Specifically document how to handle the case of explicitly starting a
bridge and then dynamically adding interfaces to it.
brctl_br0=''
bridge_add_eth0='br0'
- Use sysfs to read bridge information from the system instead of
parsing the brctl outputs.
- Allow setting of all bridge configuration parameters using new sysfs
methods, modelled after bonding configuration. Also works for per-port
bridge interface parameters.
- Document pre-starting an empty bridge for dynamic add.
- Check for interface existence before adding to bridge.
- Should fix bug #293046, #309185.
