Split BpfNetMaps constants and utilities into standalone classes

This is a no-op refactoring that splits constants and utility
methods into standalone classes which will be shared with
a bpf reader class in subsequent CLs.

NO_IFTTT=No-op refactoring

Test: atest FrameworksNetTests:android.net.connectivity.com.android.server.BpfNetMapsTest
Test: atest ConnectivityCoverageTests:android.net.connectivity.com.android.net.module.util.StructTest

Bug: 297836825
Change-Id: I6d7ea044e43180ae001573009a166be74ebe6a5d
diff --git a/framework/src/android/net/BpfNetMapsUtils.java b/framework/src/android/net/BpfNetMapsUtils.java
new file mode 100644
index 0000000..d464e3d
--- /dev/null
+++ b/framework/src/android/net/BpfNetMapsUtils.java
@@ -0,0 +1,127 @@
+/*
+ * 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.
+ */
+
+package android.net;
+
+import static android.net.BpfNetMapsConstants.DOZABLE_MATCH;
+import static android.net.BpfNetMapsConstants.LOW_POWER_STANDBY_MATCH;
+import static android.net.BpfNetMapsConstants.MATCH_LIST;
+import static android.net.BpfNetMapsConstants.NO_MATCH;
+import static android.net.BpfNetMapsConstants.OEM_DENY_1_MATCH;
+import static android.net.BpfNetMapsConstants.OEM_DENY_2_MATCH;
+import static android.net.BpfNetMapsConstants.OEM_DENY_3_MATCH;
+import static android.net.BpfNetMapsConstants.POWERSAVE_MATCH;
+import static android.net.BpfNetMapsConstants.RESTRICTED_MATCH;
+import static android.net.BpfNetMapsConstants.STANDBY_MATCH;
+import static android.net.ConnectivityManager.FIREWALL_CHAIN_DOZABLE;
+import static android.net.ConnectivityManager.FIREWALL_CHAIN_LOW_POWER_STANDBY;
+import static android.net.ConnectivityManager.FIREWALL_CHAIN_OEM_DENY_1;
+import static android.net.ConnectivityManager.FIREWALL_CHAIN_OEM_DENY_2;
+import static android.net.ConnectivityManager.FIREWALL_CHAIN_OEM_DENY_3;
+import static android.net.ConnectivityManager.FIREWALL_CHAIN_POWERSAVE;
+import static android.net.ConnectivityManager.FIREWALL_CHAIN_RESTRICTED;
+import static android.net.ConnectivityManager.FIREWALL_CHAIN_STANDBY;
+import static android.system.OsConstants.EINVAL;
+
+import android.os.ServiceSpecificException;
+import android.util.Pair;
+
+import java.util.StringJoiner;
+
+/**
+ * The classes and the methods for BpfNetMaps utilization.
+ *
+ * @hide
+ */
+// Note that this class should be put into bootclasspath instead of static libraries.
+// Because modules could have different copies of this class if this is statically linked,
+// which would be problematic if the definitions in these modules are not synchronized.
+public class BpfNetMapsUtils {
+    // Prevent this class from being accidental instantiated.
+    private BpfNetMapsUtils() {}
+
+    /**
+     * Get corresponding match from firewall chain.
+     */
+    public static long getMatchByFirewallChain(final int chain) {
+        switch (chain) {
+            case FIREWALL_CHAIN_DOZABLE:
+                return DOZABLE_MATCH;
+            case FIREWALL_CHAIN_STANDBY:
+                return STANDBY_MATCH;
+            case FIREWALL_CHAIN_POWERSAVE:
+                return POWERSAVE_MATCH;
+            case FIREWALL_CHAIN_RESTRICTED:
+                return RESTRICTED_MATCH;
+            case FIREWALL_CHAIN_LOW_POWER_STANDBY:
+                return LOW_POWER_STANDBY_MATCH;
+            case FIREWALL_CHAIN_OEM_DENY_1:
+                return OEM_DENY_1_MATCH;
+            case FIREWALL_CHAIN_OEM_DENY_2:
+                return OEM_DENY_2_MATCH;
+            case FIREWALL_CHAIN_OEM_DENY_3:
+                return OEM_DENY_3_MATCH;
+            default:
+                throw new ServiceSpecificException(EINVAL, "Invalid firewall chain: " + chain);
+        }
+    }
+
+    /**
+     * Get if the chain is allow list or not.
+     *
+     * ALLOWLIST means the firewall denies all by default, uids must be explicitly allowed
+     * DENYLIST means the firewall allows all by default, uids must be explicitly denyed
+     */
+    public static boolean isFirewallAllowList(final int chain) {
+        switch (chain) {
+            case FIREWALL_CHAIN_DOZABLE:
+            case FIREWALL_CHAIN_POWERSAVE:
+            case FIREWALL_CHAIN_RESTRICTED:
+            case FIREWALL_CHAIN_LOW_POWER_STANDBY:
+                return true;
+            case FIREWALL_CHAIN_STANDBY:
+            case FIREWALL_CHAIN_OEM_DENY_1:
+            case FIREWALL_CHAIN_OEM_DENY_2:
+            case FIREWALL_CHAIN_OEM_DENY_3:
+                return false;
+            default:
+                throw new ServiceSpecificException(EINVAL, "Invalid firewall chain: " + chain);
+        }
+    }
+
+    /**
+     * Get match string representation from the given match bitmap.
+     */
+    public static String matchToString(long matchMask) {
+        if (matchMask == NO_MATCH) {
+            return "NO_MATCH";
+        }
+
+        final StringJoiner sj = new StringJoiner(" ");
+        for (final Pair<Long, String> match : MATCH_LIST) {
+            final long matchFlag = match.first;
+            final String matchName = match.second;
+            if ((matchMask & matchFlag) != 0) {
+                sj.add(matchName);
+                matchMask &= ~matchFlag;
+            }
+        }
+        if (matchMask != 0) {
+            sj.add("UNKNOWN_MATCH(" + matchMask + ")");
+        }
+        return sj.toString();
+    }
+}