Re: [libvirt PATCH 3/3] qemu: respond to NETDEV_STREAM_DISCONNECTED event

On 2/22/23 01:35, Laine Stump wrote: > When a QEMU netdev is of type "stream", if the socket it uses for > connectivity to the host network gets closed, then QEMU will send a > NETDEV_STREAM_DISCONNECTED event. We know that any stream netdev we've > created is backed by a passt process, and if the socket was closed, > that means the passt process has disappeared. > > When we receive this event, we can respond by starting a new passt > process with the same options (including socket path) we originally > used. If we have previously created the stream netdev device with a > "reconnect" option, then QEMU will automatically reconnect to this new > passt process. (If we hadn't used "reconnect", then QEMU will never > try to reconnect to the new passt process, so there's no point in > starting it.) > > Note that NETDEV_STREAM_DISCONNECTED is an event sent for the netdev > (ie "host side") of the network device, and so it sends the > "netdev-id" to specify which device was disconnected. But libvirt's > virDomainNetDef (the object used to keep track of network devices) is > the internal representation of both the host-side "netdev", and the > guest side device, and virDomainNetDef doesn't directly keep track of > the netdev-id, only of the device's "alias" (which is the "id" > parameter of the *guest* side of the device). Fortunately, by convention > libvirt always names the host-side of devices as "host" + alias, so in > order to search for the affected NetDef, all we need to do is trim the > 1st 4 characters from the netdev-id and look for the NetDef having > that resulting trimmed string as its alias. (Contrast this to > NIC_RX_FILTER_CHANGED, which is an event received for the guest side > of the device, and so directly contains the device alias.) > > Resolves: https://bugzilla.redhat.com/2172098 > Signed-off-by: Laine Stump <laine(a)redhat.com&gt; > --- > src/qemu/qemu_domain.c | 1 + > src/qemu/qemu_domain.h | 1 + > src/qemu/qemu_driver.c | 82 ++++++++++++++++++++++++++++++++++++ > src/qemu/qemu_monitor.c | 11 +++++ > src/qemu/qemu_monitor.h | 6 +++ > src/qemu/qemu_monitor_json.c | 16 +++++++ > src/qemu/qemu_process.c | 18 ++++++++ > 7 files changed, 135 insertions(+) > > diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c > index e9bc0f375d..4cf9a259ea 100644 > --- a/src/qemu/qemu_domain.c > +++ b/src/qemu/qemu_domain.c > @@ -11238,6 +11238,7 @@ qemuProcessEventFree(struct qemuProcessEvent *event) > break; > case QEMU_PROCESS_EVENT_WATCHDOG: > case QEMU_PROCESS_EVENT_DEVICE_DELETED: > + case QEMU_PROCESS_EVENT_NETDEV_STREAM_DISCONNECTED: > case QEMU_PROCESS_EVENT_NIC_RX_FILTER_CHANGED: > case QEMU_PROCESS_EVENT_SERIAL_CHANGED: > case QEMU_PROCESS_EVENT_MONITOR_EOF: > diff --git a/src/qemu/qemu_domain.h b/src/qemu/qemu_domain.h > index 1053d1d4cb..6adc067681 100644 > --- a/src/qemu/qemu_domain.h > +++ b/src/qemu/qemu_domain.h > @@ -447,6 +447,7 @@ typedef enum { > QEMU_PROCESS_EVENT_WATCHDOG = 0, > QEMU_PROCESS_EVENT_GUESTPANIC, > QEMU_PROCESS_EVENT_DEVICE_DELETED, > + QEMU_PROCESS_EVENT_NETDEV_STREAM_DISCONNECTED, > QEMU_PROCESS_EVENT_NIC_RX_FILTER_CHANGED, > QEMU_PROCESS_EVENT_SERIAL_CHANGED, > QEMU_PROCESS_EVENT_JOB_STATUS_CHANGE, > diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c > index 6154fe9bfe..47d6a0dd95 100644 > --- a/src/qemu/qemu_driver.c > +++ b/src/qemu/qemu_driver.c > @@ -40,6 +40,7 @@ > #include "qemu_hostdev.h" > #include "qemu_hotplug.h" > #include "qemu_monitor.h" > +#include "qemu_passt.h" > #include "qemu_process.h" > #include "qemu_migration.h" > #include "qemu_migration_params.h" > @@ -3622,6 +3623,84 @@ processDeviceDeletedEvent(virQEMUDriver *driver, > } > > > +static void > +processNetdevStreamDisconnectedEvent(virDomainObj *vm, > + const char *netdevId) > +{ > + virDomainDeviceDef dev; > + virDomainNetDef *def; > + qemuDomainObjPrivate *priv; > + virQEMUCaps *qemuCaps; > + const char *devAlias = NULL; > + > + /* The event sends us the "netdev-id", but we don't store the > + * netdev-id in the NetDef and thus can't use it to find the > + * correct NetDef. We *do* keep the device alias in the NetDef. > + * By definition, the netdev-id is "host" + devAlias, so we just > + * need to remove "host" from the front of netdev-id to get > + * something we can use to find the proper NetDef. > + */ > + if (STREQLEN(netdevId, "host", 4)) > + devAlias = &netdevId[4]; This is open coding STRSKIP(): devAlias = STRSKIP(netdevId, "host");

