[PATCH] wpa_supplicant: Prefer 5 GHz networks over 2.4 GHz networks.
Gary Morain
gmorain
Fri Aug 5 16:23:12 PDT 2011
In scan.c, merge a channel's noise value into the scan results. When comparing
scan results, compute the signal-to-noise ratio and use it when available.
Prefer a 5 GHz network if its SNR is really big (> 30) or if its SNR is
relatively close to the other network's.
---
src/drivers/driver.h | 15 +++++++
src/drivers/driver_nl80211.c | 76 +++++++++++++++++++++++++++++++++++++
wpa_supplicant/driver_i.h | 8 ++++
wpa_supplicant/scan.c | 30 ++++++++++++---
wpa_supplicant/wpa_supplicant_i.h | 10 +++++
5 files changed, 133 insertions(+), 6 deletions(-)
diff --git a/src/drivers/driver.h b/src/drivers/driver.h
index e2d0f8b..1c118fb 100644
--- a/src/drivers/driver.h
+++ b/src/drivers/driver.h
@@ -1250,6 +1250,21 @@ struct wpa_driver_ops {
struct wpa_scan_results * (*get_scan_results2)(void *priv);
/**
+ * get_noise_for_scan_results - Sets the 'noise' field of struct
+ * wpa_scan_res
+ * @priv: private driver interface data
+ * @scan_results: Can results obtained through get_scan_results2.
+ *
+ * This function gets the survey results from the driver. For each
+ * frequency in the scan results, the noise is updated if the survey
+ * results have a noise value for that frequency.
+ *
+ * Returns: 0 on success. -1 on failure.
+ */
+ int (*get_noise_for_scan_results)(void *priv,
+ struct wpa_scan_results *scan_results);
+
+ /**
* set_country - Set country
* @priv: Private driver interface data
* @alpha2: country to which to switch to
diff --git a/src/drivers/driver_nl80211.c b/src/drivers/driver_nl80211.c
index 1cb2196..2501685 100644
--- a/src/drivers/driver_nl80211.c
+++ b/src/drivers/driver_nl80211.c
@@ -1278,6 +1278,81 @@ static int nl80211_get_link_noise(struct wpa_driver_nl80211_data *drv,
}
+static int get_noise_for_scan_results(struct nl_msg *msg, void *arg)
+{
+ struct nlattr *tb[NL80211_ATTR_MAX + 1];
+ struct genlmsghdr *gnlh = nlmsg_data(nlmsg_hdr(msg));
+ struct nlattr *sinfo[NL80211_SURVEY_INFO_MAX + 1];
+ static struct nla_policy survey_policy[NL80211_SURVEY_INFO_MAX + 1] = {
+ [NL80211_SURVEY_INFO_FREQUENCY] = { .type = NLA_U32 },
+ [NL80211_SURVEY_INFO_NOISE] = { .type = NLA_U8 },
+ };
+ struct wpa_scan_results *scan_results = arg;
+ struct wpa_scan_res *scan_res;
+ size_t i;
+
+ nla_parse(tb, NL80211_ATTR_MAX, genlmsg_attrdata(gnlh, 0),
+ genlmsg_attrlen(gnlh, 0), NULL);
+
+ if (!tb[NL80211_ATTR_SURVEY_INFO]) {
+ wpa_printf(MSG_DEBUG, "nl80211: survey data missing!");
+ return NL_SKIP;
+ }
+
+ if (nla_parse_nested(sinfo, NL80211_SURVEY_INFO_MAX,
+ tb[NL80211_ATTR_SURVEY_INFO],
+ survey_policy)) {
+ wpa_printf(MSG_DEBUG, "nl80211: failed to parse nested "
+ "attributes!");
+ return NL_SKIP;
+ }
+
+ if (!sinfo[NL80211_SURVEY_INFO_NOISE])
+ return NL_SKIP;
+
