net-shapers: implement delete support for NODE scope shaper

Leverage the previously introduced group operation to implement
the removal of NODE scope shaper, re-linking its leaves under the
the parent node before actually deleting the specified NODE scope
shaper.

Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Link: https://patch.msgid.link/763d484b5b69e365acccfd8031b183c647a367a4.1728460186.git.pabeni@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: Paolo Abeni

net/shaper/shaper.c

@@ -785,7 +785,8 @@ static int net_shaper_parent_from_leaves(int leaves_count,
 }
 
 static int __net_shaper_group(struct net_shaper_binding *binding,
-			      int leaves_count, struct net_shaper *leaves,
+			      bool update_node, int leaves_count,
+			      struct net_shaper *leaves,
 			      struct net_shaper *node,
 			      struct netlink_ext_ack *extack)
 {
@@ -831,12 +832,14 @@ static int __net_shaper_group(struct net_shaper_binding *binding,
 		}
 	}
 
-	/* For newly created node scope shaper, the following will update
-	 * the handle, due to id allocation.
-	 */
-	ret = net_shaper_pre_insert(binding, &node->handle, extack);
-	if (ret)
-		return ret;
+	if (update_node) {
+		/* For newly created node scope shaper, the following will
+		 * update the handle, due to id allocation.
+		 */
+		ret = net_shaper_pre_insert(binding, &node->handle, extack);
+		if (ret)
+			return ret;
+	}
 
 	for (i = 0; i < leaves_count; ++i) {
 		leaf_handle = leaves[i].handle;
@@ -864,7 +867,8 @@ static int __net_shaper_group(struct net_shaper_binding *binding,
 	 */
 	if (new_node && parent)
 		parent->leaves++;
-	net_shaper_commit(binding, 1, node);
+	if (update_node)
+		net_shaper_commit(binding, 1, node);
 	net_shaper_commit(binding, leaves_count, leaves);
 	return 0;
 
@@ -873,6 +877,64 @@ static int __net_shaper_group(struct net_shaper_binding *binding,
 	return ret;
 }
 
+static int net_shaper_pre_del_node(struct net_shaper_binding *binding,
+				   const struct net_shaper *shaper,
+				   struct netlink_ext_ack *extack)
+{
+	struct net_shaper_hierarchy *hierarchy = net_shaper_hierarchy(binding);
+	struct net_shaper *cur, *leaves, node = {};
+	int ret, leaves_count = 0;
+	unsigned long index;
+	bool update_node;
+
+	if (!shaper->leaves)
+		return 0;
+
+	/* Fetch the new node information. */
+	node.handle = shaper->parent;
+	cur = net_shaper_lookup(binding, &node.handle);
+	if (cur) {
+		node = *cur;
+	} else {
+		/* A scope NODE shaper can be nested only to the NETDEV scope
+		 * shaper without creating the latter, this check may fail only
+		 * if the data is in inconsistent status.
+		 */
+		if (WARN_ON_ONCE(node.handle.scope != NET_SHAPER_SCOPE_NETDEV))
+			return -EINVAL;
+	}
+
+	leaves = kcalloc(shaper->leaves, sizeof(struct net_shaper),
+			 GFP_KERNEL);
+	if (!leaves)
+		return -ENOMEM;
+
+	/* Build the leaves arrays. */
+	xa_for_each(&hierarchy->shapers, index, cur) {
+		if (net_shaper_handle_cmp(&cur->parent, &shaper->handle))
+			continue;
+
+		if (WARN_ON_ONCE(leaves_count == shaper->leaves)) {
+			ret = -EINVAL;
+			goto free;
+		}
+
+		leaves[leaves_count++] = *cur;
+	}
+
+	/* When re-linking to the netdev shaper, avoid the eventual, implicit,
+	 * creation of the new node, would be surprising since the user is
+	 * doing a delete operation.
+	 */
+	update_node = node.handle.scope != NET_SHAPER_SCOPE_NETDEV;
+	ret = __net_shaper_group(binding, update_node, leaves_count,
+				 leaves, &node, extack);
+
+free:
+	kfree(leaves);
+	return ret;
+}
+
 int net_shaper_nl_delete_doit(struct sk_buff *skb, struct genl_info *info)
 {
 	struct net_shaper_hierarchy *hierarchy;
@@ -905,9 +967,9 @@ int net_shaper_nl_delete_doit(struct sk_buff *skb, struct genl_info *info)
 	}
 
 	if (handle.scope == NET_SHAPER_SCOPE_NODE) {
-		/* TODO: implement support for scope NODE delete. */
-		ret = -EINVAL;
-		goto unlock;
+		ret = net_shaper_pre_del_node(binding, shaper, info->extack);
+		if (ret)
+			goto unlock;
 	}
 
 	ret = __net_shaper_delete(binding, shaper, info->extack);
@@ -1027,7 +1089,7 @@ int net_shaper_nl_group_doit(struct sk_buff *skb, struct genl_info *info)
 		}
 	}
 
-	ret = __net_shaper_group(binding, leaves_count, leaves, &node,
+	ret = __net_shaper_group(binding, true, leaves_count, leaves, &node,
 				 info->extack);
 	if (ret)
 		goto free_msg;