/*
 * Copyright (C) 2014 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 android.os.Parcel;
import android.os.Parcelable;
import android.system.ErrnoException;
import android.system.Os;
import android.system.OsConstants;
import android.util.proto.ProtoOutputStream;

import com.android.okhttp.internalandroidapi.Dns;
import com.android.okhttp.internalandroidapi.HttpURLConnectionFactory;

import libcore.io.IoUtils;

import java.io.FileDescriptor;
import java.io.IOException;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.MalformedURLException;
import java.net.Socket;
import java.net.SocketAddress;
import java.net.SocketException;
import java.net.URL;
import java.net.URLConnection;
import java.net.UnknownHostException;
import java.util.Arrays;
import java.util.concurrent.TimeUnit;

import javax.net.SocketFactory;

Identifies a Network. This is supplied to applications via NetworkCallback in response to the active ConnectivityManager.requestNetwork or passive ConnectivityManager.registerNetworkCallback calls. It is used to direct traffic to the given Network, either on a Socket basis through a targeted SocketFactory or process-wide via ConnectivityManager.bindProcessToNetwork. /**
 * Identifies a {@code Network}.  This is supplied to applications via
 * {@link ConnectivityManager.NetworkCallback} in response to the active
 * {@link ConnectivityManager#requestNetwork} or passive
 * {@link ConnectivityManager#registerNetworkCallback} calls.
 * It is used to direct traffic to the given {@code Network}, either on a {@link Socket} basis
 * through a targeted {@link SocketFactory} or process-wide via
 * {@link ConnectivityManager#bindProcessToNetwork}.
 */
public class Network implements Parcelable {

    
@hide
/**
     * @hide
     */
    public final int netId;

    // Objects used to perform per-network operations such as getSocketFactory
    // and openConnection, and a lock to protect access to them.
    private volatile NetworkBoundSocketFactory mNetworkBoundSocketFactory = null;
    // mLock should be used to control write access to mUrlConnectionFactory.
    // maybeInitUrlConnectionFactory() must be called prior to reading this field.
    private volatile HttpURLConnectionFactory mUrlConnectionFactory;
    private final Object mLock = new Object();

    // Default connection pool values. These are evaluated at startup, just
    // like the OkHttp code. Also like the OkHttp code, we will throw parse
    // exceptions at class loading time if the properties are set but are not
    // valid integers.
    private static final boolean httpKeepAlive =
            Boolean.parseBoolean(System.getProperty("http.keepAlive", "true"));
    private static final int httpMaxConnections =
            httpKeepAlive ? Integer.parseInt(System.getProperty("http.maxConnections", "5")) : 0;
    private static final long httpKeepAliveDurationMs =
            Long.parseLong(System.getProperty("http.keepAliveDuration", "300000"));  // 5 minutes.
    // Value used to obfuscate network handle longs.
    // The HANDLE_MAGIC value MUST be kept in sync with the corresponding
    // value in the native/android/net.c NDK implementation.
    private static final long HANDLE_MAGIC = 0xcafed00dL;
    private static final int HANDLE_MAGIC_SIZE = 32;

    // A boolean to control how getAllByName()/getByName() behaves in the face
    // of Private DNS.
    //
    // When true, these calls will request that DNS resolution bypass any
    // Private DNS that might otherwise apply. Use of this feature is restricted
    // and permission checks are made by netd (attempts to bypass Private DNS
    // without appropriate permission are silently turned into vanilla DNS
    // requests). This only affects DNS queries made using this network object.
    //
    // It it not parceled to receivers because (a) it can be set or cleared at
    // anytime and (b) receivers should be explicit about attempts to bypass
    // Private DNS so that the intent of the code is easily determined and
    // code search audits are possible.
    private boolean mPrivateDnsBypass = false;

    
@hide
/**
     * @hide
     */
    public Network(int netId) {
        this.netId = netId;
    }

    
@hide
/**
     * @hide
     */
    public Network(Network that) {
        this.netId = that.netId;
    }

