On 6/9/2025 9:20 AM, Daniel P. Berrangé wrote:
On Mon, Jun 09, 2025 at 09:12:27AM -0400, Steven Sistare wrote:
On 6/9/2025 4:06 AM, Daniel P. Berrangé wrote:
On Fri, Jun 06, 2025 at 03:37:56PM -0400, Steven Sistare wrote:
The easiest solution, with no interface changes, is adding wait_for_socket() in
qtest,
with this addition from Daniel:
"With the busy wait you risk looping forever if the child (target) QEMU
already exited for some reason without ever creating the socket. You
can mitigate this by using 'kill($PID, 0)' in the loop and looking
for -ERSCH, but this only works if you know the pid involved."
Daniel also suggested:
"For the tests, passing a pre-opened UNIX socket FD could work"
Note we can not use any of the standard chardev options to specify such a
socket,
because the cpr socket is created before chardevs are created.
Perhaps we could specify the fd in an extension of the MigrationChannel
MigrationAddress.
{ 'union': 'MigrationAddress',
'base': { 'transport' : 'MigrationAddressType'},
'discriminator': 'transport',
'data': {
'socket': 'SocketAddress',
'exec': 'MigrationExecCommand',
'rdma': 'InetSocketAddress',
'file': 'FileMigrationArgs',
'fd': 'FdMigrationArgs' } } <-- add this
That would be useful for all clients, but this is asking a lot from you,
when you are just trying to fix the tests.
Note, 'SocketAddress' already has an option for declaring a FD that
represents a socket.
Yes, but if I understand, you proposed passing an fd that represents a
pre-listened socket, which requires target qemu to accept() first. The
existing FdSocketAddress is ready to read. We could add a boolean to enable
the new behavior.
It can do both actually - it depends on what APIs the QEMU uses the
SocketAddress with.
If it is used with qio_channel_socket_connect* the FD must be an
active peer connection.
If it is used with qio_channel_socket_listen*/qio_net_listener* the
FD must be listener socket.
Fair enough. cpr currently listens here, and we could add a case for the FD:
QEMUFile *cpr_transfer_input(MigrationChannel *channel, Error **errp)
{
MigrationAddress *addr = channel->addr;
if (addr->transport == MIGRATION_ADDRESS_TYPE_SOCKET &&
addr->u.socket.type == SOCKET_ADDRESS_TYPE_UNIX) {
...
g_autoptr(QIONetListener) listener = qio_net_listener_new();
Or to use my socketpair() suggestion, that function would also need changes,
calling qio_channel_socket_connect.
Which do you think is better for clients -- socketpair or pre-listened?
- Steve
