Setup Wizard can result in invalid LAN DHCP pool calculation

1) consider where the LAN IP is in the subnet range and then put the
DHCP pool in the biggest remaining segment, either above or below.
2) Check the size of the available segment. If it is reasonably big then
leave some space at either end of the segment, like the old code was
doing. Otherwise give all the space to the pool.
3) Do not allow subnet mask 32 - I can't think of a use case for LAN to
have a /32 subnet mask, it kind of breaks the whole concept of LAN.
4) Provide more detailed separate messages if the user tries to use the
network address or broadcast address as the LAN IP.

1 files changed, 44 insertions, 11 deletions

diff --git a/usr/local/www/wizards/setup_wizard.xml b/usr/local/www/wizards/setup_wizard.xml
index 95582fd..0c8904f 100644
--- a/usr/local/www/wizards/setup_wizard.xml
+++ b/usr/local/www/wizards/setup_wizard.xml
@@ -534,19 +534,52 @@
 			print_info_box_np("Invalid LAN IP Address. Please press back in your browser window and correct.");
 			die;
 		}
-		if ($_POST['subnetmask'] < 31 &&
-		    ($_POST['lanipaddress'] == gen_subnet($_POST['lanipaddress'], $_POST['subnetmask']) ||
-		     $_POST['lanipaddress'] == gen_subnet_max($_POST['lanipaddress'], $_POST['subnetmask']))) {
-			print_info_box_np("Invalid LAN IP Address. Please press back in your browser window and correct.");
+
+		$lowestip = gen_subnet($_POST['lanipaddress'], $_POST['subnetmask']);
+		$highestip = gen_subnet_max($_POST['lanipaddress'], $_POST['subnetmask']);
+
+		if ($_POST['subnetmask'] < 31) {
+			if ($_POST['lanipaddress'] == $lowestip) {
+				print_info_box_np("LAN IP Address equals subnet network address. This is not allowed. Please press back in your browser window and correct.");
+				die;
+			}
+			if ($_POST['lanipaddress'] == $highestip) {
+				print_info_box_np("LAN IP Address equals subnet broadcast address. This is not allowed. Please press back in your browser window and correct.");
+				die;
+			}
+		} else {
+			print_info_box_np("Invalid subnet mask, choose a mask less than 31. Please press back in your browser window and correct.");
 			die;
 		}
-		$ft = explode(".", $_POST['lanipaddress']);
-		$ft_ip = $ft[0] . "." . $ft[1] . "." . $ft[2] . ".";
-		$config['dhcpd']['lan']['range']['from'] = $ft_ip . "10";
-		$highestip = gen_subnet_max($_POST['lanipaddress'], $config['interfaces']['lan']['subnet']);
-		$hi = explode(".", $highestip);
-		$highestip = $hi[3]-10;
-		$config['dhcpd']['lan']['range']['to'] = $ft_ip . $highestip;
+
+		$ipaddresses_before = ip_range_size_v4($lowestip, $_POST['lanipaddress']);
+		$ipaddresses_after = ip_range_size_v4($_POST['lanipaddress'], $highestip);
+
+		if ($ipaddresses_after >= $ipaddresses_before) {
+			// The LAN IP is in the 1st half of the subnet, so put DHCP in the 2nd half.
+			if ($ipaddresses_after > 30) {
+				// There is reasonable space in the subnet, use a smaller chunk of the space for DHCP
+				// This case will work out like the old defaults if the user has specified the ".1" address.
+				// The range will be something like ".10" to ".245"
+				$config['dhcpd']['lan']['range']['from'] = ip_after($_POST['lanipaddress'], 9);
+				$config['dhcpd']['lan']['range']['to'] = ip_before($highestip, 10);
+			} else {
+				// There is not much space in the subnet, so allocate everything above the LAN IP to DHCP.
+				$config['dhcpd']['lan']['range']['from'] = ip_after($_POST['lanipaddress']);
+				$config['dhcpd']['lan']['range']['to'] = ip_before($highestip);
+			}
+		} else {
+			// The LAN IP is in the 2nd half of the subnet, so put DHCP in the 1st half.
+			if ($ipaddresses_before > 30) {
+				// There is reasonable space in the subnet, use a smaller chunk of the space for DHCP
+				$config['dhcpd']['lan']['range']['from'] = ip_after($lowestip, 10);
+				$config['dhcpd']['lan']['range']['to'] = ip_before($_POST['lanipaddress'], 9);
+			} else {
+				// There is not much space in the subnet, so allocate everything below the LAN IP to DHCP.
+				$config['dhcpd']['lan']['range']['from'] = ip_after($lowestip);
+				$config['dhcpd']['lan']['range']['to'] = ip_before($_POST['lanipaddress']);
+			}
+		}
 		]]>
 	</stepsubmitphpaction>
 </step>