service-t/src/com/android/server/IpSecService.java

/*
 * Copyright (C) 2017 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;

import static android.Manifest.permission.DUMP;
import static android.net.IpSecManager.INVALID_RESOURCE_ID;
import static android.system.OsConstants.AF_INET;
import static android.system.OsConstants.AF_INET6;
import static android.system.OsConstants.AF_UNSPEC;
import static android.system.OsConstants.EINVAL;
import static android.system.OsConstants.IPPROTO_UDP;
import static android.system.OsConstants.SOCK_DGRAM;

import android.annotation.NonNull;
import android.app.AppOpsManager;
import android.content.Context;
import android.content.pm.PackageManager;
import android.net.ConnectivityManager;
import android.net.IIpSecService;
import android.net.INetd;
import android.net.InetAddresses;
import android.net.IpSecAlgorithm;
import android.net.IpSecConfig;
import android.net.IpSecManager;
import android.net.IpSecSpiResponse;
import android.net.IpSecTransform;
import android.net.IpSecTransformResponse;
import android.net.IpSecTunnelInterfaceResponse;
import android.net.IpSecUdpEncapResponse;
import android.net.LinkAddress;
import android.net.LinkProperties;
import android.net.Network;
import android.net.TrafficStats;
import android.os.Binder;
import android.os.IBinder;
import android.os.ParcelFileDescriptor;
import android.os.Process;
import android.os.RemoteException;
import android.os.ServiceSpecificException;
import android.system.ErrnoException;
import android.system.Os;
import android.system.OsConstants;
import android.text.TextUtils;
import android.util.Log;
import android.util.Range;
import android.util.SparseArray;
import android.util.SparseBooleanArray;

import com.android.internal.annotations.GuardedBy;
import com.android.internal.annotations.VisibleForTesting;
import com.android.internal.util.Preconditions;
import com.android.net.module.util.BinderUtils;
import com.android.net.module.util.NetdUtils;
import com.android.net.module.util.PermissionUtils;

import libcore.io.IoUtils;

import java.io.FileDescriptor;
import java.io.IOException;
import java.io.PrintWriter;
import java.net.Inet4Address;
import java.net.Inet6Address;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.UnknownHostException;
import java.util.ArrayList;
import java.util.List;
import java.util.Objects;

/**
 * A service to manage multiple clients that want to access the IpSec API. The service is
 * responsible for maintaining a list of clients and managing the resources (and related quotas)
 * that each of them own.
 *
 * <p>Synchronization in IpSecService is done on all entrypoints due to potential race conditions at
 * the kernel/xfrm level. Further, this allows the simplifying assumption to be made that only one
 * thread is ever running at a time.
 *
 * @hide
 */
public class IpSecService extends IIpSecService.Stub {
    private static final String TAG = "IpSecService";
    private static final boolean DBG = Log.isLoggable(TAG, Log.DEBUG);
    private static final int[] ADDRESS_FAMILIES =
            new int[] {OsConstants.AF_INET, OsConstants.AF_INET6};

    private static final int NETD_FETCH_TIMEOUT_MS = 5000; // ms
    private static final InetAddress INADDR_ANY;

    @VisibleForTesting static final int MAX_PORT_BIND_ATTEMPTS = 10;

    private final INetd mNetd;

    static {
        try {
            INADDR_ANY = InetAddress.getByAddress(new byte[] {0, 0, 0, 0});
        } catch (UnknownHostException e) {
            throw new RuntimeException(e);
        }
    }

    static final int FREE_PORT_MIN = 1024; // ports 1-1023 are reserved
    static final int PORT_MAX = 0xFFFF; // ports are an unsigned 16-bit integer

    /* Binder context for this service */
    private final Context mContext;
    private final Dependencies mDeps;

    /**
     * The next non-repeating global ID for tracking resources between users, this service, and
     * kernel data structures. Accessing this variable is not thread safe, so it is only read or
     * modified within blocks synchronized on IpSecService.this. We want to avoid -1
     * (INVALID_RESOURCE_ID) and 0 (we probably forgot to initialize it).
     */
    @GuardedBy("IpSecService.this")
    private int mNextResourceId = 1;

    /**
     * Dependencies of IpSecService, for injection in tests.
     */
    @VisibleForTesting
    public static class Dependencies {
        /**
         * Get a reference to INetd.
         */
        public INetd getNetdInstance(Context context) throws RemoteException {
            final INetd netd = INetd.Stub.asInterface((IBinder)
                    context.getSystemService(Context.NETD_SERVICE));
            if (netd == null) {
                throw new RemoteException("Failed to Get Netd Instance");
            }
            return netd;
        }
    }

    final UidFdTagger mUidFdTagger;

    /**
     * Interface for user-reference and kernel-resource cleanup.
     *
     * <p>This interface must be implemented for a resource to be reference counted.
     */
    @VisibleForTesting
    public interface IResource {
        /**
         * Invalidates a IResource object, ensuring it is invalid for the purposes of allocating new
         * objects dependent on it.
         *
         * <p>Implementations of this method are expected to remove references to the IResource
         * object from the IpSecService's tracking arrays. The removal from the arrays ensures that
         * the resource is considered invalid for user access or allocation or use in other
         * resources.
         *
         * <p>References to the IResource object may be held by other RefcountedResource objects,
         * and as such, the underlying resources and quota may not be cleaned up.
         */
        void invalidate() throws RemoteException;

        /**
         * Releases underlying resources and related quotas.
         *
         * <p>Implementations of this method are expected to remove all system resources that are
         * tracked by the IResource object. Due to other RefcountedResource objects potentially
         * having references to the IResource object, freeUnderlyingResources may not always be
         * called from releaseIfUnreferencedRecursively().
         */
        void freeUnderlyingResources() throws RemoteException;
    }

    /**
     * RefcountedResource manages references and dependencies in an exclusively acyclic graph.
     *
     * <p>RefcountedResource implements both explicit and implicit resource management. Creating a
     * RefcountedResource object creates an explicit reference that must be freed by calling
     * userRelease(). Additionally, adding this object as a child of another RefcountedResource
     * object will add an implicit reference.
     *
     * <p>Resources are cleaned up when all references, both implicit and explicit, are released
     * (ie, when userRelease() is called and when all parents have called releaseReference() on this
     * object.)
     */
    @VisibleForTesting
    public class RefcountedResource<T extends IResource> implements IBinder.DeathRecipient {
        private final T mResource;
        private final List<RefcountedResource> mChildren;
        int mRefCount = 1; // starts at 1 for user's reference.
        IBinder mBinder;

        RefcountedResource(T resource, IBinder binder, RefcountedResource... children) {
            synchronized (IpSecService.this) {
                this.mResource = resource;
                this.mChildren = new ArrayList<>(children.length);
                this.mBinder = binder;

                for (RefcountedResource child : children) {
                    mChildren.add(child);
                    child.mRefCount++;
                }

                try {
                    mBinder.linkToDeath(this, 0);
                } catch (RemoteException e) {
                    binderDied();
                    e.rethrowFromSystemServer();
                }
            }
        }

        /**
         * If the Binder object dies, this function is called to free the system resources that are
         * being tracked by this record and to subsequently release this record for garbage
         * collection
         */
        @Override
        public void binderDied() {
            synchronized (IpSecService.this) {
                try {
                    userRelease();
                } catch (Exception e) {
                    Log.e(TAG, "Failed to release resource: " + e);
                }
            }
        }

        public T getResource() {
            return mResource;
        }

        /**
         * Unlinks from binder and performs IpSecService resource cleanup (removes from resource
         * arrays)
         *
         * <p>If this method has been previously called, the RefcountedResource's binder field will
         * be null, and the method will return without performing the cleanup a second time.
         *
         * <p>Note that calling this function does not imply that kernel resources will be freed at
         * this time, or that the related quota will be returned. Such actions will only be
         * performed upon the reference count reaching zero.
         */
        @GuardedBy("IpSecService.this")
        public void userRelease() throws RemoteException {
            // Prevent users from putting reference counts into a bad state by calling
            // userRelease() multiple times.
            if (mBinder == null) {
                return;
            }

            mBinder.unlinkToDeath(this, 0);
            mBinder = null;

            mResource.invalidate();

            releaseReference();
        }

        /**
         * Removes a reference to this resource. If the resultant reference count is zero, the
         * underlying resources are freed, and references to all child resources are also dropped
         * recursively (resulting in them freeing their resources and children, etcetera)
         *
         * <p>This method also sets the reference count to an invalid value (-1) to signify that it
         * has been fully released. Any subsequent calls to this method will result in an
         * IllegalStateException being thrown due to resource already having been previously
         * released
         */
        @VisibleForTesting
        @GuardedBy("IpSecService.this")
        public void releaseReference() throws RemoteException {
            mRefCount--;

            if (mRefCount > 0) {
                return;
            } else if (mRefCount < 0) {
                throw new IllegalStateException(
                        "Invalid operation - resource has already been released.");
            }

