Squash to "selftests/bpf: Add mptcp_subflow bpf_iter subtest"

Use bpf_skc_to_mptcp_sock() and mptcp_subflow_tcp_sock() instead of
bpf_mptcp_sk() and bpf_mptcp_subflow_tcp_sock().

IPPROTO_MPTCP is checked in bpf_skc_to_mptcp_sock(), no need to check
it in BPF program.

bpf_skc_to_mptcp_sock() and bpf_mptcp_subflow_ctx() may return NULL,
need to check the return values.

Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>

tools/testing/selftests/bpf/progs/mptcp_bpf.h

@@ -46,7 +46,6 @@ mptcp_subflow_tcp_sock(const struct mptcp_subflow_context *subflow)
 extern struct mptcp_sock *bpf_mptcp_sock_acquire(struct mptcp_sock *msk) __ksym;
 extern void bpf_mptcp_sock_release(struct mptcp_sock *msk) __ksym;
 
-extern struct mptcp_sock *bpf_mptcp_sk(struct sock *sk) __ksym;
 extern struct mptcp_subflow_context *
 bpf_mptcp_subflow_ctx(const struct sock *sk) __ksym;
 extern struct sock *

tools/testing/selftests/bpf/progs/mptcp_bpf_iters.c

@@ -21,12 +21,11 @@ int iters_subflow(struct bpf_sockopt *ctx)
 	struct mptcp_sock *msk;
 	int local_ids = 0;
 
-	if (!sk || sk->protocol != IPPROTO_MPTCP ||
-	    ctx->level != SOL_TCP || ctx->optname != TCP_IS_MPTCP)
+	if (ctx->level != SOL_TCP || ctx->optname != TCP_IS_MPTCP)
 		return 1;
 
-	msk = bpf_mptcp_sk((struct sock *)sk);
-	if (msk->pm.server_side || !msk->pm.subflows)
+	msk = bpf_skc_to_mptcp_sock(sk);
+	if (!msk || msk->pm.server_side || !msk->pm.subflows)
 		return 1;
 
 	msk = bpf_mptcp_sock_acquire(msk);
@@ -41,7 +40,7 @@ int iters_subflow(struct bpf_sockopt *ctx)
 		local_ids += subflow->subflow_id;
 
 		/* only to check the following kfunc works */
-		ssk = bpf_mptcp_subflow_tcp_sock(subflow);
+		ssk = mptcp_subflow_tcp_sock(subflow);
 	}
 
 	if (!ssk)
@@ -53,7 +52,7 @@ int iters_subflow(struct bpf_sockopt *ctx)
 
 	/* only to check the following kfunc works */
 	subflow = bpf_mptcp_subflow_ctx(ssk);
-	if (subflow->token != msk->token)
+	if (!subflow || subflow->token != msk->token)
 		goto out;
 
 	ids = local_ids;