are automatically dropped when the socket is closed or when 226the process exits. 227.It Dv IPV6_ORIGDSTADDR Fa "int *" 228Get or set whether a datagram's original destination address and port are 229returned as ancillary data along with the payload in subsequent 230.Xr recvmsg 2 231calls. 232The information is stored in the ancillary data as a 233.Tn sockaddr_in6 234structure. 235.It Dv IPV6_PORTRANGE Fa "int *" 236Get or set the allocation policy of ephemeral ports for when the kernel 237automatically binds a local address to this socket. 238The following values are available: 239.Pp 240.Bl -tag -width IPV6_PORTRANGE_DEFAULT -compact 241.It Dv IPV6_PORTRANGE_DEFAULT 242Use the regular range of non-reserved ports (varies, see 243.Xr ip 4 ) . 244.It Dv IPV6_PORTRANGE_HIGH 245Use a high range (varies, see 246.Xr ip 4 ) . 247.It Dv IPV6_PORTRANGE_LOW 248Use a low, reserved range (600\-1023, see 249.Xr ip 4 ) . 250.El 251.It Dv IPV6_PKTINFO Fa "int *" 252Get or set whether additional information about subsequent packets will 253be provided as ancillary data along with the payload in subsequent 254.Xr recvmsg 2 255calls. 256The information is stored in the following structure in the ancillary 257data returned: 258.Bd -literal 259struct in6_pktinfo { 260 struct in6_addr ipi6_addr; /* src/dst IPv6 address */ 261 unsigned int ipi6_ifindex; /* send/recv if index */ 262}; 263.Ed 264.It Dv IPV6_HOPLIMIT Fa "int *" 265Get or set whether the hop limit header field from subsequent packets 266will be provided as ancillary data along with the payload in subsequent 267.Xr recvmsg 2 268calls. 269The value is stored as an 270.Vt int 271in the ancillary data returned. 272.\" .It Dv IPV6_NEXTHOP Fa "int *" 273.\" Get or set whether the address of the next hop for subsequent 274.\" packets will be provided as ancillary data along with the payload in 275.\" subsequent 276.\" .Xr recvmsg 2 277.\" calls. 278.\" The option is stored as a 279.\" .Vt sockaddr 280.\" structure in the ancillary data returned. 281.\" .Pp 282.\" This option requires superuser privileges. 283.It Dv IPV6_HOPOPTS Fa "int *" 284Get or set whether the hop-by-hop options from subsequent packets will be 285provided as ancillary data along with the payload in subsequent 286.Xr recvmsg 2 287calls. 288The option is stored in the following structure in the ancillary data 289returned: 290.Bd -literal 291struct ip6_hbh { 292 uint8_t ip6h_nxt; /* next header */ 293 uint8_t ip6h_len; /* length in units of 8 octets */ 294/* followed by options */ 295} __packed; 296.Ed 297.Pp 298The 299.Fn inet6_opt_init 300routine and family of routines may be used to manipulate this data. 301.Pp 302This option requires superuser privileges. 303.It Dv IPV6_DSTOPTS Fa "int *" 304Get or set whether the destination options from subsequent packets will 305be provided as ancillary data along with the payload in subsequent 306.Xr recvmsg 2 307calls. 308The option is stored in the following structure in the ancillary data 309returned: 310.Bd -literal 311struct ip6_dest { 312 uint8_t ip6d_nxt; /* next header */ 313 uint8_t ip6d_len; /* length in units of 8 octets */ 314/* followed by options */ 315} __packed; 316.Ed 317.Pp 318The 319.Fn inet6_opt_init 320routine and family of routines may be used to manipulate this data. 321.Pp 322This option requires superuser privileges. 323.It Dv IPV6_TCLASS Fa "int *" 324Get or set the value of the traffic class field used for outgoing datagrams 325on this socket. 326The value must be between \-1 and 255. 327A value of \-1 resets to the default value. 328.It Dv IPV6_RECVTCLASS Fa "int *" 329Get or set the status of whether the traffic class header field will be 330provided as ancillary data along with the payload in subsequent 331.Xr recvmsg 2 332calls. 333The header field is stored as a single value of type 334.Vt int . 335.It Dv IPV6_RTHDR Fa "int *" 336Get or set whether the routing header from subsequent packets will be 337provided as ancillary data along with the payload in subsequent 338.Xr recvmsg 2 339calls. 