| /* |
| * 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.ip; |
| |
| import android.net.InetAddresses; |
| import android.net.LinkAddress; |
| import android.net.LinkProperties; |
| import android.net.RouteInfo; |
| import android.util.Log; |
| |
| import com.android.server.NetworkObserver; |
| |
| import java.net.InetAddress; |
| import java.util.ArrayList; |
| import java.util.Arrays; |
| import java.util.Collections; |
| import java.util.HashMap; |
| import java.util.HashSet; |
| import java.util.Set; |
| |
| /** |
| * Keeps track of link configuration received from Netd. |
| * |
| * An instance of this class is constructed by passing in an interface name and a callback. The |
| * owner is then responsible for registering the tracker with NetworkObserverRegistry. When the |
| * class receives update notifications, it applies the update to its local LinkProperties, and if |
| * something has changed, notifies its owner of the update via the callback. |
| * |
| * The owner can then call {@code getLinkProperties()} in order to find out |
| * what changed. If in the meantime the LinkProperties stored here have changed, |
| * this class will return the current LinkProperties. Because each change |
| * triggers an update callback after the change is made, the owner may get more |
| * callbacks than strictly necessary (some of which may be no-ops), but will not |
| * be out of sync once all callbacks have been processed. |
| * |
| * Threading model: |
| * |
| * - The owner of this class is expected to create it, register it, and call |
| * getLinkProperties or clearLinkProperties on its thread. |
| * - Most of the methods in the class are implementing NetworkObserver and are called |
| * on the handler used to register the observer. |
| * - All accesses to mLinkProperties must be synchronized(this). All the other |
| * member variables are immutable once the object is constructed. |
| * |
| * @hide |
| */ |
| public class IpClientLinkObserver implements NetworkObserver { |
| private final String mTag; |
| |
| /** |
| * Callback used by {@link IpClientLinkObserver} to send update notifications. |
| */ |
| public interface Callback { |
| /** |
| * Called when some properties of the link were updated. |
| */ |
| void update(); |
| } |
| |
| private final String mInterfaceName; |
| private final Callback mCallback; |
| private final LinkProperties mLinkProperties; |
| private DnsServerRepository mDnsServerRepository; |
| |
| private static final boolean DBG = false; |
| |
| public IpClientLinkObserver(String iface, Callback callback) { |
| mTag = "NetlinkTracker/" + iface; |
| mInterfaceName = iface; |
| mCallback = callback; |
| mLinkProperties = new LinkProperties(); |
| mLinkProperties.setInterfaceName(mInterfaceName); |
| mDnsServerRepository = new DnsServerRepository(); |
| } |
| |
| private void maybeLog(String operation, String iface, LinkAddress address) { |
| if (DBG) { |
| Log.d(mTag, operation + ": " + address + " on " + iface |
| + " flags " + address.getFlags() + " scope " + address.getScope()); |
| } |
| } |
| |
| private void maybeLog(String operation, Object o) { |
| if (DBG) { |
| Log.d(mTag, operation + ": " + o.toString()); |
| } |
| } |
| |
| @Override |
| public void onInterfaceRemoved(String iface) { |
| maybeLog("interfaceRemoved", iface); |
| if (mInterfaceName.equals(iface)) { |
| // Our interface was removed. Clear our LinkProperties and tell our owner that they are |
| // now empty. Note that from the moment that the interface is removed, any further |
| // interface-specific messages (e.g., RTM_DELADDR) will not reach us, because the netd |
| // code that parses them will not be able to resolve the ifindex to an interface name. |
| clearLinkProperties(); |
| mCallback.update(); |
| } |
| } |
| |
| @Override |
| public void onInterfaceAddressUpdated(LinkAddress address, String iface) { |
| if (mInterfaceName.equals(iface)) { |
| maybeLog("addressUpdated", iface, address); |
| boolean changed; |
| synchronized (this) { |
| changed = mLinkProperties.addLinkAddress(address); |
| } |
| if (changed) { |
| mCallback.update(); |
| } |
| } |
| } |
| |
| @Override |
| public void onInterfaceAddressRemoved(LinkAddress address, String iface) { |
| if (mInterfaceName.equals(iface)) { |
| maybeLog("addressRemoved", iface, address); |
| boolean changed; |
| synchronized (this) { |
| changed = mLinkProperties.removeLinkAddress(address); |
| } |
| if (changed) { |
| mCallback.update(); |
| } |
| } |
| } |
| |
| @Override |
| public void onRouteUpdated(RouteInfo route) { |
