IPv6(7P)
ipv6 - Internet Protocol Version 6
As shipped in IRIX 6.5.19. Added in IRIX 6.5.19.
NAME ipv6 - Internet Protocol Version 6 SYNOPSIS #include <sys/socket.h> #include <netinet/in.h> s = socket(AF_INET6, SOCK_RAW, proto); DESCRIPTION IP version 6 (also known as IPv6 and IPng) is the protocol designed to eventually replace IP (also known as IPv4) as the Internet's network layer protocol. The necessity of IPv6 comes primarily from the limited address space of IPv4 in an exponentially expanding Internet, but IPv6 also supports other important functionality not present in IPv4. This version of IRIX contains support for IPv6 functionality as described by the following IETF documents: Supported RFCs: 1981 Path MTU Discovery for IP version 6 1993 Transition Mechanisms for IPv6 Hosts and Routers 2080 RIPng for IPv6 2292 Advanced Sockets API for IPv6 2373 IP Version 6 Addressing Architecture 2460 Internet Protocol, Version 6 (IPv6) Specification 2461 Neighbor Discovery for IP Version 6 (IPv6) 2462 IPv6 Stateless Address Autoconfiguration 2463 Internet Control Message Protocol (ICMPv6) 2464 Transmission of IPv6 Packets over Ethernet Network 2472 IP Version 6 over PPP 2553 Basic Socket Interface Extensions for IPv6 2675 IPv6 Jumbograms (Note: some of these RFCs are under revision and may be assigned new numbers. This man page will refer to RFCs by their titles) IRIX supports IPv6 using the Berkeley sockets system calls. The differences between using sockets for IPv4 networking and IPv6 networking are minimal. A new address family type, AF_INET6 is defined, so an IPv6 socket would be created using: s = socket(AF_INET6, type, protocol); The UDP and TCP transport layer protocols work in exactly the same way over IPv6 as they do over IPv4. A new socket address structure, sockaddr_in6 is defined to represent an IPv6 address. It is important to note that since IPv6 addresses are 128 bits long, the generic sockaddr structure cannot be used to reserve memory for an IPv6 address, since it is too small. For this a new structure is defined, sockaddr_storage, which, if used, ensures correct 64-bit alignment of IPv6 addresses. For full details of the IPv6 API, the reader is referred to the "Basic Socket Interface Extensions for IPv6" and "Advanced Sockets API for IPv6" RFCs to which this implementation conforms. SOCKET OPTIONS The following socket options are supported for IPv6: Options for use with [gs]etsockopt IPV6_MULTICAST_IF set/get IPv6 multicast interface IPV6_MULTICAST_HOPS set/get IPv6 multicast hoplimit IPV6_MULTICAST_LOOP set/get IPv6 multicast loopback IPV6_JOIN_GROUP (1) add an IPv6 group membership IPV6_LEAVE_GROUP (1) drop an IPv6 group membership IPV6_CHECKSUM calculate and insert checksum ICMP6_FILTER icmp6 packet filtering IPV6_UNICAST_HOPS unicast hop limit IPV6_USE_MIN_MTU send packets at the minimum MTU (1) these options can only be used with setsockopt() Options to control the reception of ancillary data IPV6_RECVPKTINFO receive packet information IPV6_RECVHOPLIMIT hop limit received per packet IPV6_RECVRTHDR routing header received IPV6_RECVHOPOPTS hop-by-hop options received IPV6_RECVDSTOPTS destination options received IPV6_RECVTCLASS traffic class received IPV6_RECVPATHMTU receive path MTU information Options which be used with ancillary data or socket options IPV6_PKTINFO set packet info (interface selection) IPV6_HOPLIMIT (2) IPv6 hop limit IPV6_NEXTHOP next hop address IPV6_RTHDR routing header IPV6_HOPOPTS hop by hop options IPV6_DSTOPTS destination options IPV6_RTHDRDSTOPTS per-route hop destination options IPV6_TCLASS traffic class (2) these options can only be used in ancillary data IPV6_V6ONLY only bind INET6 IPV6_DONTFRAG disable IPv6 fragmentation Many of these options are described in detail by the RFC "Advanced Sockets API for IPv6". That document should be consulted for additional background information. IPV6_MULTICAST_IF, IPV6_MULTICAST_HOPS and IPV6_MULTICAST_LOOP control IPv6 multicast. IPV6_MULTICAST_IF takes an integer argument which is the index of the interface to be used to send outgoing multicast packets. IPV6_MULTICAST_HOPS is the equivalent of IPV6_UNICAST_HOPS for multicast and also takes an integer argument. IPV6_MULTICAST_LOOP switches local loopback of outgoing multicast packets. If its integer argument is set to 1 (which is the default), then copies are made of all outgoing multicast packets on that socket and sent back into the IPv6 layer. IPV6_JOIN_GROUP and IPV6_LEAVE_GROUP are used to leave and join multicast groups and take an ipv6_mreq structure as an argument. The ipv6_mreq structure is shown below: struct ipv6_mreq { struct in6_addr