[MPTCP] [PATCH v1 5/7] Squash-to: "mptcp: Implement MPTCP receive path"

[MPTCP] [PATCH v1 5/7] Squash-to: "mptcp: Implement MPTCP receive path"

[Paolo Abeni]

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deal with fallback: we must reset sk callback to the TCP one.
Use the cached ptr in the old ctx.

RFC -> v1:
 - since mptcp_incoming_options() callers check for is_mptcp and
   the latter is always cleared on fallback, we can drop any additional
   check in mptcp_incoming_options()

Signed-off-by: Paolo Abeni <pabeni(a)redhat.com>
---
 net/mptcp/options.c  |  4 ----
 net/mptcp/protocol.h | 15 ++++++++++++++-
 net/mptcp/subflow.c  | 18 ++++++++++++------
 3 files changed, 26 insertions(+), 11 deletions(-)

diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index 015162f15576..5845c9a41ebb 100644
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -416,13 +416,9 @@ bool mptcp_synack_options(const struct request_sock *req, unsigned int *size,
 void mptcp_incoming_options(struct sock *sk, struct sk_buff *skb,
 			    struct tcp_options_received *opt_rx)
 {
-	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 	struct mptcp_options_received *mp_opt;
 	struct mptcp_ext *mpext;
 
-	if (!subflow->mp_capable)
-		return;
-
 	mp_opt = &opt_rx->mptcp;
 
 	if (!mp_opt->dss)
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index e4fce9f0ad65..c6d8217e24d4 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -121,7 +121,10 @@ struct mptcp_subflow_context {
 	struct	sock *tcp_sock;	    /* tcp sk backpointer */
 	struct	sock *conn;	    /* parent mptcp_sock */
 	const	struct inet_connection_sock_af_ops *icsk_af_ops;
-	void	(*tcp_sk_data_ready)(struct sock *sk);
+	void	(*tcp_data_ready)(struct sock *sk);
+	void	(*tcp_state_change)(struct sock *sk);
+	void	(*tcp_write_space)(struct sock *sk);
+
 	struct	rcu_head rcu;
 };
 
@@ -159,6 +162,16 @@ bool mptcp_subflow_data_available(struct sock *sk);
 void mptcp_subflow_init(void);
 int mptcp_subflow_create_socket(struct sock *sk, struct socket **new_sock);
 
+static inline void mptcp_subflow_tcp_fallback(struct sock *sk,
+					      struct mptcp_subflow_context *ctx)
+{
+	sk->sk_data_ready = ctx->tcp_data_ready;
+	sk->sk_state_change = ctx->tcp_state_change;
+	sk->sk_write_space = ctx->tcp_write_space;
+
+	inet_csk(sk)->icsk_af_ops = ctx->icsk_af_ops;
+}
+
 extern const struct inet_connection_sock_af_ops ipv4_specific;
 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 extern const struct inet_connection_sock_af_ops ipv6_specific;
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 7c51d31e6d17..a1be17926248 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -507,7 +507,7 @@ static void subflow_data_ready(struct sock *sk)
 	struct sock *parent = subflow->conn;
 
 	if (!parent || !subflow->mp_capable) {
-		subflow->tcp_sk_data_ready(sk);
+		subflow->tcp_data_ready(sk);
 
 		if (parent)
 			parent->sk_data_ready(parent);
@@ -655,7 +655,9 @@ static int subflow_ulp_init(struct sock *sk)
 	if (sk->sk_family == AF_INET6)
 		icsk->icsk_af_ops = &subflow_v6_specific;
 #endif
-	ctx->tcp_sk_data_ready = sk->sk_data_ready;
+	ctx->tcp_data_ready = sk->sk_data_ready;
+	ctx->tcp_state_change = sk->sk_state_change;
+	ctx->tcp_write_space = sk->sk_write_space;
 	sk->sk_data_ready = subflow_data_ready;
 	sk->sk_write_space = subflow_write_space;
 	sk->sk_state_change = subflow_state_change;
@@ -676,10 +678,12 @@ static void subflow_ulp_release(struct sock *sk)
 	kfree_rcu(ctx, rcu);
 }
 
-static void subflow_ulp_fallback(struct sock *sk)
+static void subflow_ulp_fallback(struct sock *sk,
+				 struct mptcp_subflow_context *old_ctx)
 {
 	struct inet_connection_sock *icsk = inet_csk(sk);
 
+	mptcp_subflow_tcp_fallback(sk, old_ctx);
 	icsk->icsk_ulp_ops = NULL;
 	rcu_assign_pointer(icsk->icsk_ulp_data, NULL);
 	tcp_sk(sk)->is_mptcp = 0;
@@ -694,19 +698,21 @@ static void subflow_ulp_clone(const struct request_sock *req,
 	struct mptcp_subflow_context *new_ctx;
 
 	if (!subflow_req->mp_capable) {
-		subflow_ulp_fallback(newsk);
+		subflow_ulp_fallback(newsk, old_ctx);
 		return;
 	}
 
 	new_ctx = subflow_create_ctx(newsk, priority);
 	if (new_ctx == NULL) {
-		subflow_ulp_fallback(newsk);
+		subflow_ulp_fallback(newsk, old_ctx);
 		return;
 	}
 
 	new_ctx->conn_finished = 1;
 	new_ctx->icsk_af_ops = old_ctx->icsk_af_ops;
-	new_ctx->tcp_sk_data_ready = old_ctx->tcp_sk_data_ready;
+	new_ctx->tcp_data_ready = old_ctx->tcp_data_ready;
+	new_ctx->tcp_state_change = old_ctx->tcp_state_change;
+	new_ctx->tcp_write_space = old_ctx->tcp_write_space;
 	new_ctx->mp_capable = 1;
 	new_ctx->fourth_ack = 1;
 	new_ctx->remote_key = subflow_req->remote_key;
-- 
2.21.0