+ /* This variable also signals whether foreign_gref has a real
+ * value or not.
+ */
+ struct xenvif_queue *foreign_queue = NULL;
+ grant_ref_t foreign_gref;
+
+ if ((skb_shinfo(skb)->tx_flags & SKBTX_DEV_ZEROCOPY) &&
+ (ubuf->callback == &xenvif_zerocopy_callback)) {
+ const struct ubuf_info *const startpoint = ubuf;
+
+ /* Ideally ubuf points to the chain element which
+ * belongs to this frag. Or if frags were removed from
+ * the beginning, then shortly before it.
+ */
+ ubuf = xenvif_find_gref(skb, i, ubuf);
+
+ /* Try again from the beginning of the list, if we
+ * haven't tried from there. This only makes sense in
+ * the unlikely event of reordering the original frags.
+ * For injected local pages it's an unnecessary second
+ * run.
+ */
+ if (unlikely(!ubuf) && startpoint != head_ubuf)
+ ubuf = xenvif_find_gref(skb, i, head_ubuf);
+
+ if (likely(ubuf)) {
+ u16 pending_idx = ubuf->desc;
+
+ foreign_queue = ubuf_to_queue(ubuf);
+ foreign_gref =
+ foreign_queue->pending_tx_info[pending_idx].req.gref;
+ /* Just a safety measure. If this was the last
+ * element on the list, the for loop will
+ * iterate again if a local page were added to
+ * the end. Using head_ubuf here prevents the
+ * second search on the chain. Or the original
+ * frags changed order, but that's less likely.
+ * In any way, ubuf shouldn't be NULL.
+ */
+ ubuf = ubuf->ctx ?
+ (struct ubuf_info *) ubuf->ctx :
+ head_ubuf;
+ } else
+ /* This frag was a local page, added to the
+ * array after the skb left netback.
+ */
+ ubuf = head_ubuf;
+ }
+ xenvif_gop_frag_copy(queue, skb, npo,