[PATCH bpf-next/net v2 3/7] bpf: Register mptcp common kfunc set

["Matthieu Baerts (NGI0)" <matttbe@xxxxxxxxxx>]

From: Geliang Tang <tanggeliang@xxxxxxxxxx>

MPTCP helper mptcp_sk() is used to convert struct sock to mptcp_sock.
Helpers mptcp_subflow_ctx() and mptcp_subflow_tcp_sock() are used to
convert between struct mptcp_subflow_context and sock. They all will
be used in MPTCP BPF programs too.

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@xxxxxxxxxx>
Reviewed-by: Mat Martineau <martineau@xxxxxxxxxx>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@xxxxxxxxxx>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@xxxxxxxxxx>
---
Notes:
 - v2:
   - Thanks to the two new previous patches, bpf_mptcp_sk() and
     bpf_mptcp_subflow_tcp_sock() are no longer needed.
   - bpf_mptcp_subflow_ctx(): make sure the socket is an MPTCP subflow,
     and add KF_RET_NULL (Martin).
   - Restrict this kfunc to BPF_PROG_TYPE_CGROUP_SOCKOPT for the moment.
---
 net/mptcp/bpf.c | 31 ++++++++++++++++++++++++++++++-
 1 file changed, 30 insertions(+), 1 deletion(-)

diff --git a/net/mptcp/bpf.c b/net/mptcp/bpf.c
index 988b22a06331ac293b36f3c6f9bc29ff0f6db048..c5bfd84c16c43230d9d8e1fd8ff781a767e647b5 100644
--- a/net/mptcp/bpf.c
+++ b/net/mptcp/bpf.c
@@ -35,8 +35,37 @@ static const struct btf_kfunc_id_set bpf_mptcp_fmodret_set = {
 	.set   = &bpf_mptcp_fmodret_ids,
 };
 
+__bpf_kfunc_start_defs();
+
+__bpf_kfunc static struct mptcp_subflow_context *
+bpf_mptcp_subflow_ctx(const struct sock *sk)
+{
+	if (sk && sk_fullsock(sk) &&
+	    sk->sk_protocol == IPPROTO_TCP && sk_is_mptcp(sk))
+		return mptcp_subflow_ctx(sk);
+
+	return NULL;
+}
+
+__bpf_kfunc_end_defs();
+
+BTF_KFUNCS_START(bpf_mptcp_common_kfunc_ids)
+BTF_ID_FLAGS(func, bpf_mptcp_subflow_ctx, KF_RET_NULL)
+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,
+};
+
 static int __init bpf_mptcp_kfunc_init(void)
 {
-	return register_btf_fmodret_id_set(&bpf_mptcp_fmodret_set);
+	int ret;
+
+	ret = register_btf_fmodret_id_set(&bpf_mptcp_fmodret_set);
+	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_CGROUP_SOCKOPT,
+					       &bpf_mptcp_common_kfunc_set);
+
+	return ret;
 }
 late_initcall(bpf_mptcp_kfunc_init);

-- 
2.47.1