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IPV6 !!!IPV6 NAME SYNOPSIS DESCRIPTION ADDRESS FORMAT SOCKET OPTIONS VERSIONS PORTING NOTES BUGS SEE ALSO ---- !!NAME ipv6, PF_INET6 - Linux IPv6 protocol implementation !!SYNOPSIS __#include __ #include __ ''tcp6_socket'' __= socket(PF_INET6, SOCK_STREAM, 0);__'' raw6_socket'' __= socket(PF_INET6, SOCK_RAW,__ ''protocol''__);__'' udp6_socket'' __= socket(PF_INET6, SOCK_DGRAM,__ ''protocol''__);__ !!DESCRIPTION Linux 2.2 optionally implements the Internet Protocol, version 6. This man page contains a description of the IPv6 basic API as implemented by the Linux kernel and glibc 2.1. The interface is based on the BSD sockets interface; see socket(7). The IPv6 API aims to be mostly compatible with the ip(7) v4 API. Only differences are described in this man page. To bind an ''AF_INET6'' socket to any process the local address should be copied from the __in6addr_any__ variable which has ''in6_addr'' type. In static initializations __IN6ADDR_ANY_INIT__ may also be used, which expands to a constant expression. Both of them are in network order. The IPv6 loopback address (::1) is available in the global __in6addr_loopback__ variable. For initializations __IN6ADDR_LOOPBACK_INIT__ should be used. IPv4 connections can be handled with the v6 API by using the v4-mapped-on-v6 address type; thus a program only needs only to support this API type to support both protocols. This is handled transparently by the address handling functions in libc. IPv4 and IPv6 share the local port space. When you get an IPv4 connection or packet to a IPv6 socket its source address will be mapped to v6 and it'll be mapped to v6. !!ADDRESS FORMAT struct sockaddr_in6 { u_int16_t sin6_family;/* AF_INET6 */ u_int16_t sin6_port;/* port number */ u_int32_t sin6_flowinfo;/* IPv6 flow information */ struct in6_addr sin6_addr;/* IPv6 address */ u_int32_t sin6_scope_id; /* Scope id (new in 2.4) */ }; struct in6_addr { unsigned char s6_addr[[16];/* IPv6 address */ }; __sin6_family__ is always set to __AF_INET6; sin6_port__ is the protocol port (see __sin_port__ in ip(7)); __sin6_flowinfo__ is the IPv6 flow identifier; __sin6_addr__ is the 128bit IPv6 address. __sin6_scope_id__ is an id of depending of on the scope of the address. It is new in Linux 2.4. Linux only supports it for link scope addresses, in that case ''sin6_scope_id'' contains the interface index (see netdevice(7)) IPv6 supports several address types: unicast to address a single host, multicast to address a group of hosts, anycast to address the nearest member of a group of hosts (not implemented in Linux), IPv4-on-IPv6 to address a IPv4 host, and other reserved address types. The address notation for IPv6 is a group of 16 2 digit hexadecimal numbers, separated with a ':'. '::' stands for a string of 0 bits. Special addresses are ::1 for loopback and FFFF:: The port space of IPv6 is shared with IPv4. !!SOCKET OPTIONS IPv6 supports some protocol specific socket options that can be set with setsockopt(2) and read with getsockopt(2). The socket option level for IPv6 is __IPPROTO_IPV6__. A boolean integer flag is zero when it is false, otherwise true. __IPV6_UNICAST_HOPS__ Set the unicast hop limit for the socket. Argument is an pointer to an integer. -1 in the value means use the route default, otherwise it should be between 0 and 255. __IPV6_MULTICAST_HOPS__ Set the multicast hop limit for the socket. Argument is a pointer to an integer. -1 in the value means use the route default, otherwise it should be between 0 and 255. __IPV6_MULTICAST_IF__ Set the device for outgoing multicast packets on the socket. This is only allowed for ''SOCK_DGRAM'' and ''SOCK_RAW'' socket. The argument is an pointer to an interface index (see netdevice(7)) in an integer. __IPV6_ADDRFORM__ Turn an ''AF_INET6'' socket into a socket of a different address family. Only ''AF_INET'' is currently supported for that. It is only allowed for IPv6 sockets that are connected and bound to a v4-mapped-on-v6 address. The argument is a pointer to a integer containing __AF_INET.