[libvirt] RFC: Admin interface for connection monitoring

Hello everyone. Trying to create new interface for the libvirt daemon, mainly for connection monitoring, I came across few things I'd like to propose/discuss. This interface will be used to manage active connections of the daemon (list/kill) and other until-now impossible things (e.g. changing logging filters on-the-fly). Connection to this interface will be: - available even when no normal/priority workers are available, - distinguished (or completely separated) from other daemon connections, - (should be) more restricted than other connections. Having the connection available with all the worker threads being blocked/deadlocked creates the possibility of for example listing the connections even when all APIs block. Such manipulations mustn't be possible over the standard connections and that's why the connections should be distinguished. The connection restriction is hard to check, but the permissions for the socket should be less or equal to the rw socket with having no authentication only when rw socket has no authentication. My idea is following: - new 'admin_protocol.x' with specification of new program, - default connection limitation to this interface to only root-owned socket with 700 (authentication optional, see above), so only root on the host can utilize it, - configurable number of admin workers, but with 1 as a default, - splitting usable parts of virsh and reusing them to create virsh-admin binary. More controversial ideas I'd like to hear somebody else's opinion (even more than for the other things): - create a new separate library (libvirt-admin.so) to be used in the client, this library will have it's own virAdminConnect{,Auth}Open(), probably without an URI parameter (or with, but disabled for now, in case we want to enable remote connections later) - it is IMHO pointless to add a driver type for this, but it should definitely be configurable at compile time as well as in config (admin_workers = 0, maybe), - keep the connection handling on the current code and instead of duplicating much of it (so there will be a new service, much like the read-only socket, but for admin API only), - create a new pool of workers just for admin connections (similarly to the priority workers pool), with the dispatching being recognized by the protocol it is created in (remote, qemu, lxc protocols will go to normal/priority workers, whether admin protocol will be dispatched to the admin workers) and of course impossible from other connections than the admin one, which leads me to the next point; - we can either add next flag for admin connection (similarly to the readonly one) or make it future-friendly and change the readonly bool into a virConnectionType enum (for example). I must admit, I'm probably doing something wrong or we have old documentation. Commands like 'make -C src rpcgen' don't work and I don't understand why admin_protocol-structs isn't automatically generated, but I've made it work for now. Have a nice day, Martin