ethernet: fix IpClient restart when link is down

Do not restart IpClient when link is down after calling
updateConfiguration().

Test: atest EthernetManagerTest
Bug: 249897651

Change-Id: Ia0f6b67cde63747a608d35b8bec6ad37bcabb110
diff --git a/service-t/src/com/android/server/ethernet/EthernetNetworkFactory.java b/service-t/src/com/android/server/ethernet/EthernetNetworkFactory.java
index 48d68d7..00f6c56 100644
--- a/service-t/src/com/android/server/ethernet/EthernetNetworkFactory.java
+++ b/service-t/src/com/android/server/ethernet/EthernetNetworkFactory.java
@@ -469,7 +469,9 @@
             // TODO: Update this logic to only do a restart if required. Although a restart may
             //  be required due to the capabilities or ipConfiguration values, not all
             //  capabilities changes require a restart.
-            restart();
+            if (mIpClient != null) {
+                restart();
+            }
         }
 
         boolean isRestricted() {
diff --git a/tests/cts/net/src/android/net/cts/EthernetManagerTest.kt b/tests/cts/net/src/android/net/cts/EthernetManagerTest.kt
index 3635b7b..1e44440 100644
--- a/tests/cts/net/src/android/net/cts/EthernetManagerTest.kt
+++ b/tests/cts/net/src/android/net/cts/EthernetManagerTest.kt
@@ -979,4 +979,23 @@
         cb.eventuallyExpectCapabilities(TEST_CAPS)
         cb.eventuallyExpectLpForStaticConfig(STATIC_IP_CONFIGURATION.staticIpConfiguration)
     }
+
+    @Test
+    fun testUpdateConfiguration_withLinkDown() {
+        assumeChangingCarrierSupported()
+        // createInterface without carrier is racy, so create it and then remove carrier.
+        val iface = createInterface()
+        val cb = requestNetwork(ETH_REQUEST)
+        cb.expectAvailable()
+
+        iface.setCarrierEnabled(false)
+        cb.eventuallyExpectLost()
+
+        updateConfiguration(iface, STATIC_IP_CONFIGURATION, TEST_CAPS).expectResult(iface.name)
+        cb.assertNoCallback()
+
+        iface.setCarrierEnabled(true)
+        cb.eventuallyExpectCapabilities(TEST_CAPS)
+        cb.eventuallyExpectLpForStaticConfig(STATIC_IP_CONFIGURATION.staticIpConfiguration)
+    }
 }