+#ifdef CONFIG_X86
+static int is_foreign(unsigned long pfn)
+{
+ /* NB. Play it safe for auto-translation mode. */
+ return (xen_feature(XENFEAT_auto_translated_physmap) ||
+ (phys_to_machine_mapping[pfn] & FOREIGN_FRAME_BIT));
+}
+#else
+/* How to detect a foreign mapping? Play it safe. */
+#define is_foreign(pfn) (1)
+#endif
+
+static int skb_remove_foreign_references(struct sk_buff *skb)
+{
+ struct page *page;
+ unsigned long pfn;
+ int i, off;
+ char *vaddr;
+
+ BUG_ON(skb_shinfo(skb)->frag_list);
+
+ for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
+ pfn = page_to_pfn(skb_shinfo(skb)->frags[i].page);
+ if (!is_foreign(pfn))
+ continue;
+
+ page = alloc_page(GFP_ATOMIC | __GFP_NOWARN);
+ if (unlikely(!page))
+ return 0;
+
+ vaddr = kmap_skb_frag(&skb_shinfo(skb)->frags[i]);
+ off = skb_shinfo(skb)->frags[i].page_offset;
+ memcpy(page_address(page) + off,
+ vaddr + off,
+ skb_shinfo(skb)->frags[i].size);
+ kunmap_skb_frag(vaddr);
+
+ put_page(skb_shinfo(skb)->frags[i].page);
+ skb_shinfo(skb)->frags[i].page = page;
+ }
+
+ return 1;
+}
+