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Module Nn_datanode_ctrl


module Nn_datanode_ctrl: sig .. end
Manage tickets and push ticket secrets to the datanodes

exception Datanode_error of Nn_datastores.datastore * exn
Datanode_error(ds,e): The communication with datastore ds caused the exception e. Usually an RPC error, or a socket error.
val reset : unit -> unit
Executes a ticket reset in the background

type ticket_verifier = {
   tv_safetrans_id : int64;
   tv_safetrans_tmo : int64;
   tv_safetrans_sec : int64;
   tv_datanodes : int list;
   mutable tv_enabled : bool;
}
This is almost the same as Nn_alloc_types.transacted_datastores
val new_ticket_verifier : unit -> ticket_verifier
val enable_ticket_verifier_e : ticket_verifier -> unit Uq_engines.engine
Pushes a safetrans secret to all enabled datanodes. If this is the first invocation, the safetrans are reset beforehand. Returns the list of datastore ID's to which the new safetrans could be pushed (which may be empty!)

May transition to Datanode_error.

val disable_ticket_verifier : ticket_verifier -> (unit -> unit) -> unit
disable_ticket_verifier tv f_post: Schedules that tv will be disabled soon. After this has happened the function f_post is called back.
val disconnect : int -> unit
Disconnects from this datanode
val post_start_hook : Netmcore.res_id -> Pfs_auth.client_auth -> unit
post_start_hook pool cauth

Note that disable_ticket_verifier does not disable the verifier immediately, but delays this to the next round of housekeeping - which usually happens once every second.

There is a security risk here: The verifier remains valid even after the transaction is closed. Although this is only for a very short period of time, this can be abused by a malicious user.

This problem is handled in this way: The verifier can be used to access blocks. There is no problem when only the blocks are accessed for which the ticket was originally valid, i.e. the blocks of the accessed files. The security hole exists only when these blocks are reused for other files - the verifier would then grant access to these other files although there is actually no permission.

So the idea is to prevent that blocks are reused for other files until the verifier is really cancelled. We already have a mechanism - the blocks need to be pinned in the blockmaps (method pin). Such blocks are not freed as long as the pinning remains.

The Nn_blockmap module has been changed so that the pinning remains intact even when a commit or rollback occurs. First when the special release method is called the pinning is revoked. We do this now right after the cancellation of the ticket, using the f_post callback of Nn_datanode_ctrl.disable_ticket_verifier.

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