[MPTCP] [RFC PATCH 4/6] options: ack pending sequence

[MPTCP] [RFC PATCH 4/6] options: ack pending sequence

[Florian Westphal]

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This allows us to include some of the bytes already pending on the subflow
in the DSS ack instead of having to wait for the next recv (which
updates msk->ack_seq value).

Signed-off-by: Florian Westphal <fw(a)strlen.de>
---
 net/mptcp/options.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index 80dbe7662cea..b488bf07ada5 100644
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -418,13 +418,20 @@ static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
 		ack_size += TCPOLEN_MPTCP_DSS_BASE;
 
 	if (ack_size <= remaining) {
+		const struct mptcp_subflow_context *subflow;
 		struct mptcp_sock *msk;
 
 		dss_size += ack_size;
 
-		msk = mptcp_sk(mptcp_subflow_ctx(sk)->conn);
+		subflow = mptcp_subflow_ctx(sk);
+		msk = mptcp_sk(subflow->conn);
 		if (msk) {
-			opts->ext_copy.data_ack = msk->ack_seq;
+			u64 ack_seq = READ_ONCE(msk->ack_seq);
+
+			if (subflow->map_valid)
+				ack_seq += subflow->data_avail;
+
+			opts->ext_copy.data_ack = ack_seq;
 		} else {
 			mptcp_crypto_key_sha1(mptcp_subflow_ctx(sk)->remote_key,
 					      NULL, &opts->ext_copy.data_ack);
-- 
2.23.0