1.\" $NetBSD: ip6.4,v 1.31 2017/07/03 21:30:58 wiz 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 June 25, 2012 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_PORTALGO Fa "int *" 235The 236.Dv IP_PORTALGO 237can be used to randomize the port selection. 238Valid algorithms are described in 239.Xr rfc6056 7 240and their respective constants are in 241.In netinet/portalgo.h . 242For example, 243.Bd -literal 244int algo = PORTALGO_ALGO_RANDOM_PICK; /* see <netinet/portalgo.h> */ 245setsockopt(s, IPPROTO_IPV6, IPV6_PORTALGO, &algo, sizeof(algo)); 246.Ed 247.Pp 248The port selection can be also viewed and controlled at a global level for all 249.Tn IPV6 250sockets using the following 251.Xr sysctl 7 252variables: 253.Dv net.inet.ip6.anonportalgo.available 254and 255.Dv net.inet.ip6.anonportalgo.selected . 256.Pp 257.It Dv IPV6_PORTRANGE Fa "int *" 258Get or set the allocation policy of ephemeral ports for when the kernel 259automatically binds a local address to this socket. 260The following values are available: 261.Pp 262.Bl -tag -width IPV6_PORTRANGE_DEFAULT -compact 263.It Dv IPV6_PORTRANGE_DEFAULT 264Use the regular range of non-reserved ports (varies, see 265.Xr sysctl 8 ) . 266.It Dv IPV6_PORTRANGE_HIGH 267Use a high range (varies, see 268.Xr sysctl 8 ) . 269.It Dv IPV6_PORTRANGE_LOW 270Use a low, reserved range (600\-1023). 271.El 272.It Dv IPV6_PKTINFO Fa "int *" 273Get or set whether additional information about subsequent packets will 274be provided as ancillary data along with the payload in subsequent 275.Xr recvmsg 2 276calls. 277The information is stored in the following structure in the ancillary 278data returned: 279.Bd -literal 280struct in6_pktinfo { 281 struct in6_addr ipi6_addr; /* src/dst IPv6 address */ 282 unsigned int ipi6_ifindex; /* send/recv if index */ 283}; 284.Ed 285.It Dv IPV6_HOPLIMIT Fa "int *" 286Get or set whether the hop limit header field from subsequent packets 287will be provided as ancillary data along with the payload in subsequent 288.Xr recvmsg 2 289calls. 290The value is stored as an 291.Vt int 292in the ancillary data returned. 293.\" .It Dv IPV6_NEXTHOP Fa "int *" 294.\" Get or set whether the address of the next hop for subsequent 295.\" packets will be provided as ancillary data along with the payload in 296.\" subsequent 297.\" .Xr recvmsg 2 298.\" calls. 299.\" The option is stored as a 300.\" .Vt sockaddr 301.\" structure in the ancillary data returned. 302.\" .Pp 303.\" This option requires superuser privileges. 304.It Dv IPV6_HOPOPTS Fa "int *" 305Get or set whether the hop-by-hop options from subsequent packets will be 306provided as ancillary data along with the payload in subsequent 307.Xr recvmsg 2 308calls. 309The option is stored in the following structure in the ancillary data 310returned: 311.Bd -literal 312struct ip6_hbh { 313 uint8_t ip6h_nxt; /* next header */ 314 uint8_t ip6h_len; /* length in units of 8 octets */ 315/* followed by options */ 316} __packed; 317.Ed 318.Pp 319The 320.Fn inet6_option_space 321routine and family of routines may be used to manipulate this data. 322.Pp 323This option requires superuser privileges. 324.It Dv IPV6_DSTOPTS Fa "int *" 325Get or set whether the destination options from subsequent packets will 326be provided as ancillary data along with the payload in subsequent 327.Xr recvmsg 2 328calls. 329The option is stored in the following structure in the ancillary data 330returned: 331.Bd -literal 332struct ip6_dest { 333 uint8_t ip6d_nxt; /* next header */ 334 uint8_t ip6d_len; /* length in units of 8 octets */ 335/* followed by options */ 336} __packed; 337.Ed 338.Pp 339The 340.Fn inet6_option_space 341routine and family of routines may be used to manipulate this data. 342.Pp 343This option requires superuser privileges. 