Bug #10550: Resolv::DNS.getaddresses returns no IPs when nameserver returns in differing case than query

• Status: Closed
• Assignee: -
• Target version: -
• ruby -v: ruby 2.1.2p95 (2014-05-08 revision 45877) [x86_64-linux]
• Backport: 2.0.0: DONE, 2.1: DONE, 2.2: DONE

[jonhyman (Jon Hyman)]

Our servers are hosted with Rackspace and following patching of BIND, their DNS servers started returning different casing for the ANSWER. For example, here is me resolving sendgrid.com. You'll see the first command returns "sendgrid.com" in the answer section, while another returns "SENDGRID.COM".

$ dig sendgrid.com

; <<>> DiG 9.8.1-P1 <<>> sendgrid.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 7895
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;sendgrid.com.			IN	A

;; ANSWER SECTION:
sendgrid.com.		5	IN	A	104.20.21.26
sendgrid.com.		5	IN	A	104.20.20.26

;; Query time: 2 msec
;; SERVER: 69.20.0.164#53(69.20.0.164)
;; WHEN: Wed Nov 26 22:21:04 2014
;; MSG SIZE  rcvd: 62

$ dig sendgrid.com

; <<>> DiG 9.8.1-P1 <<>> sendgrid.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 21767
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;sendgrid.com.			IN	A

;; ANSWER SECTION:
SENDGRID.com.		5	IN	A	104.20.20.26
SENDGRID.com.		5	IN	A	104.20.21.26

The problem here is that due to https://github.com/ruby/ruby/blob/570c028c7ebb18c6d276e5fac3a1b20f76f28db7/lib/resolv.rb#L579, the addresses won't get returned because of the case difference. As a result, Resolv::DNS sporadically returns no IP addresses. In my example, let's say that I'm calling Resolv::DNS.new.getaddresses("sendgrid.com") and it returns uppercase. The message returned will be something like this

=> #<Resolv::DNS::Message:0x007f3eff488a88 @id=26224, @qr=1, @opcode=0, @aa=0, @tc=0, @rd=1, @ra=1, @rcode=0, @question=[[#<Resolv::DNS::Name: sendgrid.com.>, Resolv::DNS::Resource::IN::A]], @answer=[[#<Resolv::DNS::Name: SENDGRID.com.>, 1, #<Resolv::DNS::Resource::IN::A:0x007f3eff47f618 @address=#<Resolv::IPv4 104.20.21.26>, @ttl=1>], [#<Resolv::DNS::Name: SENDGRID.com.>, 1, #<Resolv::DNS::Resource::IN::A:0x007f3eff47e678 @address=#<Resolv::IPv4 104.20.20.26>, @ttl=1>]], @authority=[], @additional=[]>

whereas "n0" will be

=> #<Resolv::DNS::Name: sendgrid.com.>

so the comparison in line 579 returns false.

---

Here's another example of this in an irb console on my Rackspace server

require 'resolv'
r = Resolv::DNS.new
10.times { puts r.getaddresses("sendgrid.com").inspect }
[#<Resolv::IPv4 104.20.20.26>, #<Resolv::IPv4 104.20.21.26>]
[#<Resolv::IPv4 104.20.20.26>, #<Resolv::IPv4 104.20.21.26>]
[#<Resolv::IPv4 104.20.21.26>, #<Resolv::IPv4 104.20.20.26>]
[]
[#<Resolv::IPv4 104.20.20.26>, #<Resolv::IPv4 104.20.21.26>]
[#<Resolv::IPv4 104.20.20.26>, #<Resolv::IPv4 104.20.21.26>]
[]
[]
[#<Resolv::IPv4 104.20.20.26>, #<Resolv::IPv4 104.20.21.26>]
[#<Resolv::IPv4 104.20.21.26>, #<Resolv::IPv4 104.20.20.26>]
=> 10

DNS is case-insensitive, so the comparison should be case-insensitive as well.

