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+PPoossttffiixx IIPPvv66 SSuuppppoorrtt
+
+-------------------------------------------------------------------------------
+
+IInnttrroodduuccttiioonn
+
+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 "Compatibility with Postfix <2.2 IPv6 support" below discusses the
+differences between these implementations.
+
+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.
+
+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/.
+
+This document provides information on the following topics:
+
+ * Supported platforms
+ * Configuration
+ * Known limitations
+ * Compatibility with Postfix <2.2 IPv6 support
+ * IPv6 Support for unsupported platforms
+ * Credits
+
+SSuuppppoorrtteedd PPllaattffoorrmmss
+
+Postfix version 2.2 supports IPv4 and IPv6 on the following platforms:
+
+ * AIX 5.1+
+ * Darwin 7.3+
+ * FreeBSD 4+
+ * Linux 2.4+
+ * NetBSD 1.5+
+ * OpenBSD 2+
+ * Solaris 8+
+ * Tru64Unix V5.1+
+
+On other platforms Postfix will simply use IPv4 as it has always done.
+
+See below for tips how to port Postfix IPv6 support to other environments.
+
+CCoonnffiigguurraattiioonn
+
+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.
+
+Postfix IPv6 address syntax is a little tricky, because there are a few places
+where you must enclose an IPv6 address inside "[]" characters, and a few places
+where you must not. It is a good idea to use "[]" only in the few places where
+you have to. Check out the postconf(5) manual whenever you do IPv6 related
+configuration work with Postfix.
+
+ * 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.
+
+ * 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.
+
+ /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)
+
+ By default, Postfix uses IPv4 only, because most systems aren't attached to
+ an IPv6 network.
+
+ o 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.
+
+ o Linux kernels don't even load IPv6 protocol support by default. Any
+ attempt to use it would fail immediately.
+
+ Note 1: you must stop and start Postfix after changing the inet_protocols
+ configuration parameter.
+
+ 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.
+
+ postconf: warning: inet_protocols: IPv6 support is disabled: Address
+ family not supported by protocol
+ postconf: warning: inet_protocols: configuring for IPv4 support only
+
+ 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.
+
+ * 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:
+
+ /etc/postfix/main.cf:
+ smtp_bind_address6 = 2001:240:587:0:250:56ff:fe89:1
+
+ * 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:
+
+ % postconf mynetworks
+ mynetworks = 127.0.0.0/8 168.100.189.0/28 [::1]/128 [fe80::]/10 [2001:
+ 240:587::]/64
+
+ 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 "[]", like this:
+
+ /etc/postfix/main.cf:
+ mynetworks = ...IPv4 networks... [::1]/128 [2001:240:587::]/64 ...
+
+NNOOTTEE:: wwhheenn ccoonnffiigguurriinngg PPoossttffiixx mmaattcchh lliissttss ssuucchh aass mmyynneettwwoorrkkss oorr
+ddeebbuugg__ppeeeerr__lliisstt,, yyoouu mmuusstt ssppeecciiffyy IIPPvv66 aaddddrreessss iinnffoorrmmaattiioonn iinnssiiddee ""[[]]"" iinn tthhee
+mmaaiinn..ccff ppaarraammeetteerr vvaalluuee aanndd iinn ffiilleess ssppeecciiffiieedd wwiitthh aa ""//ffiillee//nnaammee"" ppaatttteerrnn..
+IIPPvv66 aaddddrreesssseess ccoonnttaaiinn tthhee ""::"" cchhaarraacctteerr,, aanndd wwoouulldd ootthheerrwwiissee bbee ccoonnffuusseedd wwiitthh
+aa ""ttyyppee::ttaabbllee"" ppaatttteerrnn..
+
+KKnnoowwnn LLiimmiittaattiioonnss
+
+ * 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.
+
+ * Postfix versions before 2.6 do not support DNSBL (real-time blackhole list)
+ lookups for IPv6 client IP addresses.
+
+ * 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".
+
+ * 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.
+
+CCoommppaattiibbiilliittyy wwiitthh PPoossttffiixx <<22..22 IIPPvv66 ssuuppppoorrtt
+
+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.
+
+ * main.cf: The inet_interfaces parameter does not support the notation "ipv6:
+ all" or "ipv4:all". Use the inet_protocols parameter instead.
+
+ * main.cf: Specify "inet_protocols = all" or "inet_protocols = ipv4, ipv6" in
+ order to enable both IPv4 and IPv6 support.
+
+ * main.cf: The inet_protocols parameter also controls what DNS lookups
+ Postfix will attempt to make when delivering or receiving mail.
+
+ * main.cf: Specify "inet_interfaces = loopback-only" to listen on loopback
+ network interfaces only.
+
+ * 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.
+
+ * The SMTP server now requires that IPv6 addresses in SMTP commands are
+ specified as [ipv6:ipv6address], as described in RFC 2821.
+
+ * 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.
+
+IIPPvv66 SSuuppppoorrtt ffoorr uunnssuuppppoorrtteedd ppllaattffoorrmmss
+
+Getting Postfix IPv6 working on other platforms involves the following steps:
+
+ * Specify how Postfix should find the local network interfaces. Postfix needs
+ this information to avoid mailer loops and to find out if mail for user@
+ [ipaddress] is a local or remote destination.
+
+ If your system has the getifaddrs() routine then add the following to your
+ platform-specific section in src/util/sys_defs.h:
+
+ #ifndef NO_IPV6
+ # define HAS_IPV6
+ # define HAVE_GETIFADDRS
+ #endif
+
+ 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:
+
+ #ifndef NO_IPV6
+ # define HAS_IPV6
+ # define HAS_SIOCGLIF
+ #endif
+
+ 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:
+
+ #ifndef NO_IPV6
+ # define HAS_IPV6
+ #endif
+
+ * Test if Postfix can figure out its interface information.
+
+ After compiling Postfix in the usual manner, step into the src/util
+ directory and type "mmaakkee iinneett__aaddddrr__llooccaall". Running this file by hand should
+ produce all the interface addresses and network masks, for example:
+
+ % 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
+
+ The above is for an old FreeBSD machine. Other systems produce slightly
+ different results, but you get the idea.
+
+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.
+
+CCrreeddiittss
+
+The following information is in part based on information that was compiled by
+Dean Strik.
+
+ * Mark Huizer wrote the original Postfix IPv6 patch.
+
+ * Jun-ichiro 'itojun' Hagino of the KAME project made substantial
+ improvements. Since then, we speak of the KAME patch.
+
+ * 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.
+
+ * 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/.
+
+ * 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.
+