344.It Dv IPV6_RTHDR Fa "int *" 345Get or set whether the routing header from subsequent packets will be 346provided as ancillary data along with the payload in subsequent 347.Xr recvmsg 2 348calls. 349The header is stored in the following structure in the ancillary data 350returned: 351.Bd -literal 352struct ip6_rthdr { 353 uint8_t ip6r_nxt; /* next header */ 354 uint8_t ip6r_len; /* length in units of 8 octets */ 355 uint8_t ip6r_type; /* routing type */ 356 uint8_t ip6r_segleft; /* segments left */ 357/* followed by routing-type-specific data */ 358} __packed; 359.Ed 360.Pp 361The 362.Fn inet6_option_space 363routine and family of routines may be used to manipulate this data. 364.Pp 365This option requires superuser privileges. 366.It Dv IPV6_PKTOPTIONS Fa "struct cmsghdr *" 367Get or set all header options and extension headers at one time on the 368last packet sent or received on the socket. 369All options must fit within the size of an mbuf (see 370.Xr mbuf 9 ) . 371Options are specified as a series of 372.Vt cmsghdr 373structures followed by corresponding values. 374.Va cmsg_level 375is set to 376.Dv IPPROTO_IPV6 , 377.Va cmsg_type 378to one of the other values in this list, and trailing data to the option 379value. 380When setting options, if the length 381.Va optlen 382to 383.Xr setsockopt 2 384is zero, all header options will be reset to their default values. 385Otherwise, the length should specify the size the series of control 386messages consumes. 387.Pp 388Instead of using 389.Xr sendmsg 2 390to specify option values, the ancillary data used in these calls that 391correspond to the desired header options may be directly specified as 392the control message in the series of control messages provided as the 393argument to 394.Xr setsockopt 2 . 395.It Dv IPV6_CHECKSUM Fa "int *" 396Get or set the byte offset into a packet where the 16-bit checksum is 397located. 398When set, this byte offset is where incoming packets will be expected 399to have checksums of their data stored and where outgoing packets will 400have checksums of their data computed and stored by the kernel. 401A value of \-1 specifies that no checksums will be checked on incoming 402packets and that no checksums will be computed or stored on outgoing 403packets. 404The offset of the checksum for ICMPv6 sockets cannot be relocated or 405turned off. 406.It Dv IPV6_V6ONLY Fa "int *" 407Get or set whether only IPv6 connections can be made to this socket. 408For wildcard sockets, this can restrict connections to IPv6 only. 409.\"With 410.\".Ox 411.\"IPv6 sockets are always IPv6-only, so the socket option is read-only 412.\"(not modifiable). 413.It Dv IPV6_FAITH Fa "int *" 414Get or set the status of whether 415.Xr faith 4 416connections can be made to this socket. 417.It Dv IPV6_USE_MIN_MTU Fa "int *" 418Get or set whether the minimal IPv6 maximum transmission unit (MTU) size 419will be used to avoid fragmentation from occurring for subsequent 420outgoing datagrams. 421.It Dv IPV6_AUTH_LEVEL Fa "int *" 422Get or set the 423.Xr ipsec 4 424authentication level. 425.It Dv IPV6_ESP_TRANS_LEVEL Fa "int *" 426Get or set the ESP transport level. 427.It Dv IPV6_ESP_NETWORK_LEVEL Fa "int *" 428Get or set the ESP encapsulation level. 429.It Dv IPV6_IPCOMP_LEVEL Fa "int *" 430Get or set the 431.Xr ipcomp 4 432level. 433.El 434.Pp 435The 436.Dv IPV6_PKTINFO , 437.\" .Dv IPV6_NEXTHOP , 438.Dv IPV6_HOPLIMIT , 439.Dv IPV6_HOPOPTS , 440.Dv IPV6_DSTOPTS , 441and 442.Dv IPV6_RTHDR 443options will return ancillary data along with payload contents in subsequent 444.Xr recvmsg 2 445calls with 446.Va cmsg_level 447set to 448.Dv IPPROTO_IPV6 449and 450.Va cmsg_type 451set to respective option name value (e.g., 452.Dv IPV6_HOPTLIMIT ) . 