Handle failures to create an interface. Fix #14708

The function pfSense_interface_create2() may fail to create the
requested interface, in which case it returns the array:
['error'=>'Could not create interface']

src/etc/inc/interfaces.inc

@@ -418,6 +418,10 @@ function interface_vlan_configure(&$vlan, $flush = true, $skip_parent_mtu = fals
 	}
 
 	$tmpvlanif = pfSense_interface_create2("vlan");
+	if (!is_string($tmpvlanif)) {
+		log_error(sprintf(gettext('Failed to configure interface %1$s: Could not create temporary interface %2$s'), $vlan['vlanif'], 'vlan'));
+		return(NULL);
+	}
 	pfSense_interface_rename($tmpvlanif, $vlanif);
 	pfSense_ngctl_name("{$tmpvlanif}:", $vlanif);
 
@@ -711,12 +715,20 @@ function interface_bridge_configure(&$bridge, $checkmember = 0, $flush = true) {
 
 	if (!empty($bridge['bridgeif'])) {
 		pfSense_interface_destroy($bridge['bridgeif']);
-		pfSense_interface_create2($bridge['bridgeif']);
+		$tempifname = pfSense_interface_create2($bridge['bridgeif']);
+		if (!is_string($tempifname)) {
+			log_error(sprintf(gettext('Failed to configure interface %1$s: Could not create temporary interface %2$s'), $bridge['bridgeif'], $bridge['bridgeif']));
+			return;
+		}
 		$bridgeif = escapeshellarg($bridge['bridgeif']);
 	} else {
 		// if called directly, as interfaces_bridge_edit.php does, and bridgeif isn't set
 		// normally set by interfaces_bridge_configure, but not upon creation of new bridge
 		$bridgeif = pfSense_interface_create2("bridge");
+		if (!is_string($bridgeif)) {
+			log_error(sprintf(gettext('Failed to configure interface %1$s: Could not create temporary interface %2$s'), $bridge['bridgeif'], 'bridge'));
+			return;
+		}
 		$bridge['bridgeif'] = $bridgeif;
 	}
 
@@ -971,10 +983,18 @@ function interface_lagg_configure($lagg, $flush = true) {
 
 	if (is_platform_booting() || !(empty($lagg['laggif']))) {
 		pfSense_interface_destroy($lagg['laggif']);
-		pfSense_interface_create2($lagg['laggif']);
+		$tempifname = pfSense_interface_create2($lagg['laggif']);
+		if (!is_string($tempifname)) {
+			log_error(sprintf(gettext('Failed to configure interface %1$s: Could not create temporary interface %2$s'), $lagg['laggif'], $lagg['laggif']));
+			return -1;
+		}
 		$laggif = $lagg['laggif'];
 	} else {
 		$laggif = pfSense_interface_create2("lagg");
+		if (!is_string($laggif)) {
+			log_error(sprintf(gettext('Failed to configure interface %1$s: Could not create temporary interface %2$s'), $lagg['laggif'], 'lagg'));
+			return -1;
+		}
 	}
 
 	/* Check if MTU was defined for this lagg interface */
@@ -1071,10 +1091,18 @@ function interface_gre_configure(&$gre, $grekey = "", $flush = true) {
 
 	if (is_platform_booting() || !(empty($gre['greif']))) {
 		pfSense_interface_destroy($gre['greif']);
-		pfSense_interface_create2($gre['greif']);
+		$tempifname = pfSense_interface_create2($gre['greif']);
+		if (!is_string($tempifname)) {
+			log_error(sprintf(gettext('Failed to configure interface %1$s: Could not create temporary interface %2$s'), $gre['if'], $gre['greif']));
+			return -1;
+		}
 		$greif = $gre['greif'];
 	} else {
 		$greif = pfSense_interface_create2("gre");
+		if (!is_string($greif)) {
+			log_error(sprintf(gettext('Failed to configure interface %1$s: Could not create temporary interface %2$s'), $gre['if'], 'gre'));
+			return -1;
+		}
 	}
 
 	$tunnel_type = '';
@@ -1234,10 +1262,18 @@ function interface_gif_configure(&$gif, $gifkey = "", $flush = true) {
 
 	if (is_platform_booting() || !(empty($gif['gifif']))) {
 		pfSense_interface_destroy($gif['gifif']);
-		pfSense_interface_create2($gif['gifif']);
+		$tempifname = pfSense_interface_create2($gif['gifif']);
+		if (!is_string($tempifname)) {
+			log_error(sprintf(gettext('Failed to configure interface %1$s: Could not create temporary interface %2$s'), $gif['if'], $gif['gifif']));
+			return -1;
+		}
 		$gifif = $gif['gifif'];
 	} else {
 		$gifif = pfSense_interface_create2("gif");
+		if (!is_string($gifif)) {
+			log_error(sprintf(gettext('Failed to configure interface %1$s: Could not create temporary interface %2$s'), $gif['if'], 'gif'));
+			return -1;
+		}
 	}
 
 	/* Do not change the order here for more see gif(4) NOTES section. */
@@ -4608,6 +4644,10 @@ function interface_6rd_configure($interface, $wancfg) {
 		pfSense_interface_destroy($stfiface);
 	}
 	$tmpstfiface = pfSense_interface_create2("stf");
+	if (!is_string($tmpstfiface)) {
+		log_error(sprintf(gettext('Failed to configure interface %1$s: Could not create temporary interface %2$s'), $wanif, 'stf'));
+		return false;
+	}
 	pfSense_interface_rename($tmpstfiface, $stfiface);
 	pfSense_interface_flags($stfiface, IFF_LINK2);
 	mwexec("/sbin/ifconfig {$stfiface} inet6 {$rd6prefix}/{$rd6prefixlen}");
@@ -4724,6 +4764,10 @@ function interface_6to4_configure($interface, $wancfg) {
 		pfSense_interface_destroy($stfiface);
 	}
 	$tmpstfiface = pfSense_interface_create2("stf");
+	if (!is_string($tmpstfiface)) {
+		log_error(sprintf(gettext('Failed to configure interface %1$s: Could not create temporary interface %2$s'), $wanif, 'stf'));
+		return;
+	}
 	pfSense_interface_rename($tmpstfiface, $stfiface);
 	pfSense_interface_flags($stfiface, IFF_LINK2);
 	mwexec("/sbin/ifconfig {$stfiface} inet6 {$stflanpr} prefixlen 16");