340The header is stored in the following structure in the ancillary data 341returned: 342.Bd -literal 343struct ip6_rthdr { 344 uint8_t ip6r_nxt; /* next header */ 345 uint8_t ip6r_len; /* length in units of 8 octets */ 346 uint8_t ip6r_type; /* routing type */ 347 uint8_t ip6r_segleft; /* segments left */ 348/* followed by routing-type-specific data */ 349} __packed; 350.Ed 351.Pp 352The 353.Fn inet6_opt_init 354routine and family of routines may be used to manipulate this data. 355.Pp 356This option requires superuser privileges. 357.It Dv IPV6_PKTOPTIONS Fa "struct cmsghdr *" 358Get or set all header options and extension headers at one time on the 359last packet sent or received on the socket. 360All options must fit within the size of an mbuf (see 361.Xr mbuf 9 ) . 362Options are specified as a series of 363.Vt cmsghdr 364structures followed by corresponding values. 365.Va cmsg_level 366is set to 367.Dv IPPROTO_IPV6 , 368.Va cmsg_type 369to one of the other values in this list, and trailing data to the option 370value. 371When setting options, if the length 372.Va optlen 373to 374.Xr setsockopt 2 375is zero, all header options will be reset to their default values. 376Otherwise, the length should specify the size the series of control 377messages consumes. 378.Pp 379Instead of using 380.Xr sendmsg 2 381to specify option values, the ancillary data used in these calls that 382correspond to the desired header options may be directly specified as 383the control message in the series of control messages provided as the 384argument to 385.Xr setsockopt 2 . 386.It Dv IPV6_CHECKSUM Fa "int *" 387Get or set the byte offset into a packet where the 16-bit checksum is 388located. 389When set, this byte offset is where incoming packets will be expected 390to have checksums of their data stored and where outgoing packets will 391have checksums of their data computed and stored by the kernel. 392A value of \-1 specifies that no checksums will be checked on incoming 393packets and that no checksums will be computed or stored on outgoing 394packets. 395The offset of the checksum for ICMPv6 sockets cannot be relocated or 396turned off. 397.It Dv IPV6_V6ONLY Fa "int *" 398Get or set whether only IPv6 connections can be made to this socket. 399For wildcard sockets, this can restrict connections to IPv6 only. 400.\"With 401.\".Ox 402.\"IPv6 sockets are always IPv6-only, so the socket option is read-only 403.\"(not modifiable). 404.It Dv IPV6_USE_MIN_MTU Fa "int *" 405Get or set whether the minimal IPv6 maximum transmission unit (MTU) size 406will be used to avoid fragmentation from occurring for subsequent 407outgoing datagrams. 408.It Dv IPV6_AUTH_LEVEL Fa "int *" 409Get or set the 410.Xr ipsec 4 411authentication level. 412.It Dv IPV6_ESP_TRANS_LEVEL Fa "int *" 413Get or set the ESP transport level. 414.It Dv IPV6_ESP_NETWORK_LEVEL Fa "int *" 415Get or set the ESP encapsulation level. 416.It Dv IPV6_IPCOMP_LEVEL Fa "int *" 417Get or set the 418.Xr ipcomp 4 419level. 420.El 421.Pp 422The 423.Dv IPV6_PKTINFO , 424.\" .Dv IPV6_NEXTHOP , 425.Dv IPV6_HOPLIMIT , 426.Dv IPV6_HOPOPTS , 427.Dv IPV6_DSTOPTS , 428.Dv IPV6_RTHDR , 429and 430.Dv IPV6_ORIGDSTADDR 431options will return ancillary data along with payload contents in subsequent 432.Xr recvmsg 2 433calls with 434.Va cmsg_level 435set to 436.Dv IPPROTO_IPV6 437and 438.Va cmsg_type 439set to respective option name value (e.g., 440.Dv IPV6_HOPTLIMIT ) . 441Some of these options may also be used directly as ancillary 442.Va cmsg_type 443values in 444.Xr sendmsg 2 445to set options on the packet being transmitted by the call. 446The 447.Va cmsg_level 448value must be 449.Dv IPPROTO_IPV6 . 450For these options, the ancillary data object value format is the same 451as the value returned as explained for each when received with 452.Xr recvmsg 2 . 453.Pp 454Note that using 455.Xr sendmsg 2 456to specify options on particular packets works only on UDP and raw sockets. 457To manipulate header options for packets on TCP sockets, only the socket 458options may be used. 459.Pp 460In some cases, there are multiple APIs defined for manipulating an IPv6 461header field. 462A good example is the outgoing interface for multicast datagrams, which 463can be set by the 464.Dv IPV6_MULTICAST_IF 465socket option, through the 466.Dv IPV6_PKTINFO 467option, and through the 468.Va sin6_scope_id 469field of the socket address passed to the 470.Xr sendto 2 471system call. 472.Pp 473Resolving these conflicts is implementation dependent. 474This implementation determines the value in the following way: 475options specified by using ancillary data (i.e., 476.Xr sendmsg 2 ) 477are considered first, 478options specified by using 479.Dv IPV6_PKTOPTIONS 480to set 481.Dq sticky 482options are considered second, 483options specified by using the individual, basic, and direct socket 484options (e.g., 485.Dv IPV6_UNICAST_HOPS ) 486are considered third, 487and options specified in the socket address supplied to 488.Xr sendto 2 489are the last choice. 490.Ss Multicasting 491IPv6 multicasting is supported only on 492.Dv AF_INET6 493sockets of type 494.Dv SOCK_DGRAM 495and 496.Dv SOCK_RAW , 497and only on networks where the interface driver supports 498multicasting. 499Socket options (see above) that manipulate membership of 500multicast groups and other multicast options include 501.Dv IPV6_MULTICAST_IF , 502.Dv IPV6_MULTICAST_HOPS , 503.Dv IPV6_MULTICAST_LOOP , 504.Dv IPV6_LEAVE_GROUP , 505and 506.Dv IPV6_JOIN_GROUP . 507.Ss Raw Sockets 508Raw IPv6 sockets are connectionless and are normally used with the 509.Xr sendto 2 510and 511.Xr recvfrom 2 512calls, although the 513.Xr connect 2 514call may be used to fix the destination address for future outgoing 515packets so that 516.Xr send 2 517may instead be used and the 518.Xr bind 2 519call may be used to fix the source address for future outgoing 520packets instead of having the kernel choose a source address. 521.Pp 522By using 523.Xr connect 2 524or 525.Xr bind 2 , 526raw socket input is constrained to only packets with their 527source address matching the socket destination address if 528.Xr connect 2 529was used and to packets with their destination address 530matching the socket source address if 531.Xr bind 2 532was used. 533.Pp 534If the 535.Ar proto 536argument to 537.Xr socket 2 538is zero, the default protocol 539.Pq Dv IPPROTO_RAW 540is used for outgoing packets. 541For incoming packets, protocols recognized by kernel are 542.Sy not 543passed to the application socket (e.g., 544.Xr tcp 4 545and 546.Xr udp 4 ) 547except for some ICMPv6 messages. 548The ICMPv6 messages not passed to raw sockets include echo, timestamp, 549and address mask requests. 550If 551.Ar proto 552is non-zero, only packets with this protocol will be passed to the 553socket. 554.Pp 555IPv6 fragments are also not passed to application sockets until 556they have been reassembled. 557If reception of all packets is desired, link-level access (such as 558.Xr bpf 4 ) 559must be used instead. 560.Pp 561Outgoing packets automatically have an IPv6 header prepended to them 562(based on the destination address and the protocol number the socket 563was created with). 564Incoming packets are received by an application without the IPv6 header 565or any extension headers. 566.Pp 567Outgoing packets will be fragmented automatically by the kernel if they 568are too large. 569Incoming packets will be reassembled before being sent to the raw socket, 570so packet fragments or fragment headers will never be seen on a raw socket. 571.Sh EXAMPLES 572The following determines the hop limit on the next packet received: 573.Bd -literal 574struct iovec iov[2]; 575u_char buf[BUFSIZ]; 576struct cmsghdr *cm; 577struct msghdr m; 578int optval; 579bool found; 580u_char data[2048]; 581 582/* Create socket. */ 583 584(void)memset(&m, 0, sizeof(m)); 585(void)memset(&iov, 0, sizeof(iov)); 586 587iov[0].iov_base = data; /* buffer for packet payload */ 588iov[0].iov_len = sizeof(data); /* expected packet length */ 589 590m.msg_name = &from; /* sockaddr_in6 of peer */ 591m.msg_namelen = sizeof(from); 592m.msg_iov = iov; 593m.msg_iovlen = 1; 594m.msg_control = (caddr_t)buf; /* buffer for control messages */ 595m.msg_controllen = sizeof(buf); 596 597/* 598 * Enable the hop limit value from received packets to be 599 * returned along with the payload. 600 */ 601optval = 1; 602if (setsockopt(s, IPPROTO_IPV6, IPV6_HOPLIMIT, &optval, 603 sizeof(optval)) == -1) 604 err(1, "setsockopt"); 605 606found = false; 607do { 608 if (recvmsg(s, &m, 0) == -1) 609 err(1, "recvmsg"); 610 for (cm = CMSG_FIRSTHDR(&m); cm != NULL; 611 cm = CMSG_NXTHDR(&m, cm)) { 612 if (cm->cmsg_level == IPPROTO_IPV6 && 613 cm->cmsg_type == IPV6_HOPLIMIT && 614 cm->cmsg_len == CMSG_LEN(sizeof(int))) { 615 found = true; 616 (void)printf("hop limit: %d\en", 617 *(int *)CMSG_DATA(cm)); 618 break; 619 } 620 } 621} while (!found); 622.Ed 623.Sh DIAGNOSTICS 624A socket operation may fail with one of the following errors returned: 625.Bl -tag -width EADDRNOTAVAILxx 626.It Bq Er EISCONN 627when trying to establish a connection on a socket which 628already has one or when trying to send a datagram with the destination 629address specified and the socket is already connected. 630.It Bq Er ENOTCONN 631when trying to send a datagram, but 632no destination address is specified, and the socket has not been 633connected. 634.It Bq Er ENOBUFS 635when the system runs out of memory for 636an internal data structure. 637.It Bq Er EADDRNOTAVAIL 638when an attempt is made to create a 639socket with a network address for which no network interface 640exists. 641.It Bq Er EACCES 642when an attempt is made to create 643a raw IPv6 socket by a non-privileged process. 644.El 645.Pp 646The following errors specific to IPv6 may occur when setting or getting 647header options: 648.Bl -tag -width EADDRNOTAVAILxx 649.It Bq Er EINVAL 650An unknown socket option name was given. 651.It Bq Er EINVAL 652An ancillary data object was improperly formed. 653.El 654.Sh SEE ALSO 655.Xr getsockopt 2 , 656.Xr recv 2 , 657.Xr send 2 , 658.Xr setsockopt 2 , 659.Xr socket 2 , 660.Xr CMSG_DATA 3 , 661.Xr if_nametoindex 3 , 662.Xr inet6_opt_init 3 , 663.Xr bpf 4 , 664.Xr icmp6 4 , 665.Xr inet6 4 , 666.Xr ip 4 , 667.Xr netintro 4 , 668.Xr tcp 4 , 669.Xr udp 4 670.Rs 671.%A W. Stevens 672.%A M. Thomas 673.%T Advanced Sockets API for IPv6 674.%R RFC 2292 675.%D February 1998 676.Re 677.Rs 678.%A S. Deering 679.%A R. Hinden 680.%T Internet Protocol, Version 6 (IPv6) Specification 681.%R RFC 2460 682.%D December 1998 683.Re 684.Rs 685.%A R. Gilligan 686.%A S. Thomson 687.%A J. Bound 688.%A W. Stevens 689.%T Basic Socket Interface Extensions for IPv6 690.%R RFC 2553 691.%D March 1999 692.Re 693.Rs 694.%A R. Gilligan 695.%A S. Thomson 696.%A J. Bound 697.%A J. McCann 698.%A W. Stevens 699.%T Basic Socket Interface Extensions for IPv6 700.%R RFC 3493 701.%D February 2003 702.Re 703.Rs 704.%A W. Stevens 705.%A M. Thomas 706.%A E. Nordmark 707.%A T. Jinmei 708.%T Advanced Sockets Application Program Interface (API) for IPv6 709.%R RFC 3542 710.%D May 2003 711.Re 712.Rs 713.%A S. Deering 714.%A R. Hinden 715.%T Internet Protocol, Version 6 (IPv6) Specification 716.%R RFC 8200 717.%D July 2017 718.Re 719.Rs 720.%A W. Stevens 721.%A B. Fenner 722.%A A. Rudoff 723.%T UNIX Network Programming, 3rd Edition 724.%I Addison-Wesley Professional 725.%D November 2003 726.Re 727.Sh STANDARDS 728Most of the socket options are defined in RFC 2292 / 3542 or 729RFC 2553 / 3493. 730The 731.Dv IPV6_PORTRANGE 732socket option and the conflict resolution rule are not defined in the 733RFCs and should be considered implementation dependent. 734