Most protocols in IPv6 mode use link-local source addresses and expect
that there is one on each active interface. The old code depended on
assumption that if there is some IPv6 address on iface, there is also an
IPv6 link-local address on that iface (added by kernel when the iface
went up). Unfortunately, that is not generally true, as a configured
global address sometimes ceases to be tentative (finishes DOD) before
a link-local address on the same iface. In such case a protocol iface
(namely RAdv and Babel) is activated, but fails to found link-local
address and stays in failed state.
The patch fixes that by tracking 'primary' IPv6 link-local address,
sending iface restart notifications when it changes and making
protocols ignore iface-up notifications when no such address is
selected for an iface.
The patch implements Default Router Preferences and More-Specific Routes
(RFC 4191) for RAdv protocol, allowing to announce router preference and
more specific routes in router advertisements. Routes can be exported to
RAdv like to regular routing protocols.
Some cleanups, bugfixes and other changes done by Ondrej Zajicek.
Keep a cache of all the relevant prefixes we send out. When a prefix
appears, insert it into the cache. If it dies, keep it there for a
while, marked as dead.
Send out the dead prefixes with zero lifetime.
Adapt the naming conventions to be a bit closer to the other protocols.
proto_radv -> radv_proto
struct radv_proto *ra -> struct radv_proto *p
struct proto *p -> struct proto *P
The RAdv protocol could be configured to change its behavior based on
availability of routes, e.g., do not announce router lifetime when a
default route is not available.
