message: Fix multicast prefix check
diff: @@ -64,8 +64,8 @@ bool ipv4_address::is_loopback() const noexcept {
  }
  bool ipv4_address::is_multicast() const noexcept {
  - // All addresses in 224.0.0.0/8 are considered loopback addresses.
  - return (bits_ & net_order(0xFF000000)) == net_order(0xE0000000);
  + // All addresses in 224.0.0.0/4 are considered multicast addresses.
  + return (bits_ & net_order(0xF0000000)) == net_order(0xE0000000);
  }
  // -- related free functions ---------------------------------------------------
  