nl80211: Add driver capability for GTK_NOT_USED

Many drivers support operation without GTK configured, but most (if any)
today do not advertise this. Handle this by skipping GTK cipher suite
configuration if the driver did not advertise support in order to work
around cfg80211 validation steps.

Signed-hostap: Jouni Malinen <jouni@qca.qualcomm.com>

src/drivers/driver.h

@@ -875,6 +875,7 @@ struct wpa_driver_capa {
 #define WPA_DRIVER_CAPA_ENC_BIP_GMAC_128	0x00000200
 #define WPA_DRIVER_CAPA_ENC_BIP_GMAC_256	0x00000400
 #define WPA_DRIVER_CAPA_ENC_BIP_CMAC_256	0x00000800
+#define WPA_DRIVER_CAPA_ENC_GTK_NOT_USED	0x00001000
 	unsigned int enc;
 
 #define WPA_DRIVER_AUTH_OPEN		0x00000001

src/drivers/driver_nl80211.c

@@ -3525,6 +3525,9 @@ static void wiphy_info_cipher_suites(struct wiphy_info_data *info,
 		case WLAN_CIPHER_SUITE_BIP_CMAC_256:
 			info->capa->enc |= WPA_DRIVER_CAPA_ENC_BIP_CMAC_256;
 			break;
+		case WLAN_CIPHER_SUITE_NO_GROUP_ADDR:
+			info->capa->enc |= WPA_DRIVER_CAPA_ENC_GTK_NOT_USED;
+			break;
 		}
 	}
 }
@@ -5511,6 +5514,8 @@ static u32 wpa_cipher_to_cipher_suite(unsigned int cipher)
 		return WLAN_CIPHER_SUITE_WEP104;
 	case WPA_CIPHER_WEP40:
 		return WLAN_CIPHER_SUITE_WEP40;
+	case WPA_CIPHER_GTK_NOT_USED:
+		return WLAN_CIPHER_SUITE_NO_GROUP_ADDR;
 	}
 
 	return 0;
@@ -8470,7 +8475,14 @@ static int nl80211_connect_common(struct wpa_driver_nl80211_data *drv,
 		NLA_PUT_U32(msg, NL80211_ATTR_CIPHER_SUITES_PAIRWISE, cipher);
 	}
 
-	if (params->group_suite != WPA_CIPHER_NONE) {
+	if (params->group_suite == WPA_CIPHER_GTK_NOT_USED &&
+	    !(drv->capa.enc & WPA_DRIVER_CAPA_ENC_GTK_NOT_USED)) {
+		/*
+		 * This is likely to work even though many drivers do not
+		 * advertise support for operations without GTK.
+		 */
+		wpa_printf(MSG_DEBUG, "  * skip group cipher configuration for GTK_NOT_USED due to missing driver support advertisement");
+	} else if (params->group_suite != WPA_CIPHER_NONE) {
 		u32 cipher = wpa_cipher_to_cipher_suite(params->group_suite);
 		wpa_printf(MSG_DEBUG, "  * group=0x%x", cipher);
 		NLA_PUT_U32(msg, NL80211_ATTR_CIPHER_SUITE_GROUP, cipher);