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If applicable, add the following below this CDDL HEADER, with the fields enclosed by brackets "[]" replaced with your own identifying information: Portions Copyright [yyyy] [name of copyright owner] .TH inet6 7P "3 Oct 2002" "SunOS 5.11" "Protocols" .SH NAME inet6 \- Internet protocol family for Internet Protocol version 6 .SH SYNOPSIS .LP .nf \fB#include #include \fR .fi .SH DESCRIPTION .sp .LP The \fBinet6\fR protocol family implements a collection of protocols that are centered around the Internet Protocol version 6 (\fBIPv6\fR) and share a common address format. The \fBinet6\fR protocol family can be accessed using the socket interface, where it supports the \fBSOCK_STREAM\fR, \fBSOCK_DGRAM\fR, and \fBSOCK_RAW\fR socket types, or the Transport Level Interface (\fBTLI\fR), where it supports the connectionless (\fBT_CLTS\fR) and connection oriented (\fBT_COTS_ORD\fR) service types. .SH PROTOCOLS .sp .LP The Internet protocol family for \fBIPv6\fR included the Internet Protocol Version 6 (\fBIPv6\fR), the Neighbor Discovery Protocol (\fBNDP\fR), the Internet Control Message Protocol (\fBICMPv6\fR), the Transmission Control Protocol (\fBTCP\fR), and the User Datagram Protocol (\fBUDP\fR). .sp .LP \fBTCP\fR supports the socket interface's \fBSOCK_STREAM\fR abstraction and \fBTLI\fR's \fBT_COTS_ORD\fR service type. \fBUDP\fR supports the \fBSOCK_DGRAM\fR socket abstraction and the \fBTLI\fR \fBT_CLTS\fR service type. See \fBtcp\fR(7P) and \fBudp\fR(7P). A direct interface to \fBIPv6\fR is available using the socket interface. See \fBip6\fR(7P). \fBICMPv6\fR is used by the kernel to handle and report errors in protocol processing. It is also accessible to user programs. See \fBicmp6\fR(7P). \fBNDP\fR is used to translate 128-bit \fBIPv6\fR addresses into 48-bit Ethernet addresses. .sp .LP \fBIPv6\fR addresses come in three types: unicast, anycast, and multicast. A unicast address is an identifier for a single network interface. An anycast address is an identifier for a set of interfaces; a packet sent to an anycast address is delivered to the "nearest" interface identified by that address, pursuant to the routing protocol's measure of distance. A multicast address is an identifier for a set of interfaces; a packet sent to a multicast address is delivered to all interfaces identified by that address. There are no broadcast addresses as such in \fBIPv6\fR; their functionality is superseded by multicast addresses. .sp .LP For \fBIPv6\fR addresses, there are three scopes within which unicast addresses are guaranteed to be unique. The scope is indicated by the address prefix. The three varieties are link-local (the address is unique on that physical link), site-local (the address is unique within that site), and global (the address is globally unique). .sp .LP The three highest order bits for global unicast addresses are set to \fB001\fR. The ten highest order bits for site-local addresses are set to \fB1111 1110 11\fR. The ten highest order bits for link-local addresses are set to \fB1111 1110 11\fR. For multicast addresses, the eight highest order bits are set to \fB1111 1111\fR. Anycast addresses have the same format as unicast addresses. .sp .LP \fBIPv6\fR addresses do not follow the concept of "address class" seen in \fBIP\fR. .sp .LP A global unicast address is divided into the following segments: .RS +4 .TP .ie t \(bu .el o The first three bits are the Format Prefix identifying a unicast address. .RE .RS +4 .TP .ie t \(bu .el o The next 13 bits are the Top-Level Aggregation (\fBTLA\fR) identifier. For example, the identifier could specify the \fBISP\fR. .RE .RS +4 .TP .ie t \(bu .el o The next eight bits are reserved for future use. .RE .RS +4 .TP .ie t \(bu .el o The next 24 bits are the Next-Level Aggregation (\fBNLA\fR) identifier. .RE .RS +4 .TP .ie t \(bu .el o The next 16 bits are the Site-Level Aggregation (\fBSLA\fR) identifier. .RE .RS +4 .TP .ie t \(bu .el o The last 64 bits are the interface \fBID\fR. This will most often be the hardware address of the link in \fBIEEE EUI-64\fR format. .RE .sp .LP Link-local unicast addresses are divided in this manner: .RS +4 .TP .ie t \(bu .el o The first ten bits are the Format Prefix identifying a link-local address. .RE .RS +4 .TP .ie t \(bu .el o The next 54 bits are zero. .RE .RS +4 .TP .ie t \(bu .el o The last 64 bits are the interface \fBID\fR. This will most often be the hardware address of the link in \fBIEEE EUI-64\fR