Joachim Wiberg
292e87c0d1
The udev parity gaps that were blocked on IPC -- settle, trigger,
info, queue introspection, runtime rule reload -- become bus methods.
keventd serves its own socket the way Finit serves /run/finit/bus:
brokerless, libink, one socket per daemon, no forwarding between the
two.
Settle(u) -> b parked until the queue drains or the timeout
passes; true when settled
Trigger(s, s) replay events, action + subsystem glob
Info(s) -> a{ss} /run/udev/data properties for a devpath
RulesReload() -> u re-read rules dirs, returns rule count
QueueEmpty (b), SeqnumProcessed (t) properties
DeviceProcessed (ss) signal after each fully handled event
The queue state is the highest kernel seqnum keventd has handled,
baselined at startup, against /sys/kernel/uevent_seqnum. keventd -S
now asks the running daemon first and falls back to seqnum polling.
In passive mode Trigger and RulesReload refuse. Adds
link_call_connection() for the park bookkeeping.
Signed-off-by: Joachim Wiberg <troglobit@gmail.com>
libink — brokerless D-Bus for Finit
libink is a small C library implementing the D-Bus wire protocol,
both the server and the client side, without a broker and without any
dependency on libdbus, sd-bus, or GIO. It was born inside Finit to
let PID 1 be a bus of its own: clients connect straight to the listening
socket, authenticate with the standard SASL EXTERNAL handshake, and get
kernel-authenticated credentials via SO_PEERCRED.
For what the bus exposes and how to talk to it, see the User Guide, D-Bus Integration. This file covers the library itself.
Status
libink is an internal implementation detail of Finit: built as a libtool
convenience library, linked statically into finit and initctl,
nothing installed. There is deliberately no ABI promise yet — that
comes if/when libink is extracted into a project of its own. External
D-Bus clients need none of this; the wire protocol is the compatibility
surface, any standard D-Bus library works.
Layout
| File | Contents |
|---|---|
server.c |
Listening socket, accept, peer credential capture |
auth.c |
SASL EXTERNAL handshake, uid verification |
connection.c |
Per-peer state machine, message framing |
proto.c |
Wire header parse/build |
marshal.c |
Body (de)marshalling: basic types, arrays, variants |
dispatch.c |
Object tree, vtable registration, method dispatch |
builtin.c |
org.freedesktop.DBus.* stock interfaces |
match.c |
AddMatch/RemoveMatch rule parsing and signal filter |
path.c |
systemd-style _HH object path encoding |
client.c |
Outgoing connections, method calls, reply/signal wait |
io.c |
Shared EINTR-resilient read/write loops |
Public API symbols carry the link_* prefix (link.h), internal ones
__* (internal.h). Method handlers are registered as vtables of
link_method_t/link_property_t; the framework emits variant
signatures from the property table so the declared type is the single
source of truth.
The boundary to Finit is deliberate: nothing under libink/ includes a
Finit header. All glue lives in src/dbus.c — object registration,
signal emission from the service/condition/runlevel hook points, and
the uev event loop bridge. initctl uses the client half of the same
library, so one wire-format implementation serves both ends. If libink
is ever spun out, that file is the cut line.
Future work
Privileged methods over the system bus are root-only. Finit learns
the caller's uid from the broker with GetConnectionUnixUser, but that
reply carries no group list, so it cannot honour --with-group
membership there the way it does on the local bus (where the kernel
hands over the group set via SO_PEERGROUPS). Closing the gap means
asking the broker GetConnectionCredentials and reading its
UnixGroupIDs, which is a variant holding an au array — the reader
(marshal.c) only decodes single-character variant signatures today,
so it needs extending first. Finit's own direct users reach it over
the local bus, so this has not been pressing.
Testing
The test/dbus-*.sh suite exercises the library end to end against a
live Finit in a namespace, driven by test/src/dbus-auth-client.c.
Wire-format conformance against third-party tools (dbus-send,
dbus-monitor) and fuzzing of the parsers are tracked as pre-merge
work — this is PID 1's attack surface.