> + > + if (!devAlias) { > + VIR_WARN("Received NETDEV_STREAM_DISCONNECTED event for unrecognized netdev %s from domain %p %s", > + netdevId, vm, vm->def->name); > + return; > + } > + > + VIR_DEBUG("Received NETDEV_STREAM_DISCONNECTED event for device %s from domain %p %s", > + devAlias, vm, vm->def->name); > + > + if (virDomainObjBeginJob(vm, VIR_JOB_QUERY) < 0) > + return; > + > + if (!virDomainObjIsActive(vm)) { > + VIR_DEBUG("Domain is not running"); > + goto endjob; > + } > + > + if (virDomainDefFindDevice(vm->def, devAlias, &dev, true) < 0) { > + VIR_WARN("NETDEV_STREAM_DISCONNECTED event received for non-existent device %s in domain %s", > + devAlias, vm->def->name); > + goto endjob; > + } > + if (dev.type != VIR_DOMAIN_DEVICE_NET) { > + VIR_WARN("NETDEV_STREAM_DISCONNECTED event received for non-network device %s in domain %s", > + devAlias, vm->def->name); > + goto endjob; > + } > + def = dev.data.net; > + > + if (def->backend.type != VIR_DOMAIN_NET_BACKEND_PASST) { > + VIR_DEBUG("ignore NETDEV_STREAM_DISCONNECTED event for non-passt network device %s in domain %s", > + def->info.alias, vm->def->name); > + goto endjob; > + } > + > + priv = vm->privateData; > + qemuCaps = priv->qemuCaps; > + These two can be done in variable declaration. Alternatively, if you want to lose @priv variable completely you can go with: virQEMUCaps *caps = QEMU_DOMAIN_PRIVATE(vm)->qemuCaps;

> + if (!virQEMUCapsGet(qemuCaps, QEMU_CAPS_NETDEV_STREAM_RECONNECT)) { > + VIR_WARN("ignore NETDEV_STREAM_DISCONNECTED event for passt network device %s in domain %s - QEMU binary does not support reconnect", > + def->info.alias, vm->def->name); > + goto endjob; > + } > + > + /* handle the event - restart the passt process with its original > + * parameters > + */ > + VIR_DEBUG("process NETDEV_STREAM_DISCONNECTED event for network device %s in domain %s", > + def->info.alias, vm->def->name); > + > + if (qemuPasstStart(vm, def) < 0) > + goto endjob; > + > + endjob: > + virDomainObjEndJob(vm); > +} > + Michal