    
Operates the same as InetAddress.getAllByName except that host resolution is done on this network. 
Params:
host – the hostname or literal IP string to be resolved.
Throws:
UnknownHostException – if the address lookup fails.
Returns:
the array of addresses associated with the specified host./**
     * Operates the same as {@code InetAddress.getAllByName} except that host
     * resolution is done on this network.
     *
     * @param host the hostname or literal IP string to be resolved.
     * @return the array of addresses associated with the specified host.
     * @throws UnknownHostException if the address lookup fails.
     */
    public InetAddress[] getAllByName(String host) throws UnknownHostException {
        return InetAddress.getAllByNameOnNet(host, getNetIdForResolv());
    }

    
Operates the same as InetAddress.getByName except that host resolution is done on this network. 
Params:
host –  the hostName to be resolved to an address or null.
Throws:
UnknownHostException – 
            if the address lookup fails.
Returns:
the InetAddress instance representing the host./**
     * Operates the same as {@code InetAddress.getByName} except that host
     * resolution is done on this network.
     *
     * @param host
     *            the hostName to be resolved to an address or {@code null}.
     * @return the {@code InetAddress} instance representing the host.
     * @throws UnknownHostException
     *             if the address lookup fails.
     */
    public InetAddress getByName(String host) throws UnknownHostException {
        return InetAddress.getByNameOnNet(host, getNetIdForResolv());
    }

    
Specify whether or not Private DNS should be bypassed when attempting to use getAllByName()/getByName() methods on the given instance for hostname resolution. 
@hide
/**
     * Specify whether or not Private DNS should be bypassed when attempting
     * to use {@link getAllByName()}/{@link getByName()} methods on the given
     * instance for hostname resolution.
     *
     * @hide
     */
    public void setPrivateDnsBypass(boolean bypass) {
        mPrivateDnsBypass = bypass;
    }

    
Returns a netid marked with the Private DNS bypass flag.
This flag must be kept in sync with the NETID_USE_LOCAL_NAMESERVERS flag
in system/netd/include/NetdClient.h.
@hide
/**
     * Returns a netid marked with the Private DNS bypass flag.
     *
     * This flag must be kept in sync with the NETID_USE_LOCAL_NAMESERVERS flag
     * in system/netd/include/NetdClient.h.
     *
     * @hide
     */
    public int getNetIdForResolv() {
        return mPrivateDnsBypass
                ? (int) (0x80000000L | (long) netId)  // Non-portable DNS resolution flag.
                : netId;
    }

    
A SocketFactory that produces Socket's bound to this network. /**
     * A {@code SocketFactory} that produces {@code Socket}'s bound to this network.
     */
    private class NetworkBoundSocketFactory extends SocketFactory {
        private final int mNetId;

        public NetworkBoundSocketFactory(int netId) {
            super();
            mNetId = netId;
        }

        private Socket connectToHost(String host, int port, SocketAddress localAddress)
                throws IOException {
            // Lookup addresses only on this Network.
            InetAddress[] hostAddresses = getAllByName(host);
            // Try all addresses.
            for (int i = 0; i < hostAddresses.length; i++) {
                try {
                    Socket socket = createSocket();
                    boolean failed = true;
                    try {
                        if (localAddress != null) socket.bind(localAddress);
                        socket.connect(new InetSocketAddress(hostAddresses[i], port));
                        failed = false;
                        return socket;
                    } finally {
                        if (failed) IoUtils.closeQuietly(socket);
                    }
                } catch (IOException e) {
                    if (i == (hostAddresses.length - 1)) throw e;
                }
            }
            throw new UnknownHostException(host);
        }

        @Override
        public Socket createSocket(String host, int port, InetAddress localHost, int localPort) throws IOException {
            return connectToHost(host, port, new InetSocketAddress(localHost, localPort));
        }

        @Override
        public Socket createSocket(InetAddress address, int port, InetAddress localAddress,
                int localPort) throws IOException {
            Socket socket = createSocket();
            boolean failed = true;
            try {
                socket.bind(new InetSocketAddress(localAddress, localPort));
                socket.connect(new InetSocketAddress(address, port));
                failed = false;
            } finally {
                if (failed) IoUtils.closeQuietly(socket);
            }
            return socket;
        }

