From: Geliang Tang <tanggeliang@kylinos.cn>

Helpers mptcp_subflow_ctx() and mptcp_subflow_tcp_sock(), for converting
between struct mptcp_subflow_context and struct sock, are useful in MPTCP
BPF programs. This patch defines corresponding wrappers of them, and put
the wrappers into mptcp common kfunc set and register the set with the flag
BPF_PROG_TYPE_UNSPEC to let them accessible to all types of BPF programs.

Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
---
 net/mptcp/bpf.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/net/mptcp/bpf.c b/net/mptcp/bpf.c
index 6414824402e6..22d2d4d09be7 100644
--- a/net/mptcp/bpf.c
+++ b/net/mptcp/bpf.c
@@ -205,6 +205,18 @@ __diag_push();
 __diag_ignore_all("-Wmissing-prototypes",
 		  "kfuncs which will be used in BPF programs");
 
+__bpf_kfunc static struct mptcp_subflow_context *
+bpf_mptcp_subflow_ctx(const struct sock *sk)
+{
+	return mptcp_subflow_ctx(sk);
+}
+
+__bpf_kfunc static struct sock *
+bpf_mptcp_subflow_tcp_sock(const struct mptcp_subflow_context *subflow)
+{
+	return mptcp_subflow_tcp_sock(subflow);
+}
+
 __bpf_kfunc struct mptcp_subflow_context *
 bpf_mptcp_subflow_ctx_by_pos(const struct mptcp_sched_data *data, unsigned int pos)
 {
@@ -220,6 +232,16 @@ __bpf_kfunc bool bpf_mptcp_subflow_queues_empty(struct sock *sk)
 
 __diag_pop();
 
+BTF_KFUNCS_START(bpf_mptcp_common_kfunc_ids)
+BTF_ID_FLAGS(func, bpf_mptcp_subflow_ctx)
+BTF_ID_FLAGS(func, bpf_mptcp_subflow_tcp_sock)
+BTF_KFUNCS_END(bpf_mptcp_common_kfunc_ids)
+
+static const struct btf_kfunc_id_set bpf_mptcp_common_kfunc_set = {
+	.owner	= THIS_MODULE,
+	.set	= &bpf_mptcp_common_kfunc_ids,
+};
+
 BTF_KFUNCS_START(bpf_mptcp_sched_kfunc_ids)
 BTF_ID_FLAGS(func, mptcp_subflow_set_scheduled)
 BTF_ID_FLAGS(func, bpf_mptcp_subflow_ctx_by_pos)
@@ -241,6 +263,8 @@ static int __init bpf_mptcp_kfunc_init(void)
 	int ret;
 
 	ret = register_btf_fmodret_id_set(&bpf_mptcp_fmodret_set);
+	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_UNSPEC,
+					       &bpf_mptcp_common_kfunc_set);
 	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_STRUCT_OPS,
 					       &bpf_mptcp_sched_kfunc_set);
 #ifdef CONFIG_BPF_JIT
-- 
2.43.0