sk_buff: allow segmenting based on frag sizes

This patch allows segmenting a skb based on its frags sizes instead of
based on a fixed value.

Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Tested-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 4724bcf..97c32c7 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3116,9 +3116,13 @@
 		int hsize;
 		int size;
 
-		len = head_skb->len - offset;
-		if (len > mss)
-			len = mss;
+		if (unlikely(mss == GSO_BY_FRAGS)) {
+			len = list_skb->len;
+		} else {
+			len = head_skb->len - offset;
+			if (len > mss)
+				len = mss;
+		}
 
 		hsize = skb_headlen(head_skb) - offset;
 		if (hsize < 0)