Do not destroy vif's napi context, if it was not initialised during a…

…ddition

If the napi structure was not initialised during interface addition, because
of errors,  it should not be touched during the delete too, since doing a
netif_napi_del results in crash. However, there are no reliable checks to find
whether napi was initialised or not. Hence, for now we will check for the existance
poll function, which should have been set if the napi structure was initialised.

Closes BUG: #1399577

Change-Id: I8cf439dc53805801a5ba301f542dedb2aaa5dee2

linux/vr_host_interface.c

@@ -1585,8 +1585,18 @@ linux_if_del(struct vr_interface *vif)
     else if (vif->vif_type == VIF_TYPE_PHYSICAL)
         vhost_if_del_phys((struct net_device *)vif->vif_os);
     else if (vif->vif_type == VIF_TYPE_VIRTUAL) {
-        napi_disable(&vif->vr_napi);
-        netif_napi_del(&vif->vr_napi);
+        /*
+         * if the napi structure was not initialised in the first place, we
+         * should not touch it now, since doing a netif_napi_del results in a
+         * crash. however, there are no reliable checks. hence, for now we
+         * will check for poll. ideally, we should not have had the napi
+         * structure itself in the interface structure and that would have
+         * clearly told us what to do with napi
+         */
+        if (vif->vr_napi.poll) {
+            napi_disable(&vif->vr_napi);
+            netif_napi_del(&vif->vr_napi);
+        }
         skb_queue_purge(&vif->vr_skb_inputq);
     }