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<table class="head">
<tr>
<td class="head-ltitle">INET6(4)</td>
<td class="head-vol">Device Drivers Manual</td>
<td class="head-rtitle">INET6(4)</td>
</tr>
</table>
<div class="manual-text">
<section class="Sh">
<h1 class="Sh" id="NAME"><a class="permalink" href="#NAME">NAME</a></h1>
<p class="Pp"><code class="Nm">inet6</code> — <span class="Nd">Internet
protocol version 6 family</span></p>
</section>
<section class="Sh">
<h1 class="Sh" id="SYNOPSIS"><a class="permalink" href="#SYNOPSIS">SYNOPSIS</a></h1>
<p class="Pp"><code class="In">#include
<<a class="In">sys/types.h</a>></code>
<br/>
<code class="In">#include <<a class="In">netinet/in.h</a>></code></p>
</section>
<section class="Sh">
<h1 class="Sh" id="DESCRIPTION"><a class="permalink" href="#DESCRIPTION">DESCRIPTION</a></h1>
<p class="Pp">The <code class="Nm">inet6</code> family is an updated version of
<a class="Xr">inet(4)</a> family. While <a class="Xr">inet(4)</a> implements
Internet Protocol version 4, <code class="Nm">inet6</code> implements
Internet Protocol version 6.</p>
<p class="Pp" id="Internet"><code class="Nm">inet6</code> is a collection of
protocols layered atop the
<a class="permalink" href="#Internet"><i class="Em">Internet Protocol
version 6</i></a> (IPv6) transport layer, and using the IPv6 address format.
The <code class="Nm">inet6</code> family provides protocol support for the
<code class="Dv">SOCK_STREAM</code>, <code class="Dv">SOCK_DGRAM</code>, and
<code class="Dv">SOCK_RAW</code> socket types; the
<code class="Dv">SOCK_RAW</code> interface provides access to the IPv6
protocol.</p>
</section>
<section class="Sh">
<h1 class="Sh" id="ADDRESSING"><a class="permalink" href="#ADDRESSING">ADDRESSING</a></h1>
<p class="Pp">IPv6 addresses are 16 byte quantities, stored in network standard
byteorder. The include file
<code class="In"><<a class="In">netinet/in.h</a>></code> defines this
address as a discriminated union.</p>
<p class="Pp">Sockets bound to the <code class="Nm">inet6</code> family use the
following addressing structure:</p>
<div class="Bd Pp Bd-indent Li">
<pre>struct sockaddr_in6 {
uint8_t sin6_len;
sa_family_t sin6_family;
in_port_t sin6_port;
uint32_t sin6_flowinfo;
struct in6_addr sin6_addr;
uint32_t sin6_scope_id;
};</pre>
</div>
<p class="Pp">Sockets may be created with the local address
“<code class="Dv">::</code>” (which is equal to IPv6 address
<code class="Dv">0:0:0:0:0:0:0:0</code>) to effect “wildcard”
matching on incoming messages.</p>
<p class="Pp">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
RFC 2292. A compact description of the advanced API is available in
<a class="Xr">ip6(4)</a>. 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.</p>
<p class="Pp">The KAME implementation supports an extended numeric IPv6 address
notation for link-local addresses, like
“<code class="Li">fe80::1%de0</code>” to specify
“<code class="Li">fe80::1</code> on <code class="Li">de0</code>
interface”. This notation is supported by
<a class="Xr">getaddrinfo(3)</a> and <a class="Xr">getnameinfo(3)</a>. Some
of normal userland programs, such as <a class="Xr">telnet(1)</a> or
<a class="Xr">ftp(1)</a>, are able to use this notation. With special
programs like <a class="Xr">ping6(8)</a>, you can specify the outgoing
interface by an extra command line option to disambiguate scoped
addresses.</p>
<p class="Pp">Scoped addresses are handled specially in the kernel. In kernel
structures 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
<code class="Dv">PF_ROUTE</code> socket, kernel memory accesses via
<a class="Xr">kvm(3)</a> and on some other occasions. HOWEVER, users should
never use the embedded form. For details please consult
<a class="Lk" href="http://www.kame.net/dev/cvsweb2.cgi/kame/IMPLEMENTATION">http://www.kame.net/dev/cvsweb2.cgi/kame/IMPLEMENTATION</a>.
Note that the above URL describes the situation with the latest KAME tree,
not the <span class="Ux">NetBSD</span> tree.</p>
</section>
<section class="Sh">
<h1 class="Sh" id="PROTOCOLS"><a class="permalink" href="#PROTOCOLS">PROTOCOLS</a></h1>
<p class="Pp">The <code class="Nm">inet6</code> family comprises the IPv6
network protocol, Internet Control Message Protocol version 6 (ICMPv6),
Transmission Control Protocol (TCP), and User Datagram Protocol (UDP). TCP
is used to support the <code class="Dv">SOCK_STREAM</code> abstraction while
UDP is used to support the <code class="Dv">SOCK_DGRAM</code> abstraction.
