nghttpx: Don't use data_prd.source.ptr

src/shrpx_http2_downstream_connection.cc

@@ -173,7 +173,7 @@ ssize_t http2_data_read_callback(nghttp2_session *session, int32_t stream_id,
   if (!sd || !sd->dconn) {
     return NGHTTP2_ERR_DEFERRED;
   }
-  auto dconn = static_cast<Http2DownstreamConnection *>(source->ptr);
+  auto dconn = sd->dconn;
   auto downstream = dconn->get_downstream();
   if (!downstream) {
     // In this case, RST_STREAM should have been issued. But depending
@@ -453,9 +453,7 @@ int Http2DownstreamConnection::push_request_headers() {
   if (req.method == HTTP_CONNECT || chunked_encoding || content_length ||
       req.http2_expect_body) {
     // Request-body is expected.
-    nghttp2_data_provider data_prd;
-    data_prd.source.ptr = this;
-    data_prd.read_callback = http2_data_read_callback;
+    nghttp2_data_provider data_prd{{}, http2_data_read_callback};
     rv = http2session_->submit_request(this, nva.data(), nva.size(), &data_prd);
   } else {
     rv = http2session_->submit_request(this, nva.data(), nva.size(), nullptr);