Manual Pages for UNIX Darwin command on man inet6

INET6(4) BSD Kernel Interfaces Manual INET6(4)

NAME

iinneett66 - Internet protocol version 6 family

SYNOPSIS

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DESCRIPTION

The iinneett66 family is an updated version of inet(4) family. While inet(4)

implements Internet Protocol version 4, iinneett66 implements Internet Proto-

col version 6. iinneett66 is a collection of protocols layered atop the Internet Protocol version 6 (IPv6) transport layer, and utilizing the IPv6 address format. The iinneett66 family provides protocol support for the SOCKSTREAM, SOCKDGRAM, and SOCKRAW socket types; the SOCKRAW interface provides access to the IPv6 protocol. AADDDDRREESSSSIINNGG

IPv6 addresses are 16 byte quantities, stored in network standard byte-

order. The include file defines this address as a dis-

criminated union.

Sockets bound to the iinneett66 family utilize the following addressing struc-

ture: struct sockaddrin6 { uint8t sin6len; uint8t sin6family; uint16t sin6port; uint32t sin6flowinfo; struct in6addr sin6addr; uint32t sin6scopeid; }; Sockets may be created with the local address ``::'' (which is equal to IPv6 address 0:0:0:0:0:0:0:0) to affect ``wildcard'' matching on incoming messages.

The IPv6 specification defines scoped addresses, like link-local or site-

local addresses. A scoped address is ambiguous to the kernel, if it is specified without a scope identifier. To manipulate scoped addresses properly from the userland, programs must use the advanced API defined in RFC2292. A compact description of the advanced API is available in ip6(4). If a scoped address is specified without an explicit scope, the kernel may raise an error. Note that scoped addresses are not for daily use at this moment, both from a specification and an implementation point of view.

The KAME implementation supports an extended numeric IPv6 address nota-

tion for link-local addresses, like ``fe80::1%de0'' to specify ``fe80::1

on de0 interface''. This notation is supported by getaddrinfo(3) and getnameinfo(3). Some of normal userland programs, such as telnet(1) or ftp(1), are able to use this notation. With special programs like ping6(8), you can specify the outgoing interface by an extra command line option to disambiguate scoped addresses.

Scoped addresses are handled specially in the kernel. In kernel struc-

tures like routing tables or interface structures, a scoped address will have its interface index embedded into the address. Therefore, the address in some kernel structures is not the same as that on the wire. The embedded index will become visible through a PFROUTE socket, kernel memory accesses via kvm(3) and on some other occasions. HOWEVER, users should never use the embedded form. For details please consult IMPLEMENTATION supplied with KAME kit. PPRROOTTOOCCOOLLSS

The iinneett66 family is comprised of the IPv6 network protocol, Internet Con-

trol Message Protocol version 6 (ICMPv6), Transmission Control Protocol (TCP), and User Datagram Protocol (UDP). TCP is used to support the SOCKSTREAM abstraction while UDP is used to support the SOCKDGRAM abstraction. Note that TCP and UDP are common to inet(4) and iinneett66. A raw interface to IPv6 is available by creating an Internet socket of type SOCKRAW. The ICMPv6 message protocol is accessible from a raw socket. MMIIBB VVaarriiaabblleess

A number of variables are implemented in the net.inet6 branch of the

sysctl(3) MIB. In addition to the variables supported by the transport protocols (for which the respective manual pages may be consulted), the following general variables are defined:

IPV6CTLFORWARDING (ip6.forwarding) Boolean: enable/disable forward-

ing of IPv6 packets. Also, identify if the node is acting as a router. Defaults to off. IPV6CTLSENDREDIRECTS (ip6.redirect) Boolean: enable/disable sending of ICMPv6 redirects in response to unforwardable IPv6 packets. This option is ignored unless the node is routing IPv6 packets, and should normally be enabled on all systems. Defaults to on. IPV6CTLDEFHLIM (ip6.hlim) Integer: default hop limit value to use for outgoing IPv6 packets. This value applies to all the transport protocols on top of IPv6. There are APIs to override the value. IPV6CTLMAXFRAGPACKETS (ip6.maxfragpackets) Integer: default maximum number of fragmented packets the node will accept. 0 means that the node will not accept

any fragmented packets. -1 means that the node

will accept as many fragmented packets as it receives. The flag is provided basically for avoiding possible DoS attacks. IPV6CTLACCEPTRTADV (ip6.acceptrtadv) Boolean: enable/disable receiving of ICMPv6 router advertisement packets, and autoconfiguration of address prefixes and default routers. The node must be a host (not a router) for the option to be meaningful. Defaults to off. IPV6CTLKEEPFAITH (ip6.keepfaith) Boolean: enable/disable ``FAITH''

