band-steering: add band-steering component

This adds a new band-steering component to usteer.

With band-steering enabled, usteer will attempt to move clients with a
consistently good SNR / signal from 2.4 GHz to the 5 GHz band.

In contrast to existing policies usteer tracks, band-steering is
non-invasive and will not lead to forceful connection termination.

Signed-off-by: David Bauer <mail@david-bauer.net>

CMakeLists.txt

@@ -24,7 +24,7 @@ IF(NOT HAVE_PCAP_H)
 	MESSAGE(FATAL_ERROR "pcap/pcap.h is not found")
 ENDIF()
 
-SET(SOURCES main.c local_node.c node.c sta.c policy.c ubus.c remote.c parse.c netifd.c timeout.c event.c measurement.c)
+SET(SOURCES main.c local_node.c node.c sta.c policy.c ubus.c remote.c parse.c netifd.c timeout.c event.c measurement.c band_steering.c)
 
 IF(NL_CFLAGS)
 	ADD_DEFINITIONS(${NL_CFLAGS})

band_steering.c

@@ -0,0 +1,98 @@
+/*
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation; either version 2 of the License.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program; if not, write to the Free Software
+ *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
+ *
+ *   Copyright (C) 2022 David Bauer <mail@david-bauer.net>
+ */
+
+#include "usteer.h"
+#include "node.h"
+
+void usteer_band_steering_sta_update(struct sta_info *si)
+{
+	if (si->signal < usteer_snr_to_signal(si->node, config.band_steering_min_snr))
+		si->band_steering.below_snr = true;
+}
+
+bool usteer_band_steering_is_target(struct usteer_local_node *ln, struct usteer_node *node)
+{
+	if (&ln->node == node)
+		return false;
+
+	if (strcmp(ln->node.ssid, node->ssid))
+		return false;
+
+	if (node->freq < 4000)
+		return false;
+
+	if (!usteer_policy_node_below_max_assoc(node))
+		return false;
+	
+	/* ToDo: Skip nodes with active load-kick */
+	
+	return true;
+ }
+
+
+static bool usteer_band_steering_has_target_iface(struct usteer_local_node *ln)
+{
+	struct usteer_node *node;
+
+	for_each_local_node(node) {
+		if (usteer_band_steering_is_target(ln, node))
+			return true;
+	}
+
+	return false;
+}
+
+void usteer_band_steering_perform_steer(struct usteer_local_node *ln)
+{
+	unsigned int min_count = DIV_ROUND_UP(config.band_steering_interval, config.local_sta_update);
+	struct sta_info *si;
+
+	if (!config.band_steering_interval)
+		return;
+
+	/* Band-Steering is only available on 2.4 GHz interfaces */
+	if (ln->node.freq > 4000)
+		return;
+
+	/* Check if we have an interface we can steer to */
+	if (!usteer_band_steering_has_target_iface(ln))
+		return;
+
+	/* Only steer every interval */
+	if (ln->band_steering_interval < min_count) {
+		ln->band_steering_interval++;
+		return;
+	}
+
+	ln->band_steering_interval = 0;
+
+	list_for_each_entry(si, &ln->node.sta_info, node_list) {
+		if (si->connected != STA_CONNECTED)
+			continue;
+
+		/* Skip clients with insufficient SNR-state */
+		if (si->band_steering.below_snr) {
+			si->band_steering.below_snr = false;
+			continue;
+		}
+
+		if (si->bss_transition)
+			usteer_ubus_band_steering_request(si);
+
+		si->band_steering.below_snr = false;
+	}
+}

local_node.c

@@ -642,6 +642,7 @@ usteer_local_node_update(struct uloop_timeout *timeout)
 	usteer_local_node_state_reset(ln);
 	uloop_timeout_set(&ln->req_timer, 1);
 	usteer_local_node_kick(ln);
+	usteer_band_steering_perform_steer(ln);
 	uloop_timeout_set(timeout, config.local_sta_update);
 }
 

main.c

@@ -99,6 +99,9 @@ void usteer_init_defaults(void)
 
 	config.steer_reject_timeout = 60000;
 
+	config.band_steering_interval = 120000;
+	config.band_steering_min_snr = -60;
+
 	config.roam_kick_delay = 10000;
 	config.roam_process_timeout = 5 * 1000;
 	config.roam_scan_tries = 3;

node.h

@@ -59,6 +59,8 @@ struct usteer_local_node {
 
 	int beacon_interval;
 
+	uint16_t band_steering_interval;
+
 	struct {
 		bool present;
 		struct uloop_timeout update;

openwrt/usteer/files/etc/config/usteer

@@ -117,6 +117,14 @@ config usteer
 	# Reason code on client kick based on channel load (default: WLAN_REASON_DISASSOC_AP_BUSY)
 	#option load_kick_reason_code 5
 
