netdev - [PATCH bpf-next/net 3/5] bpf: Acquire and release mptcp socket

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Message-Id: <20241108-bpf-next-net-mptcp-bpf_iter-subflows-v1-3-cf16953035c1@kernel.org>
Date: Fri, 08 Nov 2024 16:52:32 +0100
From: "Matthieu Baerts (NGI0)" <matttbe@...nel.org>
To: mptcp@...ts.linux.dev, Mat Martineau <martineau@...nel.org>, 
 Geliang Tang <geliang@...nel.org>, "David S. Miller" <davem@...emloft.net>, 
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
 Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, 
 Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
 Andrii Nakryiko <andrii@...nel.org>, 
 Martin KaFai Lau <martin.lau@...ux.dev>, 
 Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
 Yonghong Song <yonghong.song@...ux.dev>, 
 John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>, 
 Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, 
 Jiri Olsa <jolsa@...nel.org>, Mykola Lysenko <mykolal@...com>, 
 Shuah Khan <shuah@...nel.org>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
 bpf@...r.kernel.org, linux-kselftest@...r.kernel.org, 
 "Matthieu Baerts (NGI0)" <matttbe@...nel.org>, 
 Geliang Tang <geliang@...nel.org>
Subject: [PATCH bpf-next/net 3/5] bpf: Acquire and release mptcp socket

From: Geliang Tang <tanggeliang@...inos.cn>

The KF_TRUSTED_ARGS flag is used for bpf_iter_mptcp_subflow_new, it
indicates that the all pointer arguments are valid. It's necessary to
add a KF_ACQUIRE helper to get valid "msk".

This patch adds bpf_mptcp_sock_acquire() and bpf_mptcp_sock_release()
helpers for this. Increase sk->sk_refcnt in _acquire() and decrease it
in _release(). Register them with KF_ACQUIRE flag and KF_RELEASE flag.

Signed-off-by: Geliang Tang <tanggeliang@...inos.cn>
Reviewed-by: Mat Martineau <martineau@...nel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@...nel.org>
---
 net/mptcp/bpf.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/net/mptcp/bpf.c b/net/mptcp/bpf.c
index d107c2865e97e6ccffb9e0720dfbbd232b63a3b8..5bd04548e846b4dc120dbc83725a604821fac772 100644
--- a/net/mptcp/bpf.c
+++ b/net/mptcp/bpf.c
@@ -90,6 +90,23 @@ bpf_iter_mptcp_subflow_destroy(struct bpf_iter_mptcp_subflow *it)
 {
 }

+__bpf_kfunc static struct
+mptcp_sock *bpf_mptcp_sock_acquire(struct mptcp_sock *msk)
+{
+	struct sock *sk = (struct sock *)msk;
+
+	if (sk && refcount_inc_not_zero(&sk->sk_refcnt))
+		return msk;
+	return NULL;
+}
+
+__bpf_kfunc static void bpf_mptcp_sock_release(struct mptcp_sock *msk)
+{
+	struct sock *sk = (struct sock *)msk;
+
+	WARN_ON_ONCE(!sk || !refcount_dec_not_one(&sk->sk_refcnt));
+}
+
 __bpf_kfunc_end_defs();

 BTF_KFUNCS_START(bpf_mptcp_common_kfunc_ids)
@@ -99,6 +116,8 @@ BTF_ID_FLAGS(func, bpf_mptcp_subflow_tcp_sock)
 BTF_ID_FLAGS(func, bpf_iter_mptcp_subflow_new, KF_ITER_NEW | KF_TRUSTED_ARGS)
 BTF_ID_FLAGS(func, bpf_iter_mptcp_subflow_next, KF_ITER_NEXT | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_iter_mptcp_subflow_destroy, KF_ITER_DESTROY)
+BTF_ID_FLAGS(func, bpf_mptcp_sock_acquire, KF_ACQUIRE | KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_mptcp_sock_release, KF_RELEASE)
 BTF_KFUNCS_END(bpf_mptcp_common_kfunc_ids)

 static const struct btf_kfunc_id_set bpf_mptcp_common_kfunc_set = {

-- 
2.45.2