        @Override
        public Socket createSocket(InetAddress host, int port) throws IOException {
            Socket socket = createSocket();
            boolean failed = true;
            try {
                socket.connect(new InetSocketAddress(host, port));
                failed = false;
            } finally {
                if (failed) IoUtils.closeQuietly(socket);
            }
            return socket;
        }

        @Override
        public Socket createSocket(String host, int port) throws IOException {
            return connectToHost(host, port, null);
        }

        @Override
        public Socket createSocket() throws IOException {
            Socket socket = new Socket();
            boolean failed = true;
            try {
                bindSocket(socket);
                failed = false;
            } finally {
                if (failed) IoUtils.closeQuietly(socket);
            }
            return socket;
        }
    }

    
Returns a SocketFactory bound to this network. Any Socket created by this factory will have its traffic sent over this Network. Note that if this Network ever disconnects, this factory and any Socket it produced in the past or future will cease to work. 
Returns:
a SocketFactory which produces Socket instances bound to this Network./**
     * Returns a {@link SocketFactory} bound to this network.  Any {@link Socket} created by
     * this factory will have its traffic sent over this {@code Network}.  Note that if this
     * {@code Network} ever disconnects, this factory and any {@link Socket} it produced in the
     * past or future will cease to work.
     *
     * @return a {@link SocketFactory} which produces {@link Socket} instances bound to this
     *         {@code Network}.
     */
    public SocketFactory getSocketFactory() {
        if (mNetworkBoundSocketFactory == null) {
            synchronized (mLock) {
                if (mNetworkBoundSocketFactory == null) {
                    mNetworkBoundSocketFactory = new NetworkBoundSocketFactory(netId);
                }
            }
        }
        return mNetworkBoundSocketFactory;
    }

    // TODO: This creates a connection pool and host resolver for
    // every Network object, instead of one for every NetId. This is
    // suboptimal, because an app could potentially have more than one
    // Network object for the same NetId, causing increased memory footprint
    // and performance penalties due to lack of connection reuse (connection
    // setup time, congestion window growth time, etc.).
    //
    // Instead, investigate only having one connection pool and host resolver
    // for every NetId, perhaps by using a static HashMap of NetIds to
    // connection pools and host resolvers. The tricky part is deciding when
    // to remove a map entry; a WeakHashMap shouldn't be used because whether
    // a Network is referenced doesn't correlate with whether a new Network
    // will be instantiated in the near future with the same NetID. A good
    // solution would involve purging empty (or when all connections are timed
    // out) ConnectionPools.
    private void maybeInitUrlConnectionFactory() {
        synchronized (mLock) {
            if (mUrlConnectionFactory == null) {
                // Set configuration on the HttpURLConnectionFactory that will be good for all
                // connections created by this Network. Configuration that might vary is left
                // until openConnection() and passed as arguments.
                Dns dnsLookup = hostname -> Arrays.asList(Network.this.getAllByName(hostname));
                HttpURLConnectionFactory urlConnectionFactory = new HttpURLConnectionFactory();
                urlConnectionFactory.setDns(dnsLookup); // Let traffic go via dnsLookup
                // A private connection pool just for this Network.
                urlConnectionFactory.setNewConnectionPool(httpMaxConnections,
                        httpKeepAliveDurationMs, TimeUnit.MILLISECONDS);
                mUrlConnectionFactory = urlConnectionFactory;
            }
        }
    }

    
Opens the specified URL on this Network, such that all traffic will be sent on this Network. The URL protocol must be HTTP or HTTPS. 
Throws:
MalformedURLException – if the URL protocol is not HTTP or HTTPS.
IOException – if an error occurs while opening the connection.
See Also:
URL.openConnection()
Returns:
a URLConnection to the resource referred to by this URL./**
     * Opens the specified {@link URL} on this {@code Network}, such that all traffic will be sent
     * on this Network. The URL protocol must be {@code HTTP} or {@code HTTPS}.
     *
     * @return a {@code URLConnection} to the resource referred to by this URL.
     * @throws MalformedURLException if the URL protocol is not HTTP or HTTPS.
     * @throws IOException if an error occurs while opening the connection.
     * @see java.net.URL#openConnection()
     */
    public URLConnection openConnection(URL url) throws IOException {
        final ConnectivityManager cm = ConnectivityManager.getInstanceOrNull();
        if (cm == null) {
            throw new IOException("No ConnectivityManager yet constructed, please construct one");
        }
        // TODO: Should this be optimized to avoid fetching the global proxy for every request?
        final ProxyInfo proxyInfo = cm.getProxyForNetwork(this);
        final java.net.Proxy proxy;
        if (proxyInfo != null) {
            proxy = proxyInfo.makeProxy();
        } else {
            proxy = java.net.Proxy.NO_PROXY;
        }
        return openConnection(url, proxy);
    }

