Implement #8057 103 Early Hint (#8058)

Co-authored-by: Ludovic Orban <lorban@bitronix.be>
Co-authored-by: Simone Bordet <simone.bordet@gmail.com>

jetty-client/src/main/java/org/eclipse/jetty/client/HttpExchange.java

@@ -291,6 +291,7 @@ public void resetResponse()
         {
             responseState = State.PENDING;
             responseFailure = null;
+            response.clearHeaders();
         }
     }
 

jetty-client/src/main/java/org/eclipse/jetty/client/HttpReceiver.java

@@ -411,9 +411,8 @@ protected boolean responseSuccess(HttpExchange exchange)
         ResponseNotifier notifier = getHttpDestination().getResponseNotifier();
         notifier.notifySuccess(listeners, response);
 
-        // Special case for 100 Continue that cannot
-        // be handled by the ContinueProtocolHandler.
-        if (exchange.getResponse().getStatus() == HttpStatus.CONTINUE_100)
+        // Interim responses do not terminate the exchange.
+        if (HttpStatus.isInterim(exchange.getResponse().getStatus()))
             return true;
 
         // Mark atomically the response as terminated, with

jetty-client/src/main/java/org/eclipse/jetty/client/HttpResponse.java

@@ -87,6 +87,11 @@ public HttpFields getHeaders()
         return headers.asImmutable();
     }
 
+    public void clearHeaders()
+    {
+        headers.clear();
+    }
+
     public HttpResponse addHeader(HttpField header)
     {
         headers.add(header);

jetty-client/src/main/java/org/eclipse/jetty/client/http/HttpReceiverOverHTTP.java

@@ -187,6 +187,7 @@ private void process()
                 }
                 else if (read == 0)
                 {
+                    assert networkBuffer.isEmpty();
                     releaseNetworkBuffer();
                     fillInterested();
                     return;
@@ -245,18 +246,21 @@ private boolean parse()
                 this.method = null;
                 if (getHttpChannel().isTunnel(method, status))
                     return true;
-            }
 
-            if (networkBuffer.isEmpty())
-                return false;
+                if (networkBuffer.isEmpty())
+                    return false;
 
-            if (complete)
-            {
-                if (LOG.isDebugEnabled())
-                    LOG.debug("Discarding unexpected content after response: {}", networkBuffer);
-                networkBuffer.clear();
+                if (!HttpStatus.isInformational(status))
+                {
+                    if (LOG.isDebugEnabled())
+                        LOG.debug("Discarding unexpected content after response {}: {}", status, networkBuffer);
+                    networkBuffer.clear();
+                }
                 return false;
             }
+
+            if (networkBuffer.isEmpty())
+                return false;
         }
     }
 
@@ -372,7 +376,7 @@ public boolean messageComplete()
         }
 
         int status = exchange.getResponse().getStatus();
-        if (status != HttpStatus.CONTINUE_100)
+        if (!HttpStatus.isInterim(status))
         {
             inMessages.increment();
             complete = true;

jetty-http/src/main/java/org/eclipse/jetty/http/HttpGenerator.java

@@ -385,15 +385,21 @@ public Result generateResponse(MetaData.Response info, boolean head, ByteBuffer
 
                     // Handle 1xx and no content responses
                     int status = info.getStatus();
-                    if (status >= 100 && status < 200)
+                    if (HttpStatus.isInformational(status))
                     {
                         _noContentResponse = true;
-
-                        if (status != HttpStatus.SWITCHING_PROTOCOLS_101)
+                        switch (status)
                         {
-                            header.put(HttpTokens.CRLF);
-                            _state = State.COMPLETING_1XX;
-                            return Result.FLUSH;
+                            case HttpStatus.SWITCHING_PROTOCOLS_101:
+                                break;
+                            case HttpStatus.EARLY_HINT_103:
+                                generateHeaders(header, content, last);
+                                _state = State.COMPLETING_1XX;
+                                return Result.FLUSH;
+                            default:
+                                header.put(HttpTokens.CRLF);
+                                _state = State.COMPLETING_1XX;
+                                return Result.FLUSH;
                         }
                     }
                     else if (status == HttpStatus.NO_CONTENT_204 || status == HttpStatus.NOT_MODIFIED_304)

jetty-http/src/main/java/org/eclipse/jetty/http/HttpHeader.java

@@ -88,6 +88,7 @@ public enum HttpHeader
     AGE("Age"),
     ALT_SVC("Alt-Svc"),
     ETAG("ETag"),
+    LINK("Link"),
     LOCATION("Location"),
     PROXY_AUTHENTICATE("Proxy-Authenticate"),
     RETRY_AFTER("Retry-After"),

jetty-http/src/main/java/org/eclipse/jetty/http/HttpStatus.java

@@ -25,6 +25,7 @@ public class HttpStatus
     public static final int CONTINUE_100 = 100;
     public static final int SWITCHING_PROTOCOLS_101 = 101;
     public static final int PROCESSING_102 = 102;
+    public static final int EARLY_HINT_103 = 103;
 
     public static final int OK_200 = 200;
     public static final int CREATED_201 = 201;
@@ -103,6 +104,7 @@ public enum Code
         CONTINUE(CONTINUE_100, "Continue"),
         SWITCHING_PROTOCOLS(SWITCHING_PROTOCOLS_101, "Switching Protocols"),
         PROCESSING(PROCESSING_102, "Processing"),
+        EARLY_HINT(EARLY_HINT_103, "Early Hint"),
 
