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policy: don't track roam_scan_done

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Don't determine a finished client scan based on whether the current node
has seen a beacon or not.

This works surprisingly bad on 5 GHz nodes, as clients may refuse to
perform active scanning on this frequency band. In case the clients does
refuse to scan the 5 GHz band but scans the 2.4 GHz band actively, we
might have a good indication about a better node on this band at least.

However, as the roam state-machine requires to have seen a probe request
from the client to direct him to a better node, thi process will not
continue, which either ends the node in being kicked due to exceeding
the number of max tries or the scan cooldown to kick in.

The solution to this is fairly simple: Don't track the roam_scan_done
state but instead just determine a better candidate after the scan
interval finished.

To ensure the indicated signal levels are as recent as 2 *
scan-interval, add a max_age parameter to find_better_candidate.

Signed-off-by: David Bauer <mail@david-bauer.net>
This commit is contained in:
David Bauer
2021-12-22 22:28:49 +01:00
parent 742236f30b
commit 022635c9bd
3 changed files with 39 additions and 25 deletions
Download Patch File Download Diff File Expand all files Collapse all files

61
policy.c
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@@ -110,7 +110,7 @@ is_better_candidate(struct sta_info *si_cur, struct sta_info *si_new)
}
static struct sta_info *
find_better_candidate(struct sta_info *si_ref, struct uevent *ev, uint32_t required_criteria)
find_better_candidate(struct sta_info *si_ref, struct uevent *ev, uint32_t required_criteria, uint64_t max_age)
{
struct sta_info *si;
struct sta *sta = si_ref->sta;
@@ -126,6 +126,9 @@ find_better_candidate(struct sta_info *si_ref, struct uevent *ev, uint32_t requi
if (strcmp(si->node->ssid, si_ref->node->ssid) != 0)
continue;
if (max_age && max_age < current_time - si->seen)
continue;
reasons = is_better_candidate(si_ref, si);
if (!reasons)
continue;
@@ -204,7 +207,7 @@ usteer_check_request(struct sta_info *si, enum usteer_event_type type)
goto out;
}
if (!find_better_candidate(si, &ev, UEV_SELECT_REASON_ALL))
if (!find_better_candidate(si, &ev, UEV_SELECT_REASON_ALL, 0))
goto out;
ev.reason = UEV_REASON_BETTER_CANDIDATE;
@@ -283,7 +286,7 @@ usteer_roam_sm_start_scan(struct sta_info *si, struct uevent *ev)
}
/* We are currently in scan timeout / cooldown.
* Check if we are in ROAM_TRIGGER_IDLE state and enter this stateif not.
* Check if we are in ROAM_TRIGGER_IDLE state. Enter this state if not.
*/
if (si->roam_state == ROAM_TRIGGER_IDLE)
return;
@@ -292,27 +295,47 @@ usteer_roam_sm_start_scan(struct sta_info *si, struct uevent *ev)
usteer_roam_set_state(si, ROAM_TRIGGER_IDLE, ev);
}
static bool
usteer_roam_sm_found_better_node(struct sta_info *si, struct uevent *ev, enum roam_trigger_state next_state)
{
uint64_t max_age = 2 * config.roam_scan_interval;
if (max_age > current_time - si->roam_scan_start)
max_age = current_time - si->roam_scan_start;
if (find_better_candidate(si, ev, (1 << UEV_SELECT_REASON_SIGNAL), max_age)) {
usteer_roam_set_state(si, next_state, ev);
return true;
}
return false;
}
static bool
usteer_roam_trigger_sm(struct sta_info *si)
{
struct uevent ev = {
.si_cur = si,
};
int min_signal;
uint64_t min_signal;
min_signal = usteer_snr_to_signal(si->node, config.roam_trigger_snr);
switch (si->roam_state) {
case ROAM_TRIGGER_SCAN:
if (!si->roam_tries) {
si->roam_scan_start = current_time;
}
/* Check if we've found a better node regardless of the scan-interval */
if (usteer_roam_sm_found_better_node(si, &ev, ROAM_TRIGGER_SCAN_DONE))
break;
/* Only scan every scan-interval */
if (current_time - si->roam_event < config.roam_scan_interval)
break;
if (find_better_candidate(si, &ev, (1 << UEV_SELECT_REASON_SIGNAL)) ||
si->roam_scan_done > si->roam_event) {
usteer_roam_set_state(si, ROAM_TRIGGER_SCAN_DONE, &ev);
break;
}
/* Check if no node was found within roam_scan_tries tries */
if (config.roam_scan_tries && si->roam_tries >= config.roam_scan_tries) {
if (!config.roam_scan_timeout) {
/* Prepare to kick client */
@@ -325,29 +348,21 @@ usteer_roam_trigger_sm(struct sta_info *si)
break;
}
/* Send beacon-request to client */
usteer_ubus_trigger_client_scan(si);
usteer_roam_sm_start_scan(si, &ev);
break;
case ROAM_TRIGGER_IDLE:
if (find_better_candidate(si, &ev, (1 << UEV_SELECT_REASON_SIGNAL))) {
usteer_roam_set_state(si, ROAM_TRIGGER_SCAN_DONE, &ev);
break;
}
usteer_roam_sm_start_scan(si, &ev);
break;
case ROAM_TRIGGER_SCAN_DONE:
/* Check for stale scan results, kick back to SCAN state if necessary */
if (current_time - si->roam_scan_done > 2 * config.roam_scan_interval) {
usteer_roam_sm_start_scan(si, &ev);
if (usteer_roam_sm_found_better_node(si, &ev, ROAM_TRIGGER_WAIT_KICK))
break;
}
if (find_better_candidate(si, &ev, (1 << UEV_SELECT_REASON_SIGNAL)))
usteer_roam_set_state(si, ROAM_TRIGGER_WAIT_KICK, &ev);
/* Kick back to SCAN state if candidate expired */
usteer_roam_sm_start_scan(si, &ev);
break;
case ROAM_TRIGGER_WAIT_KICK:
@@ -495,7 +510,7 @@ usteer_local_node_kick(struct usteer_local_node *ln)
if (is_more_kickable(kick1, si))
kick1 = si;
tmp = find_better_candidate(si, NULL, (1 << UEV_SELECT_REASON_LOAD));
tmp = find_better_candidate(si, NULL, (1 << UEV_SELECT_REASON_LOAD), 0);
if (!tmp)
continue;