MFC r287649:
Use a common subroutine to fetch and zero protocol stats instead of
duplicating roughly similar code for each protocol.

Merge r259562,r259566,r259638,r259645,r260124 by melifaro:

Switch netstat -rn to use standard API for retrieving list
of routes instead of peeking inside in-kernel radix via kget.

Merge r259562,r259566,r259638,r259645,r260124 by melifaro:

Switch netstat -rn to use standard API for retrieving list
of routes instead of peeking inside in-kernel radix via kget.