Fix HttpUtil.isKeepAlive to behave correctly when Connection is a comma separated list (#8924)

Motivation:

According to the specification, the "Connection" header's syntax is:

"
The Connection header field's value has the following grammar:

     Connection        = 1#connection-option
     connection-option = token

Connection options are case-insensitive.
"
https://tools.ietf.org/html/rfc7230#section-6.1

This means that Connection's value can have at least one element or
a comma separated list with elements
When calculating whether the connection can remain open,
HttpUtil.isKeepAlive(HttpMessage) should take this into account.

Modifications:

- Check for "close" and "keep-alive" in a comma separated list
- Add unit test

Result:

HttpUtil.isKeepAlive(HttpMessage) works correctly when "Connection: Upgrade, close"

codec-http/src/main/java/io/netty/handler/codec/http/HttpUtil.java

@@ -67,16 +67,9 @@ public final class HttpUtil {
      * {@link HttpVersion#isKeepAliveDefault()}.
      */
     public static boolean isKeepAlive(HttpMessage message) {
-        CharSequence connection = message.headers().get(HttpHeaderNames.CONNECTION);
+        return !message.headers().containsValue(HttpHeaderNames.CONNECTION, HttpHeaderValues.CLOSE, true) &&
-        if (HttpHeaderValues.CLOSE.contentEqualsIgnoreCase(connection)) {
+               (message.protocolVersion().isKeepAliveDefault() ||
-            return false;
+                message.headers().containsValue(HttpHeaderNames.CONNECTION, HttpHeaderValues.KEEP_ALIVE, true));
-        }
-
-        if (message.protocolVersion().isKeepAliveDefault()) {
-            return !HttpHeaderValues.CLOSE.contentEqualsIgnoreCase(connection);
-        } else {
-            return HttpHeaderValues.KEEP_ALIVE.contentEqualsIgnoreCase(connection);
-        }
     }
 
     /**

codec-http/src/test/java/io/netty/handler/codec/http/HttpUtilTest.java

@@ -317,4 +317,25 @@ public class HttpUtilTest {
             "http:localhost/http_1_0");
         assertFalse(HttpUtil.isKeepAlive(http10Message));
     }
+
+    @Test
+    public void testKeepAliveIfConnectionHeaderMultipleValues() {
+        HttpMessage http11Message = new DefaultHttpRequest(HttpVersion.HTTP_1_1, HttpMethod.GET,
+            "http:localhost/http_1_1");
+        http11Message.headers().set(
+                HttpHeaderNames.CONNECTION, HttpHeaderValues.UPGRADE + ", " + HttpHeaderValues.CLOSE);
+        assertFalse(HttpUtil.isKeepAlive(http11Message));
+
+        http11Message.headers().set(
+                HttpHeaderNames.CONNECTION, HttpHeaderValues.UPGRADE + ", Close");
+        assertFalse(HttpUtil.isKeepAlive(http11Message));
+
+        http11Message.headers().set(
+                HttpHeaderNames.CONNECTION, HttpHeaderValues.CLOSE + ", " + HttpHeaderValues.UPGRADE);
+        assertFalse(HttpUtil.isKeepAlive(http11Message));
+
+        http11Message.headers().set(
+                HttpHeaderNames.CONNECTION, HttpHeaderValues.UPGRADE + ", " + HttpHeaderValues.KEEP_ALIVE);
+        assertTrue(HttpUtil.isKeepAlive(http11Message));
+    }
 }