Stop setting the legacy net.dnsX system properties

These have been locked down via SELinux for a while and thus
they should be safe to delete at this point.

Test: atest FrameworksNetTest
Bug: 33308258
Bug: 148724751
Change-Id: I3a1e9c6ad92c8d2367e0048e5d6cd7d06bbc6e80

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

@@ -236,7 +236,6 @@ import java.net.UnknownHostException;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.Comparator;
 import java.util.ConcurrentModificationException;
 import java.util.HashMap;
@@ -6192,20 +6191,12 @@ public class ConnectivityService extends IConnectivityManager.Stub
             return;  // no updating necessary
         }
 
-        final NetworkAgentInfo defaultNai = getDefaultNetwork();
-        final boolean isDefaultNetwork = (defaultNai != null && defaultNai.network.netId == netId);
-
         if (DBG) {
             final Collection<InetAddress> dnses = newLp.getDnsServers();
             log("Setting DNS servers for network " + netId + " to " + dnses);
         }
         try {
             mDnsManager.noteDnsServersForNetwork(netId, newLp);
-            // TODO: netd should listen on [::1]:53 and proxy queries to the current
-            // default network, and we should just set net.dns1 to ::1, not least
-            // because applications attempting to use net.dns resolvers will bypass
-            // the privacy protections of things like DNS-over-TLS.
-            if (isDefaultNetwork) mDnsManager.setDefaultDnsSystemProperties(newLp.getDnsServers());
             mDnsManager.flushVmDnsCache();
         } catch (Exception e) {
             loge("Exception in setDnsConfigurationForNetwork: " + e);
@@ -6720,8 +6711,6 @@ public class ConnectivityService extends IConnectivityManager.Stub
                 ? newNetwork.linkProperties.getHttpProxy() : null);
         updateTcpBufferSizes(null != newNetwork
                 ? newNetwork.linkProperties.getTcpBufferSizes() : null);
-        mDnsManager.setDefaultDnsSystemProperties(null != newNetwork
-                ? newNetwork.linkProperties.getDnsServers() : Collections.EMPTY_LIST);
         notifyIfacesChangedForNetworkStats();
         // Fix up the NetworkCapabilities of any VPNs that don't specify underlying networks.
         updateAllVpnsCapabilities();

services/core/java/com/android/server/connectivity/DnsManager.java

@@ -50,7 +50,6 @@ import android.util.Slog;
 
 import java.net.InetAddress;
 import java.util.Arrays;
-import java.util.Collection;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
@@ -245,7 +244,6 @@ public class DnsManager {
     private final Map<Integer, LinkProperties> mLinkPropertiesMap;
     private final Map<Integer, int[]> mTransportsMap;
 
-    private int mNumDnsEntries;
     private int mSampleValidity;
     private int mSuccessThreshold;
     private int mMinSamples;
@@ -409,18 +407,6 @@ public class DnsManager {
         }
     }
 
-    public void setDefaultDnsSystemProperties(Collection<InetAddress> dnses) {
-        int last = 0;
-        for (InetAddress dns : dnses) {
-            ++last;
-            setNetDnsProperty(last, dns.getHostAddress());
-        }
-        for (int i = last + 1; i <= mNumDnsEntries; ++i) {
-            setNetDnsProperty(i, "");
-        }
-        mNumDnsEntries = last;
-    }
-
     /**
      * Flush DNS caches and events work before boot has completed.
      */
@@ -476,16 +462,6 @@ public class DnsManager {
         return Settings.Global.getInt(mContentResolver, which, dflt);
     }
 
