With this new API sd-bus can synthesize a local "Connected" signal when
the connection is fully established. It mirrors the local "Disconnected"
signal that is already generated when the connection is terminated. This
is useful to be notified when connection setup is done, in order to
start method calls then, in particular when using "slow" connection
methods (for example slow TCP, or most importantly the "watch_bind"
inotify logic).
Note that one could also use hook into the initial NameAcquired signal
received from the bus broker, but that scheme works only if we actually
connect to a bus. The benefit of "Connected" OTOH is that it works with
any kind of connection.
Ideally, we'd just generate this message unconditionally, but in order
not to break clients that do not expect this message it is opt-in.
This new call is much light sd_bus_is_open(), but returns true only if
the connection is fully set up, i.e. after we finished with the
authentication and Hello() phase. This API is useful for clients in
particular when using the "watch_bind" feature, as that way it can be
determined in advance whether it makes sense to sync on some operation.
Let's directly reference /run instead, so that we can work without /var
being around, or with /var/run being incorrectly set up.
Note that we keep the old socket path in place when referencing the
system bus of containers, as they might be foreign operating systems,
that still don't have adopted /run, and where it makes sense to use the
standardized name instead. On local systems, we insist on /run being set
up properly however, hence this limitation does not apply.
Also, get rid of the UNIX_SYSTEM_BUS_ADDRESS and
UNIX_USER_BUS_ADDRESS_FMT defines. They had a purpose when we still did
kdbus, as we then had to support two different backends. But since
that's gone, we don't need this indirection anymore, hence settle on a
one define only.
Let's remove a number of synchronization points from our service
startups: let's drop synchronous match installation, and let's opt for
asynchronous instead.
Also, let's use sd_bus_match_signal() instead of sd_bus_add_match()
where we can.
These are convenience helpers that hide the match string logic (which we
probably should never have exposed), and instead just takes regular C
arguments.
We usually enqueue a number of these calls on each service
initialization. Let's do this asynchronously, and thus remove
synchronization points. This improves both performance behaviour and
reduces the chances to deadlock.
We currently wait for the RemoveMatch() reply, but then ignore what it
actually says. Let's optimize this a bit, and not even ask for an answer
back: just enqueue the RemoveMatch() operation, and do not request not
wait for any answer.
They do the same thing as their synchronous counterparts, but only
enqueue the operation, thus removing synchronization points during
service initialization.
If the callback function is passed as NULL we'll fallback to generic
implementations of the reply handlers, that terminate the connection if
the requested name cannot be acquired, under the assumption that not
being able to acquire the name is a technical problem.
When kdbus was still around we always had two implementations of the
various control calls: one for dbus1 and one for kdbus. Let'sget rid of
this, simplify things, and just merge the wrappers that used to
multiplex this with the implementations.
No change in behaviour, just some merging of functions
Currently, reply callback timeouts are started the instant the method
calls are enqueued, which can be very early on. For example, the Hello()
method call is enqueued right when sd_bus_start() is called, i.e. before
the socket connection and everything is established.
With this change we instead start the method timeout the moment we
actually leave the authentication phase of the connection. This way, the
timeout the kernel applies on socket connecting, and we apply on the
authentication phase no longer runs in parallel to the Hello() method
call, but all three run serially one after the other, which is
definitely a cleaner approach.
Moreover, this makes the "watch bind" feature a lot more useful, as it
allows enqueuing method calls while we are still waiting for inotify
events, without them timeouting until the connection is actually
established, i.e. when the method call actually has a chance of being
actually run.
This is a change of behaviour of course, but I think the new behaviour
is much better than the old one, since we don't race timeouts against
each other anymore...
This adds a "watch-bind" feature to sd-bus connections. If set and the
AF_UNIX socket we are connecting to doesn't exist yet, we'll establish
an inotify watch instead, and wait for the socket to appear. In other
words, a missing AF_UNIX just makes connecting slower.
This is useful for daemons such as networkd or resolved that shall be
able to run during early-boot, before dbus-daemon is up, and want to
connect to dbus-daemon as soon as it becomes ready.
If we can't process the bus for some reason we shouldn't just disable
the event source, but log something and give up on the connection. Hence
do that, and disconnect.
Currently, when sd-bus is used to issue a method call, and we get a
reply and the specified reply handler fails, we log this locally at
debug priority and proceed. The idea is that a bad server-side reply
should not be fatal for the program, except when the developer
explicitly terminates the event loop.
The reply to the initial Hello() method call we issue when joining a bus
should not be handled like that however. Instead, propagate the error
immediately, as anything that is wrong with the Hello() reply should be
considered a fatal connection problem.
This is useful so that callers know whether anything at all and how much
was flushed.
This patches through users of this functions to ensure that the return
values > 0 which may be returned now are not propagated in public APIs.
