Add DHCP_SUBNET_MASK argument for DHCP config

This change adds a new argument for adding DHCP_SUBNET_MASK value when calling EnableDHCP()

This change is required along with updates to pi-hole/web settings.php, savesettings.php & func.php files to handle the additional field within DHCP settings form.

Signed-off-by: biodigitalfish <11165243+biodigitalfish@users.noreply.github.com>

advanced/Scripts/webpage.sh

@@ -448,7 +448,7 @@ ProcessDHCPSettings() {
 #            ANY CHANGES MADE TO THIS FILE WILL BE LOST ON CHANGE             #
 ###############################################################################
 dhcp-authoritative
-dhcp-range=${DHCP_START},${DHCP_END},${leasetime}
+dhcp-range=${DHCP_START},${DHCP_END},${DHCP_SUBNET_MASK},${leasetime}
 dhcp-option=option:router,${DHCP_ROUTER}
 dhcp-leasefile=/etc/pihole/dhcp.leases
 #quiet-dhcp
@@ -493,11 +493,12 @@ EnableDHCP() {
     addOrEditKeyValPair "${setupVars}" "DHCP_ACTIVE" "true"
     addOrEditKeyValPair "${setupVars}" "DHCP_START" "${args[2]}"
     addOrEditKeyValPair "${setupVars}" "DHCP_END" "${args[3]}"
-    addOrEditKeyValPair "${setupVars}" "DHCP_ROUTER" "${args[4]}"
-    addOrEditKeyValPair "${setupVars}" "DHCP_LEASETIME" "${args[5]}"
-    addOrEditKeyValPair "${setupVars}" "PIHOLE_DOMAIN" "${args[6]}"
-    addOrEditKeyValPair "${setupVars}" "DHCP_IPv6" "${args[7]}"
-    addOrEditKeyValPair "${setupVars}" "DHCP_rapid_commit" "${args[8]}"
+    addOrEditKeyValPair "${setupVars}" "DHCP_SUBNET_MASK" "${args[4]}"
+    addOrEditKeyValPair "${setupVars}" "DHCP_ROUTER" "${args[5]}"
+    addOrEditKeyValPair "${setupVars}" "DHCP_LEASETIME" "${args[6]}"
+    addOrEditKeyValPair "${setupVars}" "PIHOLE_DOMAIN" "${args[7]}"
+    addOrEditKeyValPair "${setupVars}" "DHCP_IPv6" "${args[8]}"
+    addOrEditKeyValPair "${setupVars}" "DHCP_rapid_commit" "${args[9]}"
 
     # Remove possible old setting from file
     removeKey "${dnsmasqconfig}" "dhcp-"