[PATCH mptcp-next 4/5] mptcp: add TCP_CONNECT_CB sock_ops hook

[Gang Yan <gang.yan@linux.dev>]

From: Gang Yan <yangang@kylinos.cn>

This patch adds a helper named 'mptcp_call_bpf' like tcp_call_bpf.
Invoke the new helper from mptcp_connect() with
BPF_SOCK_OPS_TCP_CONNECT_CB, placed after the subflow lock is acquired
and before tcp_connect(). At this point the msk lock is held by
__inet_stream_connect(), mirroring the placement of TCP_CONNECT_CB in
tcp_v4_connect()/tcp_v6_connect().

Signed-off-by: Gang Yan <yangang@kylinos.cn>
---
 net/mptcp/protocol.c |  6 ++++++
 net/mptcp/protocol.h | 30 ++++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index ffcf5a1788f6..837bb76e5c2d 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -4149,6 +4149,12 @@ static int mptcp_connect(struct sock *sk, struct sockaddr_unsized *uaddr,
 	if (!msk->fastopening)
 		lock_sock(ssk);
 
+	/* Notify cgroup BPF on the msk before initiating the subflow connect.
+	 * Mirrors BPF_SOCK_OPS_TCP_CONNECT_CB; msk lock is held by the
+	 * caller (__inet_stream_connect) and ssk is held before.
+	 */
+	mptcp_call_bpf(sk, BPF_SOCK_OPS_TCP_CONNECT_CB, 0, NULL);
+
 	/* the following mirrors closely a very small chunk of code from
 	 * __inet_stream_connect()
 	 */
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index da40c6f3705f..b4640ba83a8b 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -1374,4 +1374,34 @@ mptcp_token_join_cookie_init_state(struct mptcp_subflow_request_sock *subflow_re
 static inline void mptcp_join_cookie_init(void) {}
 #endif
 
+#ifdef CONFIG_BPF_JIT
+static inline int mptcp_call_bpf(struct sock *sk, int op, u32 nargs, u32 *args)
+{
+	struct bpf_sock_ops_kern sock_ops;
+	int ret;
+
+	memset(&sock_ops, 0, offsetof(struct bpf_sock_ops_kern, temp));
+
+	if (sk_fullsock(sk)) {
+		sock_ops.is_fullsock = 1;
+		sock_ops.is_locked_tcp_sock = 1;
+		sock_owned_by_me(sk);
+	}
+
+	sock_ops.sk = sk;
+	sock_ops.op = op;
+
+	if (nargs > 0)
+		memcpy(sock_ops.args, args, nargs * sizeof(*args));
+
+	ret = BPF_CGROUP_RUN_PROG_SOCK_OPS(&sock_ops);
+	return ret == 0 ? sock_ops.reply : -1;
+}
+#else
+static inline int mptcp_call_bpf(struct sock *sk, int op, u32 nargs, u32 *args)
+{
+	return -1;
+}
+#endif
+
 #endif /* __MPTCP_PROTOCOL_H */
-- 
2.43.0