luci-app-firewall: limit zone name length to 11 characters

Change the maximum length of a firewall zone name from 14 to 11 characters.

Longer names break iptables rule generation (max. 29 chars are allowed).

XT_EXTENSION_MAXNAMELEN = 29
29 - sizeof("postrouting_") - sizeof("_rule") - sizeof("\0") = 11

References to:
https://github.com/openwrt/luci/issues/507
https://dev.openwrt.org/ticket/20380

Signed-off-by: Hannu Nyman <hannu.nyman@iki.fi>

applications/luci-app-firewall/luasrc/model/cbi/firewall/zone-details.lua

@@ -60,7 +60,7 @@ s:tab("advanced", translate("Advanced Settings"))
 name = s:taboption("general", Value, "name", translate("Name"))
 name.optional = false
 name.forcewrite = true
-name.datatype = "and(uciname,maxlength(14))"
+name.datatype = "and(uciname,maxlength(11))"
 
 function name.write(self, section, value)
 	if zone:name() ~= value then