format. .RE .sp .LP Site-local unicast addresses are divided in this manner: .RS +4 .TP .ie t \(bu .el o The first ten bits are the Format Prefix identifying a site-local address. .RE .RS +4 .TP .ie t \(bu .el o The next 38 bits are zero. .RE .RS +4 .TP .ie t \(bu .el o The next 16 bits are the subnet \fBID\fR. .RE .RS +4 .TP .ie t \(bu .el o The last 64 bits are the interface \fBID\fR. This will most often be the hardware address of the link in \fBIEEE EUI-64\fR format. .RE .SH ADDRESSING .sp .LP \fBIPv6\fR addresses are sixteen byte quantities, stored in network byte order. The socket \fBAPI\fR uses the \fBsockaddr_in6\fR structure when passing \fBIPv6\fR addresses between an application and the kernel. The \fBsockaddr_in6\fR structure has the following members: .sp .in +2 .nf sa_familty_t sin6_family; in_port_t sin6_port; uint32_t sin6_flowinfo; struct in6_addr sin6_addr; uint32_t sin6_scope_id; uint32_t __sin6_src_id; .fi .in -2 .sp .LP Library routines are provided to manipulate structures of this form. See \fBinet\fR(3SOCKET). .sp .LP The \fBsin6_addr\fR field of the \fBsockaddr_in6\fR structure specifies a local or remote \fBIPv6\fR address. Each network interface has one or more \fBIPv6\fR addresses configured, that is, a link-local address, a site-local address, and one or more global unicast \fBIPv6\fR addresses. The special value of all zeros may be used on this field to test for "wildcard" matching. Given in a \fBbind\fR(3SOCKET) call, this value leaves the local \fBIPv6\fR address of the socket unspecified, so that the socket will receive connections or messages directed at any of the valid \fBIPv6\fR addresses of the system. This can prove useful when a process neither knows nor cares what the local \fBIPv6\fR address is, or when a process wishes to receive requests using all of its network interfaces. .sp .LP The \fBsockaddr_in6\fR structure given in the \fBbind()\fR call must specify an \fIin6_addr\fR value of either all zeros or one of the system's valid \fBIPv6\fR addresses. Requests to bind any other address will elicit the error \fBEADDRNOTAVAI\fR. When a \fBconnect\fR(3SOCKET) call is made for a socket that has a wildcard local address, the system sets the \fBsin6_addr\fR field of the socket to the \fBIPv6\fR address of the network interface through which the packets for that connection are routed. .sp .LP The \fBsin6_port\fR field of the \fBsockaddr_in6\fR structure specifies a port number used by \fBTCP\fR or \fBUDP\fR. The local port address specified in a \fBbind()\fR call is restricted to be greater than \fBIPPORT_RESERVED\fR (defined in <\fBnetinet/in.h\fR>) unless the creating process is running as the super-user, providing a space of protected port numbers. In addition, the local port address cannot be in use by any socket of the same address family and type. Requests to bind sockets to port numbers being used by other sockets return the error \fBEADDRINUSE\fR. If the local port address is specified as \fB0\fR, the system picks a unique port address greater than \fBIPPORT_RESERVED\fR. A unique local port address is also selected when a socket which is not bound is used in a \fBconnect\fR(3SOCKET) or \fBsendto()\fR call. See \fBsend\fR(3SOCKET). This allows programs that do not care which local port number is used to set up \fBTCP\fR connections by simply calling \fBsocket\fR(3SOCKET) and then \fBconnect\fR(3SOCKET), and then sending \fBUDP\fR datagrams with a \fBsocket()\fR call followed by a \fBsendto()\fR call. .sp .LP Although this implementation restricts sockets to unique local port numbers, \fBTCP\fR allows multiple simultaneous connections involving the same local port number so long as the remote \fBIPv6\fR addresses or port numbers are different for each connection. Programs may explicitly override the socket restriction by setting the \fBSO_REUSEADDR\fR socket option with \fBsetsockopt()\fR. See \fBgetsockopt\fR(3SOCKET). .sp .LP In addition, the same port may be bound by two separate sockets if one is an \fBIP\fR socket and the other an \fBIPv6\fR socket. .sp .LP \fBTLI\fR applies somewhat different semantics to the binding of local port numbers. These semantics apply when Internet family protocols are used using the \fBTLI\fR. .SH SOURCE ADDRESS SELECTION .sp .LP IPv6 source address selection is done on a per destination basis, and utilizes a list of rules from which the best source address is selected from candidate addresses. The candidate set comprises a set of local addresses assigned