[19.03 backport] Set the bip network value as the subnet

[thaJeztah]

backport of #40497
fixes #40392

Dont assign the --bip value directly to the subnet
for the default bridge. Instead use the network value
from the ParseCIDR output

- Description for the changelog

[cpuguy83]

LGTM

[thaJeztah]

@AkihiroSuda ptal

[thaJeztah]

@AkihiroSuda @arkodg ptal

[tulanian]

We are having some problems with k8s after upgrading docker-ce to a version that includes this change. If I'm reading this correctly, all of our hosts running docker require the --bip config to be changed from the bridge IP to the bridge network, e.g.
--bip=172.16.0.1/16
to
--bip=172.16.0.0/16

Is this right?

[arkodg]

edit : @tulanian you want to continue using 172.16.0.1/16 if you want the bridge-ip to be 172.16.0.1, this should only affect the Subnet value in the bridge configuration (sets it to 172.16.0.0/16 instead of 172.16.0.1/16 which is not valid)

[tulanian]

@arkodg , ok, to confirm, no change is needed to the bip config because of this commit?

Btw, the problem we're having with k8s is with pods that run docker-in-docker to build images. We're having to add the --network=host config to the pod-based dockerd or traffic won't exit the pod.

[arkodg]

that's right @tulanian no change is needed

regarding k8s traffic, you are bypassing CNI by making --network=host , its probably not related to docker

[tulanian]

@arkodg It was working without --network=host and were trying to determine what broke it. An upgrade to docker-ce is one possibility. Thanks for the clarification on the bip config.