[systemd-devel] [PATCH] bus: Add support for eavesdrop in sd_bus_add_match()

[Simon McVittie]

On 12/12/13 14:28, Lennart Poettering wrote:
> kay and Daniel are working on changing the semantics of monitoring
> entirely. Instead of turning monitoring on and off on an existing
> connection they want this to be an entirely new connection type

Colin Walters wanted to do this in dbus-daemon too (a separate
/var/run/dbus/system_bus_monitor_socket that's only accessible by root,
or something), but nobody has got round to it yet.

Another possibility might be to make the eavesdropped stream obviously
not the same thing as the normal D-Bus stream, for instance by wrapping
it in pcap format as used by bustle(1) (as in my proof-of-concept
dbus-daemon patches on
<https://bugs.freedesktop.org/show_bug.cgi?id=60859>). bustle-pcap(1) is
a standalone implementation of "connect, eavesdrop, produce a pcap
stream" for traditional D-Bus, similar to dbus-monitor.

> the
> same way as "starter" (i.e. those which may be used to take a well-known
> name and get notified when the service behind it needs to be activated)
> connections are different from normal connections

Please consider naming this differently: "starter" in the D-Bus
Specification (e.g. DBUS_STARTER_ADDRESS) is something rather different.
Maybe "placeholder"?

> (Which would break compat wit traditional dbus I figure, but that should
> be OK given that monitoring is a debugging feature anyway.)

Yes, I think anyone using eavesdropping for purposes other than a
debugging tool is wrong; when we added eavesdrop="true" to dbus-daemon,
it broke compatibility with older client libraries anyway.

    S