on the system which are up and not anycast. If just one candidate exists in the candidate set, it is selected. .sp .LP Conceptually, each selection rule prefers one address over another, or determines their equivalence. If a rule produces a tie, a subsequent rule is used to break the tie. .sp .LP The sense of some rules may be reversed on a per-socket basis using the IPV6_SRC_PREFERENCES socket option (see \fBip6\fR(7P)). The flag values for this option are defined in <\fBnetinet/in.h\fR> and are referenced in the description of the appropriate rules below. .sp .LP As the selection rules indicate, the candidate addresses are SA and SB and the destination is D. .sp .ne 2 .mk .na \fBPrefer the same address\fR .ad .RS 30n .rt If SA == D, prefer SA. If SB == D, prefer SB. .RE .sp .ne 2 .mk .na \fBPrefer appropriate scope\fR .ad .RS 30n .rt Here, Scope(X) is the scope of X according to the IPv6 Addressing Architecture. .sp If Scope(SA) < Scope(SB): If Scope(SA) < Scope(D), then prefer SB and otherwise prefer SA. .sp If Scope(SB) < Scope(SA): If Scope(SB) < Scope(D), then prefer SA and otherwise prefer SB. .RE .sp .ne 2 .mk .na \fBAvoid deprecated addresses\fR .ad .RS 30n .rt If one of the addresses is deprecated (IFF_DEPRECATED) and the other is not, prefer the one that isn't deprecated. .RE .sp .ne 2 .mk .na \fBPrefer preferred addresses\fR .ad .RS 30n .rt If one of the addresses is preferred (IFF_PREFERRED) and the other is not, prefer the one that is preferred. .RE .sp .ne 2 .mk .na \fBPrefer outgoing interface\fR .ad .RS 30n .rt If one of the addresses is assigned to the interface that will be used to send packets to D and the other is not, then prefer the former. .RE .sp .ne 2 .mk .na \fBPrefer matching label\fR .ad .RS 30n .rt This rule uses labels which are obtained through the IPv6 default address selection policy table. See \fBipaddrsel\fR(1M) for a description of the default contents of the table and how the table is configured. .sp If Label(SA) == Label(D) and Label(SB) != Label(D), then prefer SA. .sp If Label(SB) == Label(D) and Label(SA) != Label(D), then prefer SB. .RE .sp .ne 2 .mk .na \fBPrefer public addresses\fR .ad .RS 30n .rt This rule prefers public addresses over temporary addresses, as defined in \fIRFC 3041\fR. Temporary addresses are disabled by default and may be enabled by appropriate settings in \fBndpd.conf\fR(4). .sp The sense of this rule may be set on a per-socket basis using the IPV6_SRC_PREFERENCES socket option. Passing the flag IPV6_PREFER_SRC_TMP or IPV6_PREFER_SRC_PUBLIC will cause temporary or public addresses to be preferred, respectively, for that particular socket. See \fBip6\fR(7P) for more information about IPv6 socket options. .RE .sp .ne 2 .mk .na \fBUse longest matching prefix.\fR .ad .sp .6 .RS 4n This rule prefers the source address that has the longer matching prefix with the destination. Because this is the last rule and because both source addresses could have equal matching prefixes, this rule does an \fBxor\fR of each source address with the destination, then selects the source address with the smaller \fBxor\fR value in order to break any potential tie. .sp If SA ^ D < SB ^ D, then prefer SA. .sp If SB ^ D < SA ^ D, then prefer SB. .RE .sp .LP Applications can override this algorithm by calling \fBbind\fR(3SOCKET) and specifying an address. .SH SEE ALSO .sp .LP \fBioctl\fR(2), \fBbind\fR(3SOCKET), \fBconnect\fR(3SOCKET), \fBgetipnodebyaddr\fR(3SOCKET), \fBgetipnodebyname\fR(3SOCKET),\fBgetprotobyname\fR(3SOCKET), \fBgetservbyname\fR(3SOCKET), \fBgetsockopt\fR(3SOCKET), \fBinet\fR(3SOCKET), \fBsend\fR(3SOCKET), \fBicmp6\fR(7P), \fBip6\fR(7P), \fBtcp\fR(7P), \fBudp\fR(7P) .sp .LP Conta, A. and Deering, S., \fIInternet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification\fR, RFC 1885, December 1995. .sp .LP Deering, S. and Hinden, B., \fIInternet Protocol, Version 6 (IPv6) Specification\fR, RFC 1883, December 1995. .sp .LP Hinden, B. and Deering, S., \fIIP Version 6 Addressing Architecture\fR, RFC 1884, December 1995. .sp .LP Draves, R., \fIRFC 3484, Default Address Selection for IPv6.\fR The Internet Society. February 2003. .sp .LP Narten, T., and Draves, R. \fIRFC 3041, Privacy Extensions for Stateless Address Autoconfiguration in IPv6.\fR The Internet Society. January 2001. .SH NOTES .sp .LP The \fBIPv6\fR support is subject to change as the Internet protocols develop. Users should not depend on details of the current implementation, but rather the services exported.