Filter out known hop-by-hop response headers

src/main/java/io/vertx/httpproxy/impl/HttpUtils.java

@@ -18,8 +18,25 @@
 import java.time.Instant;
 import java.util.List;
 
+import static io.vertx.core.http.HttpHeaders.*;
+
 class HttpUtils {
 
+  // https://datatracker.ietf.org/doc/html/rfc2616#section-13.5.1
+  private static final MultiMap HOP_BY_HOP_HEADERS = MultiMap.caseInsensitiveMultiMap()
+    .add(CONNECTION, "whatever")
+    .add(KEEP_ALIVE, "whatever")
+    .add(PROXY_AUTHENTICATE, "whatever")
+    .add(PROXY_AUTHORIZATION, "whatever")
+    .add("te", "whatever")
+    .add("trailer", "whatever")
+    .add(TRANSFER_ENCODING, "whatever")
+    .add(UPGRADE, "whatever");
+
+  static boolean isHopByHopHeader(String name) {
+    return HOP_BY_HOP_HEADERS.contains(name);
+  }
+
   static Boolean isChunked(MultiMap headers) {
     List<String> te = headers.getAll("transfer-encoding");
     if (te != null) {

src/main/java/io/vertx/httpproxy/impl/ProxiedRequest.java

@@ -44,16 +44,6 @@ public class ProxiedRequest implements ProxyRequest {
   private static final int FLAG_FORWARD_PORT = 8;   // bit 3
   private static final int FLAG_USE_RFC7239 = 16;   // bit 4
 
-  private static final MultiMap HOP_BY_HOP_HEADERS = MultiMap.caseInsensitiveMultiMap()
-    .add(CONNECTION, "whatever")
-    .add(KEEP_ALIVE, "whatever")
-    .add(PROXY_AUTHENTICATE, "whatever")
-    .add(PROXY_AUTHORIZATION, "whatever")
-    .add("te", "whatever")
-    .add("trailer", "whatever")
-    .add(TRANSFER_ENCODING, "whatever")
-    .add(UPGRADE, "whatever");
-
   final ContextInternal context;
   private HttpMethod method;
   private final HttpVersion version;
@@ -203,7 +193,7 @@ Future<ProxyResponse> sendRequest() {
     for (Map.Entry<String, String> header : headers) {
       String name = header.getKey();
       String value = header.getValue();
-      if (!HOP_BY_HOP_HEADERS.contains(name) && !name.equalsIgnoreCase(HttpHeaders.HOST.toString())) {
+      if (!HttpUtils.isHopByHopHeader(name) && !name.equalsIgnoreCase(HttpHeaders.HOST.toString())) {
         request.headers().add(name, value);
       }
     }

src/main/java/io/vertx/httpproxy/impl/ProxiedResponse.java

@@ -212,7 +212,9 @@ public Future<Void> send() {
       String value = header.getValue();
       if (name.equals("content-type") && body != null) {
         // Skip
-      } else if (name.equalsIgnoreCase("date") || name.equalsIgnoreCase("warning") || name.equalsIgnoreCase("transfer-encoding")) {
+      } else if (name.equalsIgnoreCase("date")
+        || name.equalsIgnoreCase("warning")
+        || HttpUtils.isHopByHopHeader(name)) {
         // Skip
       } else {
         proxiedResponse.headers().add(name, value);

src/test/java/io/vertx/tests/ProxyClientKeepAliveTest.java

@@ -736,6 +736,34 @@ public void testPropagateHeaders(TestContext ctx) {
     }));
   }
 
+  @Test
+  public void testIgnoreHopByHopResponseHeaders(TestContext ctx) {
+    SocketAddress backend = startHttpBackend(ctx, 8081, req -> {
+      req.response()
+        .putHeader("Connection", "keep-alive")
+        .putHeader("Keep-Alive", "timeout=5")
+        .putHeader("X-End-To-End", "should-forward")
+        .end("ok");
+    });
+    startProxy(backend);
+    client = vertx.createHttpClient();
+    Async latch = ctx.async();
+    client.request(GET, 8080, "localhost", "/").onComplete(ctx.asyncAssertSuccess(req -> {
+      req.send()
+        .compose(resp -> {
+          ctx.assertEquals(200, resp.statusCode());
+          ctx.assertEquals("should-forward", resp.getHeader("x-end-to-end"));
+          ctx.assertNull(resp.getHeader("connection"));
+          ctx.assertNull(resp.getHeader("keep-alive"));
+          return resp.body();
+        })
+        .onComplete(ctx.asyncAssertSuccess(body -> {
+          ctx.assertEquals("ok", body.toString());
+          latch.complete();
+        }));
+    }));
+  }
+
   @Test
   public void testIPV6Authority(TestContext ctx) {
     testAuthority(ctx, HostAndPort.authority("[7a03:908:671:b520:ba27:bbff:ffff:fed2]", 1234));