            // Cleanup own resources
            mResource.freeUnderlyingResources();

            // Cleanup child resources as needed
            for (RefcountedResource<? extends IResource> child : mChildren) {
                child.releaseReference();
            }

            // Enforce that resource cleanup can only be called once
            // By decrementing the refcount (from 0 to -1), the next call will throw an
            // IllegalStateException - it has already been released fully.
            mRefCount--;
        }

        @Override
        public String toString() {
            return new StringBuilder()
                    .append("{mResource=")
                    .append(mResource)
                    .append(", mRefCount=")
                    .append(mRefCount)
                    .append(", mChildren=")
                    .append(mChildren)
                    .append("}")
                    .toString();
        }
    }

    /**
     * Very simple counting class that looks much like a counting semaphore
     *
     * <p>This class is not thread-safe, and expects that that users of this class will ensure
     * synchronization and thread safety by holding the IpSecService.this instance lock.
     */
    @VisibleForTesting
    static class ResourceTracker {
        private final int mMax;
        int mCurrent;

        ResourceTracker(int max) {
            mMax = max;
            mCurrent = 0;
        }

        boolean isAvailable() {
            return (mCurrent < mMax);
        }

        void take() {
            if (!isAvailable()) {
                Log.wtf(TAG, "Too many resources allocated!");
            }
            mCurrent++;
        }

        void give() {
            if (mCurrent <= 0) {
                Log.wtf(TAG, "We've released this resource too many times");
            }
            mCurrent--;
        }

        @Override
        public String toString() {
            return new StringBuilder()
                    .append("{mCurrent=")
                    .append(mCurrent)
                    .append(", mMax=")
                    .append(mMax)
                    .append("}")
                    .toString();
        }
    }

    @VisibleForTesting
    static final class UserRecord {
        /* Maximum number of each type of resource that a single UID may possess */

        // Up to 4 active VPNs/IWLAN with potential soft handover.
        public static final int MAX_NUM_TUNNEL_INTERFACES = 8;
        public static final int MAX_NUM_ENCAP_SOCKETS = 16;

        // SPIs and Transforms are both cheap, and are 1:1 correlated.
        public static final int MAX_NUM_TRANSFORMS = 64;
        public static final int MAX_NUM_SPIS = 64;

        /**
         * Store each of the OwnedResource types in an (thinly wrapped) sparse array for indexing
         * and explicit (user) reference management.
         *
         * <p>These are stored in separate arrays to improve debuggability and dump output clarity.
         *
         * <p>Resources are removed from this array when the user releases their explicit reference
         * by calling one of the releaseResource() methods.
         */
        final RefcountedResourceArray<SpiRecord> mSpiRecords =
                new RefcountedResourceArray<>(SpiRecord.class.getSimpleName());
        final RefcountedResourceArray<TransformRecord> mTransformRecords =
                new RefcountedResourceArray<>(TransformRecord.class.getSimpleName());
        final RefcountedResourceArray<EncapSocketRecord> mEncapSocketRecords =
                new RefcountedResourceArray<>(EncapSocketRecord.class.getSimpleName());
        final RefcountedResourceArray<TunnelInterfaceRecord> mTunnelInterfaceRecords =
                new RefcountedResourceArray<>(TunnelInterfaceRecord.class.getSimpleName());

        /**
         * Trackers for quotas for each of the OwnedResource types.
         *
         * <p>These trackers are separate from the resource arrays, since they are incremented and
         * decremented at different points in time. Specifically, quota is only returned upon final
         * resource deallocation (after all explicit and implicit references are released). Note
         * that it is possible that calls to releaseResource() will not return the used quota if
         * there are other resources that depend on (are parents of) the resource being released.
         */
        final ResourceTracker mSpiQuotaTracker = new ResourceTracker(MAX_NUM_SPIS);
        final ResourceTracker mTransformQuotaTracker = new ResourceTracker(MAX_NUM_TRANSFORMS);
        final ResourceTracker mSocketQuotaTracker = new ResourceTracker(MAX_NUM_ENCAP_SOCKETS);
        final ResourceTracker mTunnelQuotaTracker = new ResourceTracker(MAX_NUM_TUNNEL_INTERFACES);

        void removeSpiRecord(int resourceId) {
            mSpiRecords.remove(resourceId);
        }

        void removeTransformRecord(int resourceId) {
            mTransformRecords.remove(resourceId);
        }

        void removeTunnelInterfaceRecord(int resourceId) {
            mTunnelInterfaceRecords.remove(resourceId);
        }

        void removeEncapSocketRecord(int resourceId) {
            mEncapSocketRecords.remove(resourceId);
        }

        @Override
        public String toString() {
            return new StringBuilder()
                    .append("{mSpiQuotaTracker=")
                    .append(mSpiQuotaTracker)
                    .append(", mTransformQuotaTracker=")
                    .append(mTransformQuotaTracker)
                    .append(", mSocketQuotaTracker=")
                    .append(mSocketQuotaTracker)
                    .append(", mTunnelQuotaTracker=")
                    .append(mTunnelQuotaTracker)
                    .append(", mSpiRecords=")
                    .append(mSpiRecords)
                    .append(", mTransformRecords=")
                    .append(mTransformRecords)
                    .append(", mEncapSocketRecords=")
                    .append(mEncapSocketRecords)
                    .append(", mTunnelInterfaceRecords=")
                    .append(mTunnelInterfaceRecords)
                    .append("}")
                    .toString();
        }
    }

    /**
     * This class is not thread-safe, and expects that that users of this class will ensure
     * synchronization and thread safety by holding the IpSecService.this instance lock.
     */
    @VisibleForTesting
    static final class UserResourceTracker {
        private final SparseArray<UserRecord> mUserRecords = new SparseArray<>();

        /** Lazy-initialization/getter that populates or retrieves the UserRecord as needed */
        public UserRecord getUserRecord(int uid) {
            checkCallerUid(uid);

            UserRecord r = mUserRecords.get(uid);
            if (r == null) {
                r = new UserRecord();
                mUserRecords.put(uid, r);
            }
            return r;
        }

        /** Safety method; guards against access of other user's UserRecords */
        private void checkCallerUid(int uid) {
            if (uid != Binder.getCallingUid() && Process.SYSTEM_UID != Binder.getCallingUid()) {
                throw new SecurityException("Attempted access of unowned resources");
            }
        }

        @Override
        public String toString() {
            return mUserRecords.toString();
        }
    }

    @VisibleForTesting final UserResourceTracker mUserResourceTracker = new UserResourceTracker();

    /**
     * The OwnedResourceRecord class provides a facility to cleanly and reliably track system
     * resources. It relies on a provided resourceId that should uniquely identify the kernel
     * resource. To use this class, the user should implement the invalidate() and
     * freeUnderlyingResources() methods that are responsible for cleaning up IpSecService resource
     * tracking arrays and kernel resources, respectively.
     *
     * <p>This class associates kernel resources with the UID that owns and controls them.
     */
    private abstract class OwnedResourceRecord implements IResource {
        final int mPid;
        final int mUid;
        protected final int mResourceId;

        OwnedResourceRecord(int resourceId) {
            super();
            if (resourceId == INVALID_RESOURCE_ID) {
                throw new IllegalArgumentException("Resource ID must not be INVALID_RESOURCE_ID");
            }
            mResourceId = resourceId;
            mPid = Binder.getCallingPid();
            mUid = Binder.getCallingUid();

            getResourceTracker().take();
        }

        @Override
        public abstract void invalidate() throws RemoteException;

