[PATCH net-next v9 5/7] mptcp: support rstreason for passive reset

[Jason Xing <kerneljasonxing@gmail.com>]

From: Jason Xing <kernelxing@tencent.com>

It relies on what reset options in the skb are as rfc8684 says. Reusing
this logic can save us much energy. This patch replaces most of the prior
NOT_SPECIFIED reasons.

Signed-off-by: Jason Xing <kernelxing@tencent.com>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/protocol.h | 27 +++++++++++++++++++++++++++
 net/mptcp/subflow.c  | 22 +++++++++++++++++-----
 2 files changed, 44 insertions(+), 5 deletions(-)

diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index fdfa843e2d88..252618859ee8 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -581,6 +581,33 @@ mptcp_subflow_ctx_reset(struct mptcp_subflow_context *subflow)
 	WRITE_ONCE(subflow->local_id, -1);
 }
 
+/* Convert reset reasons in MPTCP to enum sk_rst_reason type */
+static inline enum sk_rst_reason
+sk_rst_convert_mptcp_reason(u32 reason)
+{
+	switch (reason) {
+	case MPTCP_RST_EUNSPEC:
+		return SK_RST_REASON_MPTCP_RST_EUNSPEC;
+	case MPTCP_RST_EMPTCP:
+		return SK_RST_REASON_MPTCP_RST_EMPTCP;
+	case MPTCP_RST_ERESOURCE:
+		return SK_RST_REASON_MPTCP_RST_ERESOURCE;
+	case MPTCP_RST_EPROHIBIT:
+		return SK_RST_REASON_MPTCP_RST_EPROHIBIT;
+	case MPTCP_RST_EWQ2BIG:
+		return SK_RST_REASON_MPTCP_RST_EWQ2BIG;
+	case MPTCP_RST_EBADPERF:
+		return SK_RST_REASON_MPTCP_RST_EBADPERF;
+	case MPTCP_RST_EMIDDLEBOX:
+		return SK_RST_REASON_MPTCP_RST_EMIDDLEBOX;
+	default:
+		/* It should not happen, or else errors may occur
+		 * in MPTCP layer
+		 */
+		return SK_RST_REASON_ERROR;
+	}
+}
+
 static inline u64
 mptcp_subflow_get_map_offset(const struct mptcp_subflow_context *subflow)
 {
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index ac867d277860..fb7abf2d01ca 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -309,8 +309,13 @@ static struct dst_entry *subflow_v4_route_req(const struct sock *sk,
 		return dst;
 
 	dst_release(dst);
-	if (!req->syncookie)
-		tcp_request_sock_ops.send_reset(sk, skb, SK_RST_REASON_NOT_SPECIFIED);
+	if (!req->syncookie) {
+		struct mptcp_ext *mpext = mptcp_get_ext(skb);
+		enum sk_rst_reason reason;
+
+		reason = sk_rst_convert_mptcp_reason(mpext->reset_reason);
+		tcp_request_sock_ops.send_reset(sk, skb, reason);
+	}
 	return NULL;
 }
 
@@ -377,8 +382,13 @@ static struct dst_entry *subflow_v6_route_req(const struct sock *sk,
 		return dst;
 
 	dst_release(dst);
-	if (!req->syncookie)
-		tcp6_request_sock_ops.send_reset(sk, skb, SK_RST_REASON_NOT_SPECIFIED);
+	if (!req->syncookie) {
+		struct mptcp_ext *mpext = mptcp_get_ext(skb);
+		enum sk_rst_reason reason;
+
+		reason = sk_rst_convert_mptcp_reason(mpext->reset_reason);
+		tcp6_request_sock_ops.send_reset(sk, skb, reason);
+	}
 	return NULL;
 }
 #endif
@@ -783,6 +793,7 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk,
 	struct mptcp_subflow_request_sock *subflow_req;
 	struct mptcp_options_received mp_opt;
 	bool fallback, fallback_is_fatal;
+	enum sk_rst_reason reason;
 	struct mptcp_sock *owner;
 	struct sock *child;
 
@@ -913,7 +924,8 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk,
 	tcp_rsk(req)->drop_req = true;
 	inet_csk_prepare_for_destroy_sock(child);
 	tcp_done(child);
-	req->rsk_ops->send_reset(sk, skb, SK_RST_REASON_NOT_SPECIFIED);
+	reason = sk_rst_convert_mptcp_reason(mptcp_get_ext(skb)->reset_reason);
+	req->rsk_ops->send_reset(sk, skb, reason);
 
 	/* The last child reference will be released by the caller */
 	return child;
-- 
2.37.3