If OS is booted with ipv6.disable=1, to disable ipv6, and docker is started on an existing bridge with an IP address then docker fails to start with the following error:

"Error starting daemon: Error initializing network controller: Error creating default "bridge" network: Failed to setup IP tables, cannot acquire Interface address: Interface docker0 has no IPv4 addresses"

Removing ipv6.disable=1 is a work around but I would prefer to run without ipv6 enabled.

I veified that there was an IP address before attempting to start docker. After attempting to start docker there is no IP address on the bridge. Docker can start if is creates the bridge but not a second time as the bridge already exists.

to duplicate:
boot os with ipv6.disable=1
create a bridge
assign and ip address to the bridge
attempt to start docker with -b bridgename
(or start docker twice without specifying a bridge when booted with ipv6.disable=1)