Allow fragmentation/RTS threshold to be disabled explicitly

hostapd configuration parameters fragm_threshold and rts_threshold were
documented to disable the threshold with value -1 and not change driver
configuration if the parameter is not included. However, -1 was mapped
into not changing the driver value, so the explicit disabling part did
not work.

Replace the default values for these to be -2 so that explicitly set
configuration value -1 can be distinguished from the case of not
including the parameter. Map the -1 value to a driver request to disable
the threshold. Ignore any error from this operation just in case to
avoid breaking functionality should some drivers not accept the (u32) -1
value as a threshold value request to disable the mechanism.

Signed-off-by: Jouni Malinen <jouni@codeaurora.org>

src/ap/ap_config.c

@@ -200,8 +200,8 @@ struct hostapd_config * hostapd_config_defaults(void)
 	conf->num_bss = 1;
 
 	conf->beacon_int = 100;
-	conf->rts_threshold = -1; /* use driver default: 2347 */
-	conf->fragm_threshold = -1; /* user driver default: 2346 */
+	conf->rts_threshold = -2; /* use driver default: 2347 */
+	conf->fragm_threshold = -2; /* user driver default: 2346 */
 	/* Set to invalid value means do not add Power Constraint IE */
 	conf->local_pwr_constraint = -1;
 

src/ap/hostapd.c

@@ -1883,15 +1883,17 @@ static int hostapd_setup_interface_complete_sync(struct hostapd_iface *iface,
 		}
 	}
 
-	if (hapd->iconf->rts_threshold > -1 &&
-	    hostapd_set_rts(hapd, hapd->iconf->rts_threshold)) {
+	if (hapd->iconf->rts_threshold >= -1 &&
+	    hostapd_set_rts(hapd, hapd->iconf->rts_threshold) &&
+	    hapd->iconf->rts_threshold >= -1) {
 		wpa_printf(MSG_ERROR, "Could not set RTS threshold for "
 			   "kernel driver");
 		goto fail;
 	}
 
-	if (hapd->iconf->fragm_threshold > -1 &&
-	    hostapd_set_frag(hapd, hapd->iconf->fragm_threshold)) {
+	if (hapd->iconf->fragm_threshold >= -1 &&
+	    hostapd_set_frag(hapd, hapd->iconf->fragm_threshold) &&
+	    hapd->iconf->fragm_threshold != -1) {
 		wpa_printf(MSG_ERROR, "Could not set fragmentation threshold "
 			   "for kernel driver");
 		goto fail;

src/drivers/driver_nl80211.c

@@ -6166,7 +6166,7 @@ static int i802_set_rts(void *priv, int rts)
 	int ret;
 	u32 val;
 
-	if (rts >= 2347)
+	if (rts >= 2347 || rts == -1)
 		val = (u32) -1;
 	else
 		val = rts;
@@ -6194,7 +6194,7 @@ static int i802_set_frag(void *priv, int frag)
 	int ret;
 	u32 val;
 
-	if (frag >= 2346)
+	if (frag >= 2346 || frag == -1)
 		val = (u32) -1;
 	else
 		val = frag;