Re: [PATCH 05/20] dbus: Add message filter logic in dbus-filter.c

[Denis Kenzior <denkenz@gmail.com>]

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Hi Andrew,

On 03/13/2016 10:41 PM, Andrew Zaborowski wrote:
> This will be used for the public API for adding and removing signal
> callbacks.
> ---
>   Makefile.am        |   1 +
>   ell/dbus-filter.c  | 358 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>   ell/dbus-private.h |  31 +++++
>   ell/dbus.h         |  13 ++
>   4 files changed, 403 insertions(+)
>   create mode 100644 ell/dbus-filter.c
>
> diff --git a/Makefile.am b/Makefile.am
> index 256b163..7283a7e 100644
> --- a/Makefile.am
> +++ b/Makefile.am
> @@ -75,6 +75,7 @@ ell_libell_la_SOURCES = $(linux_headers) \
>   			ell/dbus-message.c \
>   			ell/dbus-util.c \
>   			ell/dbus-service.c \
> +			ell/dbus-filter.c \
>   			ell/gvariant-private.h \
>   			ell/gvariant-util.c \
>   			ell/siphash-private.h \
> diff --git a/ell/dbus-filter.c b/ell/dbus-filter.c
> new file mode 100644
> index 0000000..2541374
> --- /dev/null
> +++ b/ell/dbus-filter.c
> @@ -0,0 +1,358 @@
> +/*
> + *
> + *  Embedded Linux library
> + *
> + *  Copyright (C) 2011-2014  Intel Corporation. All rights reserved.

Please make sure you update the header when copy-pasting the files :)

