[RFC PATCH 1/1] supplicant: request ACS if channel==0

[Ulrich Ölmann <u oelmann pengutronix de>]

By analogy to wpa_supplicant.conf Automatic Channel Selection (ACS) is coded as
"channel=0" within a connection. wpa_supplicant then needs to know if it shall
look out for a channel in the 2.4 GHz or the 5 GHz band. This information is
passed over via a sample frequency from the respective band.

Signed-off-by: Ulrich Ölmann <u oelmann pengutronix de>
---
 src/supplicant-manager/nm-supplicant-config.c      | 37 ++++++++++++++++++----
 .../nm-supplicant-settings-verify.c                |  1 +
 2 files changed, 31 insertions(+), 7 deletions(-)

diff --git a/src/supplicant-manager/nm-supplicant-config.c b/src/supplicant-manager/nm-supplicant-config.c
index 5ce8bb31968a..e16353a98583 100644
--- a/src/supplicant-manager/nm-supplicant-config.c
+++ b/src/supplicant-manager/nm-supplicant-config.c
@@ -381,6 +381,9 @@ wifi_freqs_to_string (gboolean bg_band)
        return str;
 }
 
+#define TWO_GHZ_SAMPLE_FREQ  2412
+#define FIVE_GHZ_SAMPLE_FREQ 5280
+
 gboolean
 nm_supplicant_config_add_setting_wireless (NMSupplicantConfig * self,
                                            NMSettingWireless * setting,
@@ -428,12 +431,34 @@ nm_supplicant_config_add_setting_wireless (NMSupplicantConfig * self,
                        return FALSE;
        }
 
-       if ((is_adhoc || is_ap) && fixed_freq) {
-               gs_free char *str_freq = NULL;
+       band = nm_setting_wireless_get_band (setting);
+       channel = nm_setting_wireless_get_channel (setting);
+       if (is_adhoc || is_ap) {
+               /* By analogy to wpa_supplicant.conf Automatic Channel Selection (ACS)
+                * is coded as "channel=0" within the connection - wpa_supplicant then
+                * needs the option "acs=1" and a sample frequency which points the ACS
+                * heuristic to the desired band.
+                */
+               if (!channel) {
+                       if (!nm_supplicant_config_add_option (self, "acs", "1", -1, FALSE, error))
+                               return FALSE;
 
-               str_freq = g_strdup_printf ("%u", fixed_freq);
-               if (!nm_supplicant_config_add_option (self, "frequency", str_freq, -1, FALSE, error))
-                       return FALSE;
+                       fixed_freq = 0;
+                       if (band) {
+                               if (!strcmp (band, "a"))
+                                       fixed_freq = FIVE_GHZ_SAMPLE_FREQ;
+                               else if (!strcmp (band, "bg"))
+                                       fixed_freq = TWO_GHZ_SAMPLE_FREQ;
+                       }
+               }
+
+               if (fixed_freq) {
+                       gs_free char *str_freq = NULL;
+
+                       str_freq = g_strdup_printf ("%u", fixed_freq);
+                       if (!nm_supplicant_config_add_option (self, "frequency", str_freq, -1, FALSE, error))
+                               return FALSE;
+               }
        }
 
        /* Except for Ad-Hoc and Hotspot, request that the driver probe for the
@@ -453,8 +478,6 @@ nm_supplicant_config_add_setting_wireless (NMSupplicantConfig * self,
                        return FALSE;
        }
 
-       band = nm_setting_wireless_get_band (setting);
-       channel = nm_setting_wireless_get_channel (setting);
        if (band) {
                if (channel) {
                        guint32 freq;
diff --git a/src/supplicant-manager/nm-supplicant-settings-verify.c 
b/src/supplicant-manager/nm-supplicant-settings-verify.c
index bb046f9361d9..4e7ebcd1d7d0 100644
--- a/src/supplicant-manager/nm-supplicant-settings-verify.c
+++ b/src/supplicant-manager/nm-supplicant-settings-verify.c
@@ -93,6 +93,7 @@ static const struct Opt opt_table[] = {
        { "bssid",              TYPE_KEYWORD, 0, 0, FALSE,  NULL },
        { "scan_ssid",          TYPE_INT,     0, 1, FALSE,  NULL },
        { "mode",               TYPE_INT,     0, 2, FALSE,  NULL },
+       { "acs",                TYPE_INT,     0, 1, FALSE,  NULL },
        { "frequency",          TYPE_INT,     2412, 5825, FALSE,  NULL },
        { "auth_alg",           TYPE_KEYWORD, 0, 0, FALSE,  auth_alg_allowed },
        { "psk",                TYPE_BYTES,   0, 0, FALSE,  NULL },
-- 
2.1.4