[MUD-Dev] Gearing up against GEAR

Alistair Milne vw_krug at ntlworld.com
Tue Jul 24 09:07:41 New Zealand Standard Time 2001


> -----Original Message-----
> From: Sean Kelly

> Is there a way to get at any other timer that isn't affected by
> GEAR?  If so, I'd report both.  Drift should be rapidly obvious.

Your server clock is the only one you can trust.  If you start to
read values from a different system clock, somebody will come along
with Gear2 to fool both clocks.

I wonder if Gear affects games like Quake and SubSpace where the
client seems to interpolate and compensate between server updates so
you're never shooting at an enemy you're shooting at his ping-lagged
shadow.  Surely no matter how rapidly a client says "I'm here...Now
I'm here...Now I'm here...Now I'm shooting this gun in this
direction...", the server has time-based rules that don't allow
these actions to all pile up-together, and so the Gear-enhanced
client will constantly be getting pulled-back in time to the
server's version of reality.

This gives me a thought actually about how to detect someone using
Gear.  If each packet from the client comes with a timestamp which
the client adds, e.g. "I'm here at 10:43:233" then the server can
compare two adjacent incoming packets and do a little check to see
if that transition is legal in the stated amount of time.  If not,
the client is lying.  Since you are basing it on the time reported
by the client, the problem with packets getting stacked-up at an
intermediate router does not matter, it does not affect the server's
judgement.  Since it is safe to assume that people are using Gear to
break the rules, e.g. going faster/slower than is possible, this
might be a good way to detect them.  So what if they're using Gear
but not breaking the rules, we're not interested in that.

Alistair

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