Re: [PATCH 2/6] station: move BasicServiceSet DBus management into station

[Denis Kenzior <denkenz@gmail.com>]

Hi James,

On 8/16/24 7:52 AM, James Prestwood wrote:
> Due to an unnoticed bug after adding the BasicServiceSet object into
> network, it became clear that since station already owns the scan_bss
> objects it makes sense for it to manage the associated DBus objects
> as well. This way network doesn't have to jump through hoops to
> determine if the scan_bss object was remove, added, or updated. It
> can just manage its list as it did prior.
> 
>  From the station side this makes things very easy. When scan results
> come in we either update or add a new DBus object. And any time a
> scan_bss is freed we remove the DBus object.
> ---
>   src/station.c | 89 +++++++++++++++++++++++++++++++++++++++++----------
>   1 file changed, 72 insertions(+), 17 deletions(-)
> 

<snip>

> @@ -431,6 +429,65 @@ static void station_print_scan_bss(const struct scan_bss *bss)
>   			optional);
>   }
>   
> +static const char *station_get_bss_path(struct station *station,
> +						struct scan_bss *bss)
> +{
> +	enum security security;
> +	char ssid[33];
> +	const char *network_path;
> +
> +	memcpy(ssid, bss->ssid, bss->ssid_len);
> +	ssid[bss->ssid_len] = '\0';
> +
> +	if (scan_bss_get_security(bss, &security) < 0)
> +		return NULL;
> +
> +	network_path = iwd_network_get_path(station, ssid, security);
> +	if (!network_path)
> +		return NULL;
> +
> +	return __network_path_append_bss(network_path, bss);
> +}
> +
> +static bool station_unregister_bss(struct station *station,
> +					struct scan_bss *bss)
> +{
> +	const char *path = station_get_bss_path(station, bss);
> +
> +	if (L_WARN_ON(!path))
> +		return false;
> +
> +	return l_dbus_unregister_object(dbus_get_bus(), path);
> +}
> +
> +static bool station_register_bss(struct station *station, struct scan_bss *bss)
> +{
> +	struct scan_bss *old;
> +	const char *path = station_get_bss_path(station, bss);
> +
> +	if (L_WARN_ON(!path))
> +		return false;
> +
> +	/*
> +	 * If we find this path in the object tree update the data to the new
> +	 * scan_bss pointer, as this one will be freed soon.
> +	 */
> +	old = l_dbus_object_get_data(dbus_get_bus(), path, IWD_BSS_INTERFACE);
> +	if (old)
> +		return l_dbus_object_set_data(dbus_get_bus(), path,
> +						IWD_BSS_INTERFACE, bss);
> +
> +	if (!l_dbus_object_add_interface(dbus_get_bus(), path,
> +						IWD_BSS_INTERFACE, bss))
> +		return false;
> +
> +	if (!l_dbus_object_add_interface(dbus_get_bus(), path,
> +					L_DBUS_INTERFACE_PROPERTIES, bss))
> +		return false;
> +
> +	return true;
> +}
> +
>   /*
>    * Returns the network object the BSS was added to or NULL if ignored.
>    */
> @@ -518,6 +575,7 @@ static struct network *station_add_seen_bss(struct station *station,
>   	}
>   
>   	network_bss_add(network, bss);
> +	station_register_bss(station, bss);

Hmm, you have the network object right above?  Can you utilize that somehow?

>   
>   	return network;
>   }
> @@ -540,7 +598,7 @@ struct bss_expiration_data {
>   	struct scan_bss *connected_bss;
>   	uint64_t now;
>   	const struct scan_freq_set *freqs;
> -	struct l_queue *free_list;
> +	struct station *station;
>   };
>   
>   #define SCAN_RESULT_BSS_RETENTION_TIME (30 * 1000000)
> @@ -562,20 +620,21 @@ static bool bss_free_if_expired(void *data, void *user_data)
>   			bss->time_stamp + SCAN_RESULT_BSS_RETENTION_TIME))
>   		return false;
>   
> -	l_queue_push_head(expiration_data->free_list, bss);
> +	station_unregister_bss(expiration_data->station, bss);
> +
> +	scan_bss_free(bss);
>   
>   	return true;
>   }
>   
>   static void station_bss_list_remove_expired_bsses(struct station *station,
> -					const struct scan_freq_set *freqs,
> -					struct l_queue *free_list)
> +					const struct scan_freq_set *freqs)
>   {
>   	struct bss_expiration_data data = {
>   		.now = l_time_now(),
>   		.connected_bss = station->connected_bss,
>   		.freqs = freqs,
> -		.free_list = free_list,
> +		.station = station,
>   	};
>   
>   	l_queue_foreach_remove(station->bss_list, bss_free_if_expired, &data);
> @@ -823,6 +882,7 @@ static bool station_owe_transition_results(int err, struct l_queue *bss_list,
>   
>   		l_queue_push_tail(station->bss_list, bss);
>   		network_bss_add(network, bss);
> +		station_register_bss(station, bss);

Same comment as above.

>   
>   		continue;
>   
> @@ -951,7 +1011,6 @@ void station_set_scan_results(struct station *station,
>   	const struct l_queue_entry *bss_entry;
>   	struct network *network;
>   	struct process_network_data data;
> -	struct l_queue *free_list = l_queue_new();
>   
>   	l_queue_foreach_remove(new_bss_list, bss_free_if_ssid_not_utf8, NULL);
>   
> @@ -963,7 +1022,7 @@ void station_set_scan_results(struct station *station,
>   	l_queue_destroy(station->autoconnect_list, NULL);
>   	station->autoconnect_list = NULL;
>   
> -	station_bss_list_remove_expired_bsses(station, freqs, free_list);
> +	station_bss_list_remove_expired_bsses(station, freqs);
>   
>   	for (bss_entry = l_queue_get_entries(station->bss_list); bss_entry;
>   						bss_entry = bss_entry->next) {
> @@ -975,12 +1034,8 @@ void station_set_scan_results(struct station *station,
>   			if (old_bss == station->connected_bss)
>   				station->connected_bss = new_bss;
>   
> -			/*
> -			 * The network object is still holding a reference to
> -			 * the BSS. Until we tell network to replace the BSS
> -			 * with a new object, don't free it.
> -			 */
> -			l_queue_push_head(free_list, old_bss);
> +			station_register_bss(station, new_bss);

Why do this here?  Can't you do this step in the loop below where we figure out 
the network object?

> +			scan_bss_free(old_bss);
>   
>   			continue;
>   		}
> @@ -1017,8 +1072,6 @@ void station_set_scan_results(struct station *station,
>   
>   	l_hashmap_foreach_remove(station->networks, process_network, &data);
>   
> -	l_queue_destroy(free_list, bss_free);
> -
>   	station->autoconnect_can_start = trigger_autoconnect;
>   	station_autoconnect_start(station);
>   }
> @@ -2652,6 +2705,7 @@ static void station_update_roam_bss(struct station *station,
>   		l_queue_remove_if(station->bss_list, bss_match, bss);
>   
>   	network_bss_update(network, bss);
> +	station_register_bss(station, bss);

Same here, can we use the network object somehow?

>   	l_queue_push_tail(station->bss_list, bss);
>   
>   	if (old)
> @@ -3160,6 +3214,7 @@ static void station_event_roamed(struct station *station, struct scan_bss *new)
>   	struct scan_bss *stale;
>   
>   	network_bss_update(station->connected_network, new);
> +	station_register_bss(station, new);

And here

>   
>   	/* Remove new BSS if it exists in past scan results */
>   	stale = l_queue_remove_if(station->bss_list, bss_match, new);

Regards,
-Denis