Return appropriate HTTP status code on RPC failure.

In this change, we return 404 if the request path is neither /json-rpc
nor /rpc. If XML feature is not enabled and /rpc is requested, return
404.  If XML parser failed, return 400. JSON parser failure has been
handled well in the existing code.

src/HttpServerBodyCommand.cc

@@ -163,7 +163,18 @@ bool HttpServerBodyCommand::execute()
         if(reqPath == "/rpc") {
 #ifdef ENABLE_XML_RPC
           std::string body = httpServer_->getBody();
-          rpc::RpcRequest req = rpc::xmlParseMemory(body.c_str(), body.size());
+          rpc::RpcRequest req;
+          try {
+            req = rpc::xmlParseMemory(body.c_str(), body.size());
+          } catch(RecoverableException& e) {
+            A2_LOG_INFO_EX
+              (fmt("CUID#%lld - Failed to parse XML-RPC request",
+                   getCuid()),
+               e);
+            httpServer_->feedResponse(400);
+            addHttpServerResponseCommand();
+            return true;
+          }
           SharedHandle<rpc::RpcMethod> method =
             rpc::RpcMethodFactory::create(req.methodName);
           A2_LOG_INFO(fmt("Executing RPC method %s", req.methodName.c_str()));
@@ -172,7 +183,10 @@ bool HttpServerBodyCommand::execute()
           std::string responseData = rpc::toXml(res, gzip);
           httpServer_->feedResponse(responseData, "text/xml");
           addHttpServerResponseCommand();
-#endif // ENABLE_XML_RPC
+#else // !ENABLE_XML_RPC
+          httpServer_->feedResponse(404);
+          addHttpServerResponseCommand();
+#endif // !ENABLE_XML_RPC
           return true;
         } else if(reqPath == "/jsonrpc") {
           std::string callback;
@@ -223,6 +237,8 @@ bool HttpServerBodyCommand::execute()
           }
           return true;
         } else {
+          httpServer_->feedResponse(404);
+          addHttpServerResponseCommand();
           return true;
         }
       } else {

src/RpcRequest.cc

@@ -38,6 +38,10 @@ namespace aria2 {
 
 namespace rpc {
 
+RpcRequest::RpcRequest()
+  : jsonRpc(false)
+{}
+
 RpcRequest::RpcRequest(const std::string& methodName,
                        const SharedHandle<List>& params)
   : methodName(methodName), params(params), jsonRpc(false)

src/RpcRequest.h

@@ -51,6 +51,8 @@ struct RpcRequest {
   SharedHandle<ValueBase> id;
   bool jsonRpc;
 
+  RpcRequest();
+
   RpcRequest(const std::string& methodName,
              const SharedHandle<List>& params);