ipv6mr_multiaddr; /* IPv6 multicast addr */ unsigned int ipv6mr_interface; /* interface index */ }; The ipv6mr_interface may be given a value of zero, which indicates that the kernel should choose the interface to be used. Otherwise it is the index of the interface to be used to send and receive multicast packets on that socket. The IPV6_CHECKSUM checksum socket option is used when a raw socket is opened and the protocol is something other than IPPROTO_ICMPV6. ICMPv6 checksums are mandatory and automatically calculated, even when using raw sockets. The application should set this to have the kernel compute the checksum and also verify the received checksum on input. Checksums will incorporate the necessary IPv6 addresses in the pseudo header. ICMP6_FILTER sets or gets the icmpv6 filtering options. The ICMP6_FILTER series of macros defined in netinet/icmp6.h and the "Advanced Sockets API for IPv6" RFC is available for manipulating the filter masks. void ICMP6_FILTER_SETBLOCK(int, struct icmp6_filter *); void ICMP6_FILTER_SETBLOCKALL(struct icmp6_filter *); void ICMP6_FILTER_SETPASS(int, struct icmp6_filter *); void ICMP6_FILTER_SETPASSALL(struct icmp6_filter *); int ICMP6_FILTER_WILLBLOCK(int, const struct icmp6_filter *); int ICMP6_FILTER_WILLPASS(int, const struct icmp6_filter *); IPV6_UNICAST_HOPS sets the value initialized in the hop-limit field of outgoing IPv6 packets. The following example sets the hop-limit of all packets sent on the socket referenced by s to 10: int hoplimit = 10; if (setsockopt(s, IPPROTO_IPV6, IPV6_UNICAST_HOPS, (char *) &hoplimit, sizeof(hoplimit)) == -1) perror("setsockopt IPV6_UNICAST_HOPS"); Applications can use IPV6_USE_MIN_MTU to control the behavior of path MTU discovery. There are three types of integer arguments: -1: perform path MTU discovery for unicast destinations but do not perform it for multicast destinations. Packets to multicast destinations are therefore sent with the minimum MTU. 0: always perform path MTU discovery. 1: always disable path MTU discovery and send packets at the minimum MTU. where the default is -1. IPV6_RECVPKTINFO, IPV6_RECVHOPLIMIT, IPV6_RECVRTHDR, IPV6_RECVHOPOPTS, IPV6_RECVDSTOPTS, IPV6_RECVPATHMTU and IPV6_RECVTCLASS are for requesting reception of ancillary data objects associated with incoming packets from the kernel. The ancillary object types are described in the "Advanced Sockets API for IPv6" RFC. When these flags are set to 1, the stack will send the relevant information to the application via the cmsghdr mechanism. int on = 1; setsockopt(s, IPPROTO_IPV6, IPV6_RECVPKTINFO, (char *)&on, sizeof(on)); Control of IPv6 and Extension Headers To control IPv6 header and extension header content when sending, the following socket option types can be used with setsockopt and with ancillary data. A description of ancillary data follows this section. opt level/ optname/ optval/ cmsg_level cmsg_type cmsg_data[] ------------ ------------ ------------------------ IPPROTO_IPV6 IPV6_PKTINFO in6_pktinfo structure IPPROTO_IPV6 IPV6_HOPLIMIT (1) int IPPROTO_IPV6 IPV6_NEXTHOP socket address structure IPPROTO_IPV6 IPV6_RTHDR ip6_rthdr structure IPPROTO_IPV6 IPV6_HOPOPTS ip6_hbh structure IPPROTO_IPV6 IPV6_DSTOPTS ip6_dest structure IPPROTO_IPV6 IPV6_RTHDRDSTOPTS ip6_dest structure IPPROTO_IPV6 IPV6_TCLASS int (1) for use as ancillary data items only IPV6_PKTINFO can be used to specify the outgoing interface using the in6_pktinfo structure's ipi6_addr and ipi6_ifindex fields. An application can clear a "sticky" IPV6_PKTINFO option by doing a setsockopt() call with ipi6_addr set to in6addr_any and ipi6_ifindex set to zero. struct in6_pktinfo { struct in6_addr ipi6_addr; /* src/dst IPv6 address */ unsigned int ipi6_ifindex; /* send/recv interface index */ }; IPV6_HOPLIMIT is ancillary only data and is used to set the IPv6 hop limit. The first byte of cmsg_data[] should be the first byte of the integer hop limit. IPV6_NEXTHOP ancillary data specifies the next hop for the datagram as a socket address structure. The next hop address must be an IPv6 address of a neighbor of the sending host. IPV6_RTHDR specifies a Routing header with the contents of the cmsg_type member containing the implementation dependent data. The Advanced Sockets API defines a set of universal functions which should be used to manipulate the routing structure. See the RFC for more details on usage. inet6_rth_space() return size required to hold header inet6_rth_init() buffer initialization inet6_rth_add() add an new address inet6_rth_reverse() create new header using reverse path inet6_rth_segments() returns number of addresses contained in header inet6_rth_getaddr() return