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datastorage: use signal strength as a metric

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This adds a few options to use the signal strength as a metric, band
dependent:

 - rssi_weight: every db of signal increases the score by this much.
 - rssi_center: if the signal is stronger than this, the score becomes
                positive; below this, it is negative.
 - initial_score:  since we are capping negative scores, it may be
   beneficial to have a positive base score to offset a possible
   negative signal value.  This is replacing the 'freq' metric.

To avoid a single-digit RSSI increase resulting in a kick, we add a
global threshold value to act as a buffer:

 - kicking_threshold: a candidate AP must have a score larger than that
                      of the current AP plus the value here.

The kicking_threshold also applies when assembling the list of roaming
neighbors we send with the "wnm_disassoc_imminent" command.

Signed-off-by: Eneas U de Queiroz <cotequeiroz@gmail.com>
This commit is contained in:
Eneas U de Queiroz 2021-08-04 09:11:06 -03:00 • committed by Polynomdivision
parent 14e0f8386c
commit c70773a171
6 changed files with 89 additions and 32 deletions
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75
src/storage/datastorage.c
View file

@ -434,12 +434,11 @@ int eval_probe_metric(struct probe_entry_s* probe_entry, ap* ap_entry) {
int band, score = 0;
// TODO: Should RCPI be used here as well?
// TODO: Should this be more scaled? Should -63dB on current and -77dB on other both score 0 if low / high are -80db and -60dB?
// TODO: That then lets device capabilites dominate score - making them more important than RSSI difference of 14dB.
band = get_band(probe_entry->freq);
score = dawn_metric.freq[band];
score = dawn_metric.initial_score[band];
score += probe_entry->signal >= dawn_metric.rssi_val[band] ? dawn_metric.rssi[band] : 0;
score += probe_entry->signal <= dawn_metric.low_rssi_val[band] ? dawn_metric.low_rssi[band] : 0;
score += (probe_entry->signal - dawn_metric.rssi_center[band]) * dawn_metric.rssi_weight[band];
// check if ap entry is available
if (ap_entry != NULL) {
@ -504,15 +503,14 @@ static int compare_station_count(ap* ap_entry_own, ap* ap_entry_to_compare, stru
return 0;
}
static struct kicking_nr *insert_kicking_nr(struct kicking_nr *nr_list, char *nr, int score) {
struct kicking_nr *new_entry;
static struct kicking_nr *find_position(struct kicking_nr *nrlist, int score) {
struct kicking_nr *ret = NULL;
if (!(new_entry = dawn_malloc(sizeof (struct kicking_nr))))
return NULL;
strncpy(new_entry->nr, nr, NEIGHBOR_REPORT_LEN);
new_entry->score = score;
new_entry->next = nr_list;
return new_entry;
while (nrlist && nrlist->score < score) {
ret = nrlist;
nrlist = nrlist->next;
}
return ret;
}
static void remove_kicking_nr_list(struct kicking_nr *nr_list) {
@ -525,6 +523,40 @@ static void remove_kicking_nr_list(struct kicking_nr *nr_list) {
}
}
static struct kicking_nr *prune_kicking_nr_list(struct kicking_nr *nr_list, int min_score) {
struct kicking_nr *next;
while (nr_list && nr_list->score <= min_score) {
next = nr_list->next;
dawn_free(nr_list);
nr_list = next;
}
return nr_list;
}
static struct kicking_nr *insert_kicking_nr(struct kicking_nr *head, char *nr, int score, bool prune) {
struct kicking_nr *new_entry, *pos;
if (prune)
head = prune_kicking_nr_list(head, score - dawn_metric.kicking_threshold);
// we are giving no error information here (not really critical)
if (!(new_entry = dawn_malloc(sizeof (struct kicking_nr))))
return head;
strncpy(new_entry->nr, nr, NEIGHBOR_REPORT_LEN);
new_entry->score = score;
pos = find_position(head, score);
if (pos) {
new_entry->next = pos->next;
pos -> next = new_entry;
} else {
new_entry->next = head;
head = new_entry;
}
return head;
}
int better_ap_available(ap *kicking_ap, struct dawn_mac client_mac, struct kicking_nr **neighbor_report) {
// This remains set to the current AP of client for rest of function
@ -577,7 +609,7 @@ int better_ap_available(ap *kicking_ap, struct dawn_mac client_mac, struct kicki
int score_to_compare = eval_probe_metric(i, candidate_ap);
// Find better score...
if (score_to_compare > max_score) {
if (score_to_compare > max_score + (kick ? 0 : dawn_metric.kicking_threshold)) {
if(neighbor_report == NULL)
{
fprintf(stderr,"Neighbor-Report is NULL!\n");
@ -586,15 +618,14 @@ int better_ap_available(ap *kicking_ap, struct dawn_mac client_mac, struct kicki
kick = 1;
// instead of returning we create a neighbor report list...
remove_kicking_nr_list(*neighbor_report);
*neighbor_report = insert_kicking_nr(NULL, candidate_ap->neighbor_report, score_to_compare);
// instead of returning we add the ap to the neighbor report list, pruning it first...
*neighbor_report = insert_kicking_nr(*neighbor_report, candidate_ap->neighbor_report, score_to_compare, true);
max_score = score_to_compare;
}
// if ap have same value but station count is different...
// TODO: Is absolute number meaningful when AP have diffeent capacity?
else if (dawn_metric.use_station_count > 0 && score_to_compare == max_score ) {
else if (dawn_metric.use_station_count > 0 && score_to_compare >= max_score ) {
int compare = compare_station_count(kicking_ap, candidate_ap, client_mac);
if (compare > 0) {
@ -605,15 +636,17 @@ int better_ap_available(ap *kicking_ap, struct dawn_mac client_mac, struct kicki
}
kick = 1;
remove_kicking_nr_list(*neighbor_report);
*neighbor_report = insert_kicking_nr(NULL, candidate_ap->neighbor_report, score_to_compare);
*neighbor_report = insert_kicking_nr(*neighbor_report, candidate_ap->neighbor_report,
score_to_compare, true);
}
else if (compare == 0 && kick) {
*neighbor_report = insert_kicking_nr(*neighbor_report, candidate_ap->neighbor_report, score_to_compare);
*neighbor_report = insert_kicking_nr(*neighbor_report, candidate_ap->neighbor_report,
score_to_compare, false);
}
}
else if (score_to_compare == max_score && kick) {
*neighbor_report = insert_kicking_nr(*neighbor_report, candidate_ap->neighbor_report, score_to_compare);
else if (score_to_compare >= max_score && kick) {
*neighbor_report = insert_kicking_nr(*neighbor_report, candidate_ap->neighbor_report,
score_to_compare, false);
}
i = i->next_probe;