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+<!doctype html public "-//W3C//DTD HTML 4.01 Transitional//EN"
+ "http://www.w3.org/TR/html4/loose.dtd">
+
+<html>
+
+<head>
+
+<title>Postfix IPv6 Support</title>
+
+<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
+
+</head>
+
+<body>
+
+<h1><img src="postfix-logo.jpg" width="203" height="98" ALT="">Postfix
+IPv6 Support</h1>
+
+<hr>
+
+<h2>Introduction</h2>
+
+<p> Postfix 2.2 introduces support for the IPv6 (IP version 6)
+protocol. IPv6 support for older Postfix versions was available as
+an add-on patch. The section "<a href="#compat">Compatibility with
+Postfix &lt;2.2 IPv6 support</a>" below discusses the differences
+between these implementations. </p>
+
+<p> The main feature of interest is that IPv6 uses 128-bit IP
+addresses instead of the 32-bit addresses used by IPv4. It can
+therefore accommodate a much larger number of hosts and networks
+without ugly kluges such as NAT. A side benefit of the much larger
+address space is that it makes random network scanning impractical.
+</p>
+
+<p> Postfix uses the same SMTP protocol over IPv6 as it already
+uses over the older IPv4 network, and does AAAA record lookups in
+the DNS in addition to the older A records. Information about IPv6
+can be found at http://www.ipv6.org/. </p>
+
+<p> This document provides information on the following topics:
+</p>
+
+<ul>
+
+<li><a href="#platforms">Supported platforms</a>
+
+<li><a href="#configuration">Configuration</a>
+
+<li><a href="#limitations">Known limitations</a>
+
+<li><a href="#compat">Compatibility with Postfix &lt;2.2 IPv6 support</a>
+
+<li><a href="#porting">IPv6 Support for unsupported platforms</a>
+
+<li><a href="#credits">Credits</a>
+
+</ul>
+
+<h2><a name="platforms">Supported Platforms</a></h2>
+
+<p> Postfix version 2.2 supports IPv4 and IPv6 on the following
+platforms: </p>
+
+<ul>
+
+<li> AIX 5.1+
+<li> Darwin 7.3+
+<li> FreeBSD 4+
+<li> Linux 2.4+
+<li> NetBSD 1.5+
+<li> OpenBSD 2+
+<li> Solaris 8+
+<li> Tru64Unix V5.1+
+
+</ul>
+
+<p> On other platforms Postfix will simply use IPv4 as it has always
+done. </p>
+
+<p> See <a href="#porting">below</a> for tips how to port Postfix
+IPv6 support to other environments. </p>
+
+<h2><a name="configuration">Configuration</a></h2>
+
+<p> Postfix IPv6 support introduces two new main.cf configuration
+parameters, and introduces an important change in address syntax
+notation in match lists such as mynetworks or
+debug_peer_list. </p>
+
+<p> Postfix IPv6 address syntax is a little tricky, because there
+are a few places where you must enclose an IPv6 address inside
+"<tt>[]</tt>" characters, and a few places where you must not. It is
+a good idea to use "<tt>[]</tt>" only in the few places where you
+have to. Check out the postconf(5) manual whenever you do IPv6
+related configuration work with Postfix. </p>
+
+<ul>
+
+<li> <p> Instead of hard-coding 127.0.0.1 and ::1 loopback addresses
+in master.cf, specify "inet_interfaces = loopback-only" in main.cf.
+This way you can use the same master.cf file regardless of whether
+or not Postfix will run on an IPv6-enabled system. </p>
+
+<li> <p> The first new parameter is called inet_protocols. This
+specifies what protocols Postfix will use when it makes or accepts
+network connections, and also controls what DNS lookups Postfix
+will use when it makes network connections. </p>
+
+<blockquote>
+<pre>
+/etc/postfix/main.cf:
+ # You must stop/start Postfix after changing this parameter.
