Add a library for DNS resolver to read bpf maps
The library provides an init function and an API for DNS resolver to
query whether the application is allowed to send DNS query based on BPF
maps settings.
Bug: 288340533
Test: atest dns_helper_unit_test (with test CL)
Change-Id: Ibfb383bfb074da2104a25aa4f04ebc32b22d11da
diff --git a/DnsResolver/include/DnsHelperPublic.h b/DnsResolver/include/DnsHelperPublic.h
new file mode 100644
index 0000000..7c9fc9e
--- /dev/null
+++ b/DnsResolver/include/DnsHelperPublic.h
@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <sys/cdefs.h>
+#include <sys/types.h>
+
+__BEGIN_DECLS
+
+/*
+ * Perform any required initialization - including opening any required BPF maps. This function
+ * needs to be called before using other functions of this library.
+ *
+ * Returns 0 on success, a negative POSIX error code (see errno.h) on other failures.
+ */
+int ADnsHelper_init();
+
+/*
+ * The function reads bpf maps and returns whether the given uid has blocked networking or not. The
+ * function is supported starting from Android T.
+ *
+ * |uid| is a Linux/Android UID to be queried. It is a combination of UserID and AppID.
+ * |metered| indicates whether the uid is currently using a billing network.
+ *
+ * Returns 0(false)/1(true) on success, a negative POSIX error code (see errno.h) on other failures.
+ */
+int ADnsHelper_isUidNetworkingBlocked(uid_t uid, bool metered);
+
+__END_DECLS