Feature #19064: UDPSocket#bind does not take AddrInfo, despite documentation saying it should

• Status: Open
• Assignee: -
• Target version: -

[mcr (Michael Richardson)]

https://docs.ruby-lang.org/en/master/Socket.html#method-i-bind says that this code should work:

require 'socket'

# use Addrinfo
socket = Socket.new(:INET, :STREAM, 0)
socket.bind(Addrinfo.tcp("127.0.0.1", 2222))
p socket.local_address #=> #<Addrinfo: 127.0.0.1:2222 TCP>

and it does, but UDPSocket does not like Addrinfo:

socket = UDPSocket.new(Socket::AF_INET6)
ai=Addrinfo.udp("127.0.0.1", 2224)
socket.bind(ai, 0)

A reason to use an Addrinfo rather than a string is because it came from, for instance, Socket.getifaddrs, and might have scope and other information attached, like:

#<Addrinfo: fe80::f58e:d5ea:41e0:2555%eth0>

Seen on versions back to 2.6.6, but tested with ruby-head to be sure.

[tomgilligan (Tom Gilligan)]

The linked documentation is for Socket, not UDPSocket. The documentation for UDPSocket does not suggest that it accepts an Addrinfo. https://docs.ruby-lang.org/en/master/UDPSocket.html
The difference between Socket/UDPSocket is confusing and could be clarified. To be honest I'm not sure if UDPSocket/TCPSocket classes are very helpful at all (especially in light of potential confusion with Socket).

If you would like to create a UDP socket using Socket and give it an Addrinfo, you can do so with

require 'socket'

socket = Socket.new(:AF_INET6, :DGRAM, 0)
ai=Addrinfo.udp("::1", 2224)
socket.bind(ai)
p socket.local_address #=> #<Addrinfo: [::1]:2224 UDP>

Or if you want to use IPv4:

require 'socket'

socket = Socket.new(:AF_INET, :DGRAM, 0)
ai=Addrinfo.udp("127.0.0.1", 2224)
socket.bind(ai)
p socket.local_address #=> #<Addrinfo: 127.0.0.1:2224 UDP>

[jeremyevans0 (Jeremy Evans)]

• Tracker changed from Bug to Feature
• ruby -v deleted (ruby 3.2.0dev (2022-10-16T09:31:08Z master ba9c0d0b9f) [x86_64-linux)
• Backport deleted (2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN)

UDPSocket is not a subclass of Socket, so the fact that Addrinfo instances work for Socket (as documented), but do not work for UDPSocket is not a bug. I agree that having UDPSocket support Addrinfo would be useful, switching to feature request.