-    private void setNetDnsProperty(int which, String value) {
-        final String key = "net.dns" + which;
-        // Log and forget errors setting unsupported properties.
-        try {
-            mSystemProperties.set(key, value);
-        } catch (Exception e) {
-            Slog.e(TAG, "Error setting unsupported net.dns property: ", e);
-        }
-    }
-
     private static String getPrivateDnsMode(ContentResolver cr) {
         String mode = getStringSetting(cr, PRIVATE_DNS_MODE);
         if (TextUtils.isEmpty(mode)) mode = getStringSetting(cr, PRIVATE_DNS_DEFAULT_MODE);

tests/net/java/com/android/server/connectivity/DnsManagerTest.java

@@ -159,7 +159,6 @@ public class DnsManagerTest {
         // Send a validation event that is tracked on the alternate netId
         mDnsManager.updateTransportsForNetwork(TEST_NETID, TEST_TRANSPORT_TYPES);
         mDnsManager.noteDnsServersForNetwork(TEST_NETID, lp);
-        mDnsManager.setDefaultDnsSystemProperties(lp.getDnsServers());
         mDnsManager.flushVmDnsCache();
         mDnsManager.updateTransportsForNetwork(TEST_NETID_ALTERNATE, TEST_TRANSPORT_TYPES);
         mDnsManager.noteDnsServersForNetwork(TEST_NETID_ALTERNATE, lp);
@@ -196,7 +195,6 @@ public class DnsManagerTest {
                     }));
         mDnsManager.updateTransportsForNetwork(TEST_NETID, TEST_TRANSPORT_TYPES);
         mDnsManager.noteDnsServersForNetwork(TEST_NETID, lp);
-        mDnsManager.setDefaultDnsSystemProperties(lp.getDnsServers());
         mDnsManager.flushVmDnsCache();
         fixedLp = new LinkProperties(lp);
         mDnsManager.updatePrivateDnsStatus(TEST_NETID, fixedLp);
@@ -232,7 +230,6 @@ public class DnsManagerTest {
         lp.addDnsServer(InetAddress.getByName("3.3.3.3"));
         mDnsManager.updateTransportsForNetwork(TEST_NETID, TEST_TRANSPORT_TYPES);
         mDnsManager.noteDnsServersForNetwork(TEST_NETID, lp);
-        mDnsManager.setDefaultDnsSystemProperties(lp.getDnsServers());
         mDnsManager.flushVmDnsCache();
         mDnsManager.updatePrivateDnsValidation(
                 new DnsManager.PrivateDnsValidationUpdate(TEST_NETID,
@@ -246,7 +243,6 @@ public class DnsManagerTest {
                 mDnsManager.getPrivateDnsConfig());
         mDnsManager.updateTransportsForNetwork(TEST_NETID, TEST_TRANSPORT_TYPES);
         mDnsManager.noteDnsServersForNetwork(TEST_NETID, lp);
-        mDnsManager.setDefaultDnsSystemProperties(lp.getDnsServers());
         mDnsManager.flushVmDnsCache();
         mDnsManager.updatePrivateDnsValidation(
                 new DnsManager.PrivateDnsValidationUpdate(TEST_NETID_UNTRACKED,
@@ -295,7 +291,6 @@ public class DnsManagerTest {
                 mDnsManager.getPrivateDnsConfig());
         mDnsManager.updateTransportsForNetwork(TEST_NETID, TEST_TRANSPORT_TYPES);
         mDnsManager.noteDnsServersForNetwork(TEST_NETID, lp);
-        mDnsManager.setDefaultDnsSystemProperties(lp.getDnsServers());
         mDnsManager.flushVmDnsCache();
         mDnsManager.updatePrivateDnsValidation(
                 new DnsManager.PrivateDnsValidationUpdate(TEST_NETID,
@@ -341,7 +336,6 @@ public class DnsManagerTest {
         lp.addDnsServer(InetAddress.getByName("4.4.4.4"));
         mDnsManager.updateTransportsForNetwork(TEST_NETID, TEST_TRANSPORT_TYPES);
         mDnsManager.noteDnsServersForNetwork(TEST_NETID, lp);
-        mDnsManager.setDefaultDnsSystemProperties(lp.getDnsServers());
         mDnsManager.flushVmDnsCache();
 
         final ArgumentCaptor<ResolverParamsParcel> resolverParamsParcelCaptor =