Bug #14612: IPv6 address inconsistency (downcase vs. upcase)

• Status: Closed
• Assignee: akr (Akira Tanaka)
• Target version: -
• ruby -v: 2.5.0
• Backport: 2.3: UNKNOWN, 2.4: UNKNOWN, 2.5: UNKNOWN

[chucke (Tiago Cardoso)]

I've noticed that sometimes ip addresses re shown using a-f characters in downcase, other times upcase. Here is a small script to show results:

require "resolv"
require "socket"
puts TCPSocket.getaddress("nghttp2.org") #=> "2400:8902::f03c:91ff:fe69:a454"
puts Resolv.getaddresses("nghttp2.org") #=> ["139.162.123.134", "2400:8902::F03C:91FF:FE69:A454"]

Results might be system-dependent (I'm using Mac OS High Sierra).

This makes compare operations a bit harder.

[shevegen (Robert A. Heiler)]

Is there a standard that mandates or prefers either variant?

If not then perhaps ruby should decide on which variant to
prefer.

[hugopeixoto (Hugo Peixoto)]

• File resolv-ipv6-to_s.patch resolv-ipv6-to_s.patch added

shevegen (Robert A. Heiler) wrote:

Is there a standard that mandates or prefers either variant?

RFC 5952 recommends the usage of lower case letters: https://tools.ietf.org/html/rfc5952#section-4.3

The Resolv module seems to be formatting the addresses in uppercase:

Resolv::IPv6.create("2400:8902::f03c:91ff:fe69:a454").to_s #=> "2400:8902::F03C:91FF:FE69:A454"

After the patch, Resolv#getaddresses now formats addresses in lowercase:

Resolv.getaddresses("nghttp2.org") #=> ["139.162.123.134", "2400:8902::f03c:91ff:fe69:a454"]

I noticed there's an ipaddr module that handles formatting as well, so in the attached patch I am using IPAddr#new to reuse the existing code. I also added some tests.

I am not sure if adding the dependency here is the right way to do it.

[jeremyevans0 (Jeremy Evans)]

• File resolv-ipv6-lowercase.patch resolv-ipv6-lowercase.patch added
• Status changed from Open to Assigned
• Assignee set to akr (Akira Tanaka)

I agree that Ruby should consistently use lowercase for IPv6 addresses. However, I don't think we should introduce a dependency on ipaddr to resolv. For one, it changes how the IPv6 addresses with noncontiguous 0 components are displayed. Attached a simpler patch that just uses %x instead of %X in sprintf.

[akr (Akira Tanaka)]

• Status changed from Assigned to Closed

Applied in changeset git|1da3a31a5f0211db121e0df4ca456838a437537f.

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Use lowercase letters for IPv6 addresses.

Reported by chucke (Tiago Cardoso).
Patch by jeremyevans0 (Jeremy Evans).
[Bug #14612]