[TCP]: Do not try to collapse multi-packet SKBs.

Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/tcp_output.c

@@ -1069,6 +1069,7 @@ int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
 	   (skb->next != sk->sk_send_head) &&
 	   (skb->next != (struct sk_buff *)&sk->sk_write_queue) &&
 	   (skb_shinfo(skb)->nr_frags == 0 && skb_shinfo(skb->next)->nr_frags == 0) &&
+	   (tcp_skb_pcount(skb) == 1 && tcp_skb_pcount(skb->next) == 1) &&
 	   (sysctl_tcp_retrans_collapse != 0))
 		tcp_retrans_try_collapse(sk, skb, cur_mss);