        /** Convenience method; retrieves the user resource record for the stored UID. */
        protected UserRecord getUserRecord() {
            return mUserResourceTracker.getUserRecord(mUid);
        }

        @Override
        public abstract void freeUnderlyingResources() throws RemoteException;

        /** Get the resource tracker for this resource */
        protected abstract ResourceTracker getResourceTracker();

        @Override
        public String toString() {
            return new StringBuilder()
                    .append("{mResourceId=")
                    .append(mResourceId)
                    .append(", pid=")
                    .append(mPid)
                    .append(", uid=")
                    .append(mUid)
                    .append("}")
                    .toString();
        }
    };

    /**
     * Thin wrapper over SparseArray to ensure resources exist, and simplify generic typing.
     *
     * <p>RefcountedResourceArray prevents null insertions, and throws an IllegalArgumentException
     * if a key is not found during a retrieval process.
     */
    static class RefcountedResourceArray<T extends IResource> {
        SparseArray<RefcountedResource<T>> mArray = new SparseArray<>();
        private final String mTypeName;

        RefcountedResourceArray(String typeName) {
            this.mTypeName = typeName;
        }

        /**
         * Accessor method to get inner resource object.
         *
         * @throws IllegalArgumentException if no resource with provided key is found.
         */
        T getResourceOrThrow(int key) {
            return getRefcountedResourceOrThrow(key).getResource();
        }

        /**
         * Accessor method to get reference counting wrapper.
         *
         * @throws IllegalArgumentException if no resource with provided key is found.
         */
        RefcountedResource<T> getRefcountedResourceOrThrow(int key) {
            RefcountedResource<T> resource = mArray.get(key);
            if (resource == null) {
                throw new IllegalArgumentException(
                        String.format("No such %s found for given id: %d", mTypeName, key));
            }

            return resource;
        }

        void put(int key, RefcountedResource<T> obj) {
            Objects.requireNonNull(obj, "Null resources cannot be added");
            mArray.put(key, obj);
        }

        void remove(int key) {
            mArray.remove(key);
        }

        @Override
        public String toString() {
            return mArray.toString();
        }
    }

    /**
     * Tracks an SA in the kernel, and manages cleanup paths. Once a TransformRecord is
     * created, the SpiRecord that originally tracked the SAs will reliquish the
     * responsibility of freeing the underlying SA to this class via the mOwnedByTransform flag.
     */
    private final class TransformRecord extends OwnedResourceRecord {
        private final IpSecConfig mConfig;
        private final SpiRecord mSpi;
        private final EncapSocketRecord mSocket;

        TransformRecord(
                int resourceId, IpSecConfig config, SpiRecord spi, EncapSocketRecord socket) {
            super(resourceId);
            mConfig = config;
            mSpi = spi;
            mSocket = socket;

            spi.setOwnedByTransform();
        }

        public IpSecConfig getConfig() {
            return mConfig;
        }

        public SpiRecord getSpiRecord() {
            return mSpi;
        }

        public EncapSocketRecord getSocketRecord() {
            return mSocket;
        }

        /** always guarded by IpSecService#this */
        @Override
        public void freeUnderlyingResources() {
            int spi = mSpi.getSpi();
            try {
                mNetd.ipSecDeleteSecurityAssociation(
                        mUid,
                        mConfig.getSourceAddress(),
                        mConfig.getDestinationAddress(),
                        spi,
                        mConfig.getMarkValue(),
                        mConfig.getMarkMask(),
                        mConfig.getXfrmInterfaceId());
            } catch (RemoteException | ServiceSpecificException e) {
                Log.e(TAG, "Failed to delete SA with ID: " + mResourceId, e);
            }

            getResourceTracker().give();
        }

        @Override
        public void invalidate() throws RemoteException {
            getUserRecord().removeTransformRecord(mResourceId);
        }

        @Override
        protected ResourceTracker getResourceTracker() {
            return getUserRecord().mTransformQuotaTracker;
        }

        @Override
        public String toString() {
            StringBuilder strBuilder = new StringBuilder();
            strBuilder
                    .append("{super=")
                    .append(super.toString())
                    .append(", mSocket=")
                    .append(mSocket)
                    .append(", mSpi.mResourceId=")
                    .append(mSpi.mResourceId)
                    .append(", mConfig=")
                    .append(mConfig)
                    .append("}");
            return strBuilder.toString();
        }
    }

    /**
     * Tracks a single SA in the kernel, and manages cleanup paths. Once used in a Transform, the
     * responsibility for cleaning up underlying resources will be passed to the TransformRecord
     * object
     */
    private final class SpiRecord extends OwnedResourceRecord {
        private final String mSourceAddress;
        private final String mDestinationAddress;
        private int mSpi;

        private boolean mOwnedByTransform = false;

        SpiRecord(int resourceId, String sourceAddress,
                String destinationAddress, int spi) {
            super(resourceId);
            mSourceAddress = sourceAddress;
            mDestinationAddress = destinationAddress;
            mSpi = spi;
        }

        /** always guarded by IpSecService#this */
        @Override
        public void freeUnderlyingResources() {
            try {
                if (!mOwnedByTransform) {
                    mNetd.ipSecDeleteSecurityAssociation(
                            mUid, mSourceAddress, mDestinationAddress, mSpi, 0 /* mark */,
                            0 /* mask */, 0 /* if_id */);
                }
            } catch (ServiceSpecificException | RemoteException e) {
                Log.e(TAG, "Failed to delete SPI reservation with ID: " + mResourceId, e);
            }

            mSpi = IpSecManager.INVALID_SECURITY_PARAMETER_INDEX;

            getResourceTracker().give();
        }

        public int getSpi() {
            return mSpi;
        }

        public String getDestinationAddress() {
            return mDestinationAddress;
        }

        public void setOwnedByTransform() {
            if (mOwnedByTransform) {
                // Programming error
                throw new IllegalStateException("Cannot own an SPI twice!");
            }

            mOwnedByTransform = true;
        }

        public boolean getOwnedByTransform() {
            return mOwnedByTransform;
        }

        @Override
        public void invalidate() throws RemoteException {
            getUserRecord().removeSpiRecord(mResourceId);
        }

        @Override
        protected ResourceTracker getResourceTracker() {
            return getUserRecord().mSpiQuotaTracker;
        }

        @Override
        public String toString() {
            StringBuilder strBuilder = new StringBuilder();
            strBuilder
                    .append("{super=")
                    .append(super.toString())
                    .append(", mSpi=")
                    .append(mSpi)
                    .append(", mSourceAddress=")
                    .append(mSourceAddress)
                    .append(", mDestinationAddress=")
                    .append(mDestinationAddress)
                    .append(", mOwnedByTransform=")
                    .append(mOwnedByTransform)
                    .append("}");
            return strBuilder.toString();
        }
    }

    private final SparseBooleanArray mTunnelNetIds = new SparseBooleanArray();
    final Range<Integer> mNetIdRange = ConnectivityManager.getIpSecNetIdRange();
    private int mNextTunnelNetId = mNetIdRange.getLower();

    /**
     * Reserves a netId within the range of netIds allocated for IPsec tunnel interfaces
     *
     * <p>This method should only be called from Binder threads. Do not call this from within the
     * system server as it will crash the system on failure.
     *
     * @return an integer key within the netId range, if successful
     * @throws IllegalStateException if unsuccessful (all netId are currently reserved)
     */
    @VisibleForTesting
    int reserveNetId() {
        final int range = mNetIdRange.getUpper() - mNetIdRange.getLower() + 1;
        synchronized (mTunnelNetIds) {
            for (int i = 0; i < range; i++) {
                final int netId = mNextTunnelNetId;
                if (++mNextTunnelNetId > mNetIdRange.getUpper()) {
                    mNextTunnelNetId = mNetIdRange.getLower();
                }
                if (!mTunnelNetIds.get(netId)) {
                    mTunnelNetIds.put(netId, true);
                    return netId;
                }
            }
        }
        throw new IllegalStateException("No free netIds to allocate");
    }

