local-node: prioritize neighbor candidates

Prioritize neighbor candidates installed to hostapd. Add a new config
option to set a limit for neighbor reports installed to hostapd. This is
due to the fact, most devices will only evaluate a certain amount of
neighbor reports. Furthermore, the number of neighbor reports possible
is limited by the maximum frame size.

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

local_node.c

@@ -287,35 +287,53 @@ usteer_local_node_req_cb(struct ubus_request *req, int ret)
 	uloop_timeout_set(&ln->req_timer, 1);
 }
 
-static void
+static bool
 usteer_add_rrm_data(struct usteer_local_node *ln, struct usteer_node *node)
 {
 	if (node == &ln->node)
-		return;
+		return false;
 
 	if (!node->rrm_nr)
-		return;
+		return false;
 
+	/* Remote node only adds same SSID. Required for local-node. */
 	if (strcmp(ln->node.ssid, node->ssid) != 0)
-		return;
+		return false;
 
 	blobmsg_add_field(&b, BLOBMSG_TYPE_ARRAY, "",
 			  blobmsg_data(node->rrm_nr),
 			  blobmsg_data_len(node->rrm_nr));
+
+	return true;
 }
 
 static void
 usteer_local_node_prepare_rrm_set(struct usteer_local_node *ln)
 {
-	struct usteer_remote_node *rn;
-	struct usteer_node *node;
+	struct usteer_node *node, *last_remote_neighbor = NULL;
+	int i = 0;
 	void *c;
 
 	c = blobmsg_open_array(&b, "list");
-	for_each_local_node(node)
-		usteer_add_rrm_data(ln, node);
-	for_each_remote_node(rn)
-		usteer_add_rrm_data(ln, &rn->node);
+	for_each_local_node(node) {
+		if (i >= config.max_neighbor_reports)
+			break;
+		if (usteer_add_rrm_data(ln, node))
+			i++;
+	}
+
+	while (i < config.max_neighbor_reports) {
+		node = usteer_node_get_next_neighbor(&ln->node, last_remote_neighbor);
+		if (!node) {
+			/* No more nodes available */
+			break;
+		}
+
+		last_remote_neighbor = node;
+		if (usteer_add_rrm_data(ln, node))
+			i++;
+	}
+		
 	blobmsg_close_array(&b, c);
 }
 

main.c

@@ -88,6 +88,7 @@ void usteer_init_defaults(void)
 	config.local_sta_timeout = 120 * 1000;
 	config.local_sta_update = 1 * 1000;
 	config.max_retry_band = 5;
+	config.max_neighbor_reports = 8;
 	config.seen_policy_timeout = 30 * 1000;
 	config.band_steering_threshold = 5;
 	config.load_balancing_threshold = 5;

node.c

@@ -17,6 +17,7 @@
  *   Copyright (C) 2020 John Crispin <john@phrozen.org> 
  */
 
+#include "node.h"
 #include "usteer.h"
 