> + *
> + *  This library is free software; you can redistribute it and/or
> + *  modify it under the terms of the GNU Lesser General Public
> + *  License as published by the Free Software Foundation; either
> + *  version 2.1 of the License, or (at your option) any later version.
> + *
> + *  This library is distributed in the hope that it will be useful,
> + *  but WITHOUT ANY WARRANTY; without even the implied warranty of
> + *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> + *  Lesser General Public License for more details.
> + *
> + *  You should have received a copy of the GNU Lesser General Public
> + *  License along with this library; if not, write to the Free Software
> + *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
> + *
> + */
> +
> +#ifdef HAVE_CONFIG_H
> +#include <config.h>
> +#endif
> +
> +#define _GNU_SOURCE
> +#include <stdlib.h>
> +#include <stdio.h>
> +
> +#include "util.h"
> +#include "queue.h"
> +#include "hashmap.h"
> +#include "string.h"
> +#include "dbus.h"
> +#include "dbus-private.h"
> +#include "gvariant-private.h"
> +#include "private.h"
> +
> +#define NODE_TYPE_CALLBACK	L_DBUS_MATCH_NONE
> +
> +struct filter_node {
> +	enum l_dbus_match_type type;
> +	union {
> +		struct {
> +			char *value;
> +			struct filter_node *children;
> +			bool remote_rule;
> +		} match;
> +		struct {
> +			l_dbus_message_func_t func;
> +			void *user_data;
> +		} callback;
> +	};
> +	unsigned int id;
> +	struct filter_node *next;
> +};
> +
> +struct _dbus_filter {
> +	struct l_dbus *dbus;
> +	struct filter_node *root;
> +	unsigned int signal_id;
> +	unsigned int last_id;
> +	const struct _dbus_filter_ops *driver;
> +};
> +
> +static void filter_subtree_free(struct filter_node *node)
> +{
> +	struct filter_node *child, *next;
> +
> +	if (node->type == NODE_TYPE_CALLBACK) {
> +		l_free(node);
> +		return;
> +	}
> +
> +	next = node->match.children;
> +
> +	l_free(node->match.value);
> +	l_free(node);
> +
> +	while (next) {
> +		child = next;
> +		next = child->next;
> +
> +		filter_subtree_free(child);
> +	}
> +}
> +
> +static void dbus_filter_destroy(void *data)
> +{
> +	struct _dbus_filter *filter = data;
> +
> +	if (filter->root)
> +		filter_subtree_free(filter->root);
> +
> +	l_free(filter);
> +}
> +
> +static void filter_dispatch_match_recurse(struct _dbus_filter *filter,
> +						struct filter_node *node,
> +						struct l_dbus_message *message)
> +{
> +	const char *value = NULL;
> +	struct filter_node *child;
> +
> +	switch ((int) node->type) {
> +	case NODE_TYPE_CALLBACK:
> +		node->callback.func(message, node->callback.user_data);
> +		return;
> +
> +	case L_DBUS_MATCH_SENDER:
> +		value = l_dbus_message_get_sender(message);
> +		break;
> +
> +	case L_DBUS_MATCH_DESTINATION:
> +		value = l_dbus_message_get_destination(message);
> +		break;
> +
> +	case L_DBUS_MATCH_TYPE:
> +		value = _dbus_message_get_type_as_string(message);
> +		break;
> +
> +	case L_DBUS_MATCH_PATH:
> +		value = l_dbus_message_get_path(message);
> +		break;
> +
> +	case L_DBUS_MATCH_INTERFACE:
> +		value = l_dbus_message_get_interface(message);
> +		break;
> +
> +	case L_DBUS_MATCH_MEMBER:
> +		value = l_dbus_message_get_member(message);
> +		break;
> +
> +	case L_DBUS_MATCH_ARG0...(L_DBUS_MATCH_ARG0 + 63):
> +		value = _dbus_message_get_nth_string_argument(message,
> +						node->type - L_DBUS_MATCH_ARG0);
> +		break;
> +	}
> +
> +	if (!value)
> +		return;
> +
> +	if (strcmp(value, node->match.value))
> +		return;
> +
> +	for (child = node->match.children; child; child = child->next)
> +		filter_dispatch_match_recurse(filter, child, message);
> +}
> +
> +void _dbus_filter_dispatch(struct l_dbus_message *message, void *user_data)
> +{
> +	struct _dbus_filter *filter = user_data;
> +
> +	filter_dispatch_match_recurse(filter, filter->root, message);
> +}
> +
