[PATCHv2 8/9] network: restart radvd/dnsmasq if needed when libvirtd is restarted

[Laine Stump <laine@xxxxxxxxx>]

A user on IRC had accidentally killed all of his libvirt-started
dnsmasq instances (due to a buggy dnsmasq service script in Fedora
16), and had hoped that libvirtd would notice this on restart and
reload all the dnsmasq daemons (as it does with iptables
rules). Unfortunately this was not the case - as long as the network
object had a pid registered for dnsmasq and/or radvd, it assumed that
the processes were running.

This patch takes advantage of the new utility functions in
bridge_driver.c to do a "refresh" of all radvd and dnsmasq processes
started by libvirt each time libvirtd is restarted - this function
attempts to do a SIGHUP of each existing process, and if that fails,
it restarts the process, rebuilding all the associated config files
and commandline parameters in the process. This normally has no
effect, but will be useful in solving the occasional "odd situation"
without needing to take the drastic step of destroying/re-starting the
network.
---
 src/network/bridge_driver.c | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/src/network/bridge_driver.c b/src/network/bridge_driver.c
index 252c964..0e38016 100644
--- a/src/network/bridge_driver.c
+++ b/src/network/bridge_driver.c
@@ -117,6 +117,7 @@ static int networkShutdownNetworkExternal(struct network_driver *driver,
                                         virNetworkObjPtr network);
 
 static void networkReloadIptablesRules(struct network_driver *driver);
+static void networkRefreshDaemons(struct network_driver *driver);
 
 static struct network_driver *driverState = NULL;
 
@@ -344,6 +345,7 @@ networkStartup(int privileged) {
 
     networkFindActiveConfigs(driverState);
     networkReloadIptablesRules(driverState);
+    networkRefreshDaemons(driverState);
     networkAutostartConfigs(driverState);
 
     networkDriverUnlock(driverState);
@@ -404,6 +406,7 @@ networkReload(void) {
                              driverState->networkConfigDir,
                              driverState->networkAutostartDir);
     networkReloadIptablesRules(driverState);
+    networkRefreshDaemons(driverState);
     networkAutostartConfigs(driverState);
     networkDriverUnlock(driverState);
     return 0;
@@ -1210,6 +1213,37 @@ networkRestartRadvd(virNetworkObjPtr network)
 }
 #endif /* #if 0 */
 
+/* SIGHUP/restart any dnsmasq or radvd daemons.
+ * This should be called when libvirtd is restarted.
+ */
+static void
+networkRefreshDaemons(struct network_driver *driver)
+{
+    unsigned int i;
+
+    VIR_INFO("Refreshing network daemons");
+
+    for (i = 0 ; i < driver->networks.count ; i++) {
+        virNetworkObjPtr network = driver->networks.objs[i];
+
+        virNetworkObjLock(network);
+        if (virNetworkObjIsActive(network) &&
+            ((network->def->forwardType == VIR_NETWORK_FORWARD_NONE) ||
+             (network->def->forwardType == VIR_NETWORK_FORWARD_NAT) ||
+             (network->def->forwardType == VIR_NETWORK_FORWARD_ROUTE))) {
+            /* Only the three L3 network types that are configured by
+             * libvirt will have a dnsmasq or radvd daemon associated
+             * with them.  Here we send a SIGHUP to an existing
+             * dnsmasq and/or radvd, or restart them if they've
+             * disappeared.
+             */
+            networkRefreshDhcpDaemon(network);
+            networkRefreshRadvd(network);
+        }
+        virNetworkObjUnlock(network);
+    }
+}
+
 static int
 networkAddMasqueradingIptablesRules(struct network_driver *driver,
                                     virNetworkObjPtr network,
-- 
1.7.11.4

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