         OK(OK_200, "OK"),
         CREATED(CREATED_201, "Created"),
@@ -339,6 +341,17 @@ public static boolean isInformational(int code)
         return ((100 <= code) && (code <= 199));
     }
 
+    /**
+     * Tests whether the status code is informational but not {@code 101 Switching Protocols}.
+     *
+     * @param code the code to test
+     * @return whether the status code is informational but not {@code 101 Switching Protocols}
+     */
+    public static boolean isInterim(int code)
+    {
+        return isInformational(code) && code != HttpStatus.SWITCHING_PROTOCOLS_101;
+    }
+
     /**
      * Simple test against an code to determine if it falls into the
      * <code>Success</code> message category as defined in the <a

jetty-http2/http2-http-client-transport/src/main/java/org/eclipse/jetty/http2/client/http/HttpReceiverOverHTTP2.java

@@ -120,8 +120,7 @@ void onHeaders(Stream stream, HeadersFrame frame)
                 if (responseHeaders(exchange))
                 {
                     int status = response.getStatus();
-                    boolean informational = HttpStatus.isInformational(status) && status != HttpStatus.SWITCHING_PROTOCOLS_101;
-                    if (frame.isEndStream() || informational)
+                    if (frame.isEndStream() || HttpStatus.isInterim(status))
                         responseSuccess(exchange);
                 }
                 else

jetty-http2/http2-server/src/main/java/org/eclipse/jetty/http2/server/HttpTransportOverHTTP2.java

@@ -98,8 +98,7 @@ public void sendHeaders(MetaData.Request request, MetaData.Response response, By
         boolean isHeadRequest = HttpMethod.HEAD.is(request.getMethod());
         boolean hasContent = BufferUtil.hasContent(content) && !isHeadRequest;
         int status = response.getStatus();
-        boolean interimResponse = status == HttpStatus.CONTINUE_100 || status == HttpStatus.PROCESSING_102;
-        if (interimResponse)
+        if (HttpStatus.isInterim(status))
         {
             // Must not commit interim responses.
             if (hasContent)

jetty-http3/http3-client/src/main/java/org/eclipse/jetty/http3/client/internal/HTTP3StreamClient.java

@@ -52,9 +52,11 @@ public void onResponse(HeadersFrame frame)
         MetaData.Response response = (MetaData.Response)frame.getMetaData();
         boolean valid;
         if (response.getStatus() == HttpStatus.CONTINUE_100)
-            valid = validateAndUpdate(EnumSet.of(FrameState.INITIAL), FrameState.CONTINUE);
+            valid = validateAndUpdate(EnumSet.of(FrameState.INITIAL), FrameState.INFORMATIONAL);
+        else if (response.getStatus() == HttpStatus.EARLY_HINT_103)
+            valid = validateAndUpdate(EnumSet.of(FrameState.INITIAL, FrameState.HEADER, FrameState.INFORMATIONAL), FrameState.INFORMATIONAL);
         else
-            valid = validateAndUpdate(EnumSet.of(FrameState.INITIAL, FrameState.CONTINUE), FrameState.HEADER);
+            valid = validateAndUpdate(EnumSet.of(FrameState.INITIAL, FrameState.INFORMATIONAL), FrameState.HEADER);
         if (valid)
         {
             notIdle();

jetty-http3/http3-common/src/main/java/org/eclipse/jetty/http3/internal/HTTP3Stream.java

@@ -315,7 +315,7 @@ public String toString()
 
     protected enum FrameState
     {
-        INITIAL, CONTINUE, HEADER, DATA, TRAILER, FAILED
+        INITIAL, INFORMATIONAL, HEADER, DATA, TRAILER, FAILED
     }
 
     private enum CloseState

jetty-http3/http3-common/src/main/java/org/eclipse/jetty/http3/internal/HTTP3StreamConnection.java

@@ -486,18 +486,18 @@ public void onHeaders(long streamId, HeadersFrame frame)
             else if (metaData.isResponse())
             {
                 MetaData.Response response = (MetaData.Response)metaData;
-                if (response.getStatus() != HttpStatus.CONTINUE_100)
+                if (HttpStatus.isInformational(response.getStatus()))
                 {
-                    // Expect DATA frames now.
-                    parserDataMode = true;
-                    parser.setDataMode(true);
                     if (LOG.isDebugEnabled())
-                        LOG.debug("switching to parserDataMode=true for response {} on {}", metaData, this);
+                        LOG.debug("staying in parserDataMode=false for response {} on {}", metaData, this);
                 }
                 else
                 {
+                    // Expect DATA frames now.
+                    parserDataMode = true;
+                    parser.setDataMode(true);
                     if (LOG.isDebugEnabled())
-                        LOG.debug("staying in parserDataMode=false for response {} on {}", metaData, this);
+                        LOG.debug("switching to parserDataMode=true for response {} on {}", metaData, this);
                 }
             }
             else

jetty-http3/http3-http-client-transport/src/main/java/org/eclipse/jetty/http3/client/http/internal/HttpReceiverOverHTTP3.java

