IPv6 only operation (wish)

[steelman]

I'd like Transmission to offer (with appropriate configuration options) IPv6 only operation. First: avoid advertising IPv4 address and accept only IPv6 incoming connections (if that's possible, I don't know the protocol). Second: don't connect with IPv4.

Such operation could be suggested if a machine has a public IPv6 address (including 6to4 and Teredo?) but only an RFC1918 (private) IPv4 address.

[jordan]

What is the use case for avoiding the overwhelming majority of peers? This sounds like an ideological option that I can't see many users choosing.

[steelman]

OK. I admit it's a bit ideological but...

There is a network (I admit it's only one in my case, but if you consider Teredo) with quite strict rules considering IPv4 traffic (incoming TCP/IPv4 connections are blocked with a stateful FW) but no one cares about tunneled IPv6. In such network it might be worth to take some measures to optimise operation for IPv6 so other peers won't try to connect us with TCP/IPv4.

There is a small tweak for honesty that could be made regardless of any optimization. If Transmission receives a list of peers from a tracker (or any other source) and there are two peers with the same peer_id and different address families, it chooses peer's IPv6 (or IPv4 if a user says so) and remove the other from the list. I've seen many times two connections to the same peer: an IPv4 and an IPv6 Teredo or 6to4 one terminated at the same IPv4 address. That enabled me to suck twice as fast but...