453These options may also be used directly as ancillary 454.Va cmsg_type 455values in 456.Xr sendmsg 2 457to set options on the packet being transmitted by the call. 458The 459.Va cmsg_level 460value must be 461.Dv IPPROTO_IPV6 . 462For these options, the ancillary data object value format is the same 463as the value returned as explained for each when received with 464.Xr recvmsg 2 . 465.Pp 466Note that using 467.Xr sendmsg 2 468to specify options on particular packets works only on UDP and raw sockets. 469To manipulate header options for packets on TCP sockets, only the socket 470options may be used. 471.Pp 472In some cases, there are multiple APIs defined for manipulating an IPv6 473header field. 474A good example is the outgoing interface for multicast datagrams, which 475can be set by the 476.Dv IPV6_MULTICAST_IF 477socket option, through the 478.Dv IPV6_PKTINFO 479option, and through the 480.Va sin6_scope_id 481field of the socket address passed to the 482.Xr sendto 2 483system call. 484.Pp 485Resolving these conflicts is implementation dependent. 486This implementation determines the value in the following way: 487options specified by using ancillary data (i.e., 488.Xr sendmsg 2 ) 489are considered first, 490options specified by using 491.Dv IPV6_PKTOPTIONS 492to set 493.Dq sticky 494options are considered second, 495options specified by using the individual, basic, and direct socket 496options (e.g., 497.Dv IPV6_UNICAST_HOPS ) 498are considered third, 499and options specified in the socket address supplied to 500.Xr sendto 2 501are the last choice. 502.Ss Multicasting 503IPv6 multicasting is supported only on 504.Dv AF_INET6 505sockets of type 506.Dv SOCK_DGRAM 507and 508.Dv SOCK_RAW , 509and only on networks where the interface driver supports 510multicasting. 511Socket options (see above) that manipulate membership of 512multicast groups and other multicast options include 513.Dv IPV6_MULTICAST_IF , 514.Dv IPV6_MULTICAST_HOPS , 515.Dv IPV6_MULTICAST_LOOP , 516.Dv IPV6_LEAVE_GROUP , 517and 518.Dv IPV6_JOIN_GROUP . 519.Ss Raw Sockets 520Raw IPv6 sockets are connectionless and are normally used with the 521.Xr sendto 2 522and 523.Xr recvfrom 2 524calls, although the 525.Xr connect 2 526call may be used to fix the destination address for future outgoing 527packets so that 528.Xr send 2 529may instead be used and the 530.Xr bind 2 531call may be used to fix the source address for future outgoing 532packets instead of having the kernel choose a source address. 533.Pp 534By using 535.Xr connect 2 536or 537.Xr bind 2 , 538raw socket input is constrained to only packets with their 539source address matching the socket destination address if 540.Xr connect 2 541was used and to packets with their destination address 542matching the socket source address if 543.Xr bind 2 544was used. 545.Pp 546If the 547.Ar proto 548argument to 549.Xr socket 2 550is zero, the default protocol 551.Pq Dv IPPROTO_RAW 552is used for outgoing packets. 553For incoming packets, protocols recognized by kernel are 554.Sy not 555passed to the application socket (e.g., 556.Xr tcp 4 557and 558.Xr udp 4 ) 559except for some ICMPv6 messages. 560The ICMPv6 messages not passed to raw sockets include echo, timestamp, 561and address mask requests. 562If 563.Ar proto 564is non-zero, only packets with this protocol will be passed to the 565socket. 566.Pp 567IPv6 fragments are also not passed to application sockets until 568they have been reassembled. 569If reception of all packets is desired, link-level access (such as 570.Xr bpf 4 ) 571must be used instead. 572.Pp 573Outgoing packets automatically have an IPv6 header prepended to them 574(based on the destination address and the protocol number the socket 575was created with). 576Incoming packets are received by an application without the IPv6 header 577or any extension headers. 578.Pp 579Outgoing packets will be fragmented automatically by the kernel if they 580are too large. 