Add session ID to VpnTransportInfo

- This will be visible only to apps with the NETWORK_SETTINGS
  permissions (signature), and will be redacted for all other callers.
- This string is expected to be the same as set by
  VpnService#setSession, and in general, VpnConfig.session. But it
  will be a general API that Vpn.java can call when setting the
  VpnTransportInfo.
- This string cannot be updated once the VPN NetworkAgent is connected.

Bug: 171872481
Test: atest ConnectivityServiceTest
      atest VpnTransportInfoTest
      atest android.net.cts.NetworkAgentTest
Change-Id: I8d09e25b83f7ee8be21ec9c9bd3c72a251f1370d

framework/api/module-lib-current.txt

@@ -115,10 +115,12 @@ package android.net {
   }
 
   public final class VpnTransportInfo implements android.os.Parcelable android.net.TransportInfo {
-    ctor public VpnTransportInfo(int);
+    ctor public VpnTransportInfo(int, @Nullable String);
     method public int describeContents();
+    method @NonNull public android.net.VpnTransportInfo makeCopy(long);
     method public void writeToParcel(@NonNull android.os.Parcel, int);
     field @NonNull public static final android.os.Parcelable.Creator<android.net.VpnTransportInfo> CREATOR;
+    field @Nullable public final String sessionId;
     field public final int type;
   }
 

framework/src/android/net/VpnTransportInfo.java

@@ -17,11 +17,14 @@
 package android.net;
 
 import static android.annotation.SystemApi.Client.MODULE_LIBRARIES;
+import static android.net.NetworkCapabilities.REDACT_FOR_NETWORK_SETTINGS;
 
 import android.annotation.NonNull;
+import android.annotation.Nullable;
 import android.annotation.SystemApi;
 import android.os.Parcel;
 import android.os.Parcelable;
+import android.text.TextUtils;
 
 import java.util.Objects;
 
@@ -38,8 +41,26 @@ public final class VpnTransportInfo implements TransportInfo, Parcelable {
     /** Type of this VPN. */
     public final int type;
 
-    public VpnTransportInfo(int type) {
+    @Nullable
+    public final String sessionId;
+
+    @Override
+    public long getApplicableRedactions() {
+        return REDACT_FOR_NETWORK_SETTINGS;
+    }
+
+    /**
+     * Create a copy of a {@link VpnTransportInfo} with the sessionId redacted if necessary.
+     */
+    @NonNull
+    public VpnTransportInfo makeCopy(long redactions) {
+        return new VpnTransportInfo(type,
+            ((redactions & REDACT_FOR_NETWORK_SETTINGS) != 0) ? null : sessionId);
+    }
+
+    public VpnTransportInfo(int type, @Nullable String sessionId) {
         this.type = type;
+        this.sessionId = sessionId;
     }
 
     @Override
@@ -47,17 +68,17 @@ public final class VpnTransportInfo implements TransportInfo, Parcelable {
         if (!(o instanceof VpnTransportInfo)) return false;
 
         VpnTransportInfo that = (VpnTransportInfo) o;
-        return this.type == that.type;
+        return (this.type == that.type) && TextUtils.equals(this.sessionId, that.sessionId);
     }
 
     @Override
     public int hashCode() {
-        return Objects.hash(type);
+        return Objects.hash(type, sessionId);
     }
 
     @Override
     public String toString() {
-        return String.format("VpnTransportInfo{type=%d}", type);
+        return String.format("VpnTransportInfo{type=%d, sessionId=%s}", type, sessionId);
     }
 
     @Override
@@ -68,12 +89,13 @@ public final class VpnTransportInfo implements TransportInfo, Parcelable {
     @Override
     public void writeToParcel(@NonNull Parcel dest, int flags) {
         dest.writeInt(type);
+        dest.writeString(sessionId);
     }
 
     public static final @NonNull Creator<VpnTransportInfo> CREATOR =
             new Creator<VpnTransportInfo>() {
         public VpnTransportInfo createFromParcel(Parcel in) {
-            return new VpnTransportInfo(in.readInt());
+            return new VpnTransportInfo(in.readInt(), in.readString());
         }
         public VpnTransportInfo[] newArray(int size) {
             return new VpnTransportInfo[size];