Flannel network not working on CoreOS

[genti-t]

On coreos I tried both cases with
kube_network_plugin: flannel
and
kube_network_plugin: canal

• using flannel, pod ip is based on docker0 subnet, and not from kube_pods_subnet.
  this is big problem for me right now, I need some help to figure it out, how to fix it

• using canal, pod ip is correct and pods are able to communicate with each other, but the host can’t connect to pod.

[genti-t]

By default on docker service uses this envs:

ExecStart=/usr/lib/coreos/dockerd daemon --host=fd:// $DOCKER_OPTS $DOCKER_CGROUPS $DOCKER_OPT_BIP $DOCKER_OPT_MTU $DOCKER_OPT_IPMASQ

$DOCKER_NETWORK_OPTIONS is not one of them,
so a solution here is to modify /etc/systemd/system/docker.service.d/docker-options.conf
accordingly, for example modifying only $DOCKER_OPTS:

[Service]
Environment="DOCKER_OPTS=--insecure-registry=10.233.0.0/18 --graph=/var/lib/docker --bip=10.233.116.1/24 --mtu=1450"

After that docker is able to use --bip=10.233.116.1/24 --mtu=1450 too.

What do you think ?

[genti-t]

A more simple and also more cleaner solution here is to change DOCKER_NETWORK_OPTIONS into DOCKER_OPT_BIP in network_plugin/templates/flannel-options.j2
This is only used on coreos AFAIK and will not brake something else.