[PATCH 2/2] supplicant: Allow limiting number of concurrent associations.

[greearb at candelatech.com]

From: Ben Greear <greearb at candelatech.com>

When using lots of virtual clients, it may be useful to
limit the number that attempt to connect to the AP at
once.  Limitting the associations per scan response is
an easy way to do this.

Signed-hostap: Ben Greear <greearb at candelatech.com>
Signed-off-by: Ben Greear <greearb at candelatech.com>
---
 wpa_supplicant/config.c |    2 ++
 wpa_supplicant/config.h |    7 +++++++
 wpa_supplicant/events.c |   21 +++++++++++++++++++++
 3 files changed, 30 insertions(+), 0 deletions(-)

diff --git a/wpa_supplicant/config.c b/wpa_supplicant/config.c
index cb5748d..a4e3d16 100644
--- a/wpa_supplicant/config.c
+++ b/wpa_supplicant/config.c
@@ -2610,6 +2610,7 @@ struct wpa_config * wpa_config_alloc_empty(const char *ctrl_interface,
 	config->wmm_ac_params[2] = ac_vi;
 	config->wmm_ac_params[3] = ac_vo;
 	config->min_scan_gap = DEFAULT_MIN_SCAN_GAP;
+	config->max_assoc_per_scan = DEFAULT_MAX_ASSOC_PER_SCAN;
 
 	if (ctrl_interface)
 		config->ctrl_interface = os_strdup(ctrl_interface);
@@ -2983,6 +2984,7 @@ static const struct global_parse_data global_fields[] = {
 	{ INT(dot11RSNAConfigPMKReauthThreshold), 0 },
 	{ INT(dot11RSNAConfigSATimeout), 0 },
 	{ INT(min_scan_gap), 0 },
+	{ INT(max_assoc_per_scan), 0 },
 #ifndef CONFIG_NO_CONFIG_WRITE
 	{ INT(update_config), 0 },
 #endif /* CONFIG_NO_CONFIG_WRITE */
diff --git a/wpa_supplicant/config.h b/wpa_supplicant/config.h
index 4e972cb..d6723c6 100644
--- a/wpa_supplicant/config.h
+++ b/wpa_supplicant/config.h
@@ -25,6 +25,7 @@
 #define DEFAULT_MAX_NUM_STA 128
 #define DEFAULT_ACCESS_NETWORK_TYPE 15
 #define DEFAULT_MIN_SCAN_GAP 0
+#define DEFAULT_MAX_ASSOC_PER_SCAN 25
 
 #include "config_ssid.h"
 #include "wps/wps.h"
@@ -650,6 +651,12 @@ struct wpa_config {
 	/* Minimum interval between scan requests, in seconds */
 	int min_scan_gap;
 
+	/* Maximum number of association requests per scan results
+	 * This can be used to stop a thundering herd of hundreds of
+	 * virtual stations from all trying to associate at once.
+	 */
+	int max_assoc_per_scan;
+
 	/**
 	 * interworking - Whether Interworking (IEEE 802.11u) is enabled
 	 */
diff --git a/wpa_supplicant/events.c b/wpa_supplicant/events.c
index 9132414..7c3a957 100644
--- a/wpa_supplicant/events.c
+++ b/wpa_supplicant/events.c
@@ -62,6 +62,8 @@ static int wpas_temp_disabled(struct wpa_supplicant *wpa_s,
 }
 
 
+static int num_assoc_reqs;
+
 static int wpa_supplicant_select_config(struct wpa_supplicant *wpa_s)
 {
 	struct wpa_ssid *ssid, *old_ssid;
@@ -916,6 +918,15 @@ int wpa_supplicant_connect(struct wpa_supplicant *wpa_s,
 			wpa_supplicant_req_new_scan(wpa_s, 10, 0);
 			return 0;
 		}
+
+		if (num_assoc_reqs >= wpa_s->conf->max_assoc_per_scan) {
+			wpa_dbg(wpa_s, MSG_DEBUG,
+				"Deferring association attempt, reqs: %i, max: %i",
+				num_assoc_reqs, wpa_s->conf->max_assoc_per_scan);
+			return 0;
+		}
+		num_assoc_reqs++;
+
 		wpa_msg(wpa_s, MSG_DEBUG, "Request association: "
 			"reassociate: %d  selected: "MACSTR "  bssid: " MACSTR
 			"  pending: " MACSTR "  wpa_state: %s",
@@ -1230,6 +1241,14 @@ int wpas_select_network_from_last_scan(struct wpa_supplicant *wpa_s)
 		wpa_dbg(wpa_s, MSG_DEBUG, "No suitable network found");
 		ssid = wpa_supplicant_pick_new_network(wpa_s);
 		if (ssid) {
+			if (num_assoc_reqs >= wpa_s->conf->max_assoc_per_scan) {
+				wpa_dbg(wpa_s, MSG_DEBUG,
+					"Deferring association, reqs: %i, max: %i",
+					num_assoc_reqs, wpa_s->conf->max_assoc_per_scan);
+				return 0;
+			}
+			num_assoc_reqs++;
+
 			wpa_dbg(wpa_s, MSG_DEBUG, "Setup a new network");
 			wpa_supplicant_associate(wpa_s, NULL, ssid);
 			wpa_supplicant_rsn_preauth_scan_results(wpa_s);
@@ -1280,6 +1299,8 @@ static void wpa_supplicant_event_scan_results(struct wpa_supplicant *wpa_s,
 	const char *rn, *rn2;
 	struct wpa_supplicant *ifs;
 
+	num_assoc_reqs = 0;
+
 	if (_wpa_supplicant_event_scan_results(wpa_s, data) != 0) {
 		/*
 		 * If no scan results could be fetched, then no need to
-- 
1.7.3.4