Note that TCP and UDP are common to <a class="Xr">inet(4)</a> and
<code class="Nm">inet6</code>. A raw interface to IPv6 is available by
creating an Internet socket of type <code class="Dv">SOCK_RAW</code>. The
ICMPv6 message protocol is accessible from a raw socket.</p>
<section class="Ss">
<h2 class="Ss" id="Interaction_between_IPv4/v6_sockets"><a class="permalink" href="#Interaction_between_IPv4/v6_sockets">Interaction
between IPv4/v6 sockets</a></h2>
<p class="Pp">By default, <span class="Ux">NetBSD</span> does not route IPv4
traffic to <code class="Dv">AF_INET6</code> sockets. The default behavior
intentionally violates RFC 2553 for security reasons. Listen to two sockets
if you want to accept both IPv4 and IPv6 traffic. IPv4 traffic may be routed
with certain per-socket/per-node configuration, however, it is not
recommended to do so. Consult <a class="Xr">ip6(4)</a> for details.</p>
<p class="Pp">The behavior of <code class="Dv">AF_INET6</code> TCP/UDP socket is
documented in RFC 2553. Basically, it says this:</p>
<ul class="Bl-bullet Bl-compact">
<li>A specific bind on an <code class="Dv">AF_INET6</code> socket
(<a class="Xr">bind(2)</a> with an address specified) should accept IPv6
traffic to that address only.</li>
<li>If you perform a wildcard bind on an <code class="Dv">AF_INET6</code>
socket (<a class="Xr">bind(2)</a> to IPv6 address
<code class="Li">::</code>), and there is no wildcard bind
<code class="Dv">AF_INET</code> socket on that TCP/UDP port, IPv6 traffic
as well as IPv4 traffic should be routed to that
<code class="Dv">AF_INET6</code> socket. IPv4 traffic should be seen as if
it came from an IPv6 address like <code class="Li">::ffff:10.1.1.1</code>.
This is called an IPv4 mapped address.</li>
<li>If there are both a wildcard bind <code class="Dv">AF_INET</code> socket
and a wildcard bind <code class="Dv">AF_INET6</code> socket on one TCP/UDP
port, they should behave separately. IPv4 traffic should be routed to the
<code class="Dv">AF_INET</code> socket and IPv6 should be routed to the
<code class="Dv">AF_INET6</code> socket.</li>
</ul>
<p class="Pp">However, RFC 2553 does not define the ordering constraint between
calls to <a class="Xr">bind(2)</a>, nor how IPv4 TCP/UDP port numbers and
IPv6 TCP/UDP port numbers relate to each other (should they be integrated or
separated). Implemented behavior is very different from kernel to kernel.
Therefore, it is unwise to rely too much upon the behavior of
<code class="Dv">AF_INET6</code> wildcard bind sockets. It is recommended to
listen to two sockets, one for <code class="Dv">AF_INET</code> and another
for <code class="Dv">AF_INET6</code>, when you would like to accept both
IPv4 and IPv6 traffic.</p>
<p class="Pp">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 <code class="Dv">AF_INET6</code>
socket. Users are advised to take care handling connections from IPv4 mapped
address to <code class="Dv">AF_INET6</code> sockets.</p>
</section>
</section>
<section class="Sh">
<h1 class="Sh" id="SEE_ALSO"><a class="permalink" href="#SEE_ALSO">SEE
ALSO</a></h1>
<p class="Pp"><a class="Xr">ioctl(2)</a>, <a class="Xr">socket(2)</a>,
<a class="Xr">sysctl(3)</a>, <a class="Xr">icmp6(4)</a>,
<a class="Xr">intro(4)</a>, <a class="Xr">ip6(4)</a>,
<a class="Xr">tcp(4)</a>, <a class="Xr">udp(4)</a></p>
<p class="Pp"><cite class="Rs"><span class="RsA">Qing Li</span>,
<span class="RsA">Tatuya Jinmei</span>, and <span class="RsA">Keiichi
Shima</span>, <i class="RsB">IPv6 Core Protocols Implementation</i>,
<i class="RsI">Morgan Kaufmann</i>,
<span class="RsD">2006</span>.</cite></p>
<p class="Pp"><cite class="Rs"><span class="RsA">Qing Li</span>,
<span class="RsA">Tatuya Jinmei</span>, and <span class="RsA">Keiichi
Shima</span>, <i class="RsB">IPv6 Advanced Protocols Implementation</i>,
<i class="RsI">Morgan Kaufmann</i>,
<span class="RsD">2007</span>.</cite></p>
</section>
<section class="Sh">
<h1 class="Sh" id="STANDARDS"><a class="permalink" href="#STANDARDS">STANDARDS</a></h1>
<p class="Pp"><cite class="Rs"><span class="RsA">Tatuya Jinmei</span> and
<span class="RsA">Atsushi Onoe</span>, <span class="RsT">An Extension of
Format for IPv6 Scoped Addresses</span>, <span class="RsR">internet
draft</span>,
<span class="RsN">draft-ietf-ipngwg-scopedaddr-format-02.txt</span>,
<span class="RsD">June 2000</span>, <span class="RsO">work in progress
material</span>.</cite></p>
</section>
<section class="Sh">
<h1 class="Sh" id="HISTORY"><a class="permalink" href="#HISTORY">HISTORY</a></h1>
<p class="Pp">The <code class="Nm">inet6</code> protocol interfaces are defined
in RFC 2553 and RFC 2292. The implementation described herein appeared in
the WIDE/KAME project.</p>
</section>
<section class="Sh">
<h1 class="Sh" id="BUGS"><a class="permalink" href="#BUGS">BUGS</a></h1>
<p class="Pp">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.</p>
<p class="Pp">Users are suggested to implement “version
independent” code as much as possible, as you will need to support
both <a class="Xr">inet(4)</a> and <code class="Nm">inet6</code>.</p>
</section>
</div>
<table class="foot">
<tr>
<td class="foot-date">March 10, 2010</td>
<td class="foot-os">NetBSD 10.1</td>
</tr>
</table>
|
