Using iptables to redirect all docker outbound traffic back into container

I've been stuck on this problem all day and am keeping my fingers crossed some iptables expert reads this and can help me please. I would like to force all my docker containers's outbound traffic to go through a socks5 proxy. This is the closest I've come:

iptables -t nat -N REDSOCKS
iptables -t nat -A REDSOCKS -s 172.20.0.0/16 -d 0.0.0.0/8 -j RETURN
iptables -t nat -A REDSOCKS -s 172.20.0.0/16 -d 10.0.0.0/8 -j RETURN
iptables -t nat -A REDSOCKS -s 172.20.0.0/16 -d 127.0.0.0/8 -j RETURN
iptables -t nat -A REDSOCKS -s 172.20.0.0/16 -d 169.254.0.0/16 -j RETURN
iptables -t nat -A REDSOCKS -s 172.20.0.0/16 -d 172.16.0.0/12 -j RETURN
iptables -t nat -A REDSOCKS -s 172.20.0.0/16 -d 192.168.0.0/16 -j RETURN
iptables -t nat -A REDSOCKS -s 172.20.0.0/16 -d 224.0.0.0/4 -j RETURN
iptables -t nat -A REDSOCKS -s 172.20.0.0/16 -d 240.0.0.0/4 -j RETURN

iptables -t nat -A REDSOCKS -s 172.20.0.0/16 -p tcp -j DNAT --to-destination 172.17.0.1:12345
iptables -t nat -A OUTPUT -s 172.20.0.0/16 -j REDSOCKS
iptables -t nat -A PREROUTING -s 172.20.0.0/16 -j REDSOCKS

It works almost perfectly, but the socks5 proxy is unable to tell the originating IP address. The remote address is always '127.0.0.1' Is there any way I can keep the originating IP address? # Example Scenario 1) I have applied the iptables rules above to my docker host 2) I have a docker container with the address 172.20.0.2 2) Inside that container, I do a curl to example.com 3) The traffic is forwarded to 172.17.0.1:12345 (the docker host machine) 4) The server running on 12345 shows the remote IP address as being '127.0.0.1' 5) I would like the remote IP address to show as 172.20.0.2 Thank to anyway who can try and help me with this.