Add Cloudflare DNS as a private DNS provider

TODO: Add tests

Also includes:
commit d82a7a0585671903ba18cd1d8fab25d9275c2a25
Author: Oliver Scott <olivercscott@gmail.com>
Date:   Fri Jan 29 10:57:26 2021 -0500

    Fix Cloudflare private DNS provider

    Change-Id: I5932d8d7e82621220eb119a212ccecf15e284421
    (cherry picked from commit 24abf646a0df5e00285d1b698adec03eb897388f)

Change-Id: I7e8a320d47e7c5ddbcb9acfaf23032ae92d5d70d
(cherry picked from commit 96ce93f7bf7233008591d22a0d24a6d7cd0a94ff)
Signed-off-by: Mohammad Hasan Keramat J <ikeramat@protonmail.com>

framework/src/android/net/ConnectivitySettingsManager.java

@@ -356,6 +356,12 @@ public class ConnectivitySettingsManager {
      */
     public static final int PRIVATE_DNS_MODE_OFF = ConnectivitySettingsUtils.PRIVATE_DNS_MODE_OFF;
 
+    /**
+     * @hide
+     */
+    public static final int PRIVATE_DNS_MODE_CLOUDFLARE =
+            ConnectivitySettingsUtils.PRIVATE_DNS_MODE_CLOUDFLARE;
+
     /**
      * One of the private DNS modes that indicates the private DNS mode is automatic, which
      * will try to use the current DNS as private DNS.
@@ -371,10 +377,18 @@ public class ConnectivitySettingsManager {
     public static final int PRIVATE_DNS_MODE_PROVIDER_HOSTNAME =
             ConnectivitySettingsUtils.PRIVATE_DNS_MODE_PROVIDER_HOSTNAME;
 
+    /**
+     * @hide
+     * Alternative: 1dot1dot1dot1.cloudflare-dns.com
+     */
+    public static final String PRIVATE_DNS_SPECIFIER_CLOUDFLARE = "one.one.one.one";
+
+
     /** @hide */
     @Retention(RetentionPolicy.SOURCE)
     @IntDef(value = {
             PRIVATE_DNS_MODE_OFF,
+            PRIVATE_DNS_MODE_CLOUDFLARE,
             PRIVATE_DNS_MODE_OPPORTUNISTIC,
             PRIVATE_DNS_MODE_PROVIDER_HOSTNAME,
     })
@@ -829,6 +843,7 @@ public class ConnectivitySettingsManager {
     public static void setPrivateDnsDefaultMode(@NonNull Context context,
             @NonNull @PrivateDnsMode int mode) {
         if (!(mode == PRIVATE_DNS_MODE_OFF
+                || mode == PRIVATE_DNS_MODE_CLOUDFLARE
                 || mode == PRIVATE_DNS_MODE_OPPORTUNISTIC
                 || mode == PRIVATE_DNS_MODE_PROVIDER_HOSTNAME)) {
             throw new IllegalArgumentException("Invalid private dns mode");

service/src/com/android/server/connectivity/DnsManager.java

@@ -23,8 +23,10 @@ import static android.net.ConnectivitySettingsManager.DNS_RESOLVER_SUCCESS_THRES
 import static android.net.ConnectivitySettingsManager.PRIVATE_DNS_DEFAULT_MODE;
 import static android.net.ConnectivitySettingsManager.PRIVATE_DNS_MODE;
 import static android.net.ConnectivitySettingsManager.PRIVATE_DNS_MODE_OFF;
+import static android.net.ConnectivitySettingsManager.PRIVATE_DNS_MODE_CLOUDFLARE;
 import static android.net.ConnectivitySettingsManager.PRIVATE_DNS_MODE_PROVIDER_HOSTNAME;
 import static android.net.ConnectivitySettingsManager.PRIVATE_DNS_SPECIFIER;
+import static android.net.ConnectivitySettingsManager.PRIVATE_DNS_SPECIFIER_CLOUDFLARE;
 import static android.net.resolv.aidl.IDnsResolverUnsolicitedEventListener.VALIDATION_RESULT_FAILURE;
 import static android.net.resolv.aidl.IDnsResolverUnsolicitedEventListener.VALIDATION_RESULT_SUCCESS;
 
@@ -142,6 +144,10 @@ public class DnsManager {
             return new PrivateDnsConfig(specifier, null);
         }
 
+        if (PRIVATE_DNS_MODE_CLOUDFLARE == mode) {
+            return new PrivateDnsConfig(PRIVATE_DNS_SPECIFIER_CLOUDFLARE, null);
+        }
+
         return new PrivateDnsConfig(useTls);
     }