581Incoming packets will be reassembled before being sent to the raw socket, 582so packet fragments or fragment headers will never be seen on a raw socket. 583.Sh EXAMPLES 584The following determines the hop limit on the next packet received: 585.Bd -literal 586struct iovec iov[2]; 587u_char buf[BUFSIZ]; 588struct cmsghdr *cm; 589struct msghdr m; 590int found, optval; 591u_char data[2048]; 592 593/* Create socket. */ 594 595(void)memset(&m, 0, sizeof(m)); 596(void)memset(&iov, 0, sizeof(iov)); 597 598iov[0].iov_base = data; /* buffer for packet payload */ 599iov[0].iov_len = sizeof(data); /* expected packet length */ 600 601m.msg_name = &from; /* sockaddr_in6 of peer */ 602m.msg_namelen = sizeof(from); 603m.msg_iov = iov; 604m.msg_iovlen = 1; 605m.msg_control = buf; /* buffer for control messages */ 606m.msg_controllen = sizeof(buf); 607 608/* 609 * Enable the hop limit value from received packets to be 610 * returned along with the payload. 611 */ 612optval = 1; 613if (setsockopt(s, IPPROTO_IPV6, IPV6_HOPLIMIT, &optval, 614 sizeof(optval)) == -1) 615 err(1, "setsockopt"); 616 617found = 0; 618while (!found) { 619 if (recvmsg(s, &m, 0) == -1) 620 err(1, "recvmsg"); 621 for (cm = CMSG_FIRSTHDR(&m); cm != NULL; 622 cm = CMSG_NXTHDR(&m, cm)) { 623 if (cm->cmsg_level == IPPROTO_IPV6 && 624 cm->cmsg_type == IPV6_HOPLIMIT && 625 cm->cmsg_len == CMSG_LEN(sizeof(int))) { 626 found = 1; 627 (void)printf("hop limit: %d\en", 628 *(int *)CMSG_DATA(cm)); 629 break; 630 } 631 } 632} 633.Ed 634.Sh DIAGNOSTICS 635A socket operation may fail with one of the following errors returned: 636.Bl -tag -width EADDRNOTAVAILxx 637.It Bq Er EISCONN 638when trying to establish a connection on a socket which 639already has one or when trying to send a datagram with the destination 640address specified and the socket is already connected. 641.It Bq Er ENOTCONN 642when trying to send a datagram, but 643no destination address is specified, and the socket hasn't been 644connected. 645.It Bq Er ENOBUFS 646when the system runs out of memory for 647an internal data structure. 648.It Bq Er EADDRNOTAVAIL 649when an attempt is made to create a 650socket with a network address for which no network interface 651exists. 652.It Bq Er EACCES 653when an attempt is made to create 654a raw IPv6 socket by a non-privileged process. 655.El 656.Pp 657The following errors specific to IPv6 may occur when setting or getting 658header options: 659.Bl -tag -width EADDRNOTAVAILxx 660.It Bq Er EINVAL 661An unknown socket option name was given. 662.It Bq Er EINVAL 663An ancillary data object was improperly formed. 664.El 665.Sh SEE ALSO 666.Xr getsockopt 2 , 667.Xr recv 2 , 668.Xr send 2 , 669.Xr setsockopt 2 , 670.Xr socket 2 , 671.Xr CMSG_DATA 3 , 672.\" .Xr inet6_option_space 3 , 673.\" .Xr inet6_rthdr_space 3 , 674.Xr if_nametoindex 3 , 675.Xr bpf 4 , 676.Xr icmp6 4 , 677.Xr inet6 4 , 678.Xr netintro 4 , 679.Xr tcp 4 , 680.Xr udp 4 681.Rs 682.%A W. Stevens 683.%A M. Thomas 684.%T Advanced Sockets API for IPv6 685.%R RFC 2292 686.%D February 1998 687.Re 688.Rs 689.%A S. Deering 690.%A R. Hinden 691.%T Internet Protocol, Version 6 (IPv6) Specification 692.%R RFC 2460 693.%D December 1998 694.Re 695.Rs 696.%A R. Gilligan 697.%A S. Thomson 698.%A J. Bound 699.%A W. Stevens 700.%T Basic Socket Interface Extensions for IPv6 701.%R RFC 2553 702.%D March 1999 703.Re 704.Rs 705.%A W. Stevens 706.%A B. Fenner 707.%A A. Rudoff 708.%T UNIX Network Programming, third edition 709.Re 710.Sh STANDARDS 711Most of the socket options are defined in RFC 2292 or RFC 2553. 712The 713.Dv IPV6_V6ONLY 714socket option is defined in RFC 3542. 715The 716.Dv IPV6_PORTRANGE 717socket option and the conflict resolution rule are not defined in the 718RFCs and should be considered implementation dependent. 719