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IPv6.txt
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/* ======================================================================== * Copyright 1988-2006 University of Washington * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * * ======================================================================== */ The following information about configuring inetd and xinetd for IPv6 was contributed by a user. I have not checked it for accuracy or completeness, but have included it as-is in the hope that it may be useful: --------------------------------------------------------------------------- One thing you might consider adding to the docs are hints for setting up inetd or xinetd to simultaneously listen on BOTH IPv4 and IPv6 for different OS. Some OS want to see separate IPv4-only and IPv6-only listening sockets configured in inetd.conf or xinetd.conf. Others will accept IPv4 connections on lines configured for IPv6 and actually generate errors if you have both configured when inetd or xinetd start up. It's not clear to me whether this difference is due to how inetd or xinetd are built or whether it's due to the kernel's IP stack implementation. I suspect it's really the latter. Below are some examples: Here's a fragment of /usr/local/etc/xinetd.conf for a FreeBSD 4.9 server: service imap { socket_type = stream protocol = tcp wait = no user = root server = /usr/local/libexec/imapd } service imap { flags = IPv6 socket_type = stream protocol = tcp wait = no user = root server = /usr/local/libexec/imapd } service imaps { socket_type = stream protocol = tcp wait = no user = root server = /usr/local/libexec/imapd } service imaps { flags = IPv6 socket_type = stream protocol = tcp wait = no user = root server = /usr/local/libexec/imapd } Note that you have to specify a nearly identical paragraph for each service which differs only by the 'flags = IPv6'. An equivalent inetd.conf would look something like: imap stream tcp nowait root /usr/local/libexec/imapd imapd imap stream tcp6 nowait root /usr/local/libexec/imapd imapd imaps stream tcp nowait root /usr/local/libexec/imapd imapd imaps stream tcp6 nowait root /usr/local/libexec/imapd imapd The man pages for inetd suggest that if you use a single entry with 'tcp46' replacing either 'tcp' or 'tcp6' the system will listen on both types of addresses. At least for the case of FreeBSD this is actually incorrect. Now if you were to use the above xinetd.conf on Fedora Linux, it would complain. What does work under Linux is to create a single service paragraph for each service which will accept connections on both IPv4 and IPv6: In /etc/xinetd.d/imap: service imap { flags = IPv6 disable = no socket_type = stream wait = no user = root server = /usr/local/sbin/imapd } In /etc/xinetd.d/imaps: service imaps { flags = IPv6 disable = no socket_type = stream wait = no user = root server = /usr/local/sbin/imapd } The man page for xinetd says the IPv6 flag means xinetd will listen ONLY on IPv6. However the actual behaviour (for Fedora Linux) is to listen on both IPv4 and IPv6. All of the above also applies to ipop3d. Anyway, this might save some folks a little bit of head scratching time. --------------------------------------------------------------------------- Addendum from the original submitter: --------------------------------------------------------------------------- I've since learned that the discrepancy really is a function of the OS. It seems those systems that force you to create separate IPv4 and IPv6 listeners in inetd (or xinetd) are the same systems that also disable IPv4-mapped IPv6 addresses by default. This is a boot-time configuration option. If you enable IPv4-mapped IPv6 addresses, then the 'tcp46' option in inetd works and the simplified config would look like: imap4 stream tcp46 nowait root /usr/local/libexec/imapd imapd imaps stream tcp46 nowait root /usr/local/libexec/imapd imapd In FreeBSD, enabling IPv4-mapped addresses is done by adding ipv6_ipv4mapping="YES" to /etc/rc.conf (in addition to ipv6_enable="YES").