Add an experiment flag for the DHCPv6 p-flag feature. am: cdeda6c0d1 am: f1993e96da

Original change: https://android-review.googlesource.com/c/platform/packages/modules/NetworkStack/+/3391866

Change-Id: Ie6d5309195d9ef40b12f566408cc07e53381d9d1
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>

src/android/net/ip/IpClient.java

diff --git a/src/android/net/ip/IpClient.java b/src/android/net/ip/IpClient.java
index b94d5e8..7447fc5 100644
--- a/src/android/net/ip/IpClient.java
+++ b/src/android/net/ip/IpClient.java
@@ -85,6 +85,7 @@
 import static com.android.networkstack.util.NetworkStackUtils.APF_HANDLE_ND_OFFLOAD;
 import static com.android.networkstack.util.NetworkStackUtils.APF_NEW_RA_FILTER_VERSION;
 import static com.android.networkstack.util.NetworkStackUtils.APF_POLLING_COUNTERS_VERSION;
+import static com.android.networkstack.util.NetworkStackUtils.IPCLIENT_DHCPV6_PD_PREFERRED_FLAG_VERSION;
 import static com.android.networkstack.util.NetworkStackUtils.IPCLIENT_DHCPV6_PREFIX_DELEGATION_VERSION;
 import static com.android.networkstack.util.NetworkStackUtils.IPCLIENT_GARP_NA_ROAMING_VERSION;
 import static com.android.networkstack.util.NetworkStackUtils.IPCLIENT_IGNORE_LOW_RA_LIFETIME_VERSION;
@@ -812,6 +813,7 @@
     private final boolean mApfShouldHandleNdOffload;
     private final boolean mApfShouldHandleMdnsOffload;
     private final boolean mIgnoreNudFailureEnabled;
+    private final boolean mDhcp6PdPreferredFlagEnabled;
 
     private InterfaceParams mInterfaceParams;
 
@@ -1091,6 +1093,8 @@
         mNudFailureCountWeeklyThreshold = mDependencies.getDeviceConfigPropertyInt(
                 CONFIG_NUD_FAILURE_COUNT_WEEKLY_THRESHOLD,
                 DEFAULT_NUD_FAILURE_COUNT_WEEKLY_THRESHOLD);
+        mDhcp6PdPreferredFlagEnabled =
+                mDependencies.isFeatureEnabled(mContext, IPCLIENT_DHCPV6_PD_PREFERRED_FLAG_VERSION);
 
         IpClientLinkObserver.Configuration config = new IpClientLinkObserver.Configuration(
                 mAcceptRaMinLft, mPopulateLinkAddressLifetime);
@@ -1143,6 +1147,7 @@
 
                     @Override
                     public void onNewPrefix(PrefixInfo info) {
+                        if (!mDhcp6PdPreferredFlagEnabled) return;
                         sendMessage(EVENT_PIO_PREFIX_UPDATE, info);
                     }
                 },