On Wed, Aug 02, 2017 at 03:02:24PM +0800, Peter Xu wrote: > On Tue, Aug 01, 2017 at 11:56:10AM +0100, Daniel P. Berrange wrote: > > On Fri, Jul 28, 2017 at 04:06:28PM +0800, Peter Xu wrote: > > > Signed-off-by: Peter Xu <pet...@redhat.com> > > > --- > > > migration/exec.c | 2 +- > > > migration/fd.c | 2 +- > > > migration/socket.c | 4 ++-- > > > 3 files changed, 4 insertions(+), 4 deletions(-) > > > > > > diff --git a/migration/exec.c b/migration/exec.c > > > index 08b599e..b4412db 100644 > > > --- a/migration/exec.c > > > +++ b/migration/exec.c > > > @@ -49,7 +49,7 @@ static gboolean > > > exec_accept_incoming_migration(QIOChannel *ioc, > > > { > > > migration_channel_process_incoming(ioc); > > > object_unref(OBJECT(ioc)); > > > - return FALSE; /* unregister */ > > > + return TRUE; /* keep it registered */ > > > } > > > > > > void exec_start_incoming_migration(const char *command, Error **errp) > > > diff --git a/migration/fd.c b/migration/fd.c > > > index 30f5258..865277a 100644 > > > --- a/migration/fd.c > > > +++ b/migration/fd.c > > > @@ -49,7 +49,7 @@ static gboolean fd_accept_incoming_migration(QIOChannel > > > *ioc, > > > { > > > migration_channel_process_incoming(ioc); > > > object_unref(OBJECT(ioc)); > > > - return FALSE; /* unregister */ > > > + return TRUE; /* keep it registered */ > > > } > > > > > > void fd_start_incoming_migration(const char *infd, Error **errp) > > > diff --git a/migration/socket.c b/migration/socket.c > > > index 757d382..f2c2d01 100644 > > > --- a/migration/socket.c > > > +++ b/migration/socket.c > > > @@ -153,8 +153,8 @@ static gboolean > > > socket_accept_incoming_migration(QIOChannel *ioc, > > > > > > out: > > > /* Close listening socket as its no longer needed */ > > > - qio_channel_close(ioc, NULL); > > > - return FALSE; /* unregister */ > > > + // qio_channel_close(ioc, NULL); > > > + return TRUE; /* keep it registered */ > > > } > > > > > > This is not a very desirable approach IMHO. > > > > There are two separate things at play - first we have the listener socket, > > and second we have the I/O watch that monitors for incoming clients. > > > > The current code here closes the listener, and returns FALSE to unregister > > the event loop watch. > > > > You're reversing both of these so that we keep the listener open and we > > keep monitoring for incoming clients. Ignoring migration resume for a > > minute, this means that the destination QEMU will now accept arbitrarily > > many incoming clients and keep trying to start a new incoming migration. > > > > The behaviour we need is diferent. We *want* to unregister the event > > loop watch once we've accepted a client. We should only keep the socket > > listener in existance, but *not* accept any more clients. Only once we > > have hit a problem and want to accept a new client to do migration > > recovery, should we be re-adding the event loop watch. > > I replied with another approach in the other thread: how about we > re-enable the listen port duing "postcopy-pause" state, and disable > the listen port when get out of that migration state?
Thinking about this agan, I realize I only considered the socket migration backend. If we are using the 'fd' backend, then we *must* have an explicit monitor command invoked on the target host to obtain the new client connection. This is because the 'fd' that QEMU has is the actual client connection, not a listener socket, so libvirt needs to be able to pass in a new fd. > Here "listen port" I mean both the IO watch and the socket object. Now > what I can think of: we keep these objects always there, meanwhile we > introduce a new bit for migration, say, "accept_incoming", to decide > whether we will really accept one connection. Then we drop the new > connection if that bit is not set. > > (Or a new QIOChannelFeature to temporarily refuse incoming > connection? E.g., QIO_CHANNEL_FEATURE_LISTEN_REFUSE?) That feature already exists - you just unregister the event loop watch and re-register it when you're ready again. The chardev socket code works this way already, since it only allows a single client at a time Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|