esp4: Use high-order sequence number bits for IV generation

I noticed we were only using the low-order bits for IV generation
when ESN is enabled.  This is very bad because it means that the
IV can repeat.  We must use the full 64 bits.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

net/ipv4/esp4.c

@@ -256,7 +256,8 @@ static int esp_output(struct xfrm_state *x, struct sk_buff *skb)
 	aead_givcrypt_set_crypt(req, sg, sg, clen, iv);
 	aead_givcrypt_set_assoc(req, asg, assoclen);
 	aead_givcrypt_set_giv(req, esph->enc_data,
-			      XFRM_SKB_CB(skb)->seq.output.low);
+			      XFRM_SKB_CB(skb)->seq.output.low +
+			      ((u64)XFRM_SKB_CB(skb)->seq.output.hi << 32));
 
 	ESP_SKB_CB(skb)->tmp = tmp;
 	err = crypto_aead_givencrypt(req);