Fix connection timeout configuration for Netty

Update `NettyWebServerFactoryCustomizer` to deal with the fact that
Netty treats `0` and negative connection timeout values differently to
Tomcat, Undertow and Jetty.

See gh-16535

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/embedded/NettyWebServerFactoryCustomizer.java

@@ -58,10 +58,12 @@ public class NettyWebServerFactoryCustomizer
 	@Override
 	public void customize(NettyReactiveWebServerFactory factory) {
 		factory.setUseForwardHeaders(getOrDeduceUseForwardHeaders(this.serverProperties, this.environment));
-		PropertyMapper propertyMapper = PropertyMapper.get();
-		propertyMapper.from(this.serverProperties::getMaxHttpHeaderSize).whenNonNull().asInt(DataSize::toBytes)
+		PropertyMapper propertyMapper = PropertyMapper.get().alwaysApplyingWhenNonNull();
+		propertyMapper.from(this.serverProperties::getMaxHttpHeaderSize).asInt(DataSize::toBytes)
 				.to((maxHttpRequestHeaderSize) -> customizeMaxHttpHeaderSize(factory, maxHttpRequestHeaderSize));
-		propertyMapper.from(this.serverProperties::getConnectionTimeout).whenNonNull().asInt(Duration::toMillis)
+		propertyMapper.from(this.serverProperties::getConnectionTimeout).asInt(Duration::toMillis)
+				.whenNot((connectionTimout) -> connectionTimout.equals(0))
+				.as((connectionTimeout) -> connectionTimeout.equals(-1) ? 0 : connectionTimeout)
 				.to((duration) -> factory.addServerCustomizers(getConnectionTimeOutCustomizer(duration)));
 	}
 

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/embedded/NettyWebServerFactoryCustomizerTests.java

@@ -16,21 +16,27 @@
 
 package org.springframework.boot.autoconfigure.web.embedded;
 
+import java.time.Duration;
+
 import org.junit.Before;
 import org.junit.Test;
 
 import org.springframework.boot.autoconfigure.web.ServerProperties;
 import org.springframework.boot.context.properties.source.ConfigurationPropertySources;
 import org.springframework.boot.web.embedded.netty.NettyReactiveWebServerFactory;
+import org.springframework.boot.web.embedded.netty.NettyServerCustomizer;
 import org.springframework.mock.env.MockEnvironment;
 
+import static org.mockito.Mockito.any;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
 
 /**
  * Tests for {@link NettyWebServerFactoryCustomizer}.
  *
  * @author Brian Clozel
+ * @author Artsiom Yudovin
  */
 public class NettyWebServerFactoryCustomizerTests {
 
@@ -48,6 +54,12 @@ public class NettyWebServerFactoryCustomizerTests {
 		this.customizer = new NettyWebServerFactoryCustomizer(this.environment, this.serverProperties);
 	}
 
+	private void clear() {
+		this.serverProperties.setUseForwardHeaders(null);
+		this.serverProperties.setMaxHttpHeaderSize(null);
+		this.serverProperties.setConnectionTimeout(null);
+	}
+
 	@Test
 	public void deduceUseForwardHeaders() {
 		this.environment.setProperty("DYNO", "-");
@@ -71,4 +83,24 @@ public class NettyWebServerFactoryCustomizerTests {
 		verify(factory).setUseForwardHeaders(true);
 	}
 
+	@Test
+	public void setConnectionTimeoutAsZero() {
+		clear();
+		this.serverProperties.setConnectionTimeout(Duration.ZERO);
+
+		NettyReactiveWebServerFactory factory = mock(NettyReactiveWebServerFactory.class);
+		this.customizer.customize(factory);
+		verify(factory, times(0)).addServerCustomizers(any(NettyServerCustomizer.class));
+	}
+
+	@Test
+	public void setConnectionTimeoutAsMinusOne() {
+		clear();
+		this.serverProperties.setConnectionTimeout(Duration.ofNanos(-1));
+
+		NettyReactiveWebServerFactory factory = mock(NettyReactiveWebServerFactory.class);
+		this.customizer.customize(factory);
+		verify(factory, times(1)).addServerCustomizers(any(NettyServerCustomizer.class));
+	}
+
 }