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dockeriptables

Disable access to LAN from docker container

I am running Gentoo host with Ubuntu container in Docker. They communicate via bridge automatically created by Docker. I would like to drop all traffic for 192.168.0.0/16 that may come out of container. 

$sudo iptables -S
-P INPUT ACCEPT
-P FORWARD ACCEPT
-P OUTPUT ACCEPT
-A FORWARD -d 172.17.0.2/32 ! -i docker0 -o docker0 -p tcp -m tcp --dport 443 -j ACCEPT
-A FORWARD -o docker0 -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A FORWARD -i docker0 ! -o docker0 -j ACCEPT
-A FORWARD -i docker0 -o docker0 -j ACCEPT
$sudo iptables -t nat -S
-P PREROUTING ACCEPT
-P INPUT ACCEPT
-P OUTPUT ACCEPT
-P POSTROUTING ACCEPT
-N DOCKER
-A PREROUTING -m addrtype --dst-type LOCAL -j DOCKER
-A OUTPUT ! -d 127.0.0.0/8 -m addrtype --dst-type LOCAL -j DOCKER
-A POSTROUTING -s 172.17.0.0/16 ! -o docker0 -j MASQUERADE
-A DOCKER ! -i docker0 -p tcp -m tcp --dport 443 -j DNAT --to-destination 172.17.0.2:443

Please let me know if I need to provide extra information

Solution

  • One option would be to run docker with --icc=false, preventing any container to communicate with other containers, you could then let containers communicate with each other by linking them with --link=container_name:alias. This will not block the container from communicating with the host at this time though.

    You could also operate with iptables with a rule like:

    iptables -A INPUT -i docker0 -d 192.168.0.0/16 -j DROP

    keep in mind that a host doesn't see dropped packet coming back by icmp error, so maybe REJECT is more appropriate in most cases.

    edit: correcting the rule to block the forward to other hosts:

    iptables -I FORWARD -i docker0 -d 192.168.0.0/16 -j DROP