+	# Attempting to steer clients to a higher frequency-band every n ms.
+	# A value of 0 disabled band-steering.
+	#option band_steering_interval 120000
+
+	# Minimal SNR or absolute signal a device has to maintain over band_steering_interval to be
+	# steered to a higher frequency band
+	#option band_steering_min_snr -60
+
 	# Script to run after bringing up a node
 	#option node_up_script ''
 

openwrt/usteer/files/etc/init.d/usteer

@@ -85,6 +85,7 @@ uci_usteer() {
 		roam_kick_delay roam_scan_tries roam_scan_timeout \
 		roam_scan_snr roam_scan_interval \
 		roam_trigger_snr roam_trigger_interval \
+		band_steering_interval band_steering_min_snr \
 		load_kick_threshold load_kick_delay load_kick_min_clients \
 		load_kick_reason_code
 	do

sta.c

@@ -160,8 +160,10 @@ usteer_sta_info_update(struct sta_info *si, int signal, bool avg)
 	if (si->connected == STA_CONNECTED && si->signal != NO_SIGNAL && !avg)
 		signal = NO_SIGNAL;
 
-	if (signal != NO_SIGNAL)
+	if (signal != NO_SIGNAL) {
 		si->signal = signal;
+		usteer_band_steering_sta_update(si);
+	}
 
 	si->seen = current_time;
 

ubus.c

@@ -181,6 +181,8 @@ struct cfg_item {
 	_cfg(U32, load_kick_delay), \
 	_cfg(U32, load_kick_min_clients), \
 	_cfg(U32, load_kick_reason_code), \
+	_cfg(U32, band_steering_interval), \
+	_cfg(I32, band_steering_min_snr), \
 	_cfg(ARRAY_CB, interfaces), \
 	_cfg(STRING_CB, node_up_script), \
 	_cfg(ARRAY_CB, event_log_types), \
@@ -654,6 +656,31 @@ int usteer_ubus_bss_transition_request(struct sta_info *si,
 	return ubus_invoke(ubus_ctx, ln->obj_id, "bss_transition_request", b.head, NULL, 0, 100);
 }
 
+int usteer_ubus_band_steering_request(struct sta_info *si)
+{
+	struct usteer_local_node *ln = container_of(si->node, struct usteer_local_node, node);
+	struct usteer_node *node;
+	void *c;
+
+	blob_buf_init(&b, 0);
+	blobmsg_printf(&b, "addr", MAC_ADDR_FMT, MAC_ADDR_DATA(si->sta->addr));
+	blobmsg_add_u32(&b, "dialog_token", 0);
+	blobmsg_add_u8(&b, "disassociation_imminent", false);
+	blobmsg_add_u8(&b, "abridged", false);
+	blobmsg_add_u32(&b, "validity_period", 100);
+
+	c = blobmsg_open_array(&b, "neighbors");
+	for_each_local_node(node) {
+		if (!usteer_band_steering_is_target(ln, node))
+			continue;
+	
+		usteer_add_nr_entry(si->node, node);
+	}
+	blobmsg_close_array(&b, c);
+
+	return ubus_invoke(ubus_ctx, ln->obj_id, "bss_transition_request", b.head, NULL, 0, 100);
+}
+
 int usteer_ubus_notify_client_disassoc(struct sta_info *si)
 {
 	struct usteer_local_node *ln = container_of(si->node, struct usteer_local_node, node);

usteer.h

@@ -188,6 +188,9 @@ struct usteer_config {
 
 	uint32_t roam_kick_delay;
 
+	uint32_t band_steering_interval;
+	int32_t band_steering_min_snr; 
+
 	uint32_t initial_connect_delay;
 
 	bool load_kick_enabled;
@@ -253,6 +256,10 @@ struct sta_info {
 		uint64_t timestamp;
 	} bss_transition_response;
 
+	struct {
+		bool below_snr;
+	} band_steering;
+
 	uint64_t kick_time;
 
 	int kick_count;
@@ -318,10 +325,15 @@ int usteer_local_node_get_beacon_interval(struct usteer_local_node *ln);
 
 bool usteer_policy_node_below_max_assoc(struct usteer_node *node);
 
+void usteer_band_steering_perform_steer(struct usteer_local_node *ln);
+void usteer_band_steering_sta_update(struct sta_info *si);
+bool usteer_band_steering_is_target(struct usteer_local_node *ln, struct usteer_node *node);
+
 void usteer_ubus_init(struct ubus_context *ctx);
 void usteer_ubus_kick_client(struct sta_info *si);
 int usteer_ubus_trigger_client_scan(struct sta_info *si);
 int usteer_ubus_notify_client_disassoc(struct sta_info *si);
+int usteer_ubus_band_steering_request(struct sta_info *si);
 int usteer_ubus_bss_transition_request(struct sta_info *si,
 				       uint8_t dialog_token,
 				       bool disassoc_imminent,