net::/ipv4:: namespace, mac/addr filter framework with default filters, dlog on registry overflow

include/dispatch.h

@@ -17,15 +17,17 @@ struct responder {
 
     template <typename T>
     void respond(const T& msg) const {
-        const auto& ns = net_get_state();
+        const auto& ns = net::get_state();
         prepend_buffer<4096> buf;
         span_writer out(buf.payload_ptr(), 2048);
         auto r = encode_response_into(out, message_id, msg);
-        if (!r) return;
+        if (!r) {
+            return;
+        }
         buf.append(*r);
         udp::prepend(buf, reply_to.mac, ns.mac, ns.ip, reply_to.ip,
                      dispatch_listen_port_be(), reply_to.port, *r);
-        net_send_raw(buf.span());
+        net::send_raw(buf.span());
     }
 };