    @VisibleForTesting
    void releaseNetId(int netId) {
        synchronized (mTunnelNetIds) {
            mTunnelNetIds.delete(netId);
        }
    }

    /**
     * Tracks an tunnel interface, and manages cleanup paths.
     *
     * <p>This class is not thread-safe, and expects that that users of this class will ensure
     * synchronization and thread safety by holding the IpSecService.this instance lock
     */
    @VisibleForTesting
    final class TunnelInterfaceRecord extends OwnedResourceRecord {
        private final String mInterfaceName;

        // outer addresses
        private final String mLocalAddress;
        private final String mRemoteAddress;

        private final int mIkey;
        private final int mOkey;

        private final int mIfId;

        private Network mUnderlyingNetwork;

        TunnelInterfaceRecord(
                int resourceId,
                String interfaceName,
                Network underlyingNetwork,
                String localAddr,
                String remoteAddr,
                int ikey,
                int okey,
                int intfId) {
            super(resourceId);

            mInterfaceName = interfaceName;
            mUnderlyingNetwork = underlyingNetwork;
            mLocalAddress = localAddr;
            mRemoteAddress = remoteAddr;
            mIkey = ikey;
            mOkey = okey;
            mIfId = intfId;
        }

        /** always guarded by IpSecService#this */
        @Override
        public void freeUnderlyingResources() {
            // Calls to netd
            //       Teardown VTI
            //       Delete global policies
            try {
                mNetd.ipSecRemoveTunnelInterface(mInterfaceName);

                for (int selAddrFamily : ADDRESS_FAMILIES) {
                    mNetd.ipSecDeleteSecurityPolicy(
                            mUid,
                            selAddrFamily,
                            IpSecManager.DIRECTION_OUT,
                            mOkey,
                            0xffffffff,
                            mIfId);
                    mNetd.ipSecDeleteSecurityPolicy(
                            mUid,
                            selAddrFamily,
                            IpSecManager.DIRECTION_IN,
                            mIkey,
                            0xffffffff,
                            mIfId);
                }
            } catch (ServiceSpecificException | RemoteException e) {
                Log.e(
                        TAG,
                        "Failed to delete VTI with interface name: "
                                + mInterfaceName
                                + " and id: "
                                + mResourceId, e);
            }

            getResourceTracker().give();
            releaseNetId(mIkey);
            releaseNetId(mOkey);
        }

        @GuardedBy("IpSecService.this")
        public void setUnderlyingNetwork(Network underlyingNetwork) {
            // When #applyTunnelModeTransform is called, this new underlying network will be used to
            // update the output mark of the input transform.
            mUnderlyingNetwork = underlyingNetwork;
        }

        @GuardedBy("IpSecService.this")
        public Network getUnderlyingNetwork() {
            return mUnderlyingNetwork;
        }

        public String getInterfaceName() {
            return mInterfaceName;
        }

        /** Returns the local, outer address for the tunnelInterface */
        public String getLocalAddress() {
            return mLocalAddress;
        }

        /** Returns the remote, outer address for the tunnelInterface */
        public String getRemoteAddress() {
            return mRemoteAddress;
        }

        public int getIkey() {
            return mIkey;
        }

        public int getOkey() {
            return mOkey;
        }

        public int getIfId() {
            return mIfId;
        }

        @Override
        protected ResourceTracker getResourceTracker() {
            return getUserRecord().mTunnelQuotaTracker;
        }

        @Override
        public void invalidate() {
            getUserRecord().removeTunnelInterfaceRecord(mResourceId);
        }

        @Override
        public String toString() {
            return new StringBuilder()
                    .append("{super=")
                    .append(super.toString())
                    .append(", mInterfaceName=")
                    .append(mInterfaceName)
                    .append(", mUnderlyingNetwork=")
                    .append(mUnderlyingNetwork)
                    .append(", mLocalAddress=")
                    .append(mLocalAddress)
                    .append(", mRemoteAddress=")
                    .append(mRemoteAddress)
                    .append(", mIkey=")
                    .append(mIkey)
                    .append(", mOkey=")
                    .append(mOkey)
                    .append("}")
                    .toString();
        }
    }

    /**
     * Tracks a UDP encap socket, and manages cleanup paths
     *
     * <p>While this class does not manage non-kernel resources, race conditions around socket
     * binding require that the service creates the encap socket, binds it and applies the socket
     * policy before handing it to a user.
     */
    private final class EncapSocketRecord extends OwnedResourceRecord {
        private FileDescriptor mSocket;
        private final int mPort;

        EncapSocketRecord(int resourceId, FileDescriptor socket, int port) {
            super(resourceId);
            mSocket = socket;
            mPort = port;
        }

        /** always guarded by IpSecService#this */
        @Override
        public void freeUnderlyingResources() {
            Log.d(TAG, "Closing port " + mPort);
            IoUtils.closeQuietly(mSocket);
            mSocket = null;

            getResourceTracker().give();
        }

        public int getPort() {
            return mPort;
        }

        public FileDescriptor getFileDescriptor() {
            return mSocket;
        }

        @Override
        protected ResourceTracker getResourceTracker() {
            return getUserRecord().mSocketQuotaTracker;
        }

        @Override
        public void invalidate() {
            getUserRecord().removeEncapSocketRecord(mResourceId);
        }

        @Override
        public String toString() {
            return new StringBuilder()
                    .append("{super=")
                    .append(super.toString())
                    .append(", mSocket=")
                    .append(mSocket)
                    .append(", mPort=")
                    .append(mPort)
                    .append("}")
                    .toString();
        }
    }

    /**
     * Constructs a new IpSecService instance
     *
     * @param context Binder context for this service
     */
    public IpSecService(Context context) {
        this(context, new Dependencies());
    }

    @NonNull
    private AppOpsManager getAppOpsManager() {
        AppOpsManager appOps = (AppOpsManager) mContext.getSystemService(Context.APP_OPS_SERVICE);
        if (appOps == null) throw new RuntimeException("System Server couldn't get AppOps");
        return appOps;
    }

    /** @hide */
    @VisibleForTesting
    public IpSecService(Context context, Dependencies deps) {
        this(
                context,
                deps,
                (fd, uid) -> {
                    try {
                        TrafficStats.setThreadStatsUid(uid);
                        TrafficStats.tagFileDescriptor(fd);
                    } finally {
                        TrafficStats.clearThreadStatsUid();
                    }
                });
    }

    /** @hide */
    @VisibleForTesting
    public IpSecService(Context context, Dependencies deps, UidFdTagger uidFdTagger) {
        mContext = context;
        mDeps = Objects.requireNonNull(deps, "Missing dependencies.");
        mUidFdTagger = uidFdTagger;
        try {
            mNetd = mDeps.getNetdInstance(mContext);
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

    /**
     * Checks that the provided InetAddress is valid for use in an IPsec SA. The address must not be
     * a wildcard address and must be in a numeric form such as 1.2.3.4 or 2001::1.
     */
    private static void checkInetAddress(String inetAddress) {
        if (TextUtils.isEmpty(inetAddress)) {
            throw new IllegalArgumentException("Unspecified address");
        }

        InetAddress checkAddr = InetAddresses.parseNumericAddress(inetAddress);

        if (checkAddr.isAnyLocalAddress()) {
            throw new IllegalArgumentException("Inappropriate wildcard address: " + inetAddress);
        }
    }

    /**
     * Checks the user-provided direction field and throws an IllegalArgumentException if it is not
     * DIRECTION_IN or DIRECTION_OUT
     */
    private void checkDirection(int direction) {
        switch (direction) {
            case IpSecManager.DIRECTION_OUT:
            case IpSecManager.DIRECTION_IN:
                return;
            case IpSecManager.DIRECTION_FWD:
                // Only NETWORK_STACK or MAINLINE_NETWORK_STACK allowed to use forward policies
                PermissionUtils.enforceNetworkStackPermission(mContext);
                return;
        }
        throw new IllegalArgumentException("Invalid Direction: " + direction);
    }

