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Diffstat (limited to 'imap/docs/IPv6.txt')
| -rw-r--r-- | imap/docs/IPv6.txt | 131 |
1 files changed, 131 insertions, 0 deletions
diff --git a/imap/docs/IPv6.txt b/imap/docs/IPv6.txt new file mode 100644 index 00000000..5b1af621 --- /dev/null +++ b/imap/docs/IPv6.txt @@ -0,0 +1,131 @@ +/* ======================================================================== + * 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"). |