Change default route in docker container

If I understand the question, the problem is : when restarting a container connected to multiple bridges, how to prefer a bridge to use for default route ?

I searched available options and made some tests, I did not found any docker command line option to specify a default route or to prefer a bridge as default when the container is connected to multiple bridges. When I restart a container connected to the default bridge (bridge) and a custom bridge (your homenet), the default route is automatically set to use the default bridge (gateway 172.17.0.1). This corresponds to the behavior you describe.

Solution 1: Specify a start script in the run command that is in charge to change the default route and start the service(s) you container has to run:

docker run \
  --cap-add NET_ADMIN \ # to allow changing net settings inside the container 
  --name container1 \
  --restart always \ # restart policy
  your_image \
  /path/to/your_start_script.sh

The your_start_script.sh:

ip route del default 
ip route add default via 192.168.130.3

# here goes instructions/services your container is supposed to run

This script has to be available inside the container, it can be on a shared folder (-v option) or loaded at image building with a Dockerfile.

Note: before connecting the container to your custom bridge (docker network connect homenet container1), your_start_script.sh will crash because the default route does not correspond to any available network.

I tested to log the output of ip route inside container1 run with --restart always, after connecting it to the custom bridge it has the wanted default route.

Solution 2: Set container default route from host on container start events

docker events --filter "container=container1" |\
  awk '/container start/ { system("/path/to/route_setting.sh") }'

Where route_setting.sh contains your instructions for changing the container's default route:

pid=$(sudo docker inspect -f '{{.State.Pid}}' container1)
sudo mkdir -p /var/run/netns
sudo ln -s /proc/$pid/ns/net /var/run/netns/$pid
sudo ip netns exec $pid ip route del default 
sudo ip netns exec $pid ip route add default via 192.168.130.3

This solution avoids giving special permissions to the container and transfers the route changing responsibility to the host.

You can enter into the namespace of a container with the nsenter command, and then execute a command in it with. Around so:

nsenter -n -t $(docker inspect --format {{.State.Pid}} $dockername) ip route add something.
nsenter -n -t $(docker inspect --format {{.State.Pid}} $dockername) ip route del something.