fix

modules/transports/core/nhttp/src/main/java/org/apache/synapse/transport/passthru/util/PassThroughTransportUtils.java

@@ -44,6 +44,7 @@
 import org.apache.synapse.transport.utils.conn.SynapseNHttpClientConnection;
 
 import java.net.InetAddress;
+import java.util.ArrayList;
 import java.util.Map;
 import java.util.Iterator;
 
@@ -117,7 +118,8 @@ public static EndpointReference getDestinationEPR(MessageContext msgContext) {
      */
     public static void removeUnwantedHeaders(MessageContext msgContext, TargetConfiguration targetConfiguration) {
         Map headers = (Map) msgContext.getProperty(MessageContext.TRANSPORT_HEADERS);
-		Map excessHeaders = (Map) msgContext.getProperty(NhttpConstants.EXCESS_TRANSPORT_HEADERS);
+
+        removeUnwantedExcessHeaders(msgContext);
 
         if (headers == null || headers.isEmpty()) {
             return;
@@ -159,6 +161,39 @@ public static void removeUnwantedHeaders(MessageContext msgContext, TargetConfig
 
     }
 
+    /**
+     * Headers that frame the message body on the connection, or that control the connection
+     * itself. These are dictated by the transport and must never be carried over from an inbound
+     * message onto the outbound one.
+     *
+     * @param headerName the http header name to test
+     * @return true if the header frames the message or controls the connection
+     */
+    public static boolean isConnectionFramingHeader(String headerName) {
+        return HTTP.TRANSFER_ENCODING.equalsIgnoreCase(headerName)
+                || HTTP.CONTENT_LEN.equalsIgnoreCase(headerName)
+                || HTTP.CONN_DIRECTIVE.equalsIgnoreCase(headerName);
+    }
+
+    /**
+     * Remove the connection framing headers from EXCESS_TRANSPORT_HEADERS.
+     *
+     * @param msgContext the Axis2 Message context holding the excess header map
+     */
+    private static void removeUnwantedExcessHeaders(MessageContext msgContext) {
+        Map excessHeaders = (Map) msgContext.getProperty(NhttpConstants.EXCESS_TRANSPORT_HEADERS);
+
+        if (excessHeaders == null || excessHeaders.isEmpty()) {
+            return;
+        }
+
+        for (Object headerName : new ArrayList(excessHeaders.keySet())) {
+            if (headerName instanceof String && isConnectionFramingHeader((String) headerName)) {
+                excessHeaders.remove(headerName);
+            }
+        }
+    }
+
     /**
      * Determine the Http Status Code depending on the message type processed <br>
      * (normal response versus fault response) as well as Axis2 message context properties set

modules/transports/core/nhttp/src/main/java/org/apache/synapse/transport/passthru/util/SourceResponseFactory.java

@@ -79,6 +79,10 @@ public static SourceResponse create(MessageContext msgContext,
 		if (excessHeaders != null) {
 			for (Iterator iterator = excessHeaders.keySet().iterator(); iterator.hasNext();) {
 				String key = (String) iterator.next();
+				if (PassThroughTransportUtils.isConnectionFramingHeader(key)) {
+					// A duplicate framing header must never be relayed onto the outbound message
+					continue;
+				}
 				for (String excessVal : (Collection<String>) excessHeaders.get(key)) {
 					sourceResponse.addHeader(key, (String) excessVal);
 				}

modules/transports/core/nhttp/src/main/java/org/apache/synapse/transport/passthru/util/TargetRequestFactory.java

@@ -133,6 +133,10 @@ public static TargetRequest create(MessageContext msgContext,
 			if (excessHeaders != null) {
 				for (Iterator iterator = excessHeaders.keySet().iterator(); iterator.hasNext();) {
 					String key = (String) iterator.next();
+					if (PassThroughTransportUtils.isConnectionFramingHeader(key)) {
+						// A duplicate framing header must never be relayed onto the outbound message
+						continue;
+					}
 					for (String excessVal : (Collection<String>) excessHeaders.get(key)) {
 						request.addHeader(key, (String) excessVal);
 					}