net: Walk fragments in __skb_splice_bits

Add walking of fragments in __skb_splice_bits.
Signed-off-by: Tom Herbert <tom@herbertland.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/skbuff.c

@@ -1918,6 +1918,7 @@ static bool __skb_splice_bits(struct sk_buff *skb, struct pipe_inode_info *pipe,
 			      struct splice_pipe_desc *spd, struct sock *sk)
 {
 	int seg;
+	struct sk_buff *iter;
 
 	/* map the linear part :
 	 * If skb->head_frag is set, this 'linear' part is backed by a
@@ -1944,6 +1945,19 @@ static bool __skb_splice_bits(struct sk_buff *skb, struct pipe_inode_info *pipe,
 			return true;
 	}
 
+	skb_walk_frags(skb, iter) {
+		if (*offset >= iter->len) {
+			*offset -= iter->len;
+			continue;
+		}
+		/* __skb_splice_bits() only fails if the output has no room
+		 * left, so no point in going over the frag_list for the error
+		 * case.
+		 */
+		if (__skb_splice_bits(iter, pipe, offset, len, spd, sk))
+			return true;
+	}
+
 	return false;
 }
 
@@ -1970,9 +1984,7 @@ ssize_t skb_socket_splice(struct sock *sk,
 
 /*
  * Map data from the skb to a pipe. Should handle both the linear part,
- * the fragments, and the frag list. It does NOT handle frag lists within
- * the frag list, if such a thing exists. We'd probably need to recurse to
- * handle that cleanly.
+ * the fragments, and the frag list.
  */
 int skb_splice_bits(struct sk_buff *skb, struct sock *sk, unsigned int offset,
 		    struct pipe_inode_info *pipe, unsigned int tlen,
@@ -1991,29 +2003,10 @@ int skb_splice_bits(struct sk_buff *skb, struct sock *sk, unsigned int offset,
 		.ops = &nosteal_pipe_buf_ops,
 		.spd_release = sock_spd_release,
 	};
-	struct sk_buff *frag_iter;
 	int ret = 0;
 
-	/*
-	 * __skb_splice_bits() only fails if the output has no room left,
-	 * so no point in going over the frag_list for the error case.
-	 */
-	if (__skb_splice_bits(skb, pipe, &offset, &tlen, &spd, sk))
-		goto done;
-	else if (!tlen)
-		goto done;
+	__skb_splice_bits(skb, pipe, &offset, &tlen, &spd, sk);
 
-	/*
-	 * now see if we have a frag_list to map
-	 */
-	skb_walk_frags(skb, frag_iter) {
-		if (!tlen)
-			break;
-		if (__skb_splice_bits(frag_iter, pipe, &offset, &tlen, &spd, sk))
-			break;
-	}
-
-done:
 	if (spd.nr_pages)
 		ret = splice_cb(sk, pipe, &spd);