netdevsim: fib: Add debugfs knob to simulate route deletion failure

The previous patch ("netdevsim: fib: Fix reference count leak on route
deletion failure") fixed a reference count leak that happens on route
deletion failure.

Such failures can only be simulated by injecting slab allocation
failures, which cannot be surgically injected.

In order to be able to specifically test this scenario, add a debugfs
knob that allows user space to fail route deletion requests when
enabled.
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Amit Cohen <amcohen@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/netdevsim/fib.c

@@ -62,6 +62,7 @@ struct nsim_fib_data {
 	bool fail_route_offload;
 	bool fail_res_nexthop_group_replace;
 	bool fail_nexthop_bucket_replace;
+	bool fail_route_delete;
 };
 
 struct nsim_fib_rt_key {
@@ -915,6 +916,10 @@ static int nsim_fib4_prepare_event(struct fib_notifier_info *info,
 		}
 		break;
 	case FIB_EVENT_ENTRY_DEL:
+		if (data->fail_route_delete) {
+			NL_SET_ERR_MSG_MOD(extack, "Failed to process route deletion");
+			return -EINVAL;
+		}
 		nsim_fib_account(&data->ipv4.fib, false);
 		break;
 	}
@@ -953,6 +958,11 @@ static int nsim_fib6_prepare_event(struct fib_notifier_info *info,
 		}
 		break;
 	case FIB_EVENT_ENTRY_DEL:
+		if (data->fail_route_delete) {
+			err = -EINVAL;
+			NL_SET_ERR_MSG_MOD(extack, "Failed to process route deletion");
+			goto err_fib6_event_fini;
+		}
 		nsim_fib_account(&data->ipv6.fib, false);
 		break;
 	}
@@ -1526,6 +1536,10 @@ nsim_fib_debugfs_init(struct nsim_fib_data *data, struct nsim_dev *nsim_dev)
 
 	debugfs_create_file("nexthop_bucket_activity", 0200, data->ddir,
 			    data, &nsim_nexthop_bucket_activity_fops);
+
+	data->fail_route_delete = false;
+	debugfs_create_bool("fail_route_delete", 0600, data->ddir,
+			    &data->fail_route_delete);
 	return 0;
 }