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

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Message-Id: <20171014072745.23462-2-den@klaipeden.com>
Date:   Sat, 14 Oct 2017 16:27:43 +0900
From:   Koichiro Den <den@...ipeden.com>
To:     netdev@...r.kernel.org
Cc:     davem@...emloft.net, kuznet@....inr.ac.ru, yoshfuji@...ux-ipv6.org
Subject: [net-next 1/3] tcp: avoid useless copying and collapsing of just one skb

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@...ipeden.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