 void usteer_node_set_blob(struct blob_attr **dest, struct blob_attr *val)
@@ -36,3 +37,106 @@ void usteer_node_set_blob(struct blob_attr **dest, struct blob_attr *val)
 		*dest = realloc(*dest, new_len);
 	memcpy(*dest, val, new_len);
 }
+
+static struct usteer_node *
+usteer_node_higher_bssid(struct usteer_node *node1, struct usteer_node *node2)
+{
+	int i;
+
+	for (i = 0; i < 6; i++) {
+		if (node1->bssid[i] == node2->bssid[i])
+			continue;
+		if (node1->bssid[i] < node2->bssid[i])
+			return node2;
+
+		break;
+	}
+
+	return node1;
+}
+
+static struct usteer_node *
+usteer_node_more_roam_interactions(struct usteer_node *node, struct usteer_node *ref)
+{
+	int roam_actions_node, roam_actions_ref;
+
+	roam_actions_node = node->roam_source + node->roam_destination;
+	roam_actions_ref = ref->roam_source + ref->roam_destination;
+	if (roam_actions_node < roam_actions_ref)
+		return ref;
+
+	return node;
+}
+
+static struct usteer_node *
+usteer_node_better_neighbor(struct usteer_node *node, struct usteer_node *ref)
+{
+	struct usteer_node *n1, *n2;
+
+	/**
+	 * 1. Return one node if the other one is NULL
+	 * 2. Return the node with the higher roam events.
+	 * 3. Return the node with the higher BSSID.
+	 * 4. Return first method argument.
+	 */
+
+	if (!ref)
+		return node;
+
+	if (!node)
+		return ref;
+
+	n1 = usteer_node_more_roam_interactions(node, ref);
+	n2 = usteer_node_more_roam_interactions(ref, node);
+	if (n1 == n2)
+		return n1;
+
+	/* Identical roam interactions. Check BSSID */
+	n1 = usteer_node_higher_bssid(node, ref);
+	n2 = usteer_node_higher_bssid(ref, node);
+	if (n1 == n2)
+		return n1;
+
+	return node;
+}
+
+struct usteer_node *
+usteer_node_get_next_neighbor(struct usteer_node *current_node, struct usteer_node *last)
+{
+	struct usteer_remote_node *rn;
+	struct usteer_node *next = NULL, *n1, *n2;
+
+	for_each_remote_node(rn) {
+		if (next == &rn->node)
+			continue;
+
+		if (strcmp(current_node->ssid, rn->node.ssid))
+			continue;
+
+		/* Check if this node is ranked lower than the last one */
+		n1 = usteer_node_better_neighbor(last, &rn->node);
+		n2 = usteer_node_better_neighbor(&rn->node, last);
+		if (n1 != n2) {
+			/* Identical rank. Skip. */
+			continue;
+		} else if (last && n1 == &rn->node) {
+			/* Candidate rank is higher than the last neighbor. Skip. */
+			continue;
+		}
+
+		/* Check with current next candidate */
+		n1 = usteer_node_better_neighbor(next, &rn->node);
+		n2 = usteer_node_better_neighbor(&rn->node, next);
+		if (n1 != n2) {
+			/* Identical rank. Skip. */
+			continue;
+		} else if (n1 != &rn->node) {
+			/* Next candidate ranked higher. */
+			continue;
+		}
+
+		next = n1;		
+	}
+
+	return next;
+}

openwrt/usteer/files/etc/config/usteer

@@ -17,6 +17,9 @@ config usteer
 	# 5 = all debug messages
 	option 'debug_level' '2'
 
+	# Maximum number of neighbor reports set for a node
+	#option max_neighbor_reports 8
+
 	# Maximum amount of time (ms) a station may be blocked due to policy decisions
 	#option sta_block_timeout 30000
 

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

@@ -75,7 +75,7 @@ uci_usteer() {
 	for opt in \
 		debug_level \
 		sta_block_timeout local_sta_timeout local_sta_update \
-		max_retry_band seen_policy_timeout \
+		max_neighbor_reports max_retry_band seen_policy_timeout \
 		load_balancing_threshold band_steering_threshold \
 		remote_update_interval \
 		min_connect_snr min_snr signal_diff_threshold \

ubus.c

@@ -146,6 +146,7 @@ struct cfg_item {
 	_cfg(U32, sta_block_timeout), \
 	_cfg(U32, local_sta_timeout), \
 	_cfg(U32, local_sta_update), \
+	_cfg(U32, max_neighbor_reports), \
 	_cfg(U32, max_retry_band), \
 	_cfg(U32, seen_policy_timeout), \
 	_cfg(U32, load_balancing_threshold), \

usteer.h

@@ -152,6 +152,8 @@ struct usteer_config {
 
 	bool assoc_steering;
 
+	uint32_t max_neighbor_reports;
+
 	uint32_t band_steering_threshold;
 	uint32_t load_balancing_threshold;
 
@@ -274,6 +276,7 @@ static inline const char *usteer_node_name(struct usteer_node *node)
 }
 void usteer_node_set_blob(struct blob_attr **dest, struct blob_attr *val);
 
+struct usteer_node *usteer_node_get_next_neighbor(struct usteer_node *current_node, struct usteer_node *last);
 bool usteer_check_request(struct sta_info *si, enum usteer_event_type type);
 
 void config_set_interfaces(struct blob_attr *data);