This and the follow-up routing-related changes target to remove or
reduce `struct rt_addrinfo` usage and use recently-landed nhop(9)
KPI instead.
Traditionally `rt_addrinfo` structure has been used to propagate all necessary
information between the protocol/rtsock and a routing layer. Many
functions inside routing subsystem uses it internally. However, using
this structure became somewhat complicated, as there are too many ways
of specifying a single state and verifying data consistency is hard.
For example, arerouting flgs consistent with mask/gateway sockaddr pointers?
Is mask really a host mask? Are sockaddr "valid" (e.g. properly zeroed, masked,
have proper length)? Are they mutable? Is the suggested interface specified
by the interface index embedded into the sockadd_dl gateway, or passed
as RTAX_IFP parameter, or directly provided by rti_ifp or it needs to
be derived from the ifa?
These (and other similar) questions have to be considered every time when
a function has `rt_addrinfo` pointer as an argument.
The new approach is to bring more control back to the protocols and
construct the desired routing objects themselves - in the end, it's the
protocol/subsystem who knows the desired outcome.
This specific diff changes the following:
* add explicit basic low-level radix operations:
add_route() (renamed from add_route_nhop())
delete_route() (factored from change_route_nhop())
change_route() (renamed from change_route_nhop)
* remove "info" parameter from change_route_conditional() as a part
of reducing rt_addrinfo usage in the internal KPIs
* add lookup_prefix_rt() wrapper for doing re-lookups after
RIB lock/unlock
Differential Revision: https://reviews.freebsd.org/D36070
MFC after: 2 weeks
0d60e88b41