Remove DNS lookups during websocket connection initiation

[ud1]

The ServletServerHttpRequest getLocalAddress and getRemoteAddress methods contain additional DNS queries. The servletRequest.getLocalName() method requests a hostname from an IP address, and the InetSocketAddress constructor calls InetAddress.getByName, which requests an IP address from a hostname.

It looks like these requests can be omitted if you use servletRequest.getLocalAddr() and servletRequest.getRemoteAddr() instead of get*Name() methods.

If DNS is not properly configured on the server, then the establishment of a websocket connection hangs (for a few seconds).

Problematic stack trace:

	at java.net.Inet4AddressImpl.getHostByAddr(Native Method)
	at java.net.InetAddress$2.getHostByAddr(InetAddress.java:933)
	at java.net.InetAddress.getHostFromNameService(InetAddress.java:618)
	at java.net.InetAddress.getHostName(InetAddress.java:560)
	at java.net.InetAddress.getHostName(InetAddress.java:532)
	at org.apache.tomcat.util.net.NioEndpoint$NioSocketWrapper.populateLocalName(NioEndpoint.java:1506)
	at org.apache.tomcat.util.net.SocketWrapperBase.getLocalName(SocketWrapperBase.java:277)
	at org.apache.coyote.AbstractProcessor.action(AbstractProcessor.java:478)
	at org.apache.coyote.Request.action(Request.java:517)
	at org.apache.catalina.connector.Request.getLocalName(Request.java:1357)
	at org.apache.catalina.connector.RequestFacade.getLocalName(RequestFacade.java:1002)
	at org.springframework.http.server.ServletServerHttpRequest.getLocalAddress(ServletServerHttpRequest.java:200)
	at org.springframework.web.socket.server.standard.AbstractStandardUpgradeStrategy.upgrade(AbstractStandardUpgradeStrategy.java:116)
	at org.springframework.web.socket.server.support.AbstractHandshakeHandler.doHandshake(AbstractHandshakeHandler.java:297)
	at org.springframework.web.socket.server.support.WebSocketHttpRequestHandler.handleRequest(WebSocketHttpRequestHandler.java:178)
	at org.springframework.web.servlet.mvc.HttpRequestHandlerAdapter.handle(HttpRequestHandlerAdapter.java:52)
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1067)
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:963)
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898)

The impression is that these addresses are not even used by Spring, but are only needed to ensure the operation of the WebSocketSession methods getLocalAddress() and getRemoteAddress(), and we don't use these methods at all.

[ud1]

There are two classes named ServletServerHttpRequest, first one org.springframework.http.server.ServletServerHttpRequest and the second org.springframework.http.server.reactive.ServletServerHttpRequest.
The reactive.ServletServerHttpRequest getLocalAddress method already uses getLocalAddr() method.

[lrgrz]

I'm afraid the issue is not resolved.

The AbstractStandardUpgradeStrategy still tries to get InetSocketAddresses during upgrade:

	@Override
	public void upgrade(ServerHttpRequest request, ServerHttpResponse response,
			@Nullable String selectedProtocol, List<WebSocketExtension> selectedExtensions,
			@Nullable Principal user, WebSocketHandler wsHandler, Map<String, Object> attrs)
			throws HandshakeFailureException {

		HttpHeaders headers = request.getHeaders();
		InetSocketAddress localAddr = null;
		try {
			localAddr = request.getLocalAddress();
		}
		catch (Exception ex) {
			// Ignore
		}
		InetSocketAddress remoteAddr = null;
		try {
			remoteAddr = request.getRemoteAddress();
		}
		catch (Exception ex) {
			// Ignore
		}

and ServerHttpRequest uses constructor of InetSocketAddress, which performs DNS lookup:

	@Override
	public InetSocketAddress getLocalAddress() {
		return new InetSocketAddress(this.servletRequest.getLocalAddr(), this.servletRequest.getLocalPort());
	}

	@Override
	public InetSocketAddress getRemoteAddress() {
		return new InetSocketAddress(this.servletRequest.getRemoteHost(), this.servletRequest.getRemotePort());
	}

(checked on spring 5.3.20 and java 17)

[sbrannen]

@lrgrz, this issue was closed back in April.

If you think you have discovered a bug or regression, please create a new issue to address that.

Thanks