LinkProperties: use ordered comparison for P-CSCFs - only on U+

to make sure a mainline update doesn't break devices in the field

Test: TreeHugger
Bug: 268479036
Signed-off-by: Maciej Żenczykowski <maze@google.com>
(cherry picked from https://android-review.googlesource.com/q/commit:f7939fa8d1c4566d056a8501e610c8fe18ac98f8)
Merged-In: Iadcd861509d31b3ed6352d452a159cd89af479dd
Change-Id: Iadcd861509d31b3ed6352d452a159cd89af479dd

framework/src/android/net/LinkProperties.java

@@ -1456,8 +1456,13 @@ public final class LinkProperties implements Parcelable {
      * @hide
      */
     public boolean isIdenticalPcscfs(@NonNull LinkProperties target) {
-        // list order is important, compare one by one
-        return target.getPcscfServers().equals(mPcscfs);
+        // Per 3GPP TS 24.229, B.2.2.1 PDP context activation and P-CSCF discovery
+        // list order is important, so on U+ compare one by one
+        if (SdkLevel.isAtLeastU()) return target.getPcscfServers().equals(mPcscfs);
+        // but for safety old behaviour on pre-U:
+        Collection<InetAddress> targetPcscfs = target.getPcscfServers();
+        return (mPcscfs.size() == targetPcscfs.size()) ?
+                    mPcscfs.containsAll(targetPcscfs) : false;
     }
 
     /**