    
Opens the specified URL on this Network, such that all traffic will be sent on this Network. The URL protocol must be HTTP or HTTPS. 
Params:
proxy – the proxy through which the connection will be established.
Throws:
MalformedURLException – if the URL protocol is not HTTP or HTTPS.
IllegalArgumentException – if the argument proxy is null.
IOException – if an error occurs while opening the connection.
See Also:
URL.openConnection()
Returns:
a URLConnection to the resource referred to by this URL./**
     * Opens the specified {@link URL} on this {@code Network}, such that all traffic will be sent
     * on this Network. The URL protocol must be {@code HTTP} or {@code HTTPS}.
     *
     * @param proxy the proxy through which the connection will be established.
     * @return a {@code URLConnection} to the resource referred to by this URL.
     * @throws MalformedURLException if the URL protocol is not HTTP or HTTPS.
     * @throws IllegalArgumentException if the argument proxy is null.
     * @throws IOException if an error occurs while opening the connection.
     * @see java.net.URL#openConnection()
     */
    public URLConnection openConnection(URL url, java.net.Proxy proxy) throws IOException {
        if (proxy == null) throw new IllegalArgumentException("proxy is null");
        maybeInitUrlConnectionFactory();
        SocketFactory socketFactory = getSocketFactory();
        return mUrlConnectionFactory.openConnection(url, socketFactory, proxy);
    }

    
Binds the specified DatagramSocket to this Network. All data traffic on the socket will be sent on this Network, irrespective of any process-wide network binding set by ConnectivityManager.bindProcessToNetwork. The socket must not be connected. /**
     * Binds the specified {@link DatagramSocket} to this {@code Network}. All data traffic on the
     * socket will be sent on this {@code Network}, irrespective of any process-wide network binding
     * set by {@link ConnectivityManager#bindProcessToNetwork}. The socket must not be
     * connected.
     */
    public void bindSocket(DatagramSocket socket) throws IOException {
        // Query a property of the underlying socket to ensure that the socket's file descriptor
        // exists, is available to bind to a network and is not closed.
        socket.getReuseAddress();
        bindSocket(socket.getFileDescriptor$());
    }

    
Binds the specified Socket to this Network. All data traffic on the socket will be sent on this Network, irrespective of any process-wide network binding set by ConnectivityManager.bindProcessToNetwork. The socket must not be connected. /**
     * Binds the specified {@link Socket} to this {@code Network}. All data traffic on the socket
     * will be sent on this {@code Network}, irrespective of any process-wide network binding set by
     * {@link ConnectivityManager#bindProcessToNetwork}. The socket must not be connected.
     */
    public void bindSocket(Socket socket) throws IOException {
        // Query a property of the underlying socket to ensure that the socket's file descriptor
        // exists, is available to bind to a network and is not closed.
        socket.getReuseAddress();
        bindSocket(socket.getFileDescriptor$());
    }

