wifi: Do not retransmit block ack request if inactivity timer has expired

Fixes #2928

src/wifi/model/block-ack-manager.cc

@@ -785,6 +785,20 @@ bool BlockAckManager::NeedBarRetransmission (uint8_t tid, uint16_t seqNumber, Ma
     {
       return false;
     }
+  else if (it->second.first.m_inactivityEvent.IsExpired ())
+    {
+      /*
+       * According to "11.5.4 Error recovery upon a peer failure",
+       * DELBA should be issued after inactivity timeout,
+       * so block ack request should not be retransmitted anymore.
+       *
+       * Otherwise we risk retransmitting BAR forever if condition
+       * above is never met and the STA is not available.
+       *
+       * See https://www.nsnam.org/bugzilla/show_bug.cgi?id=2928 for details.
+       */
+      return false;
+    }
   else
     {
       return true;