    /** Get a new SPI and maintain the reservation in the system server */
    @Override
    public synchronized IpSecSpiResponse allocateSecurityParameterIndex(
            String destinationAddress, int requestedSpi, IBinder binder) throws RemoteException {
        checkInetAddress(destinationAddress);
        // RFC 4303 Section 2.1 - 0=local, 1-255=reserved.
        if (requestedSpi > 0 && requestedSpi < 256) {
            throw new IllegalArgumentException("ESP SPI must not be in the range of 0-255.");
        }
        Objects.requireNonNull(binder, "Null Binder passed to allocateSecurityParameterIndex");

        int callingUid = Binder.getCallingUid();
        UserRecord userRecord = mUserResourceTracker.getUserRecord(callingUid);
        final int resourceId = mNextResourceId++;

        int spi = IpSecManager.INVALID_SECURITY_PARAMETER_INDEX;
        try {
            if (!userRecord.mSpiQuotaTracker.isAvailable()) {
                return new IpSecSpiResponse(
                        IpSecManager.Status.RESOURCE_UNAVAILABLE, INVALID_RESOURCE_ID, spi);
            }

            spi = mNetd.ipSecAllocateSpi(callingUid, "", destinationAddress, requestedSpi);
            Log.d(TAG, "Allocated SPI " + spi);
            userRecord.mSpiRecords.put(
                    resourceId,
                    new RefcountedResource<SpiRecord>(
                            new SpiRecord(resourceId, "",
                            destinationAddress, spi), binder));
        } catch (ServiceSpecificException e) {
            if (e.errorCode == OsConstants.ENOENT) {
                return new IpSecSpiResponse(
                        IpSecManager.Status.SPI_UNAVAILABLE, INVALID_RESOURCE_ID, spi);
            }
            throw e;
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
        return new IpSecSpiResponse(IpSecManager.Status.OK, resourceId, spi);
    }

    /* This method should only be called from Binder threads. Do not call this from
     * within the system server as it will crash the system on failure.
     */
    private void releaseResource(RefcountedResourceArray resArray, int resourceId)
            throws RemoteException {
        resArray.getRefcountedResourceOrThrow(resourceId).userRelease();
    }

    /** Release a previously allocated SPI that has been registered with the system server */
    @Override
    public synchronized void releaseSecurityParameterIndex(int resourceId) throws RemoteException {
        UserRecord userRecord = mUserResourceTracker.getUserRecord(Binder.getCallingUid());
        releaseResource(userRecord.mSpiRecords, resourceId);
    }

    /**
     * This function finds and forcibly binds to a random system port, ensuring that the port cannot
     * be unbound.
     *
     * <p>A socket cannot be un-bound from a port if it was bound to that port by number. To select
     * a random open port and then bind by number, this function creates a temp socket, binds to a
     * random port (specifying 0), gets that port number, and then uses is to bind the user's UDP
     * Encapsulation Socket forcibly, so that it cannot be un-bound by the user with the returned
     * FileHandle.
     *
     * <p>The loop in this function handles the inherent race window between un-binding to a port
     * and re-binding, during which the system could *technically* hand that port out to someone
     * else.
     */
    private int bindToRandomPort(FileDescriptor sockFd) throws IOException {
        for (int i = MAX_PORT_BIND_ATTEMPTS; i > 0; i--) {
            try {
                FileDescriptor probeSocket = Os.socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
                Os.bind(probeSocket, INADDR_ANY, 0);
                int port = ((InetSocketAddress) Os.getsockname(probeSocket)).getPort();
                Os.close(probeSocket);
                Log.v(TAG, "Binding to port " + port);
                Os.bind(sockFd, INADDR_ANY, port);
                return port;
            } catch (ErrnoException e) {
                // Someone miraculously claimed the port just after we closed probeSocket.
                if (e.errno == OsConstants.EADDRINUSE) {
                    continue;
                }
                throw e.rethrowAsIOException();
            }
        }
        throw new IOException("Failed " + MAX_PORT_BIND_ATTEMPTS + " attempts to bind to a port");
    }

    /**
     * Functional interface to do traffic tagging of given sockets to UIDs.
     *
     * <p>Specifically used by openUdpEncapsulationSocket to ensure data usage on the UDP encap
     * sockets are billed to the UID that the UDP encap socket was created on behalf of.
     *
     * <p>Separate class so that the socket tagging logic can be mocked; TrafficStats uses static
     * methods that cannot be easily mocked/tested.
     */
    @VisibleForTesting
    public interface UidFdTagger {
        /**
         * Sets socket tag to assign all traffic to the provided UID.
         *
         * <p>Since the socket is created on behalf of an unprivileged application, all traffic
         * should be accounted to the UID of the unprivileged application.
         */
        void tag(FileDescriptor fd, int uid) throws IOException;
    }

    /**
     * Open a socket via the system server and bind it to the specified port (random if port=0).
     * This will return a PFD to the user that represent a bound UDP socket. The system server will
     * cache the socket and a record of its owner so that it can and must be freed when no longer
     * needed.
     */
    @Override
    public synchronized IpSecUdpEncapResponse openUdpEncapsulationSocket(int port, IBinder binder)
            throws RemoteException {
        if (port != 0 && (port < FREE_PORT_MIN || port > PORT_MAX)) {
            throw new IllegalArgumentException(
                    "Specified port number must be a valid non-reserved UDP port");
        }
        Objects.requireNonNull(binder, "Null Binder passed to openUdpEncapsulationSocket");

        int callingUid = Binder.getCallingUid();
        UserRecord userRecord = mUserResourceTracker.getUserRecord(callingUid);
        final int resourceId = mNextResourceId++;

        ParcelFileDescriptor pFd = null;
        try {
            if (!userRecord.mSocketQuotaTracker.isAvailable()) {
                return new IpSecUdpEncapResponse(IpSecManager.Status.RESOURCE_UNAVAILABLE);
            }

            FileDescriptor sockFd = null;
            try {
                sockFd = Os.socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
                pFd = ParcelFileDescriptor.dup(sockFd);
            } finally {
                IoUtils.closeQuietly(sockFd);
            }

            mUidFdTagger.tag(pFd.getFileDescriptor(), callingUid);
            // This code is common to both the unspecified and specified port cases
            Os.setsockoptInt(
                    pFd.getFileDescriptor(),
                    OsConstants.IPPROTO_UDP,
                    OsConstants.UDP_ENCAP,
                    OsConstants.UDP_ENCAP_ESPINUDP);

            mNetd.ipSecSetEncapSocketOwner(pFd, callingUid);
            if (port != 0) {
                Log.v(TAG, "Binding to port " + port);
                Os.bind(pFd.getFileDescriptor(), INADDR_ANY, port);
            } else {
                port = bindToRandomPort(pFd.getFileDescriptor());
            }

            userRecord.mEncapSocketRecords.put(
                    resourceId,
                    new RefcountedResource<EncapSocketRecord>(
                            new EncapSocketRecord(resourceId, pFd.getFileDescriptor(), port),
                            binder));
            return new IpSecUdpEncapResponse(IpSecManager.Status.OK, resourceId, port,
                    pFd.getFileDescriptor());
        } catch (IOException | ErrnoException e) {
            try {
                if (pFd != null) {
                    pFd.close();
                }
            } catch (IOException ex) {
                // Nothing can be done at this point
                Log.e(TAG, "Failed to close pFd.");
            }
        }
        // If we make it to here, then something has gone wrong and we couldn't open a socket.
        // The only reasonable condition that would cause that is resource unavailable.
        return new IpSecUdpEncapResponse(IpSecManager.Status.RESOURCE_UNAVAILABLE);
    }

    /** close a socket that has been been allocated by and registered with the system server */
    @Override
    public synchronized void closeUdpEncapsulationSocket(int resourceId) throws RemoteException {
        UserRecord userRecord = mUserResourceTracker.getUserRecord(Binder.getCallingUid());
        releaseResource(userRecord.mEncapSocketRecords, resourceId);
    }