+ inet_protocols = ipv4 (DEFAULT: enable IPv4 only)
+ inet_protocols = all (enable IPv4, and IPv6 if supported)
+ inet_protocols = ipv4, ipv6 (enable both IPv4 and IPv6)
+ inet_protocols = ipv6 (enable IPv6 only)
+</pre>
+</blockquote>
+
+<p> By default, Postfix uses IPv4 only, because most systems aren't
+attached to an IPv6 network. </p>
+
+<ul>
+
+<li> <p> On systems with combined IPv4/IPv6 stacks, attempts to
+deliver mail via IPv6 would always fail with "network unreachable",
+and those attempts would only slow down Postfix. </p>
+
+<li> <p> Linux kernels don't even load IPv6 protocol support by
+default. Any attempt to use it would fail immediately. </p>
+
+</ul>
+
+<p> Note 1: you must stop and start Postfix after changing the
+inet_protocols configuration parameter. </p>
+
+<p> Note 2: if you see error messages like the following, then
+you're running Linux and need to turn on IPv6 in the kernel: see
+http://www.ipv6.org/ for hints and tips. Unlike other systems,
+Linux does not have a combined stack for IPv4 and IPv6, and IPv6
+protocol support is not loaded by default. </p>
+
+<blockquote>
+<pre>
+postconf: warning: inet_protocols: IPv6 support is disabled: Address family not supported by protocol
+postconf: warning: inet_protocols: configuring for IPv4 support only
+</pre>
+</blockquote>
+
+<p> Note 3: on older Linux and Solaris systems, the setting
+"inet_protocols = ipv6" will not prevent Postfix from
+accepting IPv4 connections. Postfix will present the client IP
+addresses in IPv6 format, though. In all other cases, Postfix always
+presents IPv4 client IP addresses in the traditional dotted quad
+IPv4 format. </p>
+
+<li> <p> The other new parameter is smtp_bind_address6.
+This sets the local interface address for outgoing IPv6 SMTP
+connections, just like the smtp_bind_address parameter
+does for IPv4: </p>
+
+<blockquote>
+<pre>
+/etc/postfix/main.cf:
+ smtp_bind_address6 = 2001:240:587:0:250:56ff:fe89:1
+</pre>
+</blockquote>
+
+<li> <p> If you left the value of the mynetworks parameter at its
+default (i.e. no mynetworks setting in main.cf) Postfix will figure
+out by itself what its network addresses are. This is what a typical
+setting looks like: </p>
+
+<blockquote>
+<pre>
+% postconf mynetworks
+mynetworks = 127.0.0.0/8 168.100.189.0/28 [::1]/128 [fe80::]/10 [2001:240:587::]/64
+</pre>
+</blockquote>
+
+<p> If you did specify the mynetworks parameter value in
+main.cf, you need update the mynetworks value to include
+the IPv6 networks the system is in. Be sure to specify IPv6 address
+information inside "<tt>[]</tt>", like this: </p>
+
+<blockquote>
+<pre>
+/etc/postfix/main.cf:
+ mynetworks = ...<i>IPv4 networks</i>... [::1]/128 [2001:240:587::]/64 ...
+</pre>
+</blockquote>
+
+</ul>
+
+<p> <b> NOTE: when configuring Postfix match lists such as
+mynetworks or debug_peer_list, you must specify
+IPv6 address information inside "<tt>[]</tt>" in the main.cf parameter
+value and in files specified with a "<i>/file/name</i>" pattern.
+IPv6 addresses contain the ":" character, and would otherwise be
+confused with a "<i>type:table</i>" pattern. </b> </p>
+
+<h2><a name="limitations">Known Limitations</a></h2>
+
+<ul>
+
+<li> <p> Postfix SMTP clients before version 2.8 try to connect
+over IPv6 before trying IPv4. With more recent Postfix versions,
+the order of IPv6 versus IPv4 outgoing connection attempts is
+configurable with the smtp_address_preference parameter. </p>
+
+<li> <p> Postfix versions before 2.6 do not support DNSBL (real-time
+blackhole list) lookups for IPv6 client IP addresses. </p>
+
+<li> <p> IPv6 does not have class A, B, C, etc. networks. With IPv6
+networks, the setting "mynetworks_style = class" has the
+same effect as the setting "mynetworks_style = subnet".
+</p>
+
+<li> <p> On Tru64Unix and AIX, Postfix can't figure out the local
+subnet mask
+and always assumes a /128 network. This is a problem only with
+"mynetworks_style = subnet" and no explicit mynetworks
+setting in main.cf. </p>
+
+</ul>
+
+<h2> <a name="compat">Compatibility with Postfix &lt;2.2 IPv6 support</a>
+</h2>
+
+<p> Postfix version 2.2 IPv6 support is based on the Postfix/IPv6 patch
+by Dean Strik and others, but differs in a few minor ways. </p>
+
+<ul>
+
+<li> <p> main.cf: The inet_interfaces parameter does not support
+the notation "ipv6:all" or "ipv4:all". Use the
+inet_protocols parameter instead. </p>
+
+<li> <p> main.cf: Specify "inet_protocols = all" or
+"inet_protocols = ipv4, ipv6" in order to enable both IPv4
+and IPv6 support. </p>
+
+<li> <p> main.cf: The inet_protocols parameter also controls
+what DNS lookups Postfix will attempt to make when delivering or
+receiving mail. </p>
+
+<li> <p> main.cf: Specify "inet_interfaces = loopback-only"
+to listen on loopback network interfaces only. </p>
+
+<li> <p> The lmtp_bind_address and lmtp_bind_address6
+features were omitted. The Postfix LMTP client will be absorbed
+into the SMTP client, so there is no reason to keep adding features
+to the LMTP client. </p>
+
+<li> <p> The SMTP server now requires that IPv6 addresses in SMTP
+commands are specified as [ipv6:<i>ipv6address</i>], as
+described in RFC 2821. </p>
+
+<li> <p> The IPv6 network address matching code was rewritten from
+the ground up, and is expected to be closer to the specification.
