[net-next 1/3] tcp: avoid useless copying and collapsing of just one skb

[Koichiro Den <den@klaipeden.com>]

On the starting point chosen, it could be possible that just one skb
remains in between the range provided, leading to copying and re-insertion
of rb node, which is useless with respect to the rcv buf measurement.
This is rather probable in ooo queue case, in which non-contiguous bloated
packets have been queued up.

Signed-off-by: Koichiro Den <den@klaipeden.com>
---
 net/ipv4/tcp_input.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index d0682ce2a5d6..1d785b5bf62d 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4807,7 +4807,8 @@ tcp_collapse(struct sock *sk, struct sk_buff_head *list, struct rb_root *root,
 		start = TCP_SKB_CB(skb)->end_seq;
 	}
 	if (end_of_skbs ||
-	    (TCP_SKB_CB(skb)->tcp_flags & (TCPHDR_SYN | TCPHDR_FIN)))
+	    (TCP_SKB_CB(skb)->tcp_flags & (TCPHDR_SYN | TCPHDR_FIN)) ||
+	    (TCP_SKB_CB(skb)->seq == start && TCP_SKB_CB(skb)->end_seq == end))
 		return;
 
 	__skb_queue_head_init(&tmp);
-- 
2.9.4