Trailblazer,
I can see why you thought that the quota you set (from your screenshot) would limit each user individually to the quota you set, but this particular option sets a
single combined quota for all users without explicit quotas defined. If you set the quota as shown, then look at the quota_usage page, it is listed as "all others combined". Many (most?) people are using gargoyle in a different setting to you, where there is a small pool of known MAC addresses, rather that a large and dynamic pool of unknown MAC addresses (ie: that are not known in advance) connecting to their router. In this usual setting it makes sense to have each known MAC address assigned a fixed ip address, each user's different devices (identified by MAC address) assigned to a continuous range of ip addresses, and quota's set per range. Guest users can still be accommodated with a separate small pool of dynamically assigned ip addresses, with a (smaller?) combined total. This setup makes for fair sharing of available upload/download quota per billing period, between normal users, with minimal intervention (other than telling them the router's PSK) to allow access to any temporary guests.
It looks like what you want is a captive portal/hotspot. As far as I know, as yet no easy way exists to implement this using Gargoyle. (see a couple of older threads which explain the issue(s), one from
Sept 2010, and one from
April 2010)
A little digging around on the internet suggests that none of the possible addons (nocatsplash, nodogsplash, CoovaChilli, WifiDog) have been upgraded to work with the current (Backfire) version of OpenWRT, and are not trivial to install in any case/ or may not do more than provide a splash screen without actually limiting quota/bandwidth (nocatsplash, nodogsplash). WifiDog looks closest to doing what you want, but looks like it might be a pain to get running, and require other resources than just an OpenWRT router (eg Gargoyle) to implement.
The posts referred to above suggest that a captive portal is on Eric's todo list for Gargoyle, but implementing wireless N, upgrading to 2.6 kernel and tracking down subtle bugs have been higher priority for a while now. I have no knowledge of what timeframe is involved in implementing such a feature for Gargoyle.
In the meantime, you could setting individual quotas for each ip_address in your DHCP range, with suitable throttling once the quota is reached. You would need a big enough DHCP range to allow 1 ip_address each for your usual number of campers, + some spare capacity to allow for people leaving and others arriving on the same day. If you set DHCP lease time for 24 hours, and the quotas to reset daily (as you indicated with your screenshot), each user would keep their ip_address and quota, unless they do something active (of course tech-savvy users can change their MAC or ip addresses, and therefore get a new quota).
As pbix suggested, the other way to get close to what you want is to use QoS to ensure that everyone has a fair share of the current bandwidth, but I have no experience using this feature of Gargoyle.
Ian