[jonhyman (Jon Hyman)]

My pasting got stripped:

Here is the message returned

#<Resolv::DNS::Message:0x007f3eff488a88 @id=26224, @qr=1, @opcode=0, @aa=0, @tc=0, @rd=1, @ra=1, @rcode=0, @question=[[#<Resolv::DNS::Name: sendgrid.com.>, Resolv::DNS::Resource::IN::A]], @answer=[[#<Resolv::DNS::Name: SENDGRID.com.>, 1, #<Resolv::DNS::Resource::IN::A:0x007f3eff47f618 @address=#<Resolv::IPv4 104.20.21.26>, @ttl=1>], [#<Resolv::DNS::Name: SENDGRID.com.>, 1, #<Resolv::DNS::Resource::IN::A:0x007f3eff47e678 @address=#<Resolv::IPv4 104.20.20.26>, @ttl=1>]], @authority=[], @additional=[]>

Here is "n0"

=> #<Resolv::DNS::Name: sendgrid.com.>

Here is the output from the 10.times loop.

[#<Resolv::IPv4 104.20.20.26>, #<Resolv::IPv4 104.20.21.26>]
[#<Resolv::IPv4 104.20.20.26>, #<Resolv::IPv4 104.20.21.26>]
[#<Resolv::IPv4 104.20.21.26>, #<Resolv::IPv4 104.20.20.26>]
[]
[#<Resolv::IPv4 104.20.20.26>, #<Resolv::IPv4 104.20.21.26>]
[#<Resolv::IPv4 104.20.20.26>, #<Resolv::IPv4 104.20.21.26>]
[]
[]
[#<Resolv::IPv4 104.20.20.26>, #<Resolv::IPv4 104.20.21.26>]
[#<Resolv::IPv4 104.20.21.26>, #<Resolv::IPv4 104.20.20.26>]

[bjmllr (Ben Miller)]

I ran into some case-sensitivity issues while using Resolv as well. A patch to Resolv::DNS::Name#== seemed to solve it for me.

https://github.com/ruby/ruby/pull/801

[nobu (Nobuyoshi Nakada)]

• Description updated (diff)

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Closed
• % Done changed from 0 to 100

Applied in changeset r49073.

---

resolv.rb: case-insensitive comparison

• lib/resolv.rb (Resolv::DNS::Name#==): DNS is case-insensitive, so the
  comparison should be case-insensitive as well.
  [ruby-core:66498] [Bug #10550]

[nagachika (Tomoyuki Chikanaga)]

• Backport changed from 2.0.0: UNKNOWN, 2.1: UNKNOWN to 2.0.0: REQUIRED, 2.1: REQUIRED, 2.2: REQUIRED

[nagachika (Tomoyuki Chikanaga)]

memo: r49071 and r49072 are similar fixes for resolv.rb

[duerst (Martin Dürst)]

• Related to Feature #10085: Add non-ASCII case conversion to String#upcase/downcase/swapcase/capitalize added

[usa (Usaku NAKAMURA)]

• Backport changed from 2.0.0: REQUIRED, 2.1: REQUIRED, 2.2: REQUIRED to 2.0.0: DONE, 2.1: REQUIRED, 2.2: REQUIRED

Backported r49701, r49702, r49703 and r49708 into ruby_2_0_0 at r49252.

[naruse (Yui NARUSE)]

• Backport changed from 2.0.0: DONE, 2.1: REQUIRED, 2.2: REQUIRED to 2.0.0: DONE, 2.1: REQUIRED, 2.2: DONE

ruby_2_2 r49281 merged revision(s) 49071,49072,49073,49078.

[nagachika (Tomoyuki Chikanaga)]

• Backport changed from 2.0.0: DONE, 2.1: REQUIRED, 2.2: DONE to 2.0.0: DONE, 2.1: DONE, 2.2: DONE

Backported into ruby_2_1 branch at r49775.