Also, implement nm_remote_connection_commit_changes_async() by calling
nm_remote_connection_update2(). It already was also calling the
Update2() D-Bus method.
No longer keep track if a request is already pending. Previously,
in that case, the function would return success in an idle handler.
Instead, just always issue the new request. It's up to the caller to
rate-limit the requests and trigger a scan whenever appropriate. libnm
should not add additional logic to that.
Drop uses of nmdbus_manager_call_get_permissions_sync().
Of course, we should ever call synchronous API while initizliaing the
NMClient. Needs to be fixed eventually.
We still need the bits in "nm-manager.c", to wait until the
NMActiveConnection instance is ready. This is now done by
nm_manager_complete_active_connection().
Eventually, I will refactor libnm to no longer use gdbus-codegen and
no GDBusProxy. In preparation of that, we must stop using that
API.
As first step, change nm_client_deactivate_connection(). Note how this
was done previously:
- nm_client_deactivate_connection() calls nm_manager_deactivate_connection()
- nmdbus_manager_call_deactivate_connection_sync() calls g_dbus_proxy_call_sync()
- g_dbus_proxy_call_sync() calls g_dbus_connection_call_sync()
Currently this is still a bit ugly, because NMClient doesn't directly
track the GDBusConnection nor the name owner. Instead, we need to peel
it out of the object manager. One day, that will all be nicer, but first
get rid of gdbus-codegen.
We will drop GDBusProxy and the gdbus-codegen classes. First, we need to
replace all D-Bus calls from nmdbus_*() API with plain uses of GDBusConnection.
For that, add accessors to get the dbus-connection and the name-owner.
This API is not beautiful, it's an interim solution for now.
Public API should validate input arguments with g_return_*().
Tag the task with the source function (using nm_g_task_new())
and check it in the corresponding _finish() function.
nm_client_add_and_activate_connection_async() must be completed by
nm_client_add_and_activate_connection_finish().
Fixes: be8060f42f ('libnm: add an object-creation-failed test')
Note that the server always returns TRUE for the boolean return value
of ReloadConnections. Hence, this should not change in behavior, because
the server would never have returned FALSE.
However, change behavior of the API. It's odd that the function might
return %FALSE without setting the error output. It's also not clear
what the boolean value of the "ReloadConnections" D-Bus would mean
anyway.
nm_remote_settings_load_connections() and nm_remote_settings_load_connections_async()
behave inconsistently.
It's unexpected, that a FALSE return value may leave @error unset.
Note that before commit 22e830f046 ('settings/d-bus: fix boolean
return value of "LoadConnections"'), the server boolean response
would have been bogus anyway (at least for some versions).
Unify the behavior, and ignore the boolean return value.
A function that accepts a floating variant must consume it.
Fixes: 7691fe5753 ('libnm: add new functions allowing passing options to RequestScan() D-Bus call')
The previous commit marks all synchronous libnm API as deprecated.
In practice, the macro _NM_DEPRECATED_SYNC_METHOD expands to
nothing, because there is no immediate urgency to force users
to migrate.
However nm_client_check_connectivity() is especially bad: it
makes a synchronous call and then updates the content of the
cache artificially. Usually, NMClient's cache of D-Bus objects
is only updated by "PropertiesChanged" D-Bus signals.
nm_client_check_connectivity() instead will act on the response to
the "CheckConnectivity" D-Bus call -- a response that is picked
out of order from the ordered sequence of messages -- and will
update the cache instead of honoring the usual "PropertiesChanged"
signal.
I think such behavior is fundamentally broken. For a trivial property like
NM_CLIENT_CONNECTIVITY such behavior is odd at best. Note how applying
this approach to other functions (like nm_client_deactivate_connection(),
which would affect a much larger state) would not be feasible.
I also imagine it to be complicate to preserve this behavior when
reworking libnm, as I plan to do.
See also commit b799de281b ('libnm: update property in the manager
after connectivity check'), which introduced this behavior to "fix"
bgo#784629.
Note that D-Bus is fundamentally asynchronous. Doing blocking calls
on top of D-Bus is odd, especially for libnm's NMClient. That is because
NMClient essentially is a client-side cache of the objects from the D-Bus
interface. This cache should be filled exclusively by (asynchronous) D-Bus
events (PropertiesChanged). So, making a blocking D-Bus call means to wait
for a response and return it, while queuing all messages that are received
in the meantime.
