verifyId

Verify that nid is a valid secure id for a node observed at sourceIp. Port of bool verify_id(node_id const& nid, address const& source_ip).

Local/private source addresses are always accepted (their secure-id derivation would be meaningless), matching if (aux::is_local(source_ip)) return true;. Otherwise we recompute the secure prefix using nid[19] as r and require the first two bytes to match and the top 5 bits of the third byte to match.