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dns: only write out new DNS config if it really changed

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Use a pseudo-hash to quickly check whether the DNS config has really
changed or not.  This is certainly better than the 500 line patch I
did then scrapped in favor of this approach... yay.  This helps ensure
that we don't kill then respawn caching DNS servers more often than
we have to.
This commit is contained in:
Dan Williams 2010-09-14 23:41:33 -05:00
parent 9d0775448c
commit 57f6feb102
1 changed files with 72 additions and 2 deletions
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74
src/dns-manager/nm-dns-manager.c
View file

@ -43,6 +43,7 @@
#include "nm-system.h"
#include "NetworkManagerUtils.h"
#include "nm-dns-plugin.h"
#include "nm-dns-dnsmasq.h"
#ifdef HAVE_SELINUX
@ -53,8 +54,6 @@
#define RESOLV_CONF "/etc/resolv.conf"
#endif
#define ADDR_BUF_LEN 50
G_DEFINE_TYPE(NMDnsManager, nm_dns_manager, G_TYPE_OBJECT)
#define NM_DNS_MANAGER_GET_PRIVATE(o) (G_TYPE_INSTANCE_GET_PRIVATE ((o), \
@ -69,6 +68,14 @@ struct NMDnsManagerPrivate {
GSList *configs;
char *hostname;
/* poor man's hash; we assume that the IP4 config object won't change
* after it's given to us, which is (at this time) a fair assumption. So
* we track the order of the currently applied IP configs and if they
* haven't changed we don't need to rewrite resolv.conf.
*/
#define HLEN 6
gpointer hash[HLEN];
GSList *plugins;
/* This is a hack because SUSE's netconfig always wants changes
@ -525,6 +532,37 @@ out:
return *error ? FALSE : TRUE;
}
static void
compute_hash (NMDnsManager *self, gpointer *hash)
{
NMDnsManagerPrivate *priv = NM_DNS_MANAGER_GET_PRIVATE (self);
gpointer check[HLEN];
GSList *iter;
int i = 0;
memset (check, 0, sizeof (check));
if (priv->ip4_vpn_config)
check[i++] = priv->ip4_vpn_config;
if (priv->ip4_device_config)
check[i++] = priv->ip4_device_config;
if (priv->ip6_vpn_config)
check[i++] = priv->ip6_vpn_config;
if (priv->ip6_device_config)
check[i++] = priv->ip6_device_config;
/* Add two more "other" configs if any exist */
for (iter = priv->configs; iter && i < HLEN; iter = g_slist_next (iter)) {
if ( (iter->data != priv->ip4_vpn_config)
&& (iter->data != priv->ip4_device_config)
&& (iter->data != priv->ip6_vpn_config)
&& (iter->data != priv->ip6_device_config))
check[i++] = iter->data;
}
memcpy (hash, check, sizeof (check));
}
static gboolean
update_dns (NMDnsManager *self,
const char *iface,
@ -552,6 +590,9 @@ update_dns (NMDnsManager *self,
priv->last_iface = g_strdup (iface);
}
/* Update hash with config we're applying */
compute_hash (self, priv->hash);
rc.nameservers = g_ptr_array_new ();
rc.domain = NULL;
rc.searches = g_ptr_array_new ();
@ -734,6 +775,23 @@ plugin_failed (NMDnsPlugin *plugin, gpointer user_data)
}
}
static gboolean
config_changed (NMDnsManager *self)
{
NMDnsManagerPrivate *priv = NM_DNS_MANAGER_GET_PRIVATE (self);
gpointer check[HLEN];
/* We only store HLEN configs; so if there are actually more than that,
* we have to assume that the config has changed.
*/
if (g_slist_length (priv->configs) > HLEN)
return TRUE;
/* Otherwise return TRUE if the configuration has changed */
compute_hash (self, check);
return memcmp (check, priv->hash, sizeof (check)) ? TRUE : FALSE;
}
gboolean
nm_dns_manager_add_ip4_config (NMDnsManager *mgr,
const char *iface,
@ -764,6 +822,9 @@ nm_dns_manager_add_ip4_config (NMDnsManager *mgr,
if (!g_slist_find (priv->configs, config))
priv->configs = g_slist_append (priv->configs, g_object_ref (config));
if (!config_changed (mgr))
return TRUE;
if (!update_dns (mgr, iface, FALSE, &error)) {
nm_log_warn (LOGD_DNS, "could not commit DNS changes: (%d) %s",
error ? error->code : -1,
@ -801,6 +862,9 @@ nm_dns_manager_remove_ip4_config (NMDnsManager *mgr,
g_object_unref (config);
if (config_changed (mgr))
return TRUE;
if (!update_dns (mgr, iface, FALSE, &error)) {
nm_log_warn (LOGD_DNS, "could not commit DNS changes: (%d) %s",
error ? error->code : -1,
@ -843,6 +907,9 @@ nm_dns_manager_add_ip6_config (NMDnsManager *mgr,
if (!g_slist_find (priv->configs, config))
priv->configs = g_slist_append (priv->configs, g_object_ref (config));
if (config_changed (mgr))
return TRUE;
if (!update_dns (mgr, iface, FALSE, &error)) {
nm_log_warn (LOGD_DNS, "could not commit DNS changes: (%d) %s",
error ? error->code : -1,
@ -880,6 +947,9 @@ nm_dns_manager_remove_ip6_config (NMDnsManager *mgr,
g_object_unref (config);
if (config_changed (mgr))
return TRUE;
if (!update_dns (mgr, iface, FALSE, &error)) {
nm_log_warn (LOGD_DNS, "could not commit DNS changes: (%d) %s",
error ? error->code : -1,