qemu: allow filtering events by regex

When listening for a subset of monitor events, it can be tedious
to register for each event name in series; nicer is to register
for multiple events in one go.  Implement a flag to use regex
interpretation of the event filter.

While at it, prove how much I hate the shift key, by adding a
way to filter for 'shutdown' instead of 'SHUTDOWN'. :)

* include/libvirt/libvirt-qemu.h
(virConnectDomainQemuMonitorEventRegisterFlags): New enum.
* src/libvirt-qemu.c (virConnectDomainQemuMonitorEventRegister):
Document flags.
* tools/virsh-domain.c (cmdQemuMonitorEvent): Expose them.
* tools/virsh.pod (qemu-monitor-event): Document this.
* src/conf/domain_event.c
(virDomainQemuMonitorEventStateRegisterID): Add flags.
(virDomainQemuMonitorEventFilter): Handle regex, and optimize
client side.
(virDomainQemuMonitorEventCleanup): Clean up regex.

Signed-off-by: Eric Blake <eblake@redhat.com>

include/libvirt/libvirt-qemu.h

@@ -76,6 +76,16 @@ typedef void (*virConnectDomainQemuMonitorEventCallback)(virConnectPtr conn,
                                                          const char *details,
                                                          void *opaque);
 
+
+typedef enum {
+    /* Event filter is a regex rather than a literal string */
+    VIR_CONNECT_DOMAIN_QEMU_MONITOR_EVENT_REGISTER_REGEX = (1 << 0),
+
+    /* Event filter is case insensitive */
+    VIR_CONNECT_DOMAIN_QEMU_MONITOR_EVENT_REGISTER_NOCASE = (1 << 1),
+} virConnectDomainQemuMonitorEventRegisterFlags;
+
+
 int virConnectDomainQemuMonitorEventRegister(virConnectPtr conn,
                                              virDomainPtr dom,
                                              const char *event,

src/conf/domain_event.c

@@ -24,6 +24,8 @@
 
 #include <config.h>
 
+#include <regex.h>
+
 #include "domain_event.h"
 #include "object_event.h"
 #include "object_event_private.h"
@@ -1390,6 +1392,8 @@ error:
  * deregisters.  */
 struct virDomainQemuMonitorEventData {
     char *event;
+    regex_t regex;
+    unsigned int flags;
     void *opaque;
     virFreeCallback freecb;
 };
@@ -1609,6 +1613,12 @@ virDomainQemuMonitorEventFilter(virConnectPtr conn ATTRIBUTE_UNUSED,
 
     monitorEvent = (virDomainQemuMonitorEventPtr) event;
 
+    if (data->flags == -1)
+        return true;
+    if (data->flags & VIR_CONNECT_DOMAIN_QEMU_MONITOR_EVENT_REGISTER_REGEX)
+        return regexec(&data->regex, monitorEvent->event, 0, NULL, 0) == 0;
+    if (data->flags & VIR_CONNECT_DOMAIN_QEMU_MONITOR_EVENT_REGISTER_NOCASE)
+        return STRCASEEQ(monitorEvent->event, data->event);
     return STREQ(monitorEvent->event, data->event);
 }
 
@@ -1619,6 +1629,8 @@ virDomainQemuMonitorEventCleanup(void *opaque)
     virDomainQemuMonitorEventData *data = opaque;
 
     VIR_FREE(data->event);
+    if (data->flags & VIR_CONNECT_DOMAIN_QEMU_MONITOR_EVENT_REGISTER_REGEX)
+        regfree(&data->regex);
     if (data->freecb)
         (data->freecb)(data->opaque);
     VIR_FREE(data);
@@ -1634,7 +1646,8 @@ virDomainQemuMonitorEventCleanup(void *opaque)
  * @cb: function to invoke when event occurs
  * @opaque: data blob to pass to callback
  * @freecb: callback to free @opaque
- * @flags: -1 for client, or set of registration flags on server
+ * @flags: -1 for client, valid virConnectDomainQemuMonitorEventRegisterFlags
+ *         for server
  * @callbackID: filled with callback ID
  *
  * Register the function @cb with connection @conn, from @state, for
@@ -1660,12 +1673,34 @@ virDomainQemuMonitorEventStateRegisterID(virConnectPtr conn,
         return -1;
 
