There are plans to let Bitcoin function as Tor/I2P hidden service.
To do so, we could use the established encoding provided by OnionCat
and GarliCat (without actually using those tools) to embed Tor/I2P
addresses in IPv6.
This patch makes these addresses considered routable, so they can
travel over the Bitcoin network in 'addr' messages. This will hopefully
make it easier to deploy real hidden service support later.
This will make bitcoin relay valid routable IPv6 addresses, and when
USE_IPV6 is enabled, listen on IPv6 interfaces and attempt connections
to IPv6 addresses.
This introduces CNetAddr and CService, respectively wrapping an
(IPv6) IP address and an IP+port combination. This functionality used
to be part of CAddress, which also contains network flags and
connection attempt information. These extra fields are however not
always necessary.
These classes, along with logic for creating connections and doing
name lookups, are moved to netbase.{h,cpp}, which does not depend on
headers.h.
Furthermore, CNetAddr is mostly IPv6-ready, though IPv6
functionality is not yet enabled for the application itself.