    /**
     * Create a tunnel interface for use in IPSec tunnel mode. The system server will cache the
     * tunnel interface and a record of its owner so that it can and must be freed when no longer
     * needed.
     */
    @Override
    public synchronized IpSecTunnelInterfaceResponse createTunnelInterface(
            String localAddr, String remoteAddr, Network underlyingNetwork, IBinder binder,
            String callingPackage) {
        enforceTunnelFeatureAndPermissions(callingPackage);
        Objects.requireNonNull(binder, "Null Binder passed to createTunnelInterface");
        Objects.requireNonNull(underlyingNetwork, "No underlying network was specified");
        checkInetAddress(localAddr);
        checkInetAddress(remoteAddr);

        // TODO: Check that underlying network exists, and IP addresses not assigned to a different
        //       network (b/72316676).

        int callerUid = Binder.getCallingUid();
        UserRecord userRecord = mUserResourceTracker.getUserRecord(callerUid);
        if (!userRecord.mTunnelQuotaTracker.isAvailable()) {
            return new IpSecTunnelInterfaceResponse(IpSecManager.Status.RESOURCE_UNAVAILABLE);
        }

        final int resourceId = mNextResourceId++;
        final int ikey = reserveNetId();
        final int okey = reserveNetId();
        String intfName = String.format("%s%d", INetd.IPSEC_INTERFACE_PREFIX, resourceId);

        try {
            // Calls to netd:
            //       Create VTI
            //       Add inbound/outbound global policies
            //              (use reqid = 0)
            mNetd.ipSecAddTunnelInterface(intfName, localAddr, remoteAddr, ikey, okey, resourceId);

            BinderUtils.withCleanCallingIdentity(() -> {
                NetdUtils.setInterfaceUp(mNetd, intfName);
            });

            for (int selAddrFamily : ADDRESS_FAMILIES) {
                // Always send down correct local/remote addresses for template.
                mNetd.ipSecAddSecurityPolicy(
                        callerUid,
                        selAddrFamily,
                        IpSecManager.DIRECTION_OUT,
                        localAddr,
                        remoteAddr,
                        0,
                        okey,
                        0xffffffff,
                        resourceId);
                mNetd.ipSecAddSecurityPolicy(
                        callerUid,
                        selAddrFamily,
                        IpSecManager.DIRECTION_IN,
                        remoteAddr,
                        localAddr,
                        0,
                        ikey,
                        0xffffffff,
                        resourceId);

                // Add a forwarding policy on the tunnel interface. In order to support forwarding
                // the IpSecTunnelInterface must have a forwarding policy matching the incoming SA.
                //
                // Unless a IpSecTransform is also applied against this interface in DIRECTION_FWD,
                // forwarding will be blocked by default (as would be the case if this policy was
                // absent).
                //
                // This is necessary only on the tunnel interface, and not any the interface to
                // which traffic will be forwarded to.
                mNetd.ipSecAddSecurityPolicy(
                        callerUid,
                        selAddrFamily,
                        IpSecManager.DIRECTION_FWD,
                        remoteAddr,
                        localAddr,
                        0,
                        ikey,
                        0xffffffff,
                        resourceId);
            }

            userRecord.mTunnelInterfaceRecords.put(
                    resourceId,
                    new RefcountedResource<TunnelInterfaceRecord>(
                            new TunnelInterfaceRecord(
                                    resourceId,
                                    intfName,
                                    underlyingNetwork,
                                    localAddr,
                                    remoteAddr,
                                    ikey,
                                    okey,
                                    resourceId),
                            binder));
            return new IpSecTunnelInterfaceResponse(IpSecManager.Status.OK, resourceId, intfName);
        } catch (RemoteException e) {
            // Release keys if we got an error.
            releaseNetId(ikey);
            releaseNetId(okey);
            throw e.rethrowFromSystemServer();
        } catch (Throwable t) {
            // Release keys if we got an error.
            releaseNetId(ikey);
            releaseNetId(okey);
            throw t;
        }
    }

    /**
     * Adds a new local address to the tunnel interface. This allows packets to be sent and received
     * from multiple local IP addresses over the same tunnel.
     */
    @Override
    public synchronized void addAddressToTunnelInterface(
            int tunnelResourceId, LinkAddress localAddr, String callingPackage) {
        enforceTunnelFeatureAndPermissions(callingPackage);
        UserRecord userRecord = mUserResourceTracker.getUserRecord(Binder.getCallingUid());

        // Get tunnelInterface record; if no such interface is found, will throw
        // IllegalArgumentException
        TunnelInterfaceRecord tunnelInterfaceInfo =
                userRecord.mTunnelInterfaceRecords.getResourceOrThrow(tunnelResourceId);

        try {
            // We can assume general validity of the IP address, since we get them as a
            // LinkAddress, which does some validation.
            mNetd.interfaceAddAddress(
                    tunnelInterfaceInfo.mInterfaceName,
                    localAddr.getAddress().getHostAddress(),
                    localAddr.getPrefixLength());
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

    /**
     * Remove a new local address from the tunnel interface. After removal, the address will no
     * longer be available to send from, or receive on.
     */
    @Override
    public synchronized void removeAddressFromTunnelInterface(
            int tunnelResourceId, LinkAddress localAddr, String callingPackage) {
        enforceTunnelFeatureAndPermissions(callingPackage);

        UserRecord userRecord = mUserResourceTracker.getUserRecord(Binder.getCallingUid());
        // Get tunnelInterface record; if no such interface is found, will throw
        // IllegalArgumentException
        TunnelInterfaceRecord tunnelInterfaceInfo =
                userRecord.mTunnelInterfaceRecords.getResourceOrThrow(tunnelResourceId);

        try {
            // We can assume general validity of the IP address, since we get them as a
            // LinkAddress, which does some validation.
            mNetd.interfaceDelAddress(
                            tunnelInterfaceInfo.mInterfaceName,
                            localAddr.getAddress().getHostAddress(),
                            localAddr.getPrefixLength());
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

    /** Set TunnelInterface to use a specific underlying network. */
    @Override
    public synchronized void setNetworkForTunnelInterface(
            int tunnelResourceId, Network underlyingNetwork, String callingPackage) {
        enforceTunnelFeatureAndPermissions(callingPackage);
        Objects.requireNonNull(underlyingNetwork, "No underlying network was specified");

        final UserRecord userRecord = mUserResourceTracker.getUserRecord(Binder.getCallingUid());

        // Get tunnelInterface record; if no such interface is found, will throw
        // IllegalArgumentException. userRecord.mTunnelInterfaceRecords is never null
        final TunnelInterfaceRecord tunnelInterfaceInfo =
                userRecord.mTunnelInterfaceRecords.getResourceOrThrow(tunnelResourceId);

        final ConnectivityManager connectivityManager =
                mContext.getSystemService(ConnectivityManager.class);
        final LinkProperties lp = connectivityManager.getLinkProperties(underlyingNetwork);
        if (tunnelInterfaceInfo.getInterfaceName().equals(lp.getInterfaceName())) {
            throw new IllegalArgumentException(
                    "Underlying network cannot be the network being exposed by this tunnel");
        }

        // It is meaningless to check if the network exists or is valid because the network might
        // disconnect at any time after it passes the check.

        tunnelInterfaceInfo.setUnderlyingNetwork(underlyingNetwork);
    }

    /**
     * Delete a TunnelInterface that has been been allocated by and registered with the system
     * server
     */
    @Override
    public synchronized void deleteTunnelInterface(
            int resourceId, String callingPackage) throws RemoteException {
        enforceTunnelFeatureAndPermissions(callingPackage);
        UserRecord userRecord = mUserResourceTracker.getUserRecord(Binder.getCallingUid());
        releaseResource(userRecord.mTunnelInterfaceRecords, resourceId);
    }

    @VisibleForTesting
    void validateAlgorithms(IpSecConfig config) throws IllegalArgumentException {
        IpSecAlgorithm auth = config.getAuthentication();
        IpSecAlgorithm crypt = config.getEncryption();
        IpSecAlgorithm aead = config.getAuthenticatedEncryption();