> +struct _dbus_filter *_dbus_filter_new(struct l_dbus *dbus,
> +					const struct _dbus_filter_ops *driver)
> +{
> +	struct _dbus_filter *filter;
> +
> +	filter = l_new(struct _dbus_filter, 1);
> +
> +	filter->dbus = dbus;
> +	filter->driver = driver;
> +
> +	if (!filter->driver->skip_register)
> +		filter->signal_id = l_dbus_register(dbus, _dbus_filter_dispatch,
> +							filter,
> +							dbus_filter_destroy);
> +
> +	return filter;
> +}
> +
> +void _dbus_filter_free(struct _dbus_filter *filter)
> +{
> +	if (!filter)
> +		return;
> +
> +	if (!filter->driver->skip_register)
> +		l_dbus_unregister(filter->dbus, filter->signal_id);
> +	else
> +		dbus_filter_destroy(filter);
> +}
> +
> +static int condition_compare(const void *a, const void *b)
> +{
> +	const struct _dbus_filter_condition *condition_a = a, *condition_b = b;
> +
> +	return condition_a->type - condition_b->type;
> +}
> +
> +unsigned int _dbus_filter_add_rule(struct _dbus_filter *filter,
> +					struct _dbus_filter_condition *rule,
> +					int rule_len,
> +					l_dbus_message_func_t signal_func,
> +					void *user_data)
> +{
> +	struct filter_node **node_ptr = &filter->root;
> +	struct filter_node *node;
> +	struct filter_node *parent = filter->root;
> +	bool remote_rule = false;
> +	struct _dbus_filter_condition *condition, *end = rule + rule_len;
> +
> +	qsort(rule, rule_len, sizeof(*rule), condition_compare);
> +
> +	for (condition = rule; condition < end; condition++) {
> +		/* See if this condition is already a child of the node */
> +		while (*node_ptr) {
> +			node = *node_ptr;
> +
> +			if (node->type == condition->type &&
> +					!strcmp(node->match.value,
> +						condition->value))
> +				break;
> +
> +			node_ptr = &node->next;
> +		}
> +
> +		/* Add one */
> +		if (!*node_ptr) {
> +			node = l_new(struct filter_node, 1);
> +			node->type = condition->type;
> +			node->match.value = l_strdup(condition->value);
> +
> +			*node_ptr = node;
> +		}
> +
> +		node_ptr = &node->match.children;
> +
> +		parent = node;
> +
> +		/*
> +		 * Only have to call AddMatch if none of the parent nodes
> +		 * have yet created an AddMatch rule on the server.
> +		 */
> +		remote_rule |= node->match.remote_rule;
> +	}
> +
> +	node = l_new(struct filter_node, 1);
> +	node->type = NODE_TYPE_CALLBACK;
> +	node->callback.func = signal_func;
> +	node->callback.user_data = user_data;
> +	node->id = ++filter->last_id;
> +	node->next = *node_ptr;
> +
> +	if (!remote_rule) {
> +		if (!filter->driver->add_match(filter->dbus, node->id,
> +						rule, rule_len)) {
> +			l_free(node);
> +			return 0;
> +		}
> +
> +		parent->id = node->id;
> +		parent->match.remote_rule = true;
> +	}
> +
> +	*node_ptr = node;
> +
> +	return node->id;
> +}
> +
> +static bool remove_recurse(struct _dbus_filter *filter,
> +				struct filter_node **node, unsigned int id)
> +{
> +	struct filter_node *tmp;
> +
> +	for (; *node; node = &(*node)->next) {
> +		if ((*node)->type == NODE_TYPE_CALLBACK && (*node)->id == id)
> +			break;
> +
> +		if ((*node)->type != NODE_TYPE_CALLBACK &&
> +				remove_recurse(filter, &(*node)->match.children,
> +						id))
> +			break;
> +	}
> +
> +	if (!*node)
> +		return false;
> +
> +	if ((*node)->type == NODE_TYPE_CALLBACK || !(*node)->match.children) {
> +		tmp = *node;
> +		*node = tmp->next;
> +
> +		if (tmp->match.remote_rule)
> +			filter->driver->remove_match(filter->dbus, tmp->id);
> +
> +		filter_subtree_free(tmp);
> +	}
> +
> +	return true;
> +}
> +
> +bool _dbus_filter_remove_rule(struct _dbus_filter *filter, unsigned int id)
> +{
> +	return remove_recurse(filter, &filter->root, id);
> +}
> +
> +char *_dbus_filter_rule_to_str(const struct _dbus_filter_condition *rule,
> +				int rule_len)
> +{
> +	struct l_string *str = l_string_new(63);
> +	char *key, arg_buf[6];
> +	const char *value, *endp;
> +
