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Commit 4136850b authored by Erik Kline's avatar Erik Kline
Browse files

Carefully select which DNS servers to send to netd 

Select only DNS servers that:
    - are reachable, according to routes in the LinkProperties, AND

    - have a "suitable" source address in the LinkProperites, meaning:
        - IPv4 DNS server:
            - only if LinkProperties has any IPv4 address
        - IPv6 link-local DNS server:
            - only if the server has a scopeId set
            - assume for now that LinkProperties has a suitable
              link-local address
        - IPv6 non-link-local DNS server:
            - only if LinkProperties has a global, preferred IPv6 address

Bug: 19470192
Bug: 20733156
Change-Id: Ibd95f3f7b33a4fb6c36d1cea4adb63c99068f657
parent f4d225a4

services/core/java/com/android/server/ConnectivityService.java

+45 −1
Original line number Diff line number Diff line
@@ -136,11 +136,13 @@ import java.io.FileReader; 
import java.io.IOException;

import java.io.PrintWriter;

import java.net.Inet4Address;

import java.net.Inet6Address;

import java.net.InetAddress;

import java.net.UnknownHostException;

import java.util.ArrayList;

import java.util.Arrays;

import java.util.Collection;

import java.util.Collections;

import java.util.HashMap;

import java.util.HashSet;

import java.util.Iterator;
@@ -3920,10 +3922,52 @@ public class ConnectivityService extends IConnectivityManager.Stub 
        }

        return !routeDiff.added.isEmpty() || !routeDiff.removed.isEmpty();

    }



    // TODO: investigate moving this into LinkProperties, if only to make more accurate

    // the isProvisioned() checks.

    private static Collection<InetAddress> getLikelyReachableDnsServers(LinkProperties lp) {

        final ArrayList<InetAddress> dnsServers = new ArrayList<InetAddress>();

        final List<RouteInfo> allRoutes = lp.getAllRoutes();

        for (InetAddress nameserver : lp.getDnsServers()) {

            // If the LinkProperties doesn't include a route to the nameserver, ignore it.

            final RouteInfo bestRoute = RouteInfo.selectBestRoute(allRoutes, nameserver);

            if (bestRoute == null) {

                continue;

            }



            // TODO: better source address evaluation for destination addresses.

            if (nameserver instanceof Inet4Address) {

                if (!lp.hasIPv4Address()) {

                    continue;

                }

            } else if (nameserver instanceof Inet6Address) {

                if (nameserver.isLinkLocalAddress()) {

                    if (((Inet6Address)nameserver).getScopeId() == 0) {

                        // For now, just make sure link-local DNS servers have

                        // scopedIds set, since DNS lookups will fail otherwise.

                        // TODO: verify the scopeId matches that of lp's interface.

                        continue;

                    }

                }  else {

                    if (bestRoute.isIPv6Default() && !lp.hasGlobalIPv6Address()) {

                        // TODO: reconsider all corner cases (disconnected ULA networks, ...).

                        continue;

                    }

                }

            }



            dnsServers.add(nameserver);

        }

        return Collections.unmodifiableList(dnsServers);

    }



    private void updateDnses(LinkProperties newLp, LinkProperties oldLp, int netId,

                             boolean flush, boolean useDefaultDns) {

        // TODO: consider comparing the getLikelyReachableDnsServers() lists, in case the

        // route to a DNS server has been removed (only really applicable in special cases

        // where there is no default route).

        if (oldLp == null || (newLp.isIdenticalDnses(oldLp) == false)) {

            Collection<InetAddress> dnses = newLp.getDnsServers();

            Collection<InetAddress> dnses = getLikelyReachableDnsServers(newLp);

            if (dnses.size() == 0 && mDefaultDns != null && useDefaultDns) {

                dnses = new ArrayList();

                dnses.add(mDefaultDns);