Since it's only Layer 7; just install something such as DDOS Deflate or null route the IP Range.
To null route the IP:
route add -host 222.186.129.X reject
ip route get 222.186.129.x
Output
RTNETLINK answers: Network is unreachable
To null route the whole subnet:
route add -net 222.186.0/24 gw 127.0.0.1 lo
Or to install DDOS Deflate:
wget http://www.inetbase.com/scripts/ddos/install.sh
chmod 0700 install.sh
./install.sh
(Uninstall) ->
wget http://www.inetbase.com/scripts/ddos/uninstall.ddos
chmod 0700 uninstall.ddos
./uninstall.ddos
If the attack is still to big to handle I recommend contacting your ISP; however another option is to get a reverse proxy which has DDOS Protection from Layer 7 attacks such as http://x4b.net (Quite cheap soloution)