ip6_output: do skb ufo init for peeked non ufo skb as well

Now, if user application does:
sendto len<mtu flag MSG_MORE
sendto len>mtu flag 0
The skb is not treated as fragmented one because it is not initialized
that way. So move the initialization to fix this.

introduced by:
commit e89e9cf5 "[IPv4/IPv6]: UFO Scatter-gather approach"
Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/ip6_output.c

@@ -1008,6 +1008,7 @@ static inline int ip6_ufo_append_data(struct sock *sk,
 
 {
 	struct sk_buff *skb;
+	struct frag_hdr fhdr;
 	int err;
 
 	/* There is support for UDP large send offload by network
@@ -1015,8 +1016,6 @@ static inline int ip6_ufo_append_data(struct sock *sk,
 	 * udp datagram
 	 */
 	if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL) {
-		struct frag_hdr fhdr;
-
 		skb = sock_alloc_send_skb(sk,
 			hh_len + fragheaderlen + transhdrlen + 20,
 			(flags & MSG_DONTWAIT), &err);
@@ -1036,9 +1035,14 @@ static inline int ip6_ufo_append_data(struct sock *sk,
 		skb->transport_header = skb->network_header + fragheaderlen;
 
 		skb->protocol = htons(ETH_P_IPV6);
-		skb->ip_summed = CHECKSUM_PARTIAL;
 		skb->csum = 0;
 
+		__skb_queue_tail(&sk->sk_write_queue, skb);
+	} else if (skb_is_gso(skb)) {
+		goto append;
+	}
+
+	skb->ip_summed = CHECKSUM_PARTIAL;
 	/* Specify the length of each IPv6 datagram fragment.
 	 * It has to be a multiple of 8.
 	 */
@@ -1047,9 +1051,8 @@ static inline int ip6_ufo_append_data(struct sock *sk,
 	skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
 	ipv6_select_ident(&fhdr, rt);
 	skb_shinfo(skb)->ip6_frag_id = fhdr.identification;
-		__skb_queue_tail(&sk->sk_write_queue, skb);
-	}
 
+append:
 	return skb_append_datato_frags(sk, skb, getfrag, from,
 				       (length - transhdrlen));
 }