diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 3337027..70a3f8d 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -481,6 +481,7 @@
 	union {
 		__u32		mark;
 		__u32		dropcount;
+		__u32		avail_size;
 	};
 
 	sk_buff_data_t		transport_header;
@@ -1366,6 +1367,18 @@
 }
 
 /**
+ *	skb_availroom - bytes at buffer end
+ *	@skb: buffer to check
+ *
+ *	Return the number of bytes of free space at the tail of an sk_buff
+ *	allocated by sk_stream_alloc()
+ */
+static inline int skb_availroom(const struct sk_buff *skb)
+{
+	return skb_is_nonlinear(skb) ? 0 : skb->avail_size - skb->len;
+}
+
+/**
  *	skb_reserve - adjust headroom
  *	@skb: buffer to alter
  *	@len: bytes to move