[PATCH] roaming: start a scan if the SNR is below customized threshold

Thu Sep 17 09:16:32 PDT 2009

On Tue, 2009-09-15 at 08:42 +0200, Holger Schurig wrote:
> Scanning is all what's needed, because wpa_supplicant already has logic
> to sort the scan result by quality and tries to associate to the top-most
> matching AP.

What is roam_snr supposed to be in?  dBm?  What about cards that have no
idea what their dBm is?  I forget how Johannes and I tried to specify it
in cfg80211 for Linux, but I'm not sure we ended up requiring drivers to
return dBm.  That would be very very nice if they did, but we still have
some wext drivers that may not be able to return anything other than
RSSI...

Dan

> Signed-off-by: Holger Schurig <hs4233 at mail.mn-solutions.de>
> 
> 
> Index: hostap/wpa_supplicant/roam.h
> ===================================================================
> --- /dev/null	1970-01-01 00:00:00.000000000 +0000
> +++ hostap/wpa_supplicant/roam.h	2009-09-14 14:08:51.000000000 +0200
> @@ -0,0 +1,25 @@
> +/*
> + * WPA Supplicant - Automatic roaming support
> + * Copyright (c) 2009 Holger Schurig
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * Alternatively, this software may be distributed under the terms of BSD
> + * license.
> + *
> + * See README and COPYING for more details.
> + */
> +
> +#ifndef ROAM_H
> +#define ROAM_H
> +
> +struct wpa_supplicant;
> +
> +#ifdef CONFIG_ROAM
> +
> +void roam_do_checks(struct wpa_supplicant *wpa_s, int connected);
> +
> +#endif /* CONFIG_ROAM */
> +#endif
> Index: hostap/wpa_supplicant/Makefile
> ===================================================================
> --- hostap.orig/wpa_supplicant/Makefile	2009-09-14 13:50:29.000000000 +0200
> +++ hostap/wpa_supplicant/Makefile	2009-09-14 14:08:51.000000000 +0200
> @@ -1005,6 +1005,11 @@ CFLAGS += -DCONFIG_CLIENT_MLME
>  NEED_80211_COMMON=y
>  endif
>  
> +ifdef CONFIG_ROAM
> +CFLAGS += -DCONFIG_ROAM
> +OBJS += roam.o
> +endif
> +
>  ifdef NEED_80211_COMMON
>  OBJS += ../src/common/ieee802_11_common.o
>  endif
> Index: hostap/wpa_supplicant/roam.c
> ===================================================================
> --- /dev/null	1970-01-01 00:00:00.000000000 +0000
> +++ hostap/wpa_supplicant/roam.c	2009-09-14 14:14:10.000000000 +0200
> @@ -0,0 +1,60 @@
> +/*
> + * WPA Supplicant - Automatic roaming support
> + * Copyright (c) 2009 Holger Schurig
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * Alternatively, this software may be distributed under the terms of BSD
> + * license.
> + *
> + * See README and COPYING for more details.
> + */
> +
> +#include "includes.h"
> +
> +#include "common.h"
> +#include "eloop.h"
> +#include "config_ssid.h"
> +#include "wpa_supplicant_i.h"
> +#include "driver_i.h"
> +#include "roam.h"
> +
> +
> +static void roam_check_snr(void *eloop_ctx, void *timeout_ctx)
> +{
> +	struct wpa_supplicant *wpa_s = eloop_ctx;
> +
> +	int sec  = wpa_s->current_ssid->roam_check_ms / 1000;
> +	int usec = (wpa_s->current_ssid->roam_check_ms % 1000) * 1000;
> +	int snr  =  wpa_drv_get_snr(wpa_s);
> +	wpa_printf(MSG_DEBUG, "ROAM: SNR %d, roam_snr %d", snr, wpa_s->current_ssid->roam_snr);
> +
> +	if (snr != -1 &&
> +	    // Scan if we have a SNR threshold defined
