[systemd-devel] sd-bus connections & authentication timeout

[Jan Alexander Steffens]

On Mon, Mar 20, 2017, 16:37 Stanislav Angelovič <angelovic.s at gmail.com>
wrote:

> Hi,
>
> We use sd-bus for DBus IPC in our own applications. Some applications of
> ours cause the dbus daemon to issue "Connection has not authenticated soon
> enough, closing it" message, leading to the
> org.freedesktop.DBus.Error.Timeout error at the peer side when the
> connection is used for an IPC call.
>
> The situation is the following:
> 1. We have a DBus client application.
> 2. A connection is created using sd_bus_open_system() on application
> startup.
> 3. The connection is kept open and unused (i.e. no other sd-bus functions
> invoked on it).
> 4. After 30 seconds, we get the above-mentioned authentication timeout
> message from the dbus daemon, and any attempt to issue calls against a
> service via this connection fails with immediate timeout error as mentioned
> above. However, if the call is made before the 30 seconds authentication
> timeout, the dbus daemon prints nothing and the call succeeds, just like
> any subsequent call, even if issued after 1 hour from the first one.
>
> Is that correct behavior? We would like to open dbus connections at
> application startup, and use it for communication at any time later,
> depending on user actions. Is there something we are missing?
>
> And a side suggestion: If we want to close a connection that has not been
> used for any IPC call at all, after some struggling we have realized that
> sd_bus_unref() is not enough, as there is a lingering DBus.Hello reply
> which keeps the reference count on that connection, leading to lingering
> connections. sd_bus_flush_close_unref() is needed instead. That behavior
> could be mentioned in the documentation, e.g. at
> http://0pointer.net/blog/the-new-sd-bus-api-of-systemd.html in the
> reference client implementation, to save others from pain.
>
> Thanks a lot,
>
> Stanislav.
>
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> systemd-devel at lists.freedesktop.org
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You could try calling sd_bus_process(bus, NULL) in a loop while it returns
>0 so that the initial hello is handled.

However, that only gets you past the hello. To be a good D-Bus client, you
should poll the connection and process any unexpected incoming messages.
The best approach depends on what your app and your use of sd-bus looks
like.
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