Virtual filesystems such as sysfs or procfs use kernfs, and kernfs can work
with two sorts of virtual files.
One sort uses "seq_file", and the results of the first read are buffered for
the second read. The other sort uses "raw" reads which always go direct to the
device.
In the later case, the content of the virtual file must be retrieved with a
single read otherwise subsequent read might get the new value instead of
finding EOF immediately. That's the reason why the usage of fread(3) is
prohibited in this case as it always performs a second call to read(2) looking
for EOF which is subject to the race described previously.
Fixes: #13585.
chase_symlinks() would return negative on error, and either a non-negative status
or a non-negative fd when CHASE_OPEN was given. This made the interface quite
complicated, because dependning on the flags used, we would get two different
"types" of return object. Coverity was always confused by this, and flagged
every use of chase_symlinks() without CHASE_OPEN as a resource leak (because it
would this that an fd is returned). This patch uses a saparate output parameter,
so there is no confusion.
(I think it is OK to have functions which return either an error or an fd. It's
only returning *either* an fd or a non-fd that is confusing.)
sd-netlink is not public yet, so we can change the interface.
I did not touch interfaces of functions like sd_netlink_wait() and
sd_rtnl_message_new_link() which do not modify the object that is passed in,
because in the future we might want to change the code to e.g. take a
reference to the parent object or otherwise require a non-const reference.
It is natural that n_attiributes is less than type. But in that case,
the message does not contain any message about the type. So, we should
not abort execution with assertion, but just return -ENODATA.
This avoid the use of the global variable.
Also rename cgroup_unified_update() to cgroup_unified_cached() and
cgroup_unified_flush() to cgroup_unified() to better reflect their new roles.
This code is not part of the public API of sd-netlink, nor used by it
internally and hence should not be in the sd-netlink directory.
Also, move the test case for it to src/test/.
This tweaks match installation a bit: the match callbacks are now only
called for messages read after the AddMatch() reply was received and
never anything already read before. Thus, installing a match gives you a
time guarantee: only messages received after it will be matched.
This is useful when listening to PropertiesChanged signals as an example
to ensure that only changes after the point the match was installed are
honoured, nothing before.
If AddMatch() doesn't work, let's destroy the slot for it too as soon as
we received the failure for it.
This way the mere existance of the slot tells us whether the AddMatch()
method call is still pending or is complete.
Let's count incoming messages and attach the current counter when we
first read them to the message objects. This allows us to nicely order
messages later on.
Yu Watanabe
Lennart Poettering
Susant Sahani
Franck Bui
Zbigniew Jędrzejewski-Szmek
Frantisek Sumsal
William A. Kennington III
Shreyas Behera