@@ -89,8 +89,7 @@ public void onResponse(Stream.Client stream, HeadersFrame frame)
             if (responseHeaders(exchange))
             {
                 int status = response.getStatus();
-                boolean informational = HttpStatus.isInformational(status) && status != HttpStatus.SWITCHING_PROTOCOLS_101;
-                if (frame.isLast() || informational)
+                if (frame.isLast() || HttpStatus.isInterim(status))
                     responseSuccess(exchange);
                 else
                     stream.demand();

jetty-http3/http3-server/src/main/java/org/eclipse/jetty/http3/server/internal/HttpTransportOverHTTP3.java

@@ -71,8 +71,7 @@ private void sendHeaders(MetaData.Request request, MetaData.Response response, B
         boolean isHeadRequest = HttpMethod.HEAD.is(request.getMethod());
         boolean hasContent = BufferUtil.hasContent(content) && !isHeadRequest;
         int status = response.getStatus();
-        boolean interimResponse = status == HttpStatus.CONTINUE_100 || status == HttpStatus.PROCESSING_102;
-        if (interimResponse)
+        if (HttpStatus.isInterim(status))
         {
             // Must not commit interim responses.
             if (hasContent)

jetty-server/src/main/java/org/eclipse/jetty/server/HttpChannel.java

@@ -1044,10 +1044,10 @@ protected boolean sendResponse(MetaData.Response response, ByteBuffer content, b
             _combinedListener.onResponseBegin(_request);
             _request.onResponseCommit();
 
-            // wrap callback to process 100 responses
+            // wrap callback to process informational responses
             final int status = response.getStatus();
-            final Callback committed = (status < HttpStatus.OK_200 && status >= HttpStatus.CONTINUE_100)
-                ? new Send100Callback(callback)
+            final Callback committed = HttpStatus.isInformational(status)
+                ? new Send1XXCallback(callback)
                 : new SendCallback(callback, content, true, complete);
 
             // committing write
@@ -1477,9 +1477,9 @@ public void failed(Throwable th)
         }
     }
 
-    private class Send100Callback extends SendCallback
+    private class Send1XXCallback extends SendCallback
     {
-        private Send100Callback(Callback callback)
+        private Send1XXCallback(Callback callback)
         {
             super(callback, null, false, false);
         }

jetty-server/src/main/java/org/eclipse/jetty/server/Response.java

@@ -470,6 +470,7 @@ public void sendError(int sc) throws IOException
      * <p>In addition to the servlet standard handling, this method supports some additional codes:</p>
      * <dl>
      * <dt>102</dt><dd>Send a partial PROCESSING response and allow additional responses</dd>
+     * <dt>103</dt><dd>Send a partial EARLY_HINT response as per <a href="https://datatracker.ietf.org/doc/html/rfc8297">RFC8297</a></dd>
      * <dt>-1</dt><dd>Abort the HttpChannel and close the connection/stream</dd>
      * </dl>
      * @param code The error code
@@ -490,6 +491,9 @@ public void sendError(int code, String message) throws IOException
             case HttpStatus.PROCESSING_102:
                 sendProcessing();
                 break;
+            case HttpStatus.EARLY_HINT_103:
+                sendEarlyHint();
+                break;
             default:
                 _channel.getState().sendError(code, message);
                 break;
@@ -498,9 +502,8 @@ public void sendError(int code, String message) throws IOException
 
     /**
      * Sends a 102-Processing response.
-     * If the connection is an HTTP connection, the version is 1.1 and the
-     * request has a Expect header starting with 102, then a 102 response is
-     * sent. This indicates that the request still be processed and real response
+     * If the request had an Expect header starting with 102, then
+     * a 102 response is sent. This indicates that the request still be processed and real response
      * can still be sent.   This method is called by sendError if it is passed 102.
      *
      * @throws IOException if unable to send the 102 response
@@ -514,6 +517,22 @@ public void sendProcessing() throws IOException
         }
     }
 
+    /**
+     * Sends a 103 Early Hint response.
+     *
+     * Send a 103 response as per <a href="https://datatracker.ietf.org/doc/html/rfc8297">RFC8297</a>
+     * This method is called by sendError if it is passed 103.
+     *
+     * @throws IOException if unable to send the 103 response
+     * @see javax.servlet.http.HttpServletResponse#sendError(int)
+     */
+    public void sendEarlyHint() throws IOException
+    {
+        if (!isCommitted())
+            _channel.sendResponse(new MetaData.Response(_channel.getRequest().getHttpVersion(), HttpStatus.EARLY_HINT_103,
+                _channel.getResponse()._fields.asImmutable()), null, true);
+    }
+
     /**
      * Sends a response with one of the 300 series redirection codes.
      *