> +	for (; rule_len; rule++, rule_len--) {
> +		switch ((int) rule->type) {
> +		case L_DBUS_MATCH_SENDER:
> +			key = "sender";
> +			break;
> +		case L_DBUS_MATCH_DESTINATION:
> +			key = "destination";
> +			break;
> +		case L_DBUS_MATCH_TYPE:
> +			key = "type";
> +			break;
> +		case L_DBUS_MATCH_PATH:
> +			key = "path";
> +			break;
> +		case L_DBUS_MATCH_INTERFACE:
> +			key = "interface";
> +			break;
> +		case L_DBUS_MATCH_MEMBER:
> +			key = "member";
> +			break;
> +		case L_DBUS_MATCH_ARG0...(L_DBUS_MATCH_ARG0 + 63):
> +			key = arg_buf;
> +			snprintf(arg_buf, sizeof(arg_buf), "arg%i",
> +					rule->type - L_DBUS_MATCH_ARG0);
> +			break;
> +		default:
> +			l_string_free(str, true);
> +			return NULL;
> +		}
> +
> +		l_string_append(str, key);
> +		l_string_append(str, "='");
> +
> +		/* We only need to escape single-quotes in the values */
> +		value = rule->value;
> +
> +		while ((endp = strchr(value, '\''))) {
> +			l_string_append_fixed(str, value, endp - value);
> +			l_string_append(str, "'\\''");
> +
> +			value = endp + 1;
> +		}
> +
> +		l_string_append(str, value);
> +		l_string_append_c(str, '\'');
> +
> +		if (rule_len > 1)
> +			l_string_append_c(str, ',');
> +	}
> +
> +	return l_string_free(str, false);
> +}
> diff --git a/ell/dbus-private.h b/ell/dbus-private.h
> index 607fdf4..d4a4782 100644
> --- a/ell/dbus-private.h
> +++ b/ell/dbus-private.h
> @@ -64,6 +64,9 @@ struct _dbus_property;
>   struct l_dbus_message_iter;
>   struct l_dbus_message;
>   struct l_dbus;
> +struct _dbus_filter;
> +struct _dbus_filter_condition;
> +struct _dbus_filter_ops;
>
>   void _dbus1_iter_init(struct l_dbus_message_iter *iter,
>   			struct l_dbus_message *message,
> @@ -241,6 +244,34 @@ uint8_t _dbus_get_version(struct l_dbus *dbus);
>   int _dbus_get_fd(struct l_dbus *dbus);
>   struct _dbus_object_tree *_dbus_get_tree(struct l_dbus *dbus);
>
> +struct _dbus_filter_condition {
> +	enum l_dbus_match_type type;
> +	const char *value;
> +};
> +
> +struct _dbus_filter_ops {
> +	bool skip_register;
> +	bool (*add_match)(struct l_dbus *bus, unsigned int id,
> +				const struct _dbus_filter_condition *rule,
> +				int rule_len);
> +	bool (*remove_match)(struct l_dbus *bus, unsigned int id);
> +};
> +
> +struct _dbus_filter *_dbus_filter_new(struct l_dbus *dbus,
> +					const struct _dbus_filter_ops *driver);
> +void _dbus_filter_free(struct _dbus_filter *filter);
> +
> +unsigned int _dbus_filter_add_rule(struct _dbus_filter *filter,
> +					struct _dbus_filter_condition *rule,
> +					int rule_len,
> +					l_dbus_message_func_t signal_func,
> +					void *user_data);
> +bool _dbus_filter_remove_rule(struct _dbus_filter *filter, unsigned int id);
> +
> +char *_dbus_filter_rule_to_str(const struct _dbus_filter_condition *rule,
> +				int rule_len);
> +void _dbus_filter_dispatch(struct l_dbus_message *message, void *user_data);
> +
>   struct dbus1_filter_data;
>
>   void _dbus1_filter_format_match(struct dbus1_filter_data *data, char *rule,
> diff --git a/ell/dbus.h b/ell/dbus.h
> index c8fdec1..24527e0 100644
> --- a/ell/dbus.h
> +++ b/ell/dbus.h
> @@ -42,6 +42,19 @@ enum l_dbus_bus {
>   	L_DBUS_SESSION_BUS,
>   };
>
> +enum l_dbus_match_type {
> +	L_DBUS_MATCH_NONE = 0,
> +	L_DBUS_MATCH_TYPE,
> +	L_DBUS_MATCH_SENDER,
> +	L_DBUS_MATCH_DESTINATION,

This is for eavesdropping?  Do we need this?

> +	L_DBUS_MATCH_PATH,
> +	L_DBUS_MATCH_INTERFACE,
> +	L_DBUS_MATCH_MEMBER,
> +	L_DBUS_MATCH_ARG0,
> +};
> +

Can we make this private in some way?

> +#define L_DBUS_MATCH_ARGUMENT(i)	(L_DBUS_MATCH_ARG0 + (i))
> +

It seems that l_dbus_match_type is only exposed for the sake of 
L_DBUS_MATCH_ARGUMENT() and L_DBUS_MATCH_NONE.

>   struct l_dbus;
>   struct l_dbus_interface;
>   struct l_dbus_message_builder;
>

Otherwise, this looks fine to me.

Regards,
-Denis