    
Binds the specified FileDescriptor to this Network. All data traffic on the socket represented by this file descriptor will be sent on this Network, irrespective of any process-wide network binding set by ConnectivityManager.bindProcessToNetwork. The socket must not be connected. /**
     * Binds the specified {@link FileDescriptor} to this {@code Network}. All data traffic on the
     * socket represented by this file descriptor will be sent on this {@code Network},
     * irrespective of any process-wide network binding set by
     * {@link ConnectivityManager#bindProcessToNetwork}. The socket must not be connected.
     */
    public void bindSocket(FileDescriptor fd) throws IOException {
        try {
            final SocketAddress peer = Os.getpeername(fd);
            final InetAddress inetPeer = ((InetSocketAddress) peer).getAddress();
            if (!inetPeer.isAnyLocalAddress()) {
                // Apparently, the kernel doesn't update a connected UDP socket's
                // routing upon mark changes.
                throw new SocketException("Socket is connected");
            }
        } catch (ErrnoException e) {
            // getpeername() failed.
            if (e.errno != OsConstants.ENOTCONN) {
                throw e.rethrowAsSocketException();
            }
        } catch (ClassCastException e) {
            // Wasn't an InetSocketAddress.
            throw new SocketException("Only AF_INET/AF_INET6 sockets supported");
        }

        final int err = NetworkUtils.bindSocketToNetwork(fd.getInt$(), netId);
        if (err != 0) {
            // bindSocketToNetwork returns negative errno.
            throw new ErrnoException("Binding socket to network " + netId, -err)
                    .rethrowAsSocketException();
        }
    }

    
Returns a Network object given a handle returned from getNetworkHandle. 
Params:
networkHandle – a handle returned from getNetworkHandle.
Returns:
A Network object derived from networkHandle./**
     * Returns a {@link Network} object given a handle returned from {@link #getNetworkHandle}.
     *
     * @param networkHandle a handle returned from {@link #getNetworkHandle}.
     * @return A {@link Network} object derived from {@code networkHandle}.
     */
    public static Network fromNetworkHandle(long networkHandle) {
        if (networkHandle == 0) {
            throw new IllegalArgumentException(
                    "Network.fromNetworkHandle refusing to instantiate NETID_UNSET Network.");
        }
        if ((networkHandle & ((1L << HANDLE_MAGIC_SIZE) - 1)) != HANDLE_MAGIC
                || networkHandle < 0) {
            throw new IllegalArgumentException(
                    "Value passed to fromNetworkHandle() is not a network handle.");
        }
        return new Network((int) (networkHandle >> HANDLE_MAGIC_SIZE));
    }

    
Returns a handle representing this Network, for use with the NDK API. /**
     * Returns a handle representing this {@code Network}, for use with the NDK API.
     */
    public long getNetworkHandle() {
        // The network handle is explicitly not the same as the netId.
        //
        // The netId is an implementation detail which might be changed in the
        // future, or which alone (i.e. in the absence of some additional
        // context) might not be sufficient to fully identify a Network.
        //
        // As such, the intention is to prevent accidental misuse of the API
        // that might result if a developer assumed that handles and netIds
        // were identical and passing a netId to a call expecting a handle
        // "just worked".  Such accidental misuse, if widely deployed, might
        // prevent future changes to the semantics of the netId field or
        // inhibit the expansion of state required for Network objects.
        //
        // This extra layer of indirection might be seen as paranoia, and might
        // never end up being necessary, but the added complexity is trivial.
        // At some future date it may be desirable to realign the handle with
        // Multiple Provisioning Domains API recommendations, as made by the
        // IETF mif working group.
        if (netId == 0) {
            return 0L;  // make this zero condition obvious for debugging
        }
        return (((long) netId) << HANDLE_MAGIC_SIZE) | HANDLE_MAGIC;
    }

    // implement the Parcelable interface
    public int describeContents() {
        return 0;
    }
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeInt(netId);
    }

    public static final Creator<Network> CREATOR =
        new Creator<Network>() {
            public Network createFromParcel(Parcel in) {
                int netId = in.readInt();

                return new Network(netId);
            }

            public Network[] newArray(int size) {
                return new Network[size];
            }
    };

    @Override
    public boolean equals(Object obj) {
        if (obj instanceof Network == false) return false;
        Network other = (Network)obj;
        return this.netId == other.netId;
    }

    @Override
    public int hashCode() {
        return netId * 11;
    }

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

    
@hide
/** @hide */
    public void writeToProto(ProtoOutputStream proto, long fieldId) {
        final long token = proto.start(fieldId);
        proto.write(NetworkProto.NET_ID, netId);
        proto.end(token);
    }
}