[PATCH] nwfilter: serialize execution of scripts with ebtables cmds

[Stefan Berger <stefanb@xxxxxxxxxxxxxxxxxx>]

 While testing the SIGHUP handling and reloading of the nwfilter 
driver, I found that when the filters are rebuilt and mutlipe threads 
handled the individual interfaces, concurrently running multiple 
external bash scripts causes strange failures even though the executed 
ebtables commands are working on different tables for different 
interfaces. I cannot say for sure where the concurrency problems are 
caused, but introducing this lock definitely helps.

Signed-off-by: Stefan Berger <stefanb@xxxxxxxxxx>

---
 src/nwfilter/nwfilter_ebiptables_driver.c |   14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

Index: libvirt-acl/src/nwfilter/nwfilter_ebiptables_driver.c
===================================================================
--- libvirt-acl.orig/src/nwfilter/nwfilter_ebiptables_driver.c
+++ libvirