1.\" $KAME: ip6.4,v 1.14 2001/02/26 09:31:39 itojun Exp $ 2.\" 3.\" Copyright (C) 1999 WIDE Project. 4.\" All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. Neither the name of the project nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.\" Copyright (c) 1983, 1991, 1993 31.\" The Regents of the University of California. All rights reserved. 32.\" 33.\" Redistribution and use in source and binary forms, with or without 34.\" modification, are permitted provided that the following conditions 35.\" are met: 36.\" 1. Redistributions of source code must retain the above copyright 37.\" notice, this list of conditions and the following disclaimer. 38.\" 2. Redistributions in binary form must reproduce the above copyright 39.\" notice, this list of conditions and the following disclaimer in the 40.\" documentation and/or other materials provided with the distribution. 41.\" 3. All advertising materials mentioning features or use of this software 42.\" must display the following acknowledgement: 43.\" This product includes software developed by the University of 44.\" California, Berkeley and its contributors. 45.\" 4. Neither the name of the University nor the names of its contributors 46.\" may be used to endorse or promote products derived from this software 47.\" without specific prior written permission. 48.\" 49.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 50.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 51.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 52.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 53.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 54.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 55.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 56.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 57.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 58.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 59.\" SUCH DAMAGE. 60.\" 61.\" $FreeBSD$ 62.\" 63.Dd March 13, 2000 64.Dt IP6 4 65.Os 66.\" 67.Sh NAME 68.Nm ip6 69.Nd Internet Protocol version 6 (IPv6) 70.\" 71.Sh SYNOPSIS 72.In sys/types.h 73.In sys/socket.h 74.In netinet/in.h 75.Ft int 76.Fn socket AF_INET6 SOCK_RAW proto 77.\" 78.Sh DESCRIPTION 79.Tn IPv6 80is the network layer protocol used by the Internet protocol version 6 family 81.Pq Dv AF_INET6 . 82Options may be set at the 83.Tn IPv6 84level when using higher-level protocols that are based on 85.Tn IPv6 86(such as 87.Tn TCP 88and 89.Tn UDP ) . 90It may also be accessed through a 91.Dq raw socket 92when developing new protocols, or special-purpose applications. 93.Pp 94There are several 95.Tn IPv6-level 96.Xr setsockopt 2 Ns / Ns Xr getsockopt 2 97options. 98They are separated into the basic IPv6 sockets API 99(defined in RFC2553), 100and the advanced API 101(defined in RFC2292). 102The basic API looks very similar to the API presented in 103.Xr ip 4 . 104Advanced API uses ancillary data and can handle more complex cases. 105.Pp 106To specify some of socket options, certain privilege 107(i.e. root privilege) is required. 108.\" 109.Ss Basic IPv6 sockets API 110.Dv IPV6_UNICAST_HOPS 111may be used to set the hoplimit field in the 112.Tn IPv6 113header. 114As symbol name suggests, the option controls hoplimit field on unicast packets. 115If -1 is specified, the kernel will use a default value. 116If a value of 0 to 255 is specified, the packet will have the specified 117value as hoplimit. 118Other values are considered invalid, and 119.Er EINVAL 120will be returned. 121For example: 122.Bd -literal -offset indent 123int hlim = 60; /* max = 255 */ 124setsockopt(s, IPPROTO_IPV6, IPV6_UNICAST_HOPS, &hlim, sizeof(hlim)); 125.Ed 126.Pp 127.Tn IPv6 128multicasting is supported only on 129.Dv AF_INET6 130sockets of type 131.Dv SOCK_DGRAM 132and 133.Dv SOCK_RAW, 134and only on networks where the interface driver supports multicasting. 135.Pp 136The 137.Dv IPV6_MULTICAST_HOPS 138option changes the hoplimit for outgoing multicast datagrams 139in order to control the scope of the multicasts: 140.Bd -literal -offset indent 141unsigned int hlim; /* range: 0 to 255, default = 1 */ 142setsockopt(s, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &hlim, sizeof(hlim)); 143.Ed 144.Pp 145Datagrams with a hoplimit of 1 are not forwarded beyond the local network. 146Multicast datagrams with a hoplimit of 0 will not be transmitted on any network, 147but may be delivered locally if the sending host belongs to the destination 148group and if multicast loopback has not been disabled on the sending socket 149(see below). 150Multicast datagrams with hoplimit greater than 1 may be forwarded 151to other networks if a multicast router is attached to the local network. 152.Pp 153For hosts with multiple interfaces, each multicast transmission is 154sent from the primary network interface. 155The 156.Dv IPV6_MULTICAST_IF 157option overrides the default for 158subsequent transmissions from a given socket: 159.Bd -literal -offset indent 160unsigned int outif; 161outif = if_nametoindex("ne0"); 162setsockopt(s, IPPROTO_IPV6, IPV6_MULTICAST_IF, &outif, sizeof(outif)); 163.Ed 164.Pp 165where "outif" is an interface index of the desired interface, 166or 0 to specify the default interface. 167.Pp 168If a multicast datagram is sent to a group to which the sending host itself 169belongs (on the outgoing interface), a copy of the datagram is, by default, 170looped back by the IPv6 layer for local delivery. 171The 172.Dv IPV6_MULTICAST_LOOP 173option gives the sender explicit control 174over whether or not subsequent datagrams are looped back: 175.Bd -literal -offset indent 176u_char loop; /* 0 = disable, 1 = enable (default) */ 177setsockopt(s, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, &loop, sizeof(loop)); 178.Ed 179.Pp 180This option 181improves performance for applications that may have no more than one 182instance on a single host (such as a router daemon), by eliminating 183the overhead of receiving their own transmissions. 184It should generally not be used by applications for which there 185may be more than one instance on a single host (such as a conferencing 186program) or for which the sender does not belong to the destination 187group (such as a time querying program). 188.Pp 189A multicast datagram sent with an initial hoplimit greater than 1 may be delivered 190to the sending host on a different interface from that on which it was sent, 191if the host belongs to the destination group on that other interface. 192The loopback control option has no effect on such delivery. 193.Pp 194A host must become a member of a multicast group before it can receive 195datagrams sent to the group. 196To join a multicast group, use the 197.Dv IPV6_JOIN_GROUP 198option: 199.Bd -literal -offset indent 200struct ipv6_mreq mreq6; 201setsockopt(s, IPPROTO_IPV6, IPV6_JOIN_GROUP, &mreq6, sizeof(mreq6)); 202.Ed 203.Pp 204where 205.Fa mreq6 206is the following structure: 207.Bd -literal -offset indent 208struct ipv6_mreq { 209 struct in6_addr ipv6mr_multiaddr; 210 u_int ipv6mr_interface; 211}; 212.Ed 213.Pp 214.Dv ipv6mr_interface 215should be 0 to choose the default multicast interface, or the 216interface index of a particular multicast-capable interface if 217the host is multihomed. 218Membership is associated with a single interface; 219programs running on multihomed hosts may need to 220join the same group on more than one interface. 221.Pp 222To drop a membership, use: 223.Bd -literal -offset indent 224struct ipv6_mreq mreq6; 225setsockopt(s, IPPROTO_IPV6, IPV6_LEAVE_GROUP, &mreq6, sizeof(mreq6)); 226.Ed 227.Pp 228where 229.Fa mreq6 230contains the same values as used to add the membership. 231Memberships are dropped when the socket is closed or the process exits. 232.Pp 233.Dv IPV6_PORTRANGE 234controls how ephemeral ports are allocated for 235.Dv SOCK_STREAM 236and 237.Dv SOCK_DGRAM 238sockets. 239For example, 240.Bd -literal -offset indent 241int range = IPV6_PORTRANGE_LOW; /* see <netinet/in.h> */ 242setsockopt(s, IPPROTO_IPV6, IPV6_PORTRANGE, &range, sizeof(range)); 243.Ed 244.Pp 245.Dv IPV6_V6ONLY 246controls behavior of 247.Dv AF_INET6 248wildcard listening socket. 249The following example sets the option to 1: 250.Bd -literal -offset indent 251int on = 1; 252setsockopt(s, IPPROTO_IPV6, IPV6_V6ONLY, &on, sizeof(on)); 253.Ed 254.Pp 255If set to 1, 256.Dv AF_INET6 257wildcard listening socket will accept IPv6 traffic only. 258If set to 0, it will accept IPv4 traffic as well, 259as if it was from IPv4 mapped address like 260.Li ::ffff:10.1.1.1 . 261.\" RFC2553 defines the behavior when the variable is set to 0. 262Note that if you set it this to 0, 263IPv4 access control gets much more complicated. 264For example, even if you have no listening 265.Dv AF_INET 266listening socket on port 267.Li X , 268you will end up accepting IPv4 traffic by 269.Dv AF_INET6 270listening socket on the same port. 271The default value for this flag is copied at socket instantiation time, 272from 273.Li net.inet6.ip6.v6only 274.Xr sysctl 3 275variable. 276The option affects 277.Tn TCP 278and 279.Tn UDP 280sockets only. 281.\" 282.Ss Advanced IPv6 sockets API 283The advanced IPv6 sockets API lets userland programs specify or obtain 284details about the IPv6 header and the IPv6 extension headers on packets. 285The advanced API uses ancillary data for passing data from/to the kernel. 286.Pp 287There are 288.Xr setsockopt 2 Ns / Ns Xr getsockopt 2 289options to get optional information on incoming packets. 290They are 291.Dv IPV6_PKTINFO , 292.Dv IPV6_HOPLIMIT , 293.Dv IPV6_HOPOPTS , 294.Dv IPV6_DSTOPTS , 295and 296.Dv IPV6_RTHDR . 297.Bd -literal -offset indent 298int on = 1; 299 300setsockopt(fd, IPPROTO_IPV6, IPV6_PKTINFO, &on, sizeof(on)); 301setsockopt(fd, IPPROTO_IPV6, IPV6_HOPLIMIT, &on, sizeof(on)); 302setsockopt(fd, IPPROTO_IPV6, IPV6_HOPOPTS, &on, sizeof(on)); 303setsockopt(fd, IPPROTO_IPV6, IPV6_DSTOPTS, &on, sizeof(on)); 304setsockopt(fd, IPPROTO_IPV6, IPV6_RTHDR, &on, sizeof(on)); 305.Ed 306.Pp 307When any of these options are enabled, the corresponding data is 308returned as control information by 309.Xr recvmsg 2 , 310as one or more ancillary data objects. 311.Pp 312If 313.Dv IPV6_PKTINFO 314is enabled, the destination IPv6 address and the arriving interface index 315will be available via 316.Li struct in6_pktinfo 317on ancillary data stream. 318You can pick the structure by checking for an ancillary data item with 319.Li cmsg_level 320equals to 321.Dv IPPROTO_IPV6 , 322and 323.Li cmsg_type 324equals to 325.Dv IPV6_PKTINFO . 326.Pp 327If 328.Dv IPV6_HOPLIMIT 329is enabled, hoplimit value on the packet will be made available to the 330userland program. 331Ancillary data stream will contain an integer data item with 332.Li cmsg_level 333equals to 334.Dv IPPROTO_IPV6 , 335and 336.Li cmsg_type 337equals to 338.Dv IPV6_HOPLIMIT . 339.Pp 340.Xr inet6_option_space 3 341and friends will help you parse ancillary data items for 342.Dv IPV6_HOPOPTS 343and 344.Dv IPV6_DSTOPTS . 345Similarly, 346.Xr inet6_rthdr_space 3 347and friends will help you parse ancillary data items for 348.Dv IPV6_RTHDR . 349.Pp 350.Dv IPV6_HOPOPTS 351and 352.Dv IPV6_DSTOPTS 353may appear multiple times on an ancillary data stream 354(note that the behavior is slightly different than the specification). 355Other ancillary data item will appear no more than once. 356.Pp 357For outgoing direction, 358you can pass ancillary data items with normal payload data, using 359.Xr sendmsg 2 . 360Ancillary data items will be parsed by the kernel, and used to construct 361the IPv6 header and extension headers. 362For the 5 363.Li cmsg_level 364values listed above, ancillary data format is the same as inbound case. 365Additionally, you can specify 366.Dv IPV6_NEXTHOP 367data object. 368The 369.Dv IPV6_NEXTHOP 370ancillary data object specifies the next hop for the 371datagram as a socket address structure. 372In the 373.Li cmsghdr 374structure 375containing this ancillary data, the 376.Li cmsg_level 377member will be 378.Dv IPPROTO_IPV6 , 379the 380.Li cmsg_type 381member will be 382.Dv IPV6_NEXTHOP , 383and the first byte of 384.Li cmsg_data[] 385will be the first byte of the socket address structure. 386.Pp 387If the socket address structure contains an IPv6 address (e.g., the 388sin6_family member is 389.Dv AF_INET6 ) , 390then the node identified by that 391address must be a neighbor of the sending host. 392If that address 393equals the destination IPv6 address of the datagram, then this is 394equivalent to the existing 395.Dv SO_DONTROUTE 396socket option. 397.Pp 398For applications that do not, or unable to use 399.Xr sendmsg 2 400or 401.Xr recvmsg 2 , 402.Dv IPV6_PKTOPTIONS 403socket option is defined. 404Setting the socket option specifies any of the optional output fields: 405.Bd -literal -offset indent 406setsockopt(fd, IPPROTO_IPV6, IPV6_PKTOPTIONS, &buf, len); 407.Ed 408.Pp 409The fourth argument points to a buffer containing one or more 410ancillary data objects, and the fifth argument is the total length of 411all these objects. 412The application fills in this buffer exactly as 413if the buffer were being passed to 414.Xr sendmsg 2 415as control information. 416.Pp 417The options set by calling 418.Xr setsockopt 2 419for 420.Dv IPV6_PKTOPTIONS 421are 422called "sticky" options because once set they apply to all packets 423sent on that socket. 424The application can call 425.Xr setsockopt 2 426again to 427change all the sticky options, or it can call 428.Xr setsockopt 2 429with a 430length of 0 to remove all the sticky options for the socket. 431.Pp 432The corresponding receive option 433.Bd -literal -offset indent 434getsockopt(fd, IPPROTO_IPV6, IPV6_PKTOPTIONS, &buf, &len); 435.Ed 436.Pp 437returns a buffer with one or more ancillary data objects for all the 438optional receive information that the application has previously 439specified that it wants to receive. 440The fourth argument points to 441the buffer that is filled in by the call. 442The fifth argument is a 443pointer to a value-result integer: when the function is called the 444integer specifies the size of the buffer pointed to by the fourth 445argument, and on return this integer contains the actual number of 446bytes that were returned. 447The application processes this buffer 448exactly as if the buffer were returned by 449.Xr recvmsg 2 450as control information. 451.\" 452.Ss Advanced API and TCP sockets 453When using 454.Xr getsockopt 2 455with the 456.Dv IPV6_PKTOPTIONS 457option and a 458.Tn TCP 459socket, only the options from the most recently received segment are 460retained and returned to the caller, and only after the socket option 461has been set. 462.\" That is, 463.\" .Tn TCP 464.\" need not start saving a copy of the options until the application says 465.\" to do so. 466The application is not allowed to specify ancillary data in a call to 467.Xr sendmsg 2 468on a 469.Tn TCP 470socket, and none of the ancillary data that we 471described above is ever returned as control information by 472.Xr recvmsg 2 473on a 474.Tn TCP 475socket. 476.\" 477.Ss Conflict resolution 478In some cases, there are multiple APIs defined for manipulating 479a IPv6 header field. 480A good example is the outgoing interface for multicast datagrams: 481it can be manipulated by 482.Dv IPV6_MULTICAST_IF 483in basic API, 484.Dv IPV6_PKTINFO 485in advanced API, and 486.Li sin6_scope_id 487field of the socket address passed to 488.Xr sendto 2 . 489.Pp 490When conflicting options are given to the kernel, 491the kernel will get the value in the following preference: 492(1) options specified by using ancillary data, 493(2) options specified by a sticky option of the advanced API, 494(3) options specified by using the basic API, and lastly 495(4) options specified by a socket address. 496Note that the conflict resolution is undefined in the API specification 497and implementation dependent. 498.\" 499.Ss "Raw IPv6 Sockets" 500Raw 501.Tn IPv6 502sockets are connectionless, and are normally used with the 503.Xr sendto 2 504and 505.Xr recvfrom 2 506calls, though the 507.Xr connect 2 508call may also be used to fix the destination for future 509packets (in which case the 510.Xr read 2 511or 512.Xr recv 2 513and 514.Xr write 2 515or 516.Xr send 2 517system calls may be used). 518.Pp 519If 520.Fa proto 521is 0, the default protocol 522.Dv IPPROTO_RAW 523is used for outgoing packets, and only incoming packets destined 524for that protocol are received. 525If 526.Fa proto 527is non-zero, that protocol number will be used on outgoing packets 528and to filter incoming packets. 529.Pp 530Outgoing packets automatically have an 531.Tn IPv6 532header prepended to them (based on the destination address and the 533protocol number the socket is created with). 534Incoming packets are received without 535.Tn IPv6 536header nor extension headers. 537.Pp 538All data sent via raw sockets MUST be in network byte order and all 539data received via raw sockets will be in network byte order. 540This differs from the IPv4 raw sockets, which did not specify a byte 541ordering and typically used the host's byte order. 542.Pp 543Another difference from IPv4 raw sockets is that complete packets 544(that is, IPv6 packets with extension headers) cannot be read or 545written using the IPv6 raw sockets API. 546Instead, ancillary data 547objects are used to transfer the extension headers, as described above. 548Should an application need access to the 549complete IPv6 packet, some other technique, such as the datalink 550interfaces, such as 551.Xr bpf 4 , 552must be used. 553.Pp 554All fields in the IPv6 header that an application might want to 555change (i.e., everything other than the version number) can be 556modified using ancillary data and/or socket options by the 557application for output. 558All fields in a received IPv6 header (other 559than the version number and Next Header fields) and all extension 560headers are also made available to the application as ancillary data 561on input. 562Hence there is no need for a socket option similar to the 563IPv4 564.Dv IP_HDRINCL 565socket option. 566.Pp 567When writing to a raw socket the kernel will automatically fragment 568the packet if its size exceeds the path MTU, inserting the required 569fragmentation headers. On input the kernel reassembles received 570fragments, so the reader of a raw socket never sees any fragment 571headers. 572.Pp 573Most IPv4 implementations give special treatment to a raw socket 574created with a third argument to 575.Xr socket 2 576of 577.Dv IPPROTO_RAW , 578whose value is normally 255. 579We note that this value has no special meaning to 580an IPv6 raw socket (and the IANA currently reserves the value of 255 581when used as a next-header field). 582.\" Note: This feature was added to 583.\" IPv4 in 1988 by Van Jacobson to support traceroute, allowing a 584.\" complete IP header to be passed by the application, before the 585.\" .Dv IP_HDRINCL 586.\" socket option was added. 587.Pp 588For ICMPv6 raw sockets, 589the kernel will calculate and insert the ICMPv6 checksum for 590since this checksum is mandatory. 591.Pp 592For other raw IPv6 sockets (that is, for raw IPv6 sockets created 593with a third argument other than IPPROTO_ICMPV6), the application 594must set the new IPV6_CHECKSUM socket option to have the kernel (1) 595compute and store a pseudo header checksum for output, 596and (2) verify the received 597pseudo header checksum on input, 598discarding the packet if the checksum is in error. 599This option prevents applications from having to perform source 600address selection on the packets they send. 601The checksum will 602incorporate the IPv6 pseudo-header, defined in Section 8.1 of RFC2460. 603This new socket option also specifies an integer offset into 604the user data of where the checksum is located. 605.Bd -literal -offset indent 606int offset = 2; 607setsockopt(fd, IPPROTO_IPV6, IPV6_CHECKSUM, &offset, sizeof(offset)); 608.Ed 609.Pp 610By default, this socket option is disabled. Setting the offset to -1 611also disables the option. By disabled we mean (1) the kernel will 612not calculate and store a checksum for outgoing packets, and (2) the 613kernel will not verify a checksum for received packets. 614.Pp 615Note: Since the checksum is always calculated by the kernel for an 616ICMPv6 socket, applications are not able to generate ICMPv6 packets 617with incorrect checksums (presumably for testing purposes) using this 618API. 619.\" 620.Sh ERRORS 621A socket operation may fail with one of the following errors returned: 622.Bl -tag -width Er 623.It Bq Er EISCONN 624when trying to establish a connection on a socket which already 625has one, or when trying to send a datagram with the destination 626address specified and the socket is already connected; 627.It Bq Er ENOTCONN 628when trying to send a datagram, but no destination address is 629specified, and the socket hasn't been connected; 630.It Bq Er ENOBUFS 631when the system runs out of memory for an internal data structure; 632.It Bq Er EADDRNOTAVAIL 633when an attempt is made to create a socket with a network address 634for which no network interface exists. 635.It Bq Er EACCES 636when an attempt is made to create a raw IPv6 socket by a non-privileged process. 637.El 638.Pp 639The following errors specific to 640.Tn IPv6 641may occur: 642.Bl -tag -width EADDRNOTAVAILxx 643.It Bq Er EINVAL 644An unknown socket option name was given. 645.It Bq Er EINVAL 646The ancillary data items were improperly formed, or option name was unknown. 647.El 648.\" 649.Sh SEE ALSO 650.Xr getsockopt 2 , 651.Xr recv 2 , 652.Xr send 2 , 653.Xr setsockopt 2 , 654.Xr inet6_option_space 3 , 655.Xr inet6_rthdr_space 3 , 656.Xr icmp6 4 , 657.Xr inet6 4 , 658.Xr intro 4 659.Rs 660.%A W. Stevens 661.%A M. Thomas 662.%R RFC 663.%N 2292 664.%D February 1998 665.%T "Advanced Sockets API for IPv6" 666.Re 667.Rs 668.%A S. Deering 669.%A R. Hinden 670.%R RFC 671.%N 2460 672.%D December 1998 673.%T "Internet Protocol, Version 6 (IPv6) Specification" 674.Re 675.Rs 676.%A R. Gilligan 677.%A S. Thomson 678.%A J. Bound 679.%A W. Stevens 680.%R RFC 681.%N 2553 682.%D March 1999 683.%T "Basic Socket Interface Extensions for IPv6" 684.Re 685.\" 686.Sh STANDARDS 687Most of the socket options are defined in 688RFC2292 and/or RFC2553. 689.Pp 690.Dv IPV6_V6ONLY 691socket option is defined in draft-ietf-ipngwg-rfc2553bis-03. 692.Dv IPV6_PORTRANGE 693socket option 694and 695conflict resolution rule 696are not defined in the RFCs and should be considered implementation dependent. 697.\" 698.Sh HISTORY 699The implementation is based on KAME stack 700(which is descendant of WIDE hydrangea IPv6 stack kit). 701.Pp 702Part of the document was shamelessly copied from RFC2553 and RFC2292. 703.\" 704.Sh BUGS 705The 706.Dv IPV6_NEXTHOP 707object/option is not fully implemented as of writing this. 708