> +	    snr < wpa_s->current_ssid->roam_snr)
> +	    // only scan if the last scan isn't valid anymore
> +	{
> +		wpa_printf(MSG_ERROR, "ROAM: snr %d, search for a better AP", snr);
> +		wpa_s->scan_req = 2;
> +		//wpa_s->reassociate = 1;
> +		wpa_supplicant_req_scan(wpa_s, 0, 1);
> +	}
> +
> +	/* Schedule next check */
> +	eloop_cancel_timeout(roam_check_snr, wpa_s, NULL);
> +	eloop_register_timeout(sec, usec, roam_check_snr, wpa_s, NULL);
> +}
> +
> +
> +void roam_do_checks(struct wpa_supplicant *wpa_s, int connected)
> +{
> +	//wpa_printf(MSG_ERROR, "ROAM: connected %d", connected);
> +
> +	eloop_cancel_timeout(roam_check_snr, wpa_s, NULL);
> +
> +	if (connected && wpa_s->current_ssid->roam_snr > 0)
> +		eloop_register_timeout(0, 100, roam_check_snr, wpa_s, NULL);
> +}
> +
> Index: hostap/wpa_supplicant/wpa_supplicant.c
> ===================================================================
> --- hostap.orig/wpa_supplicant/wpa_supplicant.c	2009-09-14 14:08:36.000000000 +0200
> +++ hostap/wpa_supplicant/wpa_supplicant.c	2009-09-14 14:08:51.000000000 +0200
> @@ -36,6 +36,7 @@
>  #include "pmksa_cache.h"
>  #include "wpa_ctrl.h"
>  #include "mlme.h"
> +#include "roam.h"
>  #include "ieee802_11_defs.h"
>  #include "blacklist.h"
>  #include "wpas_glue.h"
> @@ -520,6 +521,7 @@ void wpa_supplicant_set_state(struct wpa
>  
>  	wpas_notify_state_changed(wpa_s, state, wpa_s->wpa_state);
>  
> +	roam_do_checks(wpa_s, state == WPA_COMPLETED);
>  	if (state == WPA_COMPLETED && wpa_s->new_connection) {
>  #if defined(CONFIG_CTRL_IFACE) || !defined(CONFIG_NO_STDOUT_DEBUG)
>  		struct wpa_ssid *ssid = wpa_s->current_ssid;
> Index: hostap/wpa_supplicant/config_ssid.h
> ===================================================================
> --- hostap.orig/wpa_supplicant/config_ssid.h	2009-09-14 13:50:29.000000000 +0200
> +++ hostap/wpa_supplicant/config_ssid.h	2009-09-14 14:08:51.000000000 +0200
> @@ -350,6 +350,19 @@ struct wpa_ssid {
>  	 * known to not use all possible channels.
>  	 */
>  	int *scan_freq;
> +
> +#ifdef CONFIG_ROAM
> +	/**
> +	 * roam_snr - When to scan for a better AP
> +	 */
> +	int roam_snr;
> +
> +	/**
> +	 * roam_check_ms - After how many milliseconds should we check the
> +	 * SNR
> +	 */
> +	int roam_check_ms;
> +#endif /* CONFIG_ROAM */
>  };
>  
>  #endif /* CONFIG_SSID_H */
> Index: hostap/wpa_supplicant/config.c
> ===================================================================
> --- hostap.orig/wpa_supplicant/config.c	2009-09-14 13:50:29.000000000 +0200
> +++ hostap/wpa_supplicant/config.c	2009-09-14 14:08:51.000000000 +0200
> @@ -1399,6 +1399,10 @@ static const struct parse_data ssid_fiel
>  	{ FUNC(group) },
>  	{ FUNC(auth_alg) },
>  	{ FUNC(scan_freq) },
> +#ifdef CONFIG_ROAM
> +	{ INT_RANGE(roam_snr, 5, 80) },
> +	{ INT_RANGE(roam_check_ms, 100,60000) },
> +#endif /* CONFIG_ROAM */
>  #ifdef IEEE8021X_EAPOL
>  	{ FUNC(eap) },
>  	{ STR_LENe(identity) },
> @@ -1779,6 +1783,10 @@ void wpa_config_set_network_defaults(str
>  	ssid->eap_workaround = DEFAULT_EAP_WORKAROUND;
>  	ssid->eap.fragment_size = DEFAULT_FRAGMENT_SIZE;
>  #endif /* IEEE8021X_EAPOL */
> +#ifdef CONFIG_ROAM
> +	ssid->roam_snr = -1;
> +	ssid->roam_check_ms = 2000;
> +#endif /* CONFIG_ROAM */
>  }
>  
> 
> 