Basically there are three ways how a synchronous API on NMClient could behave:
1) the call just calls g_dbus_connection_call_sync(). This means
that libnm sends a D-Bus request via GDBusConnection, and blockingly
waits for the response. All D-Bus messages that get received in the
meantime are queued in the GMainContext that belongs to NMClient.
That means, none of these D-Bus events are processed until we
iterate the GMainContext after the call returns. The effect is,
that NMClient (and all cached objects in there) are unaffected by
the D-Bus request.
Most of the synchronous API calls in libnm are of this kind.
The problem is that the strict ordering of D-Bus events gets
violated.
For some API this is not an immediate problem. Take for example
nm_device_wifi_request_scan(). The call merely blockingly tells
NetworkManager to start scanning, but since NetworkManager's D-Bus
API does not directly expose any state that tells whether we are
currently scanning, this out of order processing of the D-Bus
request is a small issue.
The problem is more obvious for nm_client_networking_set_enabled().
After calling it, NM_CLIENT_NETWORKING_ENABLED is still unaffected
and unchanged, because the PropertiesChanged signal from D-Bus
is not yet processed.
This means, while you make such a blocking call, NMClient's state
does not change. But usually you perform the synchronous call
to change some state. In this form, the blocking call is not useful,
because NMClient only changes the state after iterating the GMainContext,
and not after the blocking call returns.
2) like 1), but after making the blocking g_dbus_connection_call_sync(),
update the NMClient cache artificially. This is what
nm_manager_check_connectivity() does, to "fix" bgo#784629.
This also has the problem of out-of-order events, but it kinda
solves the problem of not changing the state during the blocking
call. But it does so by hacking the state of the cache. I think
this is really wrong because the state should only be updated from
the ordered stream of D-Bus messages (PropertiesChanged signal and
similar). When libnm decides to modify the state, there may be already
D-Bus messages queued that affect this very state.
3) instead of calling g_dbus_connection_call_sync(), use the
asynchronous g_dbus_connection_call(). If we would use a sepaate
GMainContext for all D-Bus related calls, we could ensure that
while we block for the response, we iterate that internal main context.
This might be nice, because all events are processed in order and
after the blocking call returns, the NMClient state is up to date.
The are problems however: current blocking API does not do this,
so it's a significant change in behavior. Also, it might be
unexpected to the user that during the blocking call the entire
content of NMClient's cache might change and all pointers to the
cache might be invalidated. Also, of course NMClient would invoke
signals for all the changes that happen.
Another problem is that this would be more effort to implement
and it involves a small performance overhead for all D-Bus related
calls (because we have to serialize all events in an internal
GMainContext first and then invoke them on the caller's context).
Also, if the users wants this behavior, they could implement it themself
by running libnm in their own GMainContext. Note that libnm might
have bugs to make that really working, but that should be fixed
instead of adding such synchrnous API behavior.
Read also [1], for why blocking calls are wrong.
[1] https://smcv.pseudorandom.co.uk/2008/11/nonblocking/
So, all possible behaviors for synchronous API have severe behavioural
issues. Mark all this API as deprecated. Also, this serves the purpose of
identifying blocking D-Bus calls in libnm.
Note that "deprecated" here does not really mean that the API is going
to be removed. We don't break API. The user may:
- continue to use this API. It's deprecated, awkward and discouraged,
but if it works, by all means use it.
- use asynchronous API. That's the only sensible way to use D-Bus.
If libnm lacks a certain asynchronous counterpart, it should be
added.
- use GDBusConnection directly. There really isn't anything wrong
with D-Bus or GDBusConnection. This deprecated API is just a wrapper
around g_dbus_connection_call_sync(). You may call it directly
without feeling dirty.
---
The only other remainging API is the synchronous GInitable call for
NMClient. That is an entirely separate beast and not particularly
wrong (from an API point of view).
Note that synchronous API in NMSecretAgentOld, NMVpnPluginOld and
NMVpnServicePlugin as not deprecated here. These types are not part
of the D-Bus cache and while they have similar issues, it's less severe
because they have less state.
