[PATCH 0/1] nvmet: View subsystem connections on nvmeof target

[Sagi Grimberg]

> HI,
> We need to list the nqn and their IP connected to our target nvmeof server.
> In fact we can have several dozen connections on a machine and we need to know
> which server is connected to which subsystem.
> Currently there is no way to find out which machine is connected to which subsystem
> except through the nqn.
> The nqn can be modified by the initiator , so for us it’s not necessarily a source
> we can trust.
> We’ve created a POC to retrieve the nqn and associated ip when a client is connected
> to a subsystem.

No patch attached afaict.

> We’ve tested this poc on a tcp and rdma connection and it’s OK.
> For the POC we write to the attr_connected_ctrls file in the subsystems directory for
> each subsystem.
> We’re not sure this is the right implementation.
> Either we create a ctrls directory which will be created on the userland side and
> populated with information
> from the ctrl connected when the ctrl number folder is created.
> Or we use the host directory to add an entry when the machine is connected to write its
>   IP address, but this folder is also used by ACLs.
> Or we stick to a simple attribute listing all connected controllers nqn and addresses.
> That being said, given the reduced size of a configfs page and the large size of some
> addresses (ie IPv6 address), that would drastically limit the numbers of controllers
> and addresses we could list in this attribute.
> what do you think?

I don't think that this should be a configfs attribute at all. And yes,
a single attribute is going to be unnecessarily limited.

This type of information probably belongs in debugfs. It is possible to
have nvmet create a root in debugfs and build a hierarchy that the user
can traverse to get this information from something like:
/<debugfs>/nvmet/<subsys>/<ctrl>/

A controller can expose different things like host_traddr and hostnqn.