Duplicate items in trade

[Anonymous!!!]

Okay, sorry if this is the wrong place to put this but I recently stumbled across *zorro* who was trying to scam me for some of my rares. I messed with him for a bit at first like when he asked for my mask I put a Noh Mask in not my jester but after a while I realized he was putting duplicate items in the trade. I didn't even notice at first, but he was putting at first 2 desert hats and 2nd 2 yeti masks. I got a screenshot of it that I can pull out when needed but I'm not here to report him, I'm here to ask about how he is doing it. I want to know if this is a client-based thing where it will not allow you to duplicate or server based. I am feeling a little cautious towards if only one of the items is received. Basically I want to know:
A. Is it client based or server based?
B. Is it possible he could use this to scam?
C. What else could he do with this?

If you want my screenshot tell me, I'll resize it and upload it.

[Anonymous!!!]

Okay, I just got him again, this is rather interesting...
At first he was duplicating yeti masks and now he duplicated a whole warlord set and apparently only has 1 yeti mask. I'll resize the screenshots now.

EDIT:
Seems as though he isn't putting duplicate items in trade but he is actually adding items he already has in trade.

EDIT 2:
Apparently it's a manaplus function to be able to add 2 hats or whatever but it seems he is adding more than he has...

[o11c]

There is code in the server that *looks* like it is intended to prevent items from being added to trade twice, but I don't think it works.

However, at the time of actual trade, there is a check:

Code: Select all

        if (sd->deal_item_amount[trade_i] >
            sd->status.inventory[sd->deal_item_index[trade_i] - 2].amount
            || sd->deal_item_amount[trade_i] < 0)

that should prevent actually exploiting.

[Crush]

Doesn't this allow an exploit where you offer two instances of an items in a trade but only trade one on complete?

[Anonymous!!!]

I'm not sure but unless he can destroy yeti masks with a click of his fingers I think he found some bug that allows him to add the items again. O11c would that code work per item in trade or would it check each individual item? (For example he has 1 maggot slime, but has it twice in trade, would it say: Oh, he has a maggot slime for both of them?)