code: protected void validateCheckpointerAddress(InetAddress configuredRemoteAddress)
        throws IOException {
      InetAddress remoteAddress = Server.getRemoteIp();
      InjectionHandler.processEvent(InjectionEvent.NAMENODE_VERIFY_CHECKPOINTER,
          remoteAddress);
  
      LOG.info("Verify: received request from: " + remoteAddress);
  
      if (remoteAddress == null) {
        LOG.info("Verify: Remote address is NULL");
        throw new IOException("Verify: Remote address is null");
      }
  
      // if the address is not configured then skip checking
      if (configuredRemoteAddress == null
          || configuredRemoteAddress.equals(new InetSocketAddress("0.0.0.0", 0)
              .getAddress())) {
        LOG.info("Verify: Skipping check since the configured address is: "
            + configuredRemoteAddress);
        return;
      }
  
      // compare addresses
      if (!remoteAddress.equals(configuredRemoteAddress)) {
        String msg = "Verify: Configured standby is :"
            + configuredRemoteAddress + ", not allowing: " + remoteAddress
            + " to register";
        LOG.warn(msg);
        throw new IOException(msg);
      }
    }
docs: Checks if the ip of the caller is equal to the given configured address.
  
  @param configuredRemoteAddress
  @throws IOException