+ if (!sinfo[NL80211_SURVEY_INFO_FREQUENCY])
+ return NL_SKIP;
+
+ for (i = 0; i < scan_results->num; ++i) {
+ scan_res = scan_results->res[i];
+ if (!scan_res)
+ continue;
+ if (nla_get_u32(sinfo[NL80211_SURVEY_INFO_FREQUENCY]) !=
+ scan_res->freq)
+ continue;
+ if (!(scan_res->flags & WPA_SCAN_NOISE_INVALID))
+ continue;
+ scan_res->noise = (s8) nla_get_u8(sinfo[NL80211_SURVEY_INFO_NOISE]);
+ scan_res->flags &= ~WPA_SCAN_NOISE_INVALID;
+ }
+
+ return NL_SKIP;
+}
+
+
+static int nl80211_get_noise_for_scan_results(void *priv,
+ struct wpa_scan_results *scan_res)
+{
+ struct i802_bss *bss = priv;
+ struct wpa_driver_nl80211_data *drv = bss->drv;
+ struct nl_msg *msg;
+
+ msg = nlmsg_alloc();
+ if (!msg)
+ return -ENOMEM;
+
+ genlmsg_put(msg, 0, 0, genl_family_get_id(drv->nl80211), 0,
+ NLM_F_DUMP, NL80211_CMD_GET_SURVEY, 0);
+
+ NLA_PUT_U32(msg, NL80211_ATTR_IFINDEX, drv->ifindex);
+
+ return send_and_recv_msgs(drv, msg, get_noise_for_scan_results,
+ scan_res);
+ nla_put_failure:
+ return -ENOBUFS;
+}
+
+
static void nl80211_cqm_event(struct wpa_driver_nl80211_data *drv,
struct nlattr *tb[])
{
@@ -6846,6 +6921,7 @@ const struct wpa_driver_ops wpa_driver_nl80211_ops = {
.set_key = wpa_driver_nl80211_set_key,
.scan2 = wpa_driver_nl80211_scan,
.get_scan_results2 = wpa_driver_nl80211_get_scan_results,
+ .get_noise_for_scan_results = nl80211_get_noise_for_scan_results,
.deauthenticate = wpa_driver_nl80211_deauthenticate,
.disassociate = wpa_driver_nl80211_disassociate,
.authenticate = wpa_driver_nl80211_authenticate,
diff --git a/wpa_supplicant/driver_i.h b/wpa_supplicant/driver_i.h
index 79fdddd..b72d23f 100644
--- a/wpa_supplicant/driver_i.h
+++ b/wpa_supplicant/driver_i.h
@@ -87,6 +87,14 @@ static inline struct wpa_scan_results * wpa_drv_get_scan_results2(
return NULL;
}
+static inline void wpa_drv_get_noise_for_scan_results(
+ struct wpa_supplicant *wpa_s, struct wpa_scan_results *scan_results)
+{
+ if (wpa_s->driver->get_noise_for_scan_results)
+ wpa_s->driver->get_noise_for_scan_results(wpa_s->drv_priv,
+ scan_results);
+}
+
static inline int wpa_drv_get_bssid(struct wpa_supplicant *wpa_s, u8 *bssid)
{
if (wpa_s->driver->get_bssid) {
diff --git a/wpa_supplicant/scan.c b/wpa_supplicant/scan.c
index 7689ff6..c6340ea 100644
--- a/wpa_supplicant/scan.c
+++ b/wpa_supplicant/scan.c
@@ -686,11 +686,15 @@ struct wpabuf * wpa_scan_get_vendor_ie_multi_beacon(
* better. */
static int wpa_scan_result_compar(const void *a, const void *b)
{
+#define IS_5GHZ(n) (n > 4000)
+#define MIN(a,b) a < b ? a : b
+
struct wpa_scan_res **_wa = (void *) a;
struct wpa_scan_res **_wb = (void *) b;
struct wpa_scan_res *wa = *_wa;
struct wpa_scan_res *wb = *_wb;
int wpa_a, wpa_b, maxrate_a, maxrate_b;
+ int snr_a, snr_b;
/* WPA/WPA2 support preferred */
wpa_a = wpa_scan_get_vendor_ie(wa, WPA_IE_VENDOR_TYPE) != NULL ||