     if (flags != -1)
-        virCheckFlags(0, -1);
+        virCheckFlags(VIR_CONNECT_DOMAIN_QEMU_MONITOR_EVENT_REGISTER_REGEX |
+                      VIR_CONNECT_DOMAIN_QEMU_MONITOR_EVENT_REGISTER_NOCASE,
+                      -1);
     if (VIR_ALLOC(data) < 0)
         return -1;
-    if (VIR_STRDUP(data->event, event) < 0) {
+    data->flags = flags;
-        VIR_FREE(data);
+    if (flags != -1) {
-        return -1;
+        int rflags = REG_NOSUB;
+
+        if (flags & VIR_CONNECT_DOMAIN_QEMU_MONITOR_EVENT_REGISTER_NOCASE)
+            rflags |= REG_ICASE;
+        if (flags & VIR_CONNECT_DOMAIN_QEMU_MONITOR_EVENT_REGISTER_REGEX) {
+            int err = regcomp(&data->regex, event, rflags);
+
+            if (err) {
+                char error[100];
+                regerror(err, &data->regex, error, sizeof(error));
+                virReportError(VIR_ERR_INVALID_ARG,
+                               _("failed to compile regex '%s': %s"),
+                               event, error);
+                regfree(&data->regex);
+                VIR_FREE(data);
+                return -1;
+            }
+        } else if (VIR_STRDUP(data->event, event) < 0) {
+            VIR_FREE(data);
+            return -1;
+        }
     }
     data->opaque = opaque;
     data->freecb = freecb;

src/libvirt-qemu.c

@@ -227,7 +227,7 @@ error:
  * @cb: callback to the function handling monitor events
  * @opaque: opaque data to pass on to the callback
  * @freecb: optional function to deallocate opaque when not used anymore
- * @flags: extra flags; not used yet, so callers should always pass 0
+ * @flags: bitwise-OR of virConnectDomainQemuMonitorEventRegisterFlags
  *
  * This API is QEMU specific, so it will only work with hypervisor
  * connections to the QEMU driver.
@@ -242,9 +242,12 @@ error:
  * is non-NULL, then only the specific domain will be monitored.
  *
  * If @event is NULL, then all monitor events will be reported. If @event is
- * non-NULL, then only the specific monitor event will be reported.  @flags
+ * non-NULL, then only specific monitor events will be reported.  @flags
- * is currently unused, but in the future may support a flag for passing
+ * controls how the filtering is performed: 0 requests an exact match, while
- * @event as a glob instead of a literal name to match a category of events.
+ * VIR_CONNECT_DOMAIN_QEMU_MONITOR_EVENT_REGISTER_REGEX states that @event
+ * is a basic regular expression.  Additionally, including
+ * VIR_CONNECT_DOMAIN_QEMU_MONITOR_EVENT_REGISTER_NOCASE lets @event match
+ * case-insensitively.
  *
  * The virDomainPtr object handle passed into the callback upon delivery
  * of an event is only valid for the duration of execution of the callback.

tools/virsh-domain.c

@@ -7983,6 +7983,14 @@ static const vshCmdOptDef opts_qemu_monitor_event[] = {
      .type = VSH_OT_INT,
      .help = N_("timeout seconds")
     },
+    {.name = "regex",
+     .type = VSH_OT_BOOL,
+     .help = N_("treat event as a regex rather than literal filter")
+    },
+    {.name = "no-case",
+     .type = VSH_OT_BOOL,
+     .help = N_("treat event case-insensitively")
+    },
     {.name = NULL}
 };
 
@@ -7997,6 +8005,11 @@ cmdQemuMonitorEvent(vshControl *ctl, const vshCmd *cmd)
     const char *event = NULL;
     vshQemuEventData data;
 
+    if (vshCommandOptBool(cmd, "regex"))
+        flags |= VIR_CONNECT_DOMAIN_QEMU_MONITOR_EVENT_REGISTER_REGEX;
+    if (vshCommandOptBool(cmd, "no-case"))
+        flags |= VIR_CONNECT_DOMAIN_QEMU_MONITOR_EVENT_REGISTER_NOCASE;
+
     data.ctl = ctl;
     data.loop = vshCommandOptBool(cmd, "loop");
     data.pretty = vshCommandOptBool(cmd, "pretty");

tools/virsh.pod

@@ -3385,12 +3385,15 @@ failed. And when I<--block> is given, the command waits forever with blocking
 timeout.
 
 =item B<qemu-monitor-event> [I<domain>] [I<--event> I<event-name>] [I<--loop>]
-[I<--timeout> I<seconds>] [I<--pretty>]
+[I<--timeout> I<seconds>] [I<--pretty>] [I<--regex>] [I<--no-case>]
 
 Wait for arbitrary QEMU monitor events to occur, and print out the
 details of events as they happen.  The events can optionally be filtered
 by I<domain> or I<event-name>.  The 'query-events' QMP command can be
 used via I<qemu-monitor-command> to learn what events are supported.
+If I<--regex> is used, I<event-name> is a basic regular expression
+instead of a literal string.  If I<--no-case> is used, I<event-name>
+will match case-insensitively.
 
 By default, this command is one-shot, and returns success once an event
 occurs; you can send SIGINT (usually via C<Ctrl-C>) to quit immediately.