        // Validate the algorithm set
        Preconditions.checkArgument(
                aead != null || crypt != null || auth != null,
                "No Encryption or Authentication algorithms specified");
        Preconditions.checkArgument(
                auth == null || auth.isAuthentication(),
                "Unsupported algorithm for Authentication");
        Preconditions.checkArgument(
                crypt == null || crypt.isEncryption(), "Unsupported algorithm for Encryption");
        Preconditions.checkArgument(
                aead == null || aead.isAead(),
                "Unsupported algorithm for Authenticated Encryption");
        Preconditions.checkArgument(
                aead == null || (auth == null && crypt == null),
                "Authenticated Encryption is mutually exclusive with other Authentication "
                        + "or Encryption algorithms");
    }

    private int getFamily(String inetAddress) {
        int family = AF_UNSPEC;
        InetAddress checkAddress = InetAddresses.parseNumericAddress(inetAddress);
        if (checkAddress instanceof Inet4Address) {
            family = AF_INET;
        } else if (checkAddress instanceof Inet6Address) {
            family = AF_INET6;
        }
        return family;
    }

    /**
     * Checks an IpSecConfig parcel to ensure that the contents are valid and throws an
     * IllegalArgumentException if they are not.
     */
    private void checkIpSecConfig(IpSecConfig config) {
        UserRecord userRecord = mUserResourceTracker.getUserRecord(Binder.getCallingUid());

        switch (config.getEncapType()) {
            case IpSecTransform.ENCAP_NONE:
                break;
            case IpSecTransform.ENCAP_ESPINUDP:
            case IpSecTransform.ENCAP_ESPINUDP_NON_IKE:
                // Retrieve encap socket record; will throw IllegalArgumentException if not found
                userRecord.mEncapSocketRecords.getResourceOrThrow(
                        config.getEncapSocketResourceId());

                int port = config.getEncapRemotePort();
                if (port <= 0 || port > 0xFFFF) {
                    throw new IllegalArgumentException("Invalid remote UDP port: " + port);
                }
                break;
            default:
                throw new IllegalArgumentException("Invalid Encap Type: " + config.getEncapType());
        }

        validateAlgorithms(config);

        // Retrieve SPI record; will throw IllegalArgumentException if not found
        SpiRecord s = userRecord.mSpiRecords.getResourceOrThrow(config.getSpiResourceId());

        // Check to ensure that SPI has not already been used.
        if (s.getOwnedByTransform()) {
            throw new IllegalStateException("SPI already in use; cannot be used in new Transforms");
        }

        // If no remote address is supplied, then use one from the SPI.
        if (TextUtils.isEmpty(config.getDestinationAddress())) {
            config.setDestinationAddress(s.getDestinationAddress());
        }

        // All remote addresses must match
        if (!config.getDestinationAddress().equals(s.getDestinationAddress())) {
            throw new IllegalArgumentException("Mismatched remote addresseses.");
        }

        // This check is technically redundant due to the chain of custody between the SPI and
        // the IpSecConfig, but in the future if the dest is allowed to be set explicitly in
        // the transform, this will prevent us from messing up.
        checkInetAddress(config.getDestinationAddress());

        // Require a valid source address for all transforms.
        checkInetAddress(config.getSourceAddress());

        // Check to ensure source and destination have the same address family.
        String sourceAddress = config.getSourceAddress();
        String destinationAddress = config.getDestinationAddress();
        int sourceFamily = getFamily(sourceAddress);
        int destinationFamily = getFamily(destinationAddress);
        if (sourceFamily != destinationFamily) {
            throw new IllegalArgumentException(
                    "Source address ("
                            + sourceAddress
                            + ") and destination address ("
                            + destinationAddress
                            + ") have different address families.");
        }

        // Throw an error if UDP Encapsulation is not used in IPv4.
        if (config.getEncapType() != IpSecTransform.ENCAP_NONE && sourceFamily != AF_INET) {
            throw new IllegalArgumentException(
                    "UDP Encapsulation is not supported for this address family");
        }

        switch (config.getMode()) {
            case IpSecTransform.MODE_TRANSPORT:
                break;
            case IpSecTransform.MODE_TUNNEL:
                break;
            default:
                throw new IllegalArgumentException(
                        "Invalid IpSecTransform.mode: " + config.getMode());
        }

        config.setMarkValue(0);
        config.setMarkMask(0);
    }

    private static final String TUNNEL_OP = AppOpsManager.OPSTR_MANAGE_IPSEC_TUNNELS;

    private void enforceTunnelFeatureAndPermissions(String callingPackage) {
        if (!mContext.getPackageManager().hasSystemFeature(PackageManager.FEATURE_IPSEC_TUNNELS)) {
            throw new UnsupportedOperationException(
                    "IPsec Tunnel Mode requires PackageManager.FEATURE_IPSEC_TUNNELS");
        }

        Objects.requireNonNull(callingPackage, "Null calling package cannot create IpSec tunnels");

        // OP_MANAGE_IPSEC_TUNNELS will return MODE_ERRORED by default, including for the system
        // server. If the appop is not granted, require that the caller has the MANAGE_IPSEC_TUNNELS
        // permission or is the System Server.
        if (AppOpsManager.MODE_ALLOWED == getAppOpsManager().noteOpNoThrow(
                TUNNEL_OP, Binder.getCallingUid(), callingPackage)) {
            return;
        }
        mContext.enforceCallingOrSelfPermission(
                android.Manifest.permission.MANAGE_IPSEC_TUNNELS, "IpSecService");
    }

    private void createOrUpdateTransform(
            IpSecConfig c, int resourceId, SpiRecord spiRecord, EncapSocketRecord socketRecord)
            throws RemoteException {

        int encapType = c.getEncapType(), encapLocalPort = 0, encapRemotePort = 0;
        if (encapType != IpSecTransform.ENCAP_NONE) {
            encapLocalPort = socketRecord.getPort();
            encapRemotePort = c.getEncapRemotePort();
        }

        IpSecAlgorithm auth = c.getAuthentication();
        IpSecAlgorithm crypt = c.getEncryption();
        IpSecAlgorithm authCrypt = c.getAuthenticatedEncryption();

        String cryptName;
        if (crypt == null) {
            cryptName = (authCrypt == null) ? IpSecAlgorithm.CRYPT_NULL : "";
        } else {
            cryptName = crypt.getName();
        }

        mNetd.ipSecAddSecurityAssociation(
                Binder.getCallingUid(),
                c.getMode(),
                c.getSourceAddress(),
                c.getDestinationAddress(),
                (c.getNetwork() != null) ? c.getNetwork().getNetId() : 0,
                spiRecord.getSpi(),
                c.getMarkValue(),
                c.getMarkMask(),
                (auth != null) ? auth.getName() : "",
                (auth != null) ? auth.getKey() : new byte[] {},
                (auth != null) ? auth.getTruncationLengthBits() : 0,
                cryptName,
                (crypt != null) ? crypt.getKey() : new byte[] {},
                (crypt != null) ? crypt.getTruncationLengthBits() : 0,
                (authCrypt != null) ? authCrypt.getName() : "",
                (authCrypt != null) ? authCrypt.getKey() : new byte[] {},
                (authCrypt != null) ? authCrypt.getTruncationLengthBits() : 0,
                encapType,
                encapLocalPort,
                encapRemotePort,
                c.getXfrmInterfaceId());
    }

    /**
     * Create a IPsec transform, which represents a single security association in the kernel. The
     * transform will be cached by the system server and must be freed when no longer needed. It is
     * possible to free one, deleting the SA from underneath sockets that are using it, which will
     * result in all of those sockets becoming unable to send or receive data.
     */
    @Override
    public synchronized IpSecTransformResponse createTransform(
            IpSecConfig c, IBinder binder, String callingPackage) throws RemoteException {
        Objects.requireNonNull(c);
        if (c.getMode() == IpSecTransform.MODE_TUNNEL) {
            enforceTunnelFeatureAndPermissions(callingPackage);
        }
        checkIpSecConfig(c);
        Objects.requireNonNull(binder, "Null Binder passed to createTransform");
        final int resourceId = mNextResourceId++;

        UserRecord userRecord = mUserResourceTracker.getUserRecord(Binder.getCallingUid());
        List<RefcountedResource> dependencies = new ArrayList<>();

        if (!userRecord.mTransformQuotaTracker.isAvailable()) {
            return new IpSecTransformResponse(IpSecManager.Status.RESOURCE_UNAVAILABLE);
        }

