Re: [libvirt PATCH] qemu: allow passt to self-daemonize

On Wed, Feb 08, 2023 at 18:13:10 -0500, Laine Stump wrote: > I initially had the passt process being started in an identical > fashion to the slirp-helper - libvirt was daemonizing the new process > and recording its pid in a pidfile. The problem with this is that, > since it is daemonized immediately, any startup error in passt happens > after the daemonization, and thus isn't seen by libvirt - libvirt > believes that the process has started successfully and continues on > its merry way. The result was that sometimes a guest would be started, > but there would be no passt process for qemu to use for network > traffic. > > Instead, we should be starting passt in the same manner we start > dnsmasq - we just exec it as normal (along with a request that passt > create the pidfile, which is just another option on the passt > commandline) and wait for the child process to exit; passt then has a > chance to parse its commandline and complete all the setup prior to > daemonizing itself; if it encounters an error and exits with a non-0 > code, libvirt will see the code and know about the failure. We can > then grab the output from stderr, log that so the "user" has some idea > of what went wrong, and then fail the guest startup. > > Signed-off-by: Laine Stump <laine(a)redhat.com&gt; > --- > src/qemu/qemu_passt.c | 9 ++++----- > 1 file changed, 4 insertions(+), 5 deletions(-) [..] > if (cmdret < 0 || exitstatus != 0) { > virReportError(VIR_ERR_INTERNAL_ERROR, > - _("Could not start 'passt'. exitstatus: %d"), exitstatus); > + _("Could not start 'passt': %s"), errbuf); > goto error; > } So the 'passt' binary doesn't do any logging later on during runtime which we'd have to capture into a specific log file?