[RFE] Provide attachment hints for VIF attach

[Zhenguo Niu]

The vif attach API can only accept vif name or id, then ironic will help to choose a portgroup or port to associate with that neutron port.But there may be different types of port/portgroup in ironic like GE or 10GE, and users would like to specify certain port to use, This is useful in standalone senario or ironic with other projects instead of nova.

[Sam Betts (sambetts)]

The vif attach/detach API was designed to specifically not include the port/portgroup ID to allow network drivers the most freedom to operate and handle the mappings. For example there are scenarios where there won't be an ironic ports for a node until a vif is attached when supporting composable hardware where NICs are created on the fly. Now that doesn't mean we can't support more advanced mapping like what your asking for, and this is something we've planned to do for a while, it seems to me that a better/more generic solution would be to provide a means to specify attachment hints, similar to Ironic's existing root device hints, where you could specify information like "speed>=10gE,mac-address==<mac address>" or "type==infiniband"

[Ruby Loo (rloo)]

I'd like to see a spec for this, that describes the flow of information (how the hints get into the system, where they are stored, what hints are supported, etc.)