Bug #11152: Resolv::DNS should use Search Domains provided in /etc/resolv.conf by default

• Status: Closed
• Assignee: -
• Target version: -
• Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN

[IronYuppie (David Aronchick)]

For some reason Resolv::DNS does not use search domains. Many downstream projects rely on Resolv, and this appears broken. I'm showing this below in Kubernetes, but it's based on the search domain(s), rather than a cluster issue.

[1] pry(main)> require 'resolv'
=> true
[2] pry(main)> Resolv::DNS.new.getaddresses('client')
=> []
[3] pry(main)> nameservers = ["10.0.0.10", "169.254.169.254", "10.240.0.1"]
[4] pry(main)> search_domains = ["default.kubernetes.local", "kubernetes.local", "c.bar-foobar-91020.internal.", "55618245300.google.internal.", "google.internal."]
[5] pry(main)> a = Resolv::DNS.new(:nameserver => nameservers, :search => search_domains)
[...output...]
[6] pry(main)> a.getaddresses('client')
=> [#<Resolv::IPv4 10.0.118.178>]

[tenderlovemaking (Aaron Patterson)]

• Status changed from Open to Feedback

Hi,

It should parse your /etc/resolv.conf file. Can you post your /etc/resolv.conf? Maybe it's a problem with the parser.

[lisinge (Micke Lisinge)]

Aaron Patterson wrote:

Hi,

It should parse your /etc/resolv.conf file. Can you post your /etc/resolv.conf? Maybe it's a problem with the parser.

I am seeing the same problem, tested with Ruby 2.2.5 and 2.3.1.

My code is running on a kubernetes cluster with docker just like David's.

This is the resolv.conf and David's probably looks the same:

search staging.svc.cluster.local svc.cluster.local cluster.local c.foo-project.internal. google.internal.
nameserver 10.7.240.10
options ndots:5

With the config above Resolv::DNS::Config.default_config_hash returns:

Resolv::DNS::Config.default_config_hash
=> {:nameserver=>["10.0.1.1"], :search=>nil, :ndots=>1}

[jeremyevans0 (Jeremy Evans)]

It looks like the problem is a kubernetes-specific issue. With your resolv.conf file, I get the following for Resolv::DNS::Config.default_config_hash:

{:nameserver=>["10.7.240.10"], :search=>["staging.svc.cluster.local", "svc.cluster.local", "cluster.local", "c.foo-project.internal.", "google.internal."], :ndots=>5}

Based on the results of yourResolv::DNS::Config.default_config_hash output, I think the only explanation is that it is the /etc/resolv.conf is different from what is displayed. What is File.read('/etc/resolv.conf') if run directly after require 'resolv'? Alternatively, you can provide a self-contained reproducible example showing the problem?

[jeremyevans0 (Jeremy Evans)]

• Status changed from Feedback to Closed