Also, users that ignore the return value are changed to do so explicitly
now.
Also, drop UID/GID validity checks from getpeercred() as the kernel will
never pass us invalid UID/GID on userns, but the overflow UID/GID
instead. Add a comment about this.
This ensures that in all threads we fork off in the background in our
code we mask out all signals, so that our thread won't end up getting
signals delivered the main process should be getting.
We always set the signal mask before forking off the thread, so that the
thread has the right mask set from its earliest existance on.
Using wait_for_terminate_and_check() instead of wait_for_terminate()
let's us simplify, shorten and unify the return value checking and
logging of waitid(). Hence, let's use it all over the place.
This adds a new safe_fork() wrapper around fork() and makes use of it
everywhere. The new wrapper does a couple of things we previously did
manually and separately in a safer, more correct and automatic way:
1. Optionally resets signal handlers/mask in the child
2. Sets a name on all processes we fork off right after forking off (and
the patch assigns useful names for all processes we fork off now,
following a systematic naming scheme: always enclosed in () – in order
to indicate that these are not proper, exec()ed processes, but only
forked off children, and if the process is long-running with only our
own code, without execve()'ing something else, it gets am "sd-" prefix.)
3. Optionally closes all file descriptors in the child
4. Optionally sets a PR_SET_DEATHSIG to SIGTERM in the child, in a safe
way so that the parent dying before this happens being handled
safely.
5. Optionally reopens the logs
6. Optionally connects stdin/stdout/stderr to /dev/null
7. Debug logs about the forked off processes.
We already use the "_static" suffix for libshared_static ("shared" is the name
of the library, "static" is the format) and other libs, so let's rename for
consistency.
Also change libsystemd_static_sources to libsystemd_sources, since the same
list is used for both and shorter is better.
Quoting Lennart Poettering in
https://github.com/systemd/systemd/pull/6464#issuecomment-319029293:
> If the kernel allows us to query that data we should also be Ok with passing
> it on to our own caller, regardless if selinux is technically on or off...
The advantage is that this allows gcc to be smarter and reduce linkage:
(before)$ ldd build/libnss_systemd.so.2
linux-vdso.so.1 (0x00007ffeb46ff000)
librt.so.1 => /lib64/librt.so.1 (0x00007f2f60da6000)
libcap.so.2 => /lib64/libcap.so.2 (0x00007f2f60ba1000)
libselinux.so.1 => /lib64/libselinux.so.1 (0x00007f2f60978000)
libpthread.so.0 => /lib64/libpthread.so.0 (0x00007f2f60759000)
libc.so.6 => /lib64/libc.so.6 (0x00007f2f60374000)
/lib64/ld-linux-x86-64.so.2 (0x00007f2f61294000)
libpcre2-8.so.0 => /lib64/libpcre2-8.so.0 (0x00007f2f600f0000)
libdl.so.2 => /lib64/libdl.so.2 (0x00007f2f5feec000)
(after )$ ldd build/libnss_systemd.so.2
linux-vdso.so.1 (0x00007ffe5f543000)
librt.so.1 => /lib64/librt.so.1 (0x00007f427dcaa000)
libcap.so.2 => /lib64/libcap.so.2 (0x00007f427daa5000)
libpthread.so.0 => /lib64/libpthread.so.0 (0x00007f427d886000)
libc.so.6 => /lib64/libc.so.6 (0x00007f427d4a1000)
/lib64/ld-linux-x86-64.so.2 (0x00007f427e196000)
Note that this only works in conjuction with the previous commit: either
of the two commits alone does not have the desired effect on linkage.
Replaces #6464.
Let's replace usage of fputc_unlocked() and friends by __fsetlocking(f,
FSETLOCKING_BYCALLER). This turns off locking for the entire FILE*,
instead of doing individual per-call decision whether to use normal
calls or _unlocked() calls.
This has various benefits:
1. It's easier to read and easier not to forget
2. It's more comprehensive, as fprintf() and friends are covered too
(as these functions have no _unlocked() counterpart)
3. Philosophically, it's a bit more correct, because it's more a
property of the file handle really whether we ever pass it on to another
thread, not of the operations we then apply to it.
This patch reworks all pieces of codes that so far used fxyz_unlocked()
calls to use __fsetlocking() instead. It also reworks all places that
use open_memstream(), i.e. use stdio FILE* for string manipulations.
Note that this in some way a revert of 4b61c87511.
RequiredForOnline= denotes a link/network that does/does not require being up
for systemd-networkd-wait-online to consider the system online; this makes it
possible to ignore devices without modifying parameters to wait-online.
If test-resolve is running in some CI environment that doesn't have
reliably working DNS, it's a good idea not to hang forever, let's
time-out after 20s