__ This is useful to pass v4-mapped sockets as filedescriptors to programs that don't know how to deal with the IPv6 API. __IPV6_PKTINFO__ Set delivery of the __IPV6_PKTINFO__ control message on incoming datagrams. Only allowed for __SOCK_DGRAM__ or __SOCK_RAW__ sockets. Argument is a pointer to a boolean value in an integer. __IPV6_RTHDR, IPV6_AUTHHDR, IPV6_DSTOPS, IPV6_HOPOPTS, IPV6_FLOWINFO, IPV6_HOPLIMIT__ Set delivery of control messages for incoming data- grams containing extension headers from the re- ceived packet. ''IPV6_RTHDR'' delivers the routing header, ''IPV6_AUTHHDR'' delivers the authentication header, ''IPV6_DSTOPTS'' delivers the destination op- tions, ''IPV6_HOPOPTS'' delivers the hop options, ''IPV6_FLOWINFO'' delivers an integer containing the flow id, ''IPV6_HOPLIMIT'' delivers an integer contain- ing the hop count of the packet. The control mes- sages have the same type as the socket option. All these header options can also be set for outgoing packets by putting the appropriate control message into the control buffer of sendmsg(2). Only al- lowed for __SOCK_DGRAM__ or __SOCK_RAW__ sockets. Argument is a pointer to a boolean value. __IPV6_MULTICAST_LOOP__ Control whether the socket sees multicast packets that is has send itself. Argument is a pointer to boolean. __IPV6_ADD_MEMBERSHIP, IPV6_DROP_MEMBERSHIP__ Control membership in multicast groups. Argument is a pointer to a __struct ipv6_mreq__ structure. __IPV6_MTU__ Set the MTU to be used for the socket. The MTU is limited by the device MTU or the path mtu when path mtu discovery is enabled. Argument is a pointer to integer. __IPV6_MTU_DISCOVER__ Control path mtu discovery on the socket. See ''IP_MTU_DISCOVER'' in ip(7) for details. __IPV6_RECVERR__ Control receiving of asynchronous error options. See ''IP_RECVERR'' in ip(7) for details. Argument is a pointer to boolean. __IPV6_ROUTER_ALERT__ Pass all forwarded packets containing an router alert option to this socket. Only allowed for datagram sockets and for root. Argument is a point- er to boolean. !!VERSIONS The older ''libinet6'' libc5 based IPv6 API implementation for Linux is not described here and may vary in details. Linux 2.4 will break binary compatibility for the sockad- dr_in6 for 64bit hosts by changing the alignment of ''in6_addr'' and adding an additional ''sin6_scope_id'' field. The kernel interfaces stay compatible, but a program including sockaddr_in6 or in6_addr into other structures may not be. This is not a problem for 32bit hosts like i386. The __sin6_flowinfo__ field is new in Linux 2.4. It is trans- parently passed/read by the kernel when the passed address length contains it. Some programs that pass a longer ad- dress buffer and then check the outgoing address length may break. !!PORTING NOTES The __sockaddr_in6__ structure is bigger than the generic __sockaddr.__ Programs that assume that all address types can be stored safely in a __struct sockaddr__ need to be changed to use __struct sockaddr_storage__ for that instead. !!BUGS The IPv6 extended API as in RFC2292 is currently only partly implemented; although the 2.2 kernel has near com- plete support for receiving options, the macros for gener- ating IPv6 options are missing in glibc 2.1. IPSec support for EH and AH headers is missing. Flow label management is not complete and not documented here. This man page is not complete. !!SEE ALSO ip(7), cmsg(3) RFC2553: IPv6 BASIC API. Linux tries to be compliant to this. RFC2460: IPv6 specification. ----
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