Split in6_selectsrc() into in6_selectsrc_addr() and in6_selectsrc_socket().
in6_selectsrc() has 2 class of users: socket-based one (raw/udp/pcb/etc) and
socket-less (ND code). The main reason for that change is inability to specify non-default FIB for callers w/o socket since (internally) inpcb is used to determine fib.
As as result, add 2 wrappers for in6_selectsrc() (making in6_selectsrc()
- in6_selectsrc_socket() for the former class. Embed scope_ambiguous check along with returning hop limit when needed.
- in6_selectsrc_addr() for the latter case. Add 'fibnum' argument and pass IPv6 address w/ explicitly specified scope as separate argument.
Reviewed by: ae (previous version)