This module, which catches segmentation faults and prints a backtrace
before exiting, was useful for a while, but I believe that it has now
outlived its purpose. It is altogether better to have a core dump from
which one can extract much more information than a usually-poor backtrace,
and core dumps are much better integrated into a typical Unix system.
In addition, the "fault" module was of course not all that portable.
This reduces the amount of redundancy in the source tree, by making all of
the current implementations of a vconn simply delegate to the "stream"
abstraction.
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.
When the switch is configured to connect to a controller that accepts
connections, waits a few seconds, and then disconnects without setting up
flows, currently this causes "fail-open" to flush the flow table and
stop setting up new flows during the connection duration. This is OK if
it happens once, but it can easily happen every 8 seconds with typical
backoff settings, and that isn't so great.
This commit changes fail-open to only flush the flow table once the switch
appears to have been admitted by the controller, which prevents these
frequent network interruptions.
Thanks to Jesse Gross for especially valuable feedback.
QA notes: Behavior in fail-open and especially behavior with a controller
that rejects the switch after it connects needs to be re-tested. The
ovs-controller --mute switch added by this commit is one simple way to
create such a controller.
CC: Peter Balland <peter@nicira.com>
Bug #1695. Bug #2055.
