gluon-packages/net/respondd-module-airtime/src/airtime.c

/*
  Copyright (c) 2016, Julian Kornberger <jk+freifunk@digineo.de>
                      Martin Müller <geno+ffhb@fireorbit.de>
                      Jan-Philipp Litza <janphilipp@litza.de>
  All rights reserved.

  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions are met:

    1. Redistributions of source code must retain the above copyright notice,
       this list of conditions and the following disclaimer.
    2. Redistributions in binary form must reproduce the above copyright notice,
       this list of conditions and the following disclaimer in the documentation
       and/or other materials provided with the distribution.

  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
  FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

#include <linux/nl80211.h>
#include <netlink/genl/genl.h>

#include "netlink.h"
#include "airtime.h"

/*
 * Excerpt from nl80211.h:
 * enum nl80211_survey_info - survey information
 *
 * These attribute types are used with %NL80211_ATTR_SURVEY_INFO
 * when getting information about a survey.
 *
 * @__NL80211_SURVEY_INFO_INVALID: attribute number 0 is reserved
 * @NL80211_SURVEY_INFO_FREQUENCY: center frequency of channel
 * @NL80211_SURVEY_INFO_NOISE: noise level of channel (u8, dBm)
 * @NL80211_SURVEY_INFO_IN_USE: channel is currently being used
 * @NL80211_SURVEY_INFO_CHANNEL_TIME: amount of time (in ms) that the radio
 *	spent on this channel
 * @NL80211_SURVEY_INFO_CHANNEL_TIME_BUSY: amount of the time the primary
 *	channel was sensed busy (either due to activity or energy detect)
 * @NL80211_SURVEY_INFO_CHANNEL_TIME_EXT_BUSY: amount of time the extension
 *	channel was sensed busy
 * @NL80211_SURVEY_INFO_CHANNEL_TIME_RX: amount of time the radio spent
 *	receiving data
 * @NL80211_SURVEY_INFO_CHANNEL_TIME_TX: amount of time the radio spent
 *	transmitting data
 * @NL80211_SURVEY_INFO_MAX: highest survey info attribute number
 *	currently defined
 * @__NL80211_SURVEY_INFO_AFTER_LAST: internal use
 */

static const char *const msg_names[NL80211_SURVEY_INFO_MAX + 1] = {
	[NL80211_SURVEY_INFO_FREQUENCY] = "frequency",
	[NL80211_SURVEY_INFO_CHANNEL_TIME] = "active",
	[NL80211_SURVEY_INFO_CHANNEL_TIME_BUSY] = "busy",
	[NL80211_SURVEY_INFO_CHANNEL_TIME_RX] = "rx",
	[NL80211_SURVEY_INFO_CHANNEL_TIME_TX] = "tx",
	[NL80211_SURVEY_INFO_NOISE] = "noise",
};

static int survey_airtime_handler(struct nl_msg *msg, void *arg) {
	struct json_object **result = arg;
	struct json_object *freq_json = NULL;

	struct genlmsghdr *gnlh = nlmsg_data(nlmsg_hdr(msg));
	struct nlattr *survey_info = nla_find(genlmsg_attrdata(gnlh, 0), genlmsg_attrlen(gnlh, 0), NL80211_ATTR_SURVEY_INFO);

	if (*result) {
		fprintf(stderr, "respondd-module-airtime: callback called again after NL_STOP\n");
		return NL_STOP;
	}

	if (!survey_info) {
		fprintf(stderr, "respondd-module-airtime: survey data missing in netlink message\n");
		return NL_STOP;
	}

	freq_json = json_object_new_object();
	if (!freq_json) {
		fprintf(stderr, "respondd-module-airtime: failed allocating JSON object\n");
		return NL_STOP;
	}

	// This variable counts the number of required attributes that are
	// found in the message and is afterwards checked against the number of
	// required attributes.
	unsigned int req_fields = 0;

	int rem;
	struct nlattr *nla;
	nla_for_each_nested(nla, survey_info, rem) {
		int type = nla_type(nla);

		if (type > NL80211_SURVEY_INFO_MAX)
			continue;

		switch (type) {
			// these are the required fields
			case NL80211_SURVEY_INFO_IN_USE:
			case NL80211_SURVEY_INFO_FREQUENCY:
			case NL80211_SURVEY_INFO_CHANNEL_TIME:
				req_fields++;
		}

		if (!msg_names[type])
			continue;

		struct json_object *data_json = NULL;
		switch (nla_len(nla)) {
			case sizeof(uint64_t):
				data_json = json_object_new_int64(nla_get_u64(nla));
				break;
			case sizeof(uint32_t):
				data_json = json_object_new_int(nla_get_u32(nla));
				break;
			case sizeof(uint8_t):
				if (type == NL80211_SURVEY_INFO_NOISE)
					data_json = json_object_new_int((int8_t)nla_get_u8(nla));
				else
					data_json = json_object_new_int(nla_get_u8(nla));
				break;
			default:
				fprintf(stderr, "respondd-module-airtime: Unexpected NL attribute length: %d\n", nla_len(nla));
		}

		if (data_json)
			json_object_object_add(freq_json, msg_names[type], data_json);
	}

	/* The kernel didn't report all required fields: continue with next
	 * record, this entry was off-channel */
	if (req_fields != 3) {
		json_object_put(freq_json);
		return NL_OK;
	}

	*result = freq_json;
	return NL_STOP;
}

struct json_object * get_airtime(int ifx) {
	struct json_object *result = NULL;
	nl_send_dump(survey_airtime_handler, &result, NL80211_CMD_GET_SURVEY, ifx);
	return result;
}