TCP relay IPv6-to-IPv4 translator code in the

kernel. Refer faith(4) and faithd(8) for detail. Defaults to off. IPV6CTLLOGINTERVAL (ip6.loginterval) Integer: default interval between IPv6 packet forwarding engine log output (in seconds). IPV6CTLHDRNESTLIMIT (ip6.hdrnestlimit) Integer: default number of the maximum IPv6 extension headers permitted on incoming IPv6 packets. If set to 0, the node

will accept as many extension headers as possi-

ble. IPV6CTLDADCOUNT (ip6.dadcount) Integer: default number of IPv6 DAD (duplicated address detection) probe packets. The packets will be generated when IPv6 interface addresses are configured. IPV6CTLAUTOFLOWLABEL (ip6.autoflowlabel) Boolean: enable/disable automatic filling of IPv6 flowlabel field, for outstanding connected transport protocol packets. The field might be used by intermediate routers to identify packet flows. Defaults to on. IPV6CTLDEFMCASTHLIM (ip6.defmcasthlim) Integer: default hop limit value for an IPv6 multicast packet sourced by the node. This value applies to all the transport protocols on top of IPv6. There are APIs to override the value as documented in ip6(4). IPV6CTLGIFHLIM (ip6.gifhlim) Integer: default maximum hop limit

value for an IPv6 packet generated by gif(4) tun-

nel interface. IPV6CTLKAMEVERSION (ip6.kameversion) String: identifies the version of KAME IPv6 stack implemented in the kernel. IPV6CTLUSEDEPRECATED (ip6.usedeprecated) Boolean: enable/disable use of deprecated address, specified in RFC2462 5.5.4. Defaults to on. IPV6CTLRRPRUNE (ip6.rrprune) Integer: default interval between IPv6 router renumbering prefix babysitting, in seconds. IPV6CTLMAPPEDADDR (ip6.mappedaddr) Boolean: enable/disable use of IPv4 mapped address on AFINET6 sockets. Defaults to on. IPV6CTLRTEXPIRE (ip6.rtexpire) Integer: lifetime in seconds of

protocol-cloned IP routes after the last refer-

ence drops (default one hour). IPV6CTLRTMINEXPIRE (ip6.rtminexpire) Integer: minimum value of ip.rtexpire (default ten seconds). IPV6CTLRTMAXCACHE (ip6.rtmaxcache) Integer: trigger level of

cached, unreferenced, protocol-cloned routes

which initiates dynamic adaptation (default 128). IInntteerraaccttiioonn bbeettwweeeenn IIPPvv44//vv66 ssoocckkeettss

The behavior of AFINET6 TCP/UDP socket is documented in RFC2553. Basi-

cally, it says this:

++oo A specific bind on an AFINET6 socket (bind(2) with an address speci-

fied) should accept IPv6 traffic to that address only. ++oo If you perform a wildcard bind on an AFINET6 socket (bind(2) to IPv6 address ::), and there is no wildcard bind AFINET socket on that TCP/UDP port, IPv6 traffic as well as IPv4 traffic should be routed to that AFINET6 socket. IPv4 traffic should be seen as if it came from an IPv6 address like ::ffff:10.1.1.1. This is called an IPv4 mapped address. ++oo If there are both a wildcard bind AFINET socket and a wildcard bind AFINET6 socket on one TCP/UDP port, they should behave separately. IPv4 traffic should be routed to the AFINET socket and IPv6 should be routed to the AFINET6 socket. However, RFC2553 does not define the ordering constraint between calls to bind(2), nor how IPv4 TCP/UDP port numbers and IPv6 TCP/UDP port numbers

relate to each other (should they be integrated or separated). Imple-

mented behavior is very different from kernel to kernel. Therefore, it is unwise to rely too much upon the behavior of AFINET6 wildcard bind sockets. It is recommended to listen to two sockets, one for AFINET and another for AFINET6, when you would like to accept both IPv4 and IPv6 traffic. It should also be noted that malicious parties can take advantage of the complexity presented above, and are able to bypass access control, if the target node routes IPv4 traffic to AFINET6 socket. Users are advised to

take care handling connections from IPv4 mapped address to AFINET6 sock-

ets.

BUGS

The IPv6 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. Users are suggested to implement ``version independent'' code as much as possible, as you will need to support both inet(4) and iinneett66. BSD January 29, 1999 BSD