[CLATJ#7] ClatCoordinator: select IPv4 address for clatd

Introduce ClatCoordinator to replace netd/ClatdController. This is a startup commit. Starting clatd needs to prepare local 464xlat ipv4 address, local 464xlat ipv6 address, tun interface, clat read/write sockets. These will be implemented from this and followup commits. This commit implements that prepare local 464xlat ipv4 address. Bug: 212345928 Test: flash and boot Run "atest ClatCoordinatorTest" in a followup commit. Change-Id: I486db8aef0181ee1aedd7cd7702f95d5a1cef812
2021-12-25 17:05:41 +08:00
parent 8ff032b990
commit e2cf055590
4 changed files with 180 additions and 0 deletions
--- a/service/src/com/android/server/connectivity/ClatCoordinator.java
+++ b/service/src/com/android/server/connectivity/ClatCoordinator.java
@@ -0,0 +1,100 @@
+/*
+ * Copyright (C) 2022 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 com.android.server.connectivity;
+
+import android.annotation.NonNull;
+import android.annotation.Nullable;
+import android.net.INetd;
+import android.net.IpPrefix;
+
+import com.android.internal.annotations.VisibleForTesting;
+
+import java.io.IOException;
+
+/**
+ * This coordinator is responsible for providing clat relevant functionality.
+ *
+ * {@hide}
+ */
+public class ClatCoordinator {
+    private static final String TAG = ClatCoordinator.class.getSimpleName();
+
+    // For historical reasons, start with 192.0.0.4, and after that, use all subsequent addresses
+    // in 192.0.0.0/29 (RFC 7335).
+    @VisibleForTesting
+    static final String INIT_V4ADDR_STRING = "192.0.0.4";
+    @VisibleForTesting
+    static final int INIT_V4ADDR_PREFIX_LEN = 29;
+
+    private static final int INVALID_PID = 0;
+
+    @NonNull
+    private final INetd mNetd;
+    @NonNull
+    private final Dependencies mDeps;
+    @Nullable
+    private String mIface = null;
+    private int mPid = INVALID_PID;
+
+    @VisibleForTesting
+    abstract static class Dependencies {
+        /**
+          * Get netd.
+          */
+        @NonNull
+        public abstract INetd getNetd();
+
+        /**
+         * Pick an IPv4 address for clat.
+         */
+        @NonNull
+        public String jniSelectIpv4Address(@NonNull String v4addr, int prefixlen)
+                throws IOException {
+            return selectIpv4Address(v4addr, prefixlen);
+        }
+    }
+
+    public ClatCoordinator(@NonNull Dependencies deps) {
+        mDeps = deps;
+        mNetd = mDeps.getNetd();
+    }
+
+    /**
+     * Start clatd for a given interface and NAT64 prefix.
+     */
+    public String clatStart(final String iface, final int netId,
+            @NonNull final IpPrefix nat64Prefix)
+            throws IOException {
+        if (nat64Prefix.getPrefixLength() != 96) {
+            throw new IOException("Prefix must be 96 bits long: " + nat64Prefix);
+        }
+
+        // [1] Pick an IPv4 address from 192.0.0.4, 192.0.0.5, 192.0.0.6 ..
+        final String v4;
+        try {
+            v4 = mDeps.jniSelectIpv4Address(INIT_V4ADDR_STRING, INIT_V4ADDR_PREFIX_LEN);
+        } catch (IOException e) {
+            throw new IOException("no IPv4 addresses were available for clat: " + e);
+        }
+
+        // TODO: start clatd and returns local xlat464 v6 address.
+        return null;
+    }
+
+    private static native String selectIpv4Address(String v4addr, int prefixlen)
+            throws IOException;
+}