        EncapSocketRecord socketRecord = null;
        if (c.getEncapType() != IpSecTransform.ENCAP_NONE) {
            RefcountedResource<EncapSocketRecord> refcountedSocketRecord =
                    userRecord.mEncapSocketRecords.getRefcountedResourceOrThrow(
                            c.getEncapSocketResourceId());
            dependencies.add(refcountedSocketRecord);
            socketRecord = refcountedSocketRecord.getResource();
        }

        RefcountedResource<SpiRecord> refcountedSpiRecord =
                userRecord.mSpiRecords.getRefcountedResourceOrThrow(c.getSpiResourceId());
        dependencies.add(refcountedSpiRecord);
        SpiRecord spiRecord = refcountedSpiRecord.getResource();

        createOrUpdateTransform(c, resourceId, spiRecord, socketRecord);

        // SA was created successfully, time to construct a record and lock it away
        userRecord.mTransformRecords.put(
                resourceId,
                new RefcountedResource<TransformRecord>(
                        new TransformRecord(resourceId, c, spiRecord, socketRecord),
                        binder,
                        dependencies.toArray(new RefcountedResource[dependencies.size()])));
        return new IpSecTransformResponse(IpSecManager.Status.OK, resourceId);
    }

    /**
     * Delete a transport mode transform that was previously allocated by + registered with the
     * system server. If this is called on an inactive (or non-existent) transform, it will not
     * return an error. It's safe to de-allocate transforms that may have already been deleted for
     * other reasons.
     */
    @Override
    public synchronized void deleteTransform(int resourceId) throws RemoteException {
        UserRecord userRecord = mUserResourceTracker.getUserRecord(Binder.getCallingUid());
        releaseResource(userRecord.mTransformRecords, resourceId);
    }

    /**
     * Apply an active transport mode transform to a socket, which will apply the IPsec security
     * association as a correspondent policy to the provided socket
     */
    @Override
    public synchronized void applyTransportModeTransform(
            ParcelFileDescriptor socket, int direction, int resourceId) throws RemoteException {
        int callingUid = Binder.getCallingUid();
        UserRecord userRecord = mUserResourceTracker.getUserRecord(callingUid);
        checkDirection(direction);
        // Get transform record; if no transform is found, will throw IllegalArgumentException
        TransformRecord info = userRecord.mTransformRecords.getResourceOrThrow(resourceId);

        // TODO: make this a function.
        if (info.mPid != getCallingPid() || info.mUid != callingUid) {
            throw new SecurityException("Only the owner of an IpSec Transform may apply it!");
        }

        // Get config and check that to-be-applied transform has the correct mode
        IpSecConfig c = info.getConfig();
        Preconditions.checkArgument(
                c.getMode() == IpSecTransform.MODE_TRANSPORT,
                "Transform mode was not Transport mode; cannot be applied to a socket");

        mNetd.ipSecApplyTransportModeTransform(
                socket,
                callingUid,
                direction,
                c.getSourceAddress(),
                c.getDestinationAddress(),
                info.getSpiRecord().getSpi());
    }

    /**
     * Remove transport mode transforms from a socket, applying the default (empty) policy. This
     * ensures that NO IPsec policy is applied to the socket (would be the equivalent of applying a
     * policy that performs no IPsec). Today the resourceId parameter is passed but not used:
     * reserved for future improved input validation.
     */
    @Override
    public synchronized void removeTransportModeTransforms(ParcelFileDescriptor socket)
            throws RemoteException {
        mNetd.ipSecRemoveTransportModeTransform(socket);
    }

    /**
     * Apply an active tunnel mode transform to a TunnelInterface, which will apply the IPsec
     * security association as a correspondent policy to the provided interface
     */
    @Override
    public synchronized void applyTunnelModeTransform(
            int tunnelResourceId, int direction,
            int transformResourceId, String callingPackage) throws RemoteException {
        enforceTunnelFeatureAndPermissions(callingPackage);
        checkDirection(direction);

        int callingUid = Binder.getCallingUid();
        UserRecord userRecord = mUserResourceTracker.getUserRecord(callingUid);

        // Get transform record; if no transform is found, will throw IllegalArgumentException
        TransformRecord transformInfo =
                userRecord.mTransformRecords.getResourceOrThrow(transformResourceId);

        // Get tunnelInterface record; if no such interface is found, will throw
        // IllegalArgumentException
        TunnelInterfaceRecord tunnelInterfaceInfo =
                userRecord.mTunnelInterfaceRecords.getResourceOrThrow(tunnelResourceId);

        // Get config and check that to-be-applied transform has the correct mode
        IpSecConfig c = transformInfo.getConfig();
        Preconditions.checkArgument(
                c.getMode() == IpSecTransform.MODE_TUNNEL,
                "Transform mode was not Tunnel mode; cannot be applied to a tunnel interface");

        EncapSocketRecord socketRecord = null;
        if (c.getEncapType() != IpSecTransform.ENCAP_NONE) {
            socketRecord =
                    userRecord.mEncapSocketRecords.getResourceOrThrow(c.getEncapSocketResourceId());
        }
        SpiRecord spiRecord = transformInfo.getSpiRecord();

        int mark =
                (direction == IpSecManager.DIRECTION_OUT)
                        ? tunnelInterfaceInfo.getOkey()
                        : tunnelInterfaceInfo.getIkey(); // Ikey also used for FWD policies

        try {
            // Default to using the invalid SPI of 0 for inbound SAs. This allows policies to skip
            // SPI matching as part of the template resolution.
            int spi = IpSecManager.INVALID_SECURITY_PARAMETER_INDEX;
            c.setXfrmInterfaceId(tunnelInterfaceInfo.getIfId());

            // TODO: enable this when UPDSA supports updating marks. Adding kernel support upstream
            //     (and backporting) would allow us to narrow the mark space, and ensure that the SA
            //     and SPs have matching marks (as VTI are meant to be built).
            // Currently update does nothing with marks. Leave empty (defaulting to 0) to ensure the
            //     config matches the actual allocated resources in the kernel.
            // All SAs will have zero marks (from creation time), and any policy that matches the
            //     same src/dst could match these SAs. Non-IpSecService governed processes that
            //     establish floating policies with the same src/dst may result in undefined
            //     behavior. This is generally limited to vendor code due to the permissions
            //     (CAP_NET_ADMIN) required.
            //
            // c.setMarkValue(mark);
            // c.setMarkMask(0xffffffff);

            if (direction == IpSecManager.DIRECTION_OUT) {
                // Set output mark via underlying network (output only)
                c.setNetwork(tunnelInterfaceInfo.getUnderlyingNetwork());

                // Set outbound SPI only. We want inbound to use any valid SA (old, new) on rekeys,
                // but want to guarantee outbound packets are sent over the new SA.
                spi = spiRecord.getSpi();
            }

            // Always update the policy with the relevant XFRM_IF_ID
            for (int selAddrFamily : ADDRESS_FAMILIES) {
                mNetd.ipSecUpdateSecurityPolicy(
                        callingUid,
                        selAddrFamily,
                        direction,
                        transformInfo.getConfig().getSourceAddress(),
                        transformInfo.getConfig().getDestinationAddress(),
                        spi, // If outbound, also add SPI to the policy.
                        mark, // Must always set policy mark; ikey/okey for VTIs
                        0xffffffff,
                        c.getXfrmInterfaceId());
            }

            // Update SA with tunnel mark (ikey or okey based on direction)
            createOrUpdateTransform(c, transformResourceId, spiRecord, socketRecord);
        } catch (ServiceSpecificException e) {
            if (e.errorCode == EINVAL) {
                throw new IllegalArgumentException(e.toString());
            } else {
                throw e;
            }
        }
    }

    @Override
    protected synchronized void dump(FileDescriptor fd, PrintWriter pw, String[] args) {
        mContext.enforceCallingOrSelfPermission(DUMP, TAG);

        pw.println("IpSecService dump:");
        pw.println();

        pw.println("mUserResourceTracker:");
        pw.println(mUserResourceTracker);
    }
}