Fixed scan buffer increasing with WEXT

We can now handle up to 65535 byte result buffer which is the maximum
due to WEXT using 16-bit length field. Previously, this was limited to
32768 bytes in practice even through we tried with 65536 and 131072
buffers which we just truncated into 0 in the 16-bit variable.

This more or less doubles the number of BSSes we can received from scan
results.

hostapd/driver_nl80211.c

@@ -2291,10 +2291,12 @@ static int i802_get_ht_scan_res(struct i802_driver_data *drv)
 		if (ioctl(drv->ioctl_sock, SIOCGIWSCAN, &iwr) == 0)
 			break;
 
-		if (errno == E2BIG && res_buf_len < 100000) {
+		if (errno == E2BIG && res_buf_len < 65535) {
 			os_free(res_buf);
 			res_buf = NULL;
 			res_buf_len *= 2;
+			if (res_buf_len > 65535)
+				res_buf_len = 65535; /* 16-bit length field */
 			wpa_printf(MSG_DEBUG, "Scan results did not fit - "
 				   "trying larger buffer (%lu bytes)",
 				   (unsigned long) res_buf_len);

src/drivers/driver_nl80211.c

@@ -1565,10 +1565,12 @@ static u8 * wpa_driver_nl80211_giwscan(struct wpa_driver_nl80211_data *drv,
 		if (ioctl(drv->ioctl_sock, SIOCGIWSCAN, &iwr) == 0)
 			break;
 
-		if (errno == E2BIG && res_buf_len < 100000) {
+		if (errno == E2BIG && res_buf_len < 65535) {
 			os_free(res_buf);
 			res_buf = NULL;
 			res_buf_len *= 2;
+			if (res_buf_len > 65535)
+				res_buf_len = 65535; /* 16-bit length field */
 			wpa_printf(MSG_DEBUG, "Scan results did not fit - "
 				   "trying larger buffer (%lu bytes)",
 				   (unsigned long) res_buf_len);

src/drivers/driver_wext.c

@@ -1140,10 +1140,12 @@ static u8 * wpa_driver_wext_giwscan(struct wpa_driver_wext_data *drv,
 		if (ioctl(drv->ioctl_sock, SIOCGIWSCAN, &iwr) == 0)
 			break;
 
-		if (errno == E2BIG && res_buf_len < 100000) {
+		if (errno == E2BIG && res_buf_len < 65535) {
 			os_free(res_buf);
 			res_buf = NULL;
 			res_buf_len *= 2;
+			if (res_buf_len > 65535)
+				res_buf_len = 65535; /* 16-bit length field */
 			wpa_printf(MSG_DEBUG, "Scan results did not fit - "
 				   "trying larger buffer (%lu bytes)",
 				   (unsigned long) res_buf_len);

wpa_supplicant/ChangeLog

@@ -3,6 +3,8 @@ ChangeLog for wpa_supplicant
 ????-??-?? - v0.7.0
 	* increased wpa_cli ping interval to 5 seconds and made this
 	  configurable with a new command line options (-G<seconds>)
+	* fixed scan buffer processing with WEXT to handle up to 65535
+	  byte result buffer (previously, limited to 32768 bytes)
 
 2009-01-06 - v0.6.7
 	* added support for Wi-Fi Protected Setup (WPS)