Re-add use of locking with iptables/ip6tables/ebtables

A previous commit introduced use of locking with invocation
of iptables in the viriptables.c module

  commit ba95426d6f
  Author: Serge Hallyn <serge.hallyn@ubuntu.com>
  Date:   Fri Nov 1 12:36:59 2013 -0500

    util: use -w flag when calling iptables

This only ever had effect with the virtual network driver,
as it was not wired up into the nwfilter driver. Unfortunately
in the firewall refactoring the use of the -w flag was
accidentally lost.

This patch introduces it to the virfirewall.c module so that
both the virtual network and nwfilter drivers will be using
it. It also ensures that the equivalent --concurrent flag
to ebtables is used.

src/util/virfirewall.c

@@ -104,6 +104,44 @@ virFirewallOnceInit(void)
 
 VIR_ONCE_GLOBAL_INIT(virFirewall)
 
+static bool iptablesUseLock;
+static bool ip6tablesUseLock;
+static bool ebtablesUseLock;
+
+static void
+virFirewallCheckUpdateLock(bool *lockflag,
+                           const char *const*args)
+{
+    virCommandPtr cmd = virCommandNewArgs(args);
+    if (virCommandRun(cmd, NULL) < 0) {
+        VIR_INFO("locking not supported by %s", args[0]);
+    } else {
+        VIR_INFO("using locking for %s", args[0]);
+        *lockflag = true;
+    }
+    virCommandFree(cmd);
+}
+
+static void
+virFirewallCheckUpdateLocking(void)
+{
+    const char *iptablesArgs[] = {
+        IPTABLES_PATH, "-w", "-L", "-n", NULL,
+    };
+    const char *ip6tablesArgs[] = {
+        IP6TABLES_PATH, "-w", "-L", "-n", NULL,
+    };
+    const char *ebtablesArgs[] = {
+        EBTABLES_PATH, "--concurrent", "-L", NULL,
+    };
+    virFirewallCheckUpdateLock(&iptablesUseLock,
+                               iptablesArgs);
+    virFirewallCheckUpdateLock(&ip6tablesUseLock,
+                               ip6tablesArgs);
+    virFirewallCheckUpdateLock(&ebtablesUseLock,
+                               ebtablesArgs);
+}
+
 static int
 virFirewallValidateBackend(virFirewallBackend backend)
 {
@@ -161,6 +199,9 @@ virFirewallValidateBackend(virFirewallBackend backend)
     }
 
     currentBackend = backend;
+
+    virFirewallCheckUpdateLocking();
+
     return 0;
 }
 
@@ -201,6 +242,9 @@ virFirewallPtr virFirewallNew(void)
 {
     virFirewallPtr firewall;
 
+    if (virFirewallInitialize() < 0)
+        return NULL;
+
     if (VIR_ALLOC(firewall) < 0)
         return NULL;
 
@@ -321,6 +365,23 @@ virFirewallAddRuleFullV(virFirewallPtr firewall,
     rule->queryOpaque = opaque;
     rule->ignoreErrors = ignoreErrors;
 
+    switch (rule->layer) {
+    case VIR_FIREWALL_LAYER_ETHERNET:
+        if (ebtablesUseLock)
+            ADD_ARG(rule, "--concurrent");
+        break;
+    case VIR_FIREWALL_LAYER_IPV4:
+        if (iptablesUseLock)
+            ADD_ARG(rule, "-w");
+        break;
+    case VIR_FIREWALL_LAYER_IPV6:
+        if (ip6tablesUseLock)
+            ADD_ARG(rule, "-w");
+        break;
+    case VIR_FIREWALL_LAYER_LAST:
+        break;
+    }
+
     while ((str = va_arg(args, char *)) != NULL) {
         ADD_ARG(rule, str);
     }
@@ -840,8 +901,8 @@ virFirewallApplyGroup(virFirewallPtr firewall,
     bool ignoreErrors = (group->actionFlags & VIR_FIREWALL_TRANSACTION_IGNORE_ERRORS);
     size_t i;
 
-    VIR_INFO("Starting transaction for %p flags=%x",
-             group, group->actionFlags);
+    VIR_INFO("Starting transaction for firewall=%p group=%p flags=%x",
+             firewall, group, group->actionFlags);
     firewall->currentGroup = idx;
     group->addingRollback = false;
     for (i = 0; i < group->naction; i++) {
@@ -879,8 +940,6 @@ virFirewallApply(virFirewallPtr firewall)
     int ret = -1;
 
     virMutexLock(&ruleLock);
-    if (virFirewallInitialize() < 0)
-        goto cleanup;
 
     if (!firewall || firewall->err == ENOMEM) {
         virReportOOMError();

src/util/viriptables.c

@@ -52,8 +52,6 @@
 
 VIR_LOG_INIT("util.iptables");
 
-bool iptables_supports_xlock = false;
-
 #define VIR_FROM_THIS VIR_FROM_NONE
 
 enum {