IPv6 support

[Renich Bon Ciric]

Description

Kemal should be able to listen over IPv6.

If i set it up like this:

Kemal.config.host_binding = "::/0" 

It should listen on all IPv6 ranges.

Steps to Reproduce

1. Create a brand new project
2. Setup host_binding to ::/0
3. Watch it fail.

Expected behavior: [What you expect to happen]
Kemal should be listening on all IPv6 ranges.

Actual behavior: [What actually happens]
It fails:

[renich@introdesk myapp]$ crystal run src/myapp.cr 
Unhandled exception: Hostname lookup for ::/0 failed: No address found (Socket::Addrinfo::Error)
  from /usr/share/crystal/src/socket/addrinfo.cr:176:9 in 'initialize:reuse_port'
  from /usr/share/crystal/src/socket/tcp_server.cr:34:3 in 'new:reuse_port'
  from /usr/share/crystal/src/http/server.cr:211:18 in 'bind_tcp'
  from lib/kemal/src/kemal.cr:52:7 in 'run'
  from lib/kemal/src/kemal.cr:16:5 in 'run'
  from lib/kemal/src/kemal.cr:15:3 in 'run'
  from src/myapp.cr:9:1 in '__crystal_main'
  from /usr/share/crystal/src/crystal/main.cr:115:5 in 'main_user_code'
  from /usr/share/crystal/src/crystal/main.cr:101:7 in 'main'
  from /usr/share/crystal/src/crystal/main.cr:127:3 in 'main'
  from /lib64/libc.so.6 in '??'
  from /lib64/libc.so.6 in '__libc_start_main'
  from /home/renich/.cache/crystal/crystal-run-myapp.tmp in '_start'
  from ???

Reproduces how often: [What percentage of the time does it reproduce?]
All the time.

Versions

Crystal 1.3.2 (2022-01-18)

LLVM: 13.0.0
Default target: x86_64-redhat-linux-gnu

Running on Fedora 35.

[Renich Bon Ciric]

OK, it seems: Kemal.config.host_binding = "::" works fine. It doesn't accept the mask /0. I dunno how intuitive that is though.

[Renich Bon Ciric]

Working example:

require "kemal"

get "/" do
  "Hello, world!"
end

Kemal.config.host_binding = "::"
Kemal.run

[Johannes Müller]

I understand the reason your original approach failed is that ::/0 technically isn't a single address, it's an address range. The IP address stack doesn't recognize this.

[Renich Bon Ciric]

Yes, correct. I was hoping to be able to listen to an address range probably. thank you for explaining, @straight-shoota. :D