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station: roam blacklist BSS's, and consider when roaming

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If the BSS is requesting IWD roam elsewhere add this BSS to the
blacklist using BLACKLIST_REASON_ROAM_REQUESTED. This will lower
the chances of IWD roaming/connecting back to this BSS in the
future.

This then allows IWD to consider this blacklist state when picking
a roam candidate. Its undesireable to fully ban a roam blacklisted
BSS, so some additional sorting logic has been added. Prior to
comparing based on rank, BSS's will be sorted into two higher level
groups:

Above Threshold - BSS is above the RoamThreshold
Below Threshold - BSS is below the RoamThreshold

Within each of these groups the BSS may be roam blacklisted which
will position it at the bottom of the list within its respecitve
group.
This commit is contained in:
James Prestwood 2025-03-28 07:42:49 -07:00 committed by Denis Kenzior
parent bf69e6210c
commit 224afbb9ca
1 changed files with 69 additions and 6 deletions
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75
src/station.c
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@ -155,6 +155,55 @@ struct anqp_entry {
uint32_t pending;
};
/*
* Rather than sorting BSS's purely based on ranking a higher level grouping
* is used. The purpose of this higher order grouping is the consider the BSS's
* roam blacklist status. The roam blacklist is a "soft" blacklist in that we
* still should connect to these BSS's if they are the only "good" option.
* The question here is: what makes a BSS "good" vs "bad".
*
* For an initial (probably naive) approach here we can use the
* RoamThreshold[5G] which indicates the signal level that would not
* be of an acceptable connection quality. BSS can then be sorted either
* above or below this threshold. Within each of these groups a BSS may be
* blacklisted, meaning it should get sorted lower on the list compared to
* others within the same group.
*
* This sorting is achieved by extending rank to a uint32_t where the first 16
* bits are the standard rank calculated by scan.c. Above that bits can be
* reserved for this higher level grouping:
*
* Bit 16 indicates the BSS is not blacklisted
* Bit 17 indicates the BSS is above the critical signal threshold
*/
#define ABOVE_THRESHOLD_BIT 17
#define NOT_BLACKLISTED_BIT 16
static uint32_t evaluate_bss_group_rank(const uint8_t *addr, uint32_t freq,
int16_t signal_strength, uint16_t rank)
{
int signal = signal_strength / 100;
bool roam_blacklist;
bool good_signal;
uint32_t rank_out = (uint32_t) rank;
if (blacklist_contains_bss(addr, BLACKLIST_REASON_CONNECT_FAILED))
return 0;
roam_blacklist = blacklist_contains_bss(addr,
BLACKLIST_REASON_ROAM_REQUESTED);
good_signal = signal >= netdev_get_low_signal_threshold(freq);
if (good_signal)
set_bit(&rank_out, ABOVE_THRESHOLD_BIT);
if (!roam_blacklist)
set_bit(&rank_out, NOT_BLACKLISTED_BIT);
return rank_out;
}
/*
* Used as entries for the roam list since holding scan_bss pointers directly
* from station->bss_list is not 100% safe due to the possibility of the
@ -162,13 +211,13 @@ struct anqp_entry {
*/
struct roam_bss {
uint8_t addr[6];
uint16_t rank;
uint32_t rank;
int32_t signal_strength;
bool ft_failed: 1;
};
static struct roam_bss *roam_bss_from_scan_bss(const struct scan_bss *bss,
uint16_t rank)
uint32_t rank)
{
struct roam_bss *rbss = l_new(struct roam_bss, 1);
@ -2805,7 +2854,7 @@ static bool station_roam_scan_notify(int err, struct l_queue *bss_list,
struct handshake_state *hs = netdev_get_handshake(station->netdev);
struct scan_bss *current_bss = station->connected_bss;
struct scan_bss *bss;
double cur_bss_rank = 0.0;
uint32_t cur_bss_group_rank = 0;
static const double RANK_FT_FACTOR = 1.3;
uint16_t mdid;
enum security orig_security, security;
@ -2834,10 +2883,15 @@ static bool station_roam_scan_notify(int err, struct l_queue *bss_list,
*/
bss = l_queue_find(bss_list, bss_match_bssid, current_bss->addr);
if (bss && !station->ap_directed_roaming) {
cur_bss_rank = bss->rank;
double cur_bss_rank = bss->rank;
if (hs->mde && bss->mde_present && l_get_le16(bss->mde) == mdid)
cur_bss_rank *= RANK_FT_FACTOR;
cur_bss_group_rank = evaluate_bss_group_rank(bss->addr,
bss->frequency,
bss->signal_strength,
(uint16_t) cur_bss_rank);
}
/*
@ -2859,6 +2913,7 @@ static bool station_roam_scan_notify(int err, struct l_queue *bss_list,
while ((bss = l_queue_pop_head(bss_list))) {
double rank;
struct roam_bss *rbss;
uint32_t group_rank;
station_print_scan_bss(bss);
@ -2889,7 +2944,11 @@ static bool station_roam_scan_notify(int err, struct l_queue *bss_list,
if (hs->mde && bss->mde_present && l_get_le16(bss->mde) == mdid)
rank *= RANK_FT_FACTOR;
if (rank <= cur_bss_rank)
group_rank = evaluate_bss_group_rank(bss->addr, bss->frequency,
bss->signal_strength,
(uint16_t) rank);
if (group_rank <= cur_bss_group_rank)
goto next;
/*
@ -2898,7 +2957,7 @@ static bool station_roam_scan_notify(int err, struct l_queue *bss_list,
*/
station_update_roam_bss(station, bss);
rbss = roam_bss_from_scan_bss(bss, rank);
rbss = roam_bss_from_scan_bss(bss, group_rank);
l_queue_insert(station->roam_bss_list, rbss,
roam_bss_rank_compare, NULL);
@ -3268,6 +3327,10 @@ static void station_ap_directed_roam(struct station *station,
l_timeout_remove(station->roam_trigger_timeout);
station->roam_trigger_timeout = NULL;
blacklist_add_bss(station->connected_bss->addr,
BLACKLIST_REASON_ROAM_REQUESTED);
station_debug_event(station, "ap-roam-blacklist-added");
if (req_mode & WNM_REQUEST_MODE_PREFERRED_CANDIDATE_LIST) {
l_debug("roam: AP sent a preferred candidate list");
station_neighbor_report_cb(station->netdev, 0, body + pos,