From: sean@...
Date: 2019-12-07T02:35:25+00:00
Subject: [ruby-core:96138] [Ruby master Feature#14922] Resolv getaddresses ignores AAAA records for IPv6

Issue #14922 has been updated by sean@duke.edu (Sean Dilda).


I was recently bit by this as well.  The documentation at https://ruby-doc.org/stdlib-2.6.5/libdoc/resolv/rdoc/Resolv/DNS.html clearly states that getaddresses will return IPv6 addresses, but doesn't list any conditions.  Based on this I'd say the code is not following the documented behavior.

The current behavior makes sense for something like TCPSocket.new, but not when the devloper is actively querying DNS outside of opening a socket.

While I consider it a bug, I would welcome the proposed patch as a fix along with updated documentation.

----------------------------------------
Feature #14922: Resolv getaddresses ignores AAAA records for IPv6
https://bugs.ruby-lang.org/issues/14922#change-83007

* Author: dlampa (Donovan Lampa)
* Status: Assigned
* Priority: Normal
* Assignee: akr (Akira Tanaka)
* Target version: 
----------------------------------------
I'd like some feedback here as I'm not totally convinced this is a bug quite yet. I may have done something silly with my DNS configuration.

I have a local DNS server set up with the following /etc/resolv.conf
~~~
[root@ip-10-20-0-181 ~]# cat /etc/resolv.conf
# Generated by NetworkManager
search us-east-2.compute.internal
nameserver ::1
~~~

And the following zone configured in bind
~~~
[root@ip-10-20-0-181 ~]# cat /var/named/test.net.zone
$TTL    86400

@       IN      SOA     test.net root.test.net (
        2016050204
        3600
        900
        604800
        86400
)

@               IN      NS         testbox
testbox         IN      AAAA       2600:1f16:a82:9b01:5a89:f06f:dde4:7b5e
malware         IN      AAAA       2600:1f16:a82:9b01:cab2:a7c0:e2cb:1162
goodware        IN      A          10.20.0.181
~~~

It appears that Resolv needs me to explicitly request the AAAA resource for malware.test.net in order to get the IPv6 address in this situation. It doesn't seem to need that for IPv4.

~~~
irb(main):001:0> require 'resolv'
=> true
irb(main):002:0> resolver = Resolv.new
=> #<Resolv:0x0000000001db3c78 @resolvers=[#<Resolv::Hosts:0x0000000001db3c28 @filename="/etc/hosts", @mutex=#<Thread::Mutex:0x0000000001db3bd8>, @initialized=nil>, #<Resolv::DNS:0x0000000001db3b88 @mutex=#<Thread::Mutex:0x0000000001db3b38>, @config=#<Resolv::DNS::Config:0x0000000001db3ae8 @mutex=#<Thread::Mutex:0x0000000001db3a48>, @config_info=nil, @initialized=nil, @timeouts=nil>, @initialized=nil>]>
irb(main):003:0> resolver.getaddresses("malware.test.net")
=> []
irb(main):004:0> resolver.getaddresses("goodware.test.net")
=> ["10.20.0.181"]
irb(main):005:0> dns_resolver = Resolv::DNS.new
=> #<Resolv::DNS:0x0000000001d2a040 @mutex=#<Thread::Mutex:0x0000000001d29fa0>, @config=#<Resolv::DNS::Config:0x0000000001d29f78 @mutex=#<Thread::Mutex:0x0000000001d29e60>, @config_info=nil, @initialized=nil, @timeouts=nil>, @initialized=nil>
irb(main):006:0> dns_resolver.getresource("malware.test.net", Resolv::DNS::Resource::IN::AAAA)
=> #<Resolv::DNS::Resource::IN::AAAA:0x0000000001cbaf38 @address=#<Resolv::IPv6 2600:1F16:A82:9B01:CAB2:A7C0:E2CB:1162>, @ttl=86400>
~~~

Based on Resolv's documentation I would expect to get back the IPv6 address for malware.test.net

---Files--------------------------------
resolv-use_ipv6-14922.patch (2.08 KB)


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