pointer to address specified by index IPV6_HOPOPTS is used to create a single or variable number of hop-by-hop options. A set of utility functions is available to build and examine hop-by-hop options headers. inet6_opt_init() initialize buffer data for options header inet6_opt_append() add one TLV option to the options header inet6_opt_finish() finish adding TLV options to the options header inet6_opt_set_val() add one component of the option content to the option Three functions deal with a returned options header: inet6_opt_next() extract the next option from the options header inet6_opt_find() extract an option of a specified type from the header inet6_opt_get_val() retrieve one component of the option content To send an Destinations options header use the IPV6_DSTOPTS or IPV6_RTHDRDSTOPTS options. The header specification can be done with either ancillary data in a call to sendmsg() or using setsockopt(). To precede the routing header, use IPV6_RTHDRDSTOPTS. IPV6_DSTOPTS places the header after the routing header, if it exists. IPV6_TCLASS specifes the traffic class of the packets. Specify the control information as ancillary data using sendmsg() or setsockopt(). Using setsockopt to specify the options will affect all outgoing packets on the socket until changed with new setsockopt call or overridden with new ancillary data. In this case, they are treated as "sticky" options. When using ancillary data to specify the options, it applies to that particular outgoing datagram. Using getsockopt with the flags above will retreive the current setting. In the case of IPV6_NEXTHOP, only setsockopt() can be used. IPV6_V6ONLY controls behavior of AF_INET6 wildcard listening socket. The following example sets the option to 1: int on = 1; setsockopt(s, IPPROTO_IPV6, IPV6_V6ONLY, &on, sizeof(on)); If set to 1, AF_INET6 wildcard listening socket will accept IPv6 traffic only. If set to 0, it will accept IPv4 traffic as well, as if it were from an IPv4 mapped address like ::ffff:10.1.1.1. Note that if you set it to 0, IPv4 access control gets much more complicated. For example, even if you have no listening AF_INET listening socket on port X, you will end up accepting IPv4 traffic by AF_INET6 listening socket on the same port. The option affects TCP and UDP sockets only. IPV6_DONTFRAG causes the kernel to not fragment the ipv6 packet. The caller must assure that total size of the packet fits within IPv6 packet size contraints, else the call will return with an error of EMSGSIZE. TCP sticky options For TCP connections it is not usual to use the sendmsg system call to send data. If the application needs to set any of the above mentioned IPv6 options for all packets of a TCP connection, it can use setsockopt to specify the desired options. For example, setsockopt(fd, IPPROTO_IPV6, IPV6_HOPLIMIT, &buf, len); where buf is a byte array containing one or more ancillary data objects (as described below) and len is the total length of all the objects passed in. When the TCP protocol sends a packet, it behaves as if the user had specifed the options for that packet by passing the ancillary data objects to sendmsg(). Ancillary data objects Ancillary data objects are passed to sendmsg() and and received from recvmsg() in a cmsghdr structure as header, as shown below: struct cmsghdr { size_t cmsg_len; /* #bytes, including this header */ int cmsg_level; /* originating protocol */ int cmsg_type; /* protocol-specific type */ /* followed by u_char cmsg_data[]; */ }; Application source should include <sys/socket.h> to use this structure. cmsg_len is the total length of the object, including the cmsghdr header, but excluding any bytes required for alignment padding at the end of the data object (see below). cmsg_level is the level of the ancillary data object, which is IPPROTO_IPV6 for IPv6 and cmsg_type is the type of message being passed, as described above. This header is followed by the ancillary data object itself, as described above. When more than one message is passed to a function, it may be necessary for padding bytes to be inserted between the end of one ancillary data object and the start of the next. Since the padding requirements are architecture-dependent, several macros are provided for manipulating these objects: CMSG_DATA() , CMSG_NXTHDR() , and CMSG_FIRSTHDR() These are described in the "Advanced Sockets API for IPv6" RFC SEE ALSO getsockopt(2), setsockopt(2), send(2), recv(2), recvmsg(2), intro(3), icmp(7P), inet(7F), route(7F), route6d(7), netstat(1), ifconfig(1), getaddrinfo(3C), IRIX Network Programming Guide "Basic Socket Interface Extensions for IPv6" RFC "Advanced Sockets API for IPv6" RFC