IPv6 support

[dsalt]

The servers (both game and master) on unvanquished.net also listen on IPv6. Would be nice to have apelsin handle that.

[Cadynum]

How does the IPv6 support work:

• Does the server simply listen on two sockets and tell two master servers?
• If a client and server supports both v4 and v6, which should be preferred?
• Is a server uniquely identified by the port number?
• Is it possible, from just getting the two master responses, to somehow avoid sending the same server two requests, thus wasting bandwidth?

(Unfortunately my current ISP does not have have v6 support)

[dsalt]

• The server connects separately over IPv4 and IPv6 to the master server. Consequently, the master server (if it's listening for both types) will see two game servers where there's really one. (We need to fix this.)
• Which should be preferred depends on various factors: ping time, for one.
• Servers are identified by the combination of IP address and port number.
• Maybe. You could make inferences about 6to4 addresses and usually be right.

getserversExt UNVANQUISHED protocol [ipv4|ipv6] [full] [empty]

You'll see one or more getserversExtResponse packets which contain the following, in this order:

• NUL
• Packet no. (as string)
• NUL
• Packet count (as string)
• NUL
• Label information (number and text, for all servers in this packet), terminated by \ or / according to following content
• 0 or more server addresses, each being one of the following:
  • IPv4 address – \, address, port (network byte order); or
  • IPv6 address – /, address, port (network byte order)
• Terminating \

For testing, you can run a local master server (ours supports IPv6) or – and this works well with static IP – set up 6to4 (or equivalent).