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[mptcp-next,v4,10/12] mptcp: Skip unnecessary skb extension allocation for bare acks

Message ID 20200724011127.363638-11-mathew.j.martineau@linux.intel.com
State Accepted, archived
Delegated to: Matthieu Baerts
Headers show
Series DATA_FIN support | expand

Commit Message

Mat Martineau July 24, 2020, 1:11 a.m. UTC 
Bare TCP ack skbs are freed right after MPTCP sees them, so the work to
allocate, zero, and populate the MPTCP skb extension is wasted. Detect
these skbs and do not add skb extensions to them.

Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
---
 net/mptcp/options.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)
diff mbox series

Patch

diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index b4458ecd01f8..7fa822b55c34 100644
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -868,15 +868,18 @@  void mptcp_incoming_options(struct sock *sk, struct sk_buff *skb,
 	if (mp_opt.use_ack)
 		update_una(msk, &mp_opt);
 
-	/* Zero-length packets, like bare ACKs carrying a DATA_FIN, are
-	 * dropped by the caller and not propagated to the MPTCP layer.
-	 * Copy the DATA_FIN information now.
+	/* Zero-data-length packets are dropped by the caller and not
+	 * propagated to the MPTCP layer, so the skb extension does not
+	 * need to be allocated or populated. DATA_FIN information, if
+	 * present, needs to be updated here before the skb is freed.
 	 */
 	if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) {
 		if (mp_opt.data_fin && mp_opt.data_len == 1 &&
 		    mptcp_update_rcv_data_fin(msk, mp_opt.data_seq) &&
 		    schedule_work(&msk->work))
 			sock_hold(subflow->conn);
+
+		return;
 	}
 
 	mpext = skb_ext_add(skb, SKB_EXT_MPTCP);