** Description changed:
- This is a wish. It is requested that the bind9 package include a
- resolvconf hook script /etc/resolvconf/update.d/bind9 which writes a
- forwarders{} statement to /var/run/named/forwarders based on the
- nameserver information in resolvconf's database. Then in order to use
- named in whole or in part as a forwarding nameserver the administrator
- can simply modify named.conf so that the latter includes
- /var/run/named/forwarders at the right place in the file. If this
- inclusion could be controlled by a setting in, e.g., /etc/default/bind9,
- then that would be even nicer.
+ It is requested that the bind9 package be enhanced such that named uses
+ forwarder addresses obtained from resolvconf's database.
- The file /etc/resolvconf/update.d/bind included in resolvconf versions
- 1.52 and earlier illustrates how such a hook script should be written.
- The latter file was written for BIND 8 and worked well; but due to
- limitations in BIND 8 it had to generate a whole "options" statement
- instead of just the "forwarders" part, which was less nice.
+ Such a feature would normally be implemented by means of a resolvconf
+ update hook script, in this case /etc/resolvconf/update.d/bind9. (It
+ must *not* be called /etc/resolvconf/update.d/bind since that was the
+ name of a script written for BIND 8 and included in earlier versions of
+ resolvconf.) Resolvconf update hook scripts get run every time the
+ database changes.
- I am prepared to write the needed script for BIND 9 and attach it here.
+ There are various ways to implement this proposal.
+
+ 1. Write out a forwarders{} statement
+
+ The script writes out a forwarders{} statement in the format of
+ named.conf(5) to /var/run/named/named.conf.forwarders and then does
+ "/etc/init.d/bind9 reload" to cause named to re-read its configuration
+ files.
+
+ To activate this, the admin has to edit /etc/bind/named.conf.options
+ such that it includes /var/run/named/named.conf.forwarders at the right
+ place.
+
+ The script /etc/resolvconf/update.d/bind that was included in resolvconf
+ versions 1.52 and earlier illustrates how such a hook script should be
+ written. The latter script was written for BIND 8 and worked well, but
+ due to limitations in BIND 8 it had to generate a whole options{}
+ statement instead of just the forwarders{} part.
+
+ 2. Write a list of forwarder addresses and enhance named to read this
+
+ The script writes out a simple list of IP addresses to
+ /var/run/named/forwarders and then triggers named to re-read its
+ forwarders list from this file. When run with a new option,
+ "--forwarders-list=/var/run/named/forwarders", named uses the list in
+ /var/run/named/forwarders as its list of forwarder addresses instead of
+ whatever list was specified in the configuration file.
+
+ This approach requires that the option in question be added to named but
+ it has a number of advantages over the first approach. (1) It allows the
+ script to be much simpler. (2) It avoids run-time generation of
+ configuration files. (3) It avoids triggering the re-reading of
+ configuration files. (4) It allows the use of the resolvconf-based
+ forwarders list to be enabled and disabled via a variable in
+ /etc/default/bind9. (5) Some machines are still using an old script
+ written for bind8 which works as in #1 except that it writes out a whole
+ options{} statement instead of just a forwarders{} statement; the
+ present approach upgrades such machines cleanly.
--- BACKGROUND INFORMATION ---
As of Ubuntu 12.04, nameserver information is handled by resolvconf in
both the Server and Desktop editions of Ubuntu. Resolvconf maintains a
database of nameserver information, filed by interface name and
configuration agent. This is the information that is needed if named is
to be used in whole or in part as a forwarding nameserver.
BIND 9.7.x manual section 1.4.5.1: "__Forwarding__. Even a caching name
server does not necessarily perform the complete recursive lookup
itself. Instead, it can forward some or all of the queries that it
cannot satisfy from its cache to another caching name server, commonly
referred to as a forwarder. There may be one or more forwarders, and
they are queried in turn until the list is exhausted or an answer is
found. Forwarders are typically used when you do not wish all the
servers at a given site to interact directly with the rest of the
Internet servers. A typical scenario would involve a number of internal
DNS servers and an Internet firewall. Servers unable to pass packets
through the firewall would forward to the server that can do it, and
that server would query the Internet DNS servers on the internal
server’s behalf."
-
- Currently it's possible to configure named to use a static list of
- forwarders, but to make use of a dynamic list a resolvconf hook script
- is needed.
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https://bugs.launchpad.net/bugs/1091602
Title:
Please add resolvconf hook script to generate dynamic forwarders list
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