Coverity was complaining that CMSG_NXTHDR is used without
checking the return value. In this case it cannot fail, but
it is a good excuse to simplify the function a bit.
CID #1261726.
/dev/pts/ptmx is as important as /dev/pts, so error out if that
fails. Others seem less important, since the namespace is usable
without them, so ignore failures.
CID #123755, #123754.
Do not rely on nl_pid == 0, but check the groups instead. We currently avoid using
nl_pid == 0 for unicast anyway, so this should be redundant, but let's try to be
correct.
The error code is called EDEADLK, stop using legacy names like EDEADLOCK.
Note that _some_ weird architectures define them differently (namely, mips
and sparc), but on all sane architectures they're exactly the same. So
stay with the widely used code, which is EDEADLK.
journal-remote buffers input, and then parses it handling one journal entry at a time.
It was possible for useful data to be left in the buffer after some entries were
processesed. But all data would be already read from the fd, so there would be
no reason for the event loop to call the handler again. After some new data came in,
the handler would be called again, and would then process the "old" data in the buffer.
Fix this by enabling a handler wherever we process input data and do not exhaust data
from the input buffer (i.e. when EAGAIN was not encountered). The handler runs until
we encounter EAGAIN.
Looping over the input data is done in this roundabout way to allow the event loop
to dispatch other events in the meanwhile. If the loop was inside the handler, a
source which produced data fast enough could completely monopolize the process.
https://bugs.freedesktop.org/show_bug.cgi?id=89516
"Notifications are of informal nature and no reply is expected, therefore the
sequence number is typically set to 0."[1]
If networkd is started soon after recent netlink activity, then there
will be messages with sequence number 0 in the buffer.
The first thing networkd does is to request a dump of all the links. If
it uses sequence number 0 for this, then it may confuse the dump request's
response with that of a notification.
This will result in it failing to properly enumerate all the links,
but more importantly, when it comes to enumerate all the addresses, it
will still have the link dump in progress, so the address enumeration
will fail with -EBUSY.
[1]: http://www.infradead.org/~tgr/libnl/doc/core.html#core_msg_types
[tomegun: sequence -> serial]
Zbigniew Jędrzejewski-Szmek