network-functions: Add check_subnet()

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>

config/cfgroot/network-functions.pl

@@ -163,6 +163,21 @@ sub check_ip_address_and_netmask($$) {
 	return &check_netmask($netmask);
 }
 
+# Returns True for all valid subnets like a.b.c.d/e or a.b.c.d/a.b.c.d
+sub check_subnet($) {
+	my $subnet = shift;
+
+	my ($address, $network) = split(/\//, $subnet, 2);
+
+	# Check if the IP address is fine.
+	my $result = &check_ip_address($address);
+	unless ($result) {
+		return $result;
+	}
+
+	return &check_prefix($network) || &check_netmask($network);
+}
+
 # For internal use only. Will take an IP address and
 # return it in a normalised style. Like 8.8.8.010 -> 8.8.8.8.
 sub _normalise_ip_address($) {

config/rootfiles/core/94/filelists/files

@@ -5,3 +5,4 @@ srv/web/ipfire/cgi-bin/logs.cgi/log.dat
 srv/web/ipfire/cgi-bin/mail.cgi
 var/ipfire/langs
 var/ipfire/menu/40-services.menu
+var/ipfire/network-functions.pl