+The result may be incompatible with the Postfix/IPv6 patch.
+</p>
+
+</ul>
+
+<h2><a name="porting">IPv6 Support for unsupported platforms</a></h2>
+
+<p> Getting Postfix IPv6 working on other platforms involves the
+following steps: </p>
+
+<ul>
+
+<li> <p> Specify how Postfix should find the local network interfaces.
+Postfix needs this information to avoid mailer loops and to find out
+if mail for <i>user@[ipaddress]</i> is a local or remote destination. </p>
+
+<p> If your system has the getifaddrs() routine then add
+the following to your platform-specific section in
+src/util/sys_defs.h: </p>
+
+<blockquote>
+<pre>
+#ifndef NO_IPV6
+# define HAS_IPV6
+# define HAVE_GETIFADDRS
+#endif
+</pre>
+</blockquote>
+
+<p> Otherwise, if your system has the SIOCGLIF ioctl()
+command in /usr/include/*/*.h, add the following to your
+platform-specific section in src/util/sys_defs.h: </p>
+
+<blockquote>
+<pre>
+#ifndef NO_IPV6
+# define HAS_IPV6
+# define HAS_SIOCGLIF
+#endif
+</pre>
+</blockquote>
+
+<p> Otherwise, Postfix will have to use the old SIOCGIF commands
+and get along with reduced IPv6 functionality (it won't be able to
+figure out your IPv6 netmasks, which are needed for "mynetworks_style
+= subnet". Add this to your platform-specific section in
+src/util/sys_defs.h: </p>
+
+<blockquote>
+<pre>
+#ifndef NO_IPV6
+# define HAS_IPV6
+#endif
+</pre>
+</blockquote>
+
+<li> <p> Test if Postfix can figure out its interface information. </p>
+
+<p> After compiling Postfix in the usual manner, step into the
+src/util directory and type "<b>make inet_addr_local</b>".
+Running this file by hand should produce all the interface addresses
+and network masks, for example: </p>
+
+<blockquote>
+<pre>
+% make
+% cd src/util
+% make inet_addr_local
+[... some messages ...]
+% ./inet_addr_local
+[... some messages ...]
+./inet_addr_local: inet_addr_local: configured 2 IPv4 addresses
+./inet_addr_local: inet_addr_local: configured 4 IPv6 addresses
+168.100.189.2/255.255.255.224
+127.0.0.1/255.0.0.0
+fe80:1::2d0:b7ff:fe88:2ca7/ffff:ffff:ffff:ffff::
+2001:240:587:0:2d0:b7ff:fe88:2ca7/ffff:ffff:ffff:ffff::
+fe80:5::1/ffff:ffff:ffff:ffff::
+::1/ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff
+</pre>
+</blockquote>
+
+<p> The above is for an old FreeBSD machine. Other systems produce
+slightly different results, but you get the idea. </p>
+
+</ul>
+
+<p> If none of all this produces a usable result, send email to the
+postfix-users@postfix.org mailing list and we'll try to help you
+through this. </p>
+
+<h2><a name="credits">Credits</a></h2>
+
+<p> The following information is in part based on information that
+was compiled by Dean Strik. </p>
+
+<ul>
+
+<li> <p> Mark Huizer wrote the original Postfix IPv6 patch. </p>
+
+<li> <p> Jun-ichiro 'itojun' Hagino of the KAME project made
+substantial improvements. Since then, we speak of the KAME patch.
+</p>
+
+<li> <p> The PLD Linux Distribution ported the code to other stacks
+(notably USAGI). We speak of the PLD patch. A very important
+feature of the PLD patch was that it can work with Lutz Jaenicke's
+TLS patch for Postfix. </p>
+
+<li> <p> Dean Strik extended IPv6 support to platforms other than
+KAME and USAGI, updated the patch to keep up with Postfix development,
+and provided a combined IPv6 + TLS patch. Information about his
+effort can be found on Dean Strik's Postfix website at
+http://www.ipnet6.org/postfix/. </p>
+
+<li> <p> Wietse Venema took Dean Strik's IPv6 patch, merged it into
+Postfix 2.2, and took the opportunity to eliminate all IPv4-specific
+code from Postfix that could be removed. For systems without IPv6
+support in the kernel and system libraries, Postfix has a simple
+compatibility layer, so that it will use IPv4 as before. </p>
+
+</ul>
+
+</body>
+
+</html>