@@ -711,23 +715,36 @@ static int wpa_scan_result_compar(const void *a, const void *b)
(wb->caps & IEEE80211_CAP_PRIVACY) == 0)
return -1;
- /* best/max rate preferred if signal level close enough XXX */
- if ((wa->level && wb->level && abs(wb->level - wa->level) < 5) ||
+ snr_a = MIN(wa->level - wa->noise, GREAT_SNR);
+ snr_b = MIN(wb->level - wb->noise, GREAT_SNR);
+
+ wpa_printf(MSG_DEBUG, "Channel a: freq:%d level:%d noise:%d snr:%d",
+ wa->freq, wa->level, wa->noise, snr_a);
+ wpa_printf(MSG_DEBUG, "Channel b: freq:%d level:%d noise:%d snr:%d",
+ wb->freq, wb->level, wb->noise, snr_b);
+
+
+ /* best/max rate preferred if SNR close enough XXX */
+ if ((snr_a && snr_b && abs(snr_b - snr_a) < 5) ||
(wa->qual && wb->qual && abs(wb->qual - wa->qual) < 10)) {
maxrate_a = wpa_scan_get_max_rate(wa);
maxrate_b = wpa_scan_get_max_rate(wb);
if (maxrate_a != maxrate_b)
return maxrate_b - maxrate_a;
+ if (IS_5GHZ(wa->freq) ^ IS_5GHZ(wb->freq))
+ return IS_5GHZ(wa->freq) ? -1 : 1;
}
/* use freq for channel preference */
- /* all things being equal, use signal level; if signal levels are
+ /* all things being equal, use SNR; if SNRs are
* identical, use quality values since some drivers may only report
* that value and leave the signal level zero */
- if (wb->level == wa->level)
+ if (snr_b == snr_a)
return wb->qual - wa->qual;
- return wb->level - wa->level;
+ return snr_b - snr_a;
+#undef MIN
+#undef IS_5GHZ
}
@@ -778,7 +795,6 @@ static int wpa_scan_result_wps_compar(const void *a, const void *b)
}
#endif /* CONFIG_WPS */
-
/**
* wpa_supplicant_get_scan_results - Get scan results
* @wpa_s: Pointer to wpa_supplicant data
@@ -807,6 +823,8 @@ wpa_supplicant_get_scan_results(struct wpa_supplicant *wpa_s,
return NULL;
}
+ wpa_drv_get_noise_for_scan_results(wpa_s, scan_res);
+
#ifdef CONFIG_WPS
if (wpas_wps_in_progress(wpa_s)) {
wpa_dbg(wpa_s, MSG_DEBUG, "WPS: Order scan results with WPS "
diff --git a/wpa_supplicant/wpa_supplicant_i.h b/wpa_supplicant/wpa_supplicant_i.h
index c1a8808..ef5760f 100644
--- a/wpa_supplicant/wpa_supplicant_i.h
+++ b/wpa_supplicant/wpa_supplicant_i.h
@@ -29,6 +29,16 @@ extern const char *wpa_supplicant_full_license4;
extern const char *wpa_supplicant_full_license5;
#endif /* CONFIG_NO_STDOUT_DEBUG */
+/*
+ * Channels with a great SNR can operate at full rate. What is a great SNR?
+ * This doc https://supportforums.cisco.com/docs/DOC-12954 says, "the general
+ * rule of thumb is that any SNR above 20 is good." This one
+ * http://www.cisco.com/en/US/tech/tk722/tk809/technologies_q_and_a_item09186a00805e9a96.shtml#qa23
+ * recommends 25 as a minimum SNR for 54 Mbps data rate. 30 is chosen here as a
+ * conservative value.
+ */
+#define GREAT_SNR 30
+
struct wpa_sm;
struct wpa_supplicant;
struct ibss_rsn;
--
1.7.3.1
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