[libvirt] [PATCH 1/2] network: improve error report when firewall chain creation fails

[Daniel P. Berrangé]

During startup we create some top level chains in which all
virtual network firewall rules will be placed. The upfront
creation is done to avoid slowing down creation of individual
virtual networks by checking for chain existance every time.

There are some factors which can cause this upfront creation
to fail and while a message will get into the libvirtd log
this won't be seen by users who later try to start a virtual
network. Instead they'll just get a message saying that the
libvirt top level chain does not exist. This message is
accurate, but unhelpful for solving the root cause.

This patch thus saves any error during daemon startup and
reports it when trying to create a virtual network later.

Signed-off-by: Daniel P. Berrangé <berrange at redhat.com>
---
 src/network/bridge_driver.c          |  3 +--
 src/network/bridge_driver_linux.c    | 29 ++++++++++++++++++++++------
 src/network/bridge_driver_nop.c      |  3 +--
 src/network/bridge_driver_platform.h |  2 +-
 4 files changed, 26 insertions(+), 11 deletions(-)

diff --git a/src/network/bridge_driver.c b/src/network/bridge_driver.c
index 6789dafd15..27d7d072ce 100644
--- a/src/network/bridge_driver.c
+++ b/src/network/bridge_driver.c
@@ -2095,8 +2095,7 @@ static void
 networkReloadFirewallRules(virNetworkDriverStatePtr driver, bool startup)
 {
     VIR_INFO("Reloading iptables rules");
-    if (networkPreReloadFirewallRules(startup) < 0)
-        return;
+    networkPreReloadFirewallRules(startup);
     virNetworkObjListForEach(driver->networks,
                              networkReloadFirewallRulesHelper,
                              NULL);
diff --git a/src/network/bridge_driver_linux.c b/src/network/bridge_driver_linux.c
index b10d0a6c4d..04b9c079ff 100644
--- a/src/network/bridge_driver_linux.c
+++ b/src/network/bridge_driver_linux.c
@@ -35,11 +35,25 @@ VIR_LOG_INIT("network.bridge_driver_linux");
 
 #define PROC_NET_ROUTE "/proc/net/route"
 
-int networkPreReloadFirewallRules(bool startup)
+static virErrorPtr errInit;
+
+void networkPreReloadFirewallRules(bool startup)
 {
-    int ret = iptablesSetupPrivateChains();
-    if (ret < 0)
-        return -1;
+    int ret;
+
+    /* We create global rules upfront as we don't want
+     * the perf hit of conditionally figuring out whether
+     * to create them each time a network is started.
+     *
+     * Any errors here are saved to be reported at time
+     * of starting the network though as that makes them
+     * more likely to be seen by a human
+     */
+    ret = iptablesSetupPrivateChains();
+    if (ret < 0) {
+        errInit = virSaveLastError();
+        virResetLastError();
+    }
 
     /*
      * If this is initial startup, and we just created the
@@ -56,8 +70,6 @@ int networkPreReloadFirewallRules(bool startup)
      */
     if (startup && ret == 1)
         iptablesSetDeletePrivate(false);
-
-    return 0;
 }
 
 
@@ -671,6 +683,11 @@ int networkAddFirewallRules(virNetworkDefPtr def)
     virFirewallPtr fw = NULL;
     int ret = -1;
 
+    if (errInit) {
+        virSetError(errInit);
+        return -1;
+    }
+
     if (def->bridgeZone) {
 
         /* if a firewalld zone has been specified, fail/log an error
diff --git a/src/network/bridge_driver_nop.c b/src/network/bridge_driver_nop.c
index a0e57012f9..ea9db338cb 100644
--- a/src/network/bridge_driver_nop.c
+++ b/src/network/bridge_driver_nop.c
@@ -19,9 +19,8 @@
 
 #include <config.h>
 
-int networkPreReloadFirewallRules(bool startup ATTRIBUTE_UNUSED)
+void networkPreReloadFirewallRules(bool startup ATTRIBUTE_UNUSED)
 {
-    return 0;
 }
 
 
diff --git a/src/network/bridge_driver_platform.h b/src/network/bridge_driver_platform.h
index baeb22bc3e..95fd64bdc7 100644
--- a/src/network/bridge_driver_platform.h
+++ b/src/network/bridge_driver_platform.h
@@ -58,7 +58,7 @@ struct _virNetworkDriverState {
 typedef struct _virNetworkDriverState virNetworkDriverState;
 typedef virNetworkDriverState *virNetworkDriverStatePtr;
 
-int networkPreReloadFirewallRules(bool startup);
+void networkPreReloadFirewallRules(bool startup);
 void networkPostReloadFirewallRules(bool startup);
 
 int networkCheckRouteCollision(virNetworkDefPtr def);
-- 
2.20.1