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Diffstat (limited to 'contrib/bind9/doc/misc/ipv6')
| -rw-r--r-- | contrib/bind9/doc/misc/ipv6 | 113 |
1 files changed, 0 insertions, 113 deletions
diff --git a/contrib/bind9/doc/misc/ipv6 b/contrib/bind9/doc/misc/ipv6 deleted file mode 100644 index 4060bc3..0000000 --- a/contrib/bind9/doc/misc/ipv6 +++ /dev/null @@ -1,113 +0,0 @@ -Copyright (C) 2004 Internet Systems Consortium, Inc. ("ISC") -Copyright (C) 2000, 2001 Internet Software Consortium. -See COPYRIGHT in the source root or http://isc.org/copyright.html for terms. - -Currently, there are multiple interesting problems with ipv6 -implementations on various platforms. These problems range from not -being able to use ipv6 with bind9 (or in particular the ISC socket -library, contained in libisc) to listen-on lists not being respected, -to strange warnings but seemingly correct behavior of named. - -COMPILE-TIME ISSUES -------------------- - -The socket library requires a certain level of support from the -operating system. In particular, it must follow the advanced ipv6 -socket API to be usable. The systems which do not follow this will -currently not get any warnings or errors, but ipv6 will simply not -function on them. - -These systems currently include, but are not limited to: - - AIX 3.4 (with ipv6 patches) - - -RUN-TIME ISSUES ---------------- - -In the original drafts of the ipv6 RFC documents, binding an ipv6 -socket to the ipv6 wildcard address would also cause the socket to -accept ipv4 connections and datagrams. When an ipv4 packet is -received on these systems, it is mapped into an ipv6 address. For -example, 1.2.3.4 would be mapped into ::ffff:1.2.3.4. The intent of -this mapping was to make transition from an ipv4-only application into -ipv6 easier, by only requiring one socket to be open on a given port. - -Later, it was discovered that this was generally a bad idea. For one, -many firewalls will block connection to 1.2.3.4, but will let through -::ffff:1.2.3.4. This, of course, is bad. Also, access control lists -written to accept only ipv4 addresses were suddenly ignored unless -they were rewritten to handle the ipv6 mapped addresses as well. - -Partly because of these problems, the latest IPv6 API introduces an -explicit knob (the "IPV6_V6ONLY" socket option ) to turn off the ipv6 -mapped address usage. - -In bind9, we first check if both the advanced API and the IPV6_V6ONLY -socket option are available. If both of them are available, bind9 -named will bind to the ipv6 wildcard port for both TCP and UDP. -Otherwise named will make a warning and try to bind to all available -ipv6 addresses separately. - -In any case, bind9 named binds to specific addresses for ipv4 sockets. - -The followings are historical notes when we always bound to the ipv6 -wildcard port regardless of the availability of the API support. -These problems should not happen with the closer checks above. - - -IPV6 Sockets Accept IPV4, Specific IPV4 Addresses Bindings Fail ---------------------------------------------------------------- - -The only OS which seems to do this is (some kernel versions of) linux. -If an ipv6 socket is bound to the ipv6 wildcard socket, and a specific -ipv4 socket is later bound (say, to 1.2.3.4 port 53) the ipv4 binding -will fail. - -What this means to bind9 is that the application will log warnings -about being unable to bind to a socket because the address is already -in use. Since the ipv6 socket will accept ipv4 packets and map them, -however, the ipv4 addresses continue to function. - -The effect is that the config file listen-on directive will not be -respected on these systems. - - -IPV6 Sockets Accept IPV4, Specific IPV4 Address Bindings Succeed ----------------------------------------------------------------- - -In this case, the system allows opening an ipv6 wildcard address -socket and then binding to a more specific ipv4 address later. An -example of this type of system is Digital Unix with ipv6 patches -applied. - -What this means to bind9 is that the application will respect -listen-on in regards to ipv4 sockets, but it will use mapped ipv6 -addresses for any that do not match the listen-on list. This, in -effect, makes listen-on useless for these machines as well. - - -IPV6 Sockets Do Not Accept IPV4 -------------------------------- - -On these systems, opening an IPV6 socket does not implicitly open any -ipv4 sockets. An example of these systems are NetBSD-current with the -latest KAME patch, and other systems which use the latest KAME patches -as their ipv6 implementation. - -On these systems, listen-on is fully functional, as the ipv6 socket -only accepts ipv6 packets, and the ipv4 sockets will handle the ipv4 -packets. - - -RELEVANT RFCs -------------- - -3513: Internet Protocol Version 6 (IPv6) Addressing Architecture - -3493: Basic Socket Interface Extensions for IPv6 - -3542: Advanced Sockets Application Program Interface (API) for IPv6 - - -$Id: ipv6,v 1.9 2004/08/10 04:27:51 jinmei Exp $ |
