tcp: force mss equality with the next skb too.

Also make if-goto forest nicer looking.
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/tcp_input.c

@@ -1575,11 +1575,10 @@ static struct sk_buff *tcp_shift_skb_data(struct sock *sk, struct sk_buff *skb,
 		goto out;
 	skb = tcp_write_queue_next(sk, prev);
 
-	if (!skb_can_shift(skb))
-		goto out;
-	if (skb == tcp_send_head(sk))
-		goto out;
-	if ((TCP_SKB_CB(skb)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED)
+	if (!skb_can_shift(skb) ||
+	    (skb == tcp_send_head(sk)) ||
+	    ((TCP_SKB_CB(skb)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED) ||
+	    (mss != tcp_shift_mss(skb)))
 		goto out;
 
 	len = skb->len;