| if (mInterfaceName.equals(route.getInterface())) { |
| maybeLog("routeUpdated", route); |
| boolean changed; |
| synchronized (this) { |
| changed = mLinkProperties.addRoute(route); |
| } |
| if (changed) { |
| mCallback.update(); |
| } |
| } |
| } |
| |
| @Override |
| public void onRouteRemoved(RouteInfo route) { |
| if (mInterfaceName.equals(route.getInterface())) { |
| maybeLog("routeRemoved", route); |
| boolean changed; |
| synchronized (this) { |
| changed = mLinkProperties.removeRoute(route); |
| } |
| if (changed) { |
| mCallback.update(); |
| } |
| } |
| } |
| |
| @Override |
| public void onInterfaceDnsServerInfo(String iface, long lifetime, String[] addresses) { |
| if (mInterfaceName.equals(iface)) { |
| maybeLog("interfaceDnsServerInfo", Arrays.toString(addresses)); |
| boolean changed = mDnsServerRepository.addServers(lifetime, addresses); |
| if (changed) { |
| synchronized (this) { |
| mDnsServerRepository.setDnsServersOn(mLinkProperties); |
| } |
| mCallback.update(); |
| } |
| } |
| } |
| |
| /** |
| * Returns a copy of this object's LinkProperties. |
| */ |
| public synchronized LinkProperties getLinkProperties() { |
| return new LinkProperties(mLinkProperties); |
| } |
| |
| /** |
| * Reset this object's LinkProperties. |
| */ |
| public synchronized void clearLinkProperties() { |
| // Clear the repository before clearing mLinkProperties. That way, if a clear() happens |
| // while interfaceDnsServerInfo() is being called, we'll end up with no DNS servers in |
| // mLinkProperties, as desired. |
| mDnsServerRepository = new DnsServerRepository(); |
| mLinkProperties.clear(); |
| mLinkProperties.setInterfaceName(mInterfaceName); |
| } |
| |
| /** |
| * Tracks DNS server updates received from Netlink. |
| * |
| * The network may announce an arbitrary number of DNS servers in Router Advertisements at any |
| * time. Each announcement has a lifetime; when the lifetime expires, the servers should not be |
| * used any more. In this way, the network can gracefully migrate clients from one set of DNS |
| * servers to another. Announcements can both raise and lower the lifetime, and an announcement |
| * can expire servers by announcing them with a lifetime of zero. |
| * |
| * Typically the system will only use a small number (2 or 3; {@code NUM_CURRENT_SERVERS}) of |
| * DNS servers at any given time. These are referred to as the current servers. In case all the |
| * current servers expire, the class also keeps track of a larger (but limited) number of |
| * servers that are promoted to current servers when the current ones expire. In order to |
| * minimize updates to the rest of the system (and potentially expensive cache flushes) this |
| * class attempts to keep the list of current servers constant where possible. More |
| * specifically, the list of current servers is only updated if a new server is learned and |
| * there are not yet {@code NUM_CURRENT_SERVERS} current servers, or if one or more of the |
| * current servers expires or is pushed out of the set. Therefore, the current servers will not |
| * necessarily be the ones with the highest lifetime, but the ones learned first. |
| * |
| * This is by design: if instead the class always preferred the servers with the highest |
| * lifetime, a (misconfigured?) network where two or more routers announce more than |
| * {@code NUM_CURRENT_SERVERS} unique servers would cause persistent oscillations. |
| * |
| * TODO: Currently servers are only expired when a new DNS update is received. |
| * Update them using timers, or possibly on every notification received by NetlinkTracker. |
| * |
| * Threading model: run by NetlinkTracker. Methods are synchronized(this) just in case netlink |
| * notifications are sent by multiple threads. If future threads use alarms to expire, those |
| * alarms must also be synchronized(this). |
| * |
| */ |
| private static class DnsServerRepository { |
| |
| /** How many DNS servers we will use. 3 is suggested by RFC 6106. */ |
| static final int NUM_CURRENT_SERVERS = 3; |
| |
| /** How many DNS servers we'll keep track of, in total. */ |
| static final int NUM_SERVERS = 12; |
| |
| /** Stores up to {@code NUM_CURRENT_SERVERS} DNS servers we're currently using. */ |
| private Set<InetAddress> mCurrentServers; |
| |
| public static final String TAG = "DnsServerRepository"; |
| |
| /** |
| * Stores all the DNS servers we know about, for use when the current servers expire. |
| * Always sorted in order of decreasing expiry. The elements in this list are also the |
| * values of mIndex, and may be elements in mCurrentServers. |
| */ |
| private ArrayList<DnsServerEntry> mAllServers; |
| |
| /** |
| * Indexes the servers so we can update their lifetimes more quickly in the common case |
| * where servers are not being added, but only being refreshed. |
| */ |
| private HashMap<InetAddress, DnsServerEntry> mIndex; |
| |
| DnsServerRepository() { |
| mCurrentServers = new HashSet<>(); |
| mAllServers = new ArrayList<>(NUM_SERVERS); |
| mIndex = new HashMap<>(NUM_SERVERS); |
| } |
| |
| /** Sets the DNS servers of the provided LinkProperties object to the current servers. */ |
| public synchronized void setDnsServersOn(LinkProperties lp) { |
| lp.setDnsServers(mCurrentServers); |
| } |
| |
| /** |
| * Notifies the class of new DNS server information. |
| * @param lifetime the time in seconds that the DNS servers are valid. |
| * @param addresses the string representations of the IP addresses of DNS servers to use. |
| */ |
| public synchronized boolean addServers(long lifetime, String[] addresses) { |
| // The lifetime is actually an unsigned 32-bit number, but Java doesn't have unsigned. |
| // Technically 0xffffffff (the maximum) is special and means "forever", but 2^32 seconds |
| // (136 years) is close enough. |
| long now = System.currentTimeMillis(); |
| long expiry = now + 1000 * lifetime; |
| |
| // Go through the list of servers. For each one, update the entry if one exists, and |
| // create one if it doesn't. |
| for (String addressString : addresses) { |
| InetAddress address; |
| try { |
| address = InetAddresses.parseNumericAddress(addressString); |
| } catch (IllegalArgumentException ex) { |
| continue; |
| } |
| |
| if (!updateExistingEntry(address, expiry)) { |
| // There was no entry for this server. Create one, unless it's already expired |
| // (i.e., if the lifetime is zero; it cannot be < 0 because it's unsigned). |
| if (expiry > now) { |
| DnsServerEntry entry = new DnsServerEntry(address, expiry); |
| mAllServers.add(entry); |
| mIndex.put(address, entry); |
| } |
| } |
| } |
| |
| // Sort the servers by expiry. |
| Collections.sort(mAllServers); |
| |
| // Prune excess entries and update the current server list. |
| return updateCurrentServers(); |
| } |
| |
| private synchronized boolean updateExistingEntry(InetAddress address, long expiry) { |
| DnsServerEntry existing = mIndex.get(address); |
| if (existing != null) { |
| existing.expiry = expiry; |
| return true; |
| } |
| return false; |
| } |
| |
| private synchronized boolean updateCurrentServers() { |
| long now = System.currentTimeMillis(); |
| boolean changed = false; |
| |
| // Prune excess or expired entries. |
| for (int i = mAllServers.size() - 1; i >= 0; i--) { |
| if (i >= NUM_SERVERS || mAllServers.get(i).expiry < now) { |
| DnsServerEntry removed = mAllServers.remove(i); |
| mIndex.remove(removed.address); |
| changed |= mCurrentServers.remove(removed.address); |
| } else { |
| break; |
| } |
| } |
| |
| // Add servers to the current set, in order of decreasing lifetime, until it has enough. |
| // Prefer existing servers over new servers in order to minimize updates to the rest of |
| // the system and avoid persistent oscillations. |
| for (DnsServerEntry entry : mAllServers) { |
| if (mCurrentServers.size() < NUM_CURRENT_SERVERS) { |
| changed |= mCurrentServers.add(entry.address); |
| } else { |
| break; |
| } |
| } |
| return changed; |
| } |
| } |
| |
| /** |
| * Represents a DNS server entry with an expiry time. |
| * |
| * Implements Comparable so DNS server entries can be sorted by lifetime, longest-lived first. |
| * The ordering of entries with the same lifetime is unspecified, because given two servers with |
| * identical lifetimes, we don't care which one we use, and only comparing the lifetime is much |
| * faster than comparing the IP address as well. |
| * |
| * Note: this class has a natural ordering that is inconsistent with equals. |
| */ |
| private static class DnsServerEntry implements Comparable<DnsServerEntry> { |
| /** The IP address of the DNS server. */ |
| public final InetAddress address; |
| /** The time until which the DNS server may be used. A Java millisecond time as might be |
| * returned by currentTimeMillis(). */ |
| public long expiry; |
| |
| DnsServerEntry(InetAddress address, long expiry) throws IllegalArgumentException { |
| this.address = address; |
| this.expiry = expiry; |
| } |
| |
| public int compareTo(DnsServerEntry other) { |
| return Long.compare(other.expiry, this.expiry); |
| } |
| } |
| } |