2.9 KiB
| title | description | keywords |
|---|---|---|
| Docker and iptables | The basics of how Docker works with iptables | network, iptables |
On Linux, Docker manipulates iptables rules to provide network isolation.
This is an implementation detail, and you should not modify the rules Docker
inserts into your iptables policies.
Add iptables policies before Docker's rules
All of Docker's iptables rules are added to the DOCKER chain. Do not
manipulate this table manually. If you need to add rules which load before
Docker's rules, add them to the DOCKER-USER chain. These rules are loaded
before any rules Docker creates automatically.
Restrict connections to the Docker daemon
By default, all external source IPs are allowed to connect to the Docker daemon. To allow only a specific IP or network to access the containers, insert a negated rule at the top of the DOCKER filter chain. For example, the following rule restricts external access to all IP addresses except 192.168.1.1:
$ iptables -I DOCKER-USER -i ext_if ! -s 192.168.1.1 -j DROP
Please note that you will need to change ext_if to correspond with your
host's actual external interface. You could instead allow connections from a
source subnet. The following rule only allows access from the subnet 192.168.1.0/24:
$ iptables -I DOCKER-USER -i ext_if ! -s 192.168.1.0/24 -j DROP
Finally, you can specify a range of IP addresses to accept using --src-range
(Remember to also add -m iprange when using --src-range or --dst-range):
$ iptables -I DOCKER-USER -m iprange -i ext_if ! --src-range 192.168.1.1-192.168.1.3 -j DROP
You can combine -s or --src-range with -d or --dst-range to control both
the source and destination. For instance, if the Docker daemon listens on both
192.168.1.99 and 10.1.2.3, you can make rules specific to 10.1.2.3 and leave
192.168.1.99 open.
iptables is complicated and more complicated rule are out of scope for this
topic. See the Netfilter.org HOWTO
for a lot more information.
Prevent Docker from manipulating iptables
It is possible to set the iptables key to false in the Docker engine's configuration file at /etc/docker.daemon.json, but this option is not appropriate for most users. It is not possible to completely prevent Docker from creating iptables rules, and creating them after-the-fact is extremely involved and beyond the scope of these instructions. Setting iptables to false will more than likely break container networking for the Docker engine.
For system integrators who wish to build the Docker runtime into other applications, explore the moby project.