Enabling IPMI double bridge support

This blueprint proposes IPMI double bridging support in ironic. Currently, IPMI power driver in ironic does not support bridging.
Many of the recent server architecture is based on distributed management. For a chassis that has “n” number of servers, the management is delegated from the core controller to many satellite controllers, which mandates the need for bridging.

Bridging provides a mechanism for routing IPMI Messages between different channels. The double bridge option is used to send a IPMI message to a management controller that is not directly connected to the BMC/IPMC i.e. double bridging is required when the IPMI message should be routed through a transit address to reach target address.

For example: Below is the ipmitool command that uses double bridging to power on the target node (0x72) through a satellite controller (0x82)

# ipmitool -I lanplus -H xx.xx.xx.xx -U xxxx -P xxxxx -B 0 –T 0x82 –b 7 –t 0x72 -m 0x20 chassis power on
where:
• –B <transit channel for bridged request (dual bridge)>
• –T <transit address for bridge request (dual bridge)>
• -b <ipmi channel number>
• -t <target slave address>
• -m <source slave address>