Allow NetworkFactories to match any network specifier on a request

Current usage of NetworkSpecifier: network factory will match a request
if the request has either a (1) empty network specifier, or (2) a
network specifier which is identical to that of the network factory.
Note: 'matching' w.r.t. network specifier - all other matching rules
are still in effect.

Change: add rule (3) or the network specifier of the network factory
is the special string (which is defined as "*" and which user-facing
network requests aren't allowed to use).

Rationale: allows on-demand network creation.

Example:
- Can specify a Wi-Fi NetworkRequest with NetworkSpecifier="ssid"
- It will match a Wi-Fi network factory specifying NetworkSpecifier="*"
- That network factory will bring up a Wi-Fi network, connecting to the
  specified SSID.
- Once the network is created it will create a NetworkAgent which will
  now have a NetworkSpecifier matching that of the request (not the
  match-all special string!)

That final step of making sure that the NetworkAgent matches the request
and not the match-all is critical to delivering any subsequent callbacks
correctly. I.e. your network will only get callbacks which match it.

Bug: 26192833
Change-Id: I49e3b492e0bb48a3f6e9a34e3f94f0e1cf89741f

2 files changed, 19 insertions, 1 deletions

diff --git a/core/java/android/net/NetworkCapabilities.java b/core/java/android/net/NetworkCapabilities.java
index 3bd12c060748..e27c0fb2ddea 100644
--- a/core/java/android/net/NetworkCapabilities.java
+++ b/core/java/android/net/NetworkCapabilities.java
@@ -197,6 +197,19 @@ public final class NetworkCapabilities implements Parcelable {
             (1 << NET_CAPABILITY_CAPTIVE_PORTAL);
 
     /**
+     * Network specifier for factories which want to match any network specifier
+     * (NS) in a request. Behavior:
+     * <li>Empty NS in request matches any network factory NS</li>
+     * <li>Empty NS in the network factory NS only matches a request with an
+     * empty NS</li>
+     * <li>"*" (this constant) NS in the network factory matches requests with
+     * any NS</li>
+     *
+     * @hide
+     */
+    public static final String MATCH_ALL_REQUESTS_NETWORK_SPECIFIER = "*";
+
+    /**
      * Network capabilities that are not allowed in NetworkRequests. This exists because the
      * NetworkFactory / NetworkAgent model does not deal well with the situation where a
      * capability's presence cannot be known in advance. If such a capability is requested, then we
@@ -596,7 +609,8 @@ public final class NetworkCapabilities implements Parcelable {
     }
     private boolean satisfiedBySpecifier(NetworkCapabilities nc) {
         return (TextUtils.isEmpty(mNetworkSpecifier) ||
-                mNetworkSpecifier.equals(nc.mNetworkSpecifier));
+                mNetworkSpecifier.equals(nc.mNetworkSpecifier) ||
+                MATCH_ALL_REQUESTS_NETWORK_SPECIFIER.equals(nc.mNetworkSpecifier));
     }
     private boolean equalsSpecifier(NetworkCapabilities nc) {
         if (TextUtils.isEmpty(mNetworkSpecifier)) {
diff --git a/core/java/android/net/NetworkRequest.java b/core/java/android/net/NetworkRequest.java
index 7da4818991b6..f1edcbe30df6 100644
--- a/core/java/android/net/NetworkRequest.java
+++ b/core/java/android/net/NetworkRequest.java
@@ -188,6 +188,10 @@ public class NetworkRequest implements Parcelable {
          *                         networks.
          */
         public Builder setNetworkSpecifier(String networkSpecifier) {
+            if (NetworkCapabilities.MATCH_ALL_REQUESTS_NETWORK_SPECIFIER.equals(networkSpecifier)) {
+                throw new IllegalArgumentException("Invalid network specifier - must not be '"
+                        + NetworkCapabilities.MATCH_ALL_REQUESTS_NETWORK_SPECIFIER + "'");
+            }
             mNetworkCapabilities.setNetworkSpecifier(networkSpecifier);
             return this;
         }