[Accton][wedge800cact] Fix VerifyCallbacksOnMacEntryChange warmboot timeout

fboss/agent/test/agent_hw_tests/AgentMacLearningTests.cpp

@@ -376,6 +376,38 @@ class AgentMacLearningTest : public AgentHwTest {
 
   L2LearningUpdateObserverUtil l2LearningObserver_;
 
+  /*
+   * Helper to safely bring down a port that may already be DOWN after warmboot.
+   * Polls for the port to come UP (with timeout), then calls bringDownPort().
+   * If the port stays DOWN (already in desired state), skips the call to avoid
+   * LinkStateToggler hanging indefinitely waiting for a DOWN notification that
+   * SDK won't generate.
+   */
+  void bringDownPortIfUp(PortID port) {
+    constexpr int kMaxWaitMs = 10000;
+    constexpr int kPollIntervalMs = 100;
+    XLOG(DBG2) << "Waiting up to " << kMaxWaitMs << "ms for port " << port
+               << " to come UP before bringDown";
+    for (int elapsed = 0; elapsed < kMaxWaitMs; elapsed += kPollIntervalMs) {
+      auto ports = getProgrammedState()->getPorts();
+      auto portState = ports->getNodeIf(port);
+      if (portState && portState->isUp()) {
+        XLOG(DBG2) << "Port " << port << " is UP after " << elapsed
+                   << "ms, proceeding with bringDownPort";
+        getAgentEnsemble()->bringDownPort(port);
+        return;
+      }
+      /* sleep override */
+      std::this_thread::sleep_for(std::chrono::milliseconds(kPollIntervalMs));
+    }
+    // Port never came UP ??this is expected after warmboot if the port was
+    // already DOWN in coldboot state. Log at WARN level so it's visible in
+    // test output for debugging warmboot regressions.
+    XLOG(WARN) << "Port " << port << " still DOWN after " << kMaxWaitMs
+               << "ms ??skipping bringDownPort. If this port should have come "
+               << "UP, investigate a potential warmboot regression.";
+  }
+
  private:
   bool wasMacLearntInHw(bool shouldExist, MacAddress mac) {
     bringUpPort(masterLogicalPortIds()[1]);
@@ -911,7 +943,14 @@ TEST_F(AgentMacSwLearningModeTest, VerifyCallbacksOnMacEntryChange) {
     // Disable aging, so entry stays in L2 table when we verify.
     utility::setMacAgeTimerSeconds(getAgentEnsemble(), 0);
     enum class MacOp { ASSOCIATE, DISSOASSOCIATE, DELETE };
-    getAgentEnsemble()->bringDownPort(masterLogicalPortIds()[1]);
+
+    // After warmboot, the flood-prevention port may remain DOWN (preserved from
+    // coldboot state) or may be in a transient state due to link flap. If we
+    // call bringDownPort directly and the port is already DOWN, SDK won't
+    // generate a new DOWN notification, causing LinkStateToggler to wait
+    // indefinitely.
+    bringDownPortIfUp(masterLogicalPortIds()[1]);
+
     l2LearningObserver_.startObserving(getAgentEnsemble());
     induceMacLearning(physPortDescr());
     auto doMacOp = [this, isTH3](MacOp op) {