Before SSH terminates, it waits for the PTYs that it creates for use as
stdin, stdout, and stderr to be closed. When any of the Open vSwitch
daemons were started in the background over an SSH session, they held
those file descriptors open and thus the SSH session hung. This commit
fixes the problem by closing those file descriptors, allowing SSH to
terminate.
There are conflicting pressures in startup of a daemon process:
* The parent process should exit with an error code if the daemon
cannot start up successfully.
* Some startup actions must be performed in the child process, not in
the parent. The most obvious of these are file locking, since
child processes do not inherit locks, and anything that requires
knowing the child process's PID (e.g. unixctl sockets).
Until now, this conflict has usually been handled by giving up part of the
first property, i.e. in some cases the parent process would exit
successfully and the child immediately afterward exit with a failure code.
This commit introduces a better approach, by allowing daemons to perform
startup work in the child and only then signal the parent that they have
successfully started. If the child instead exits without signaling
success, the parent passes this exit code along to its own parent.
This commit also modifies the daemons that can usefully take advantage of
this new feature to do so.
Some systems complain when certain functions' return values are not
checked. This commit fixes those warnings.
Creating ignore() function suggested by Ben Pfaff.
Before this commit, "ovsdb-server --detach" would detach after it opened
the database file, which meant that the child process did not hold the
file lock on the database file (because a forked child process does not
inherit its parents' locks). This commit fixes the problem by making
ovsdb-server open the database only after it has detached. This fix, in
turn, required that daemonize() not chdir to /, because this would break
databases whose names are given relative to the current directory, and so
this commit also changes ovsdb-server to do so later.
Open vSwitch uses an interval timer signal to tell it that its cached idea
of the current time has expired. However, this didn't work in a daemon
detached from the foreground session (invoked with --detach) because a
child created with fork() does not inherit the parent's interval timer and
we did not re-set it after calling fork().
This commit fixes the problem by setting the interval timer back up after
calling fork() from daemonize().
This fix is based on code inspection (which was then verified to be correct
through testing). It may not fix any actual problems in practice, because
time_refresh() is called every time through the poll loop, and the poll
loop typically runs more quickly than the periodic timer fires (1 ms or so
average in ovs-vswitchd, vs. 100 ms timer interval).
The daemon library provides a few short options, but these then take
away their availability from programs that wish to use the library.
Since the daemon options are generally going to be called from a script
(which doesn't care how much typing is involved), we'll only provide
long options.
By default, Open vSwitch daemons change their working directories to the
root directory. This commit provides a --no-chdir option to prevent this
behavior.
