[MPTCP] [PATCH v2 1/6] mptcp: Reference icsk_af_ops routines through saved pointer

[Peter Krystad <peter.krystad at linux.intel.com>]

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Save a pointer to the original TCP address-family-specific routines
in the subflow context, which can then be called by the MPTCP versions
of the same routines.

This eliminates the need to directly reference inet_xxx routines, or
indirectly through the ipv4_specific struct. This approach will also
save a lot of cut-n-paste code for IPv6 support.

squashto:  Handle MP_CAPABLE options for outgoing connections
           (new ctx field and sk_rx_dst_set changes)
           Create SUBFLOW socket for incoming connections
           (conn_request and syn_recv_sock changes)
           Add key generation and token tree
           (subflow_rebuild_header changes)

Signed-off-by: Peter Krystad <peter.krystad(a)linux.intel.com>
---
 net/mptcp/protocol.h |  1 +
 net/mptcp/subflow.c  | 13 ++++++++-----
 2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 56e1b8d097b3..7f783ca65f43 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -227,6 +227,7 @@ struct mptcp_subflow_context {
 
 	struct	socket *tcp_sock;   /* underlying tcp_sock */
 	struct	sock *conn;	    /* parent mptcp_sock */
+	const	struct inet_connection_sock_af_ops *icsk_af_ops;
 	void	(*tcp_sk_data_ready)(struct sock *sk);
 	struct	rcu_head rcu;
 };
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 704dfc49f0d5..6aa02001a06d 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -45,7 +45,7 @@ static int subflow_rebuild_header(struct sock *sk)
 	if (err)
 		return err;
 
-	return inet_sk_rebuild_header(sk);
+	return subflow->icsk_af_ops->rebuild_header(sk);
 }
 
 static void subflow_req_destructor(struct request_sock *req)
@@ -169,7 +169,7 @@ static void subflow_finish_connect(struct sock *sk, const struct sk_buff *skb)
 {
 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 
-	inet_sk_rx_dst_set(sk, skb);
+	subflow->icsk_af_ops->sk_rx_dst_set(sk, skb);
 
 	if (!subflow->conn)
 		return;
@@ -208,7 +208,7 @@ static void subflow_finish_connect(struct sock *sk, const struct sk_buff *skb)
 static struct request_sock_ops subflow_request_sock_ops;
 static struct tcp_request_sock_ops subflow_request_sock_ipv4_ops;
 
-static int subflow_conn_request(struct sock *sk, struct sk_buff *skb)
+static int subflow_v4_conn_request(struct sock *sk, struct sk_buff *skb)
 {
 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 
@@ -276,7 +276,8 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk,
 			return NULL;
 	}
 
-	child = tcp_v4_syn_recv_sock(sk, skb, req, dst, req_unhash, own_req);
+	child = listener->icsk_af_ops->syn_recv_sock(sk, skb, req, dst,
+						     req_unhash, own_req);
 
 	if (child && *own_req) {
 		struct mptcp_subflow_context *ctx = mptcp_subflow_ctx(child);
@@ -768,6 +769,7 @@ static int subflow_ulp_init(struct sock *sk)
 	pr_debug("subflow=%p", ctx);
 
 	tp->is_mptcp = 1;
+	ctx->icsk_af_ops = icsk->icsk_af_ops;
 	icsk->icsk_af_ops = &subflow_specific;
 	ctx->tcp_sk_data_ready = sk->sk_data_ready;
 	sk->sk_data_ready = subflow_data_ready;
@@ -805,6 +807,7 @@ static void subflow_ulp_clone(const struct request_sock *req,
 
 	new_ctx->conn = NULL;
 	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;
 
 	if (subflow_req->mp_capable) {
@@ -861,7 +864,7 @@ void mptcp_subflow_init(void)
 	subflow_request_sock_ipv4_ops.init_req = subflow_v4_init_req;
 
 	subflow_specific = ipv4_specific;
-	subflow_specific.conn_request = subflow_conn_request;
+	subflow_specific.conn_request = subflow_v4_conn_request;
 	subflow_specific.syn_recv_sock = subflow_syn_recv_sock;
 	subflow_specific.sk_rx_dst_set = subflow_finish_connect;
 	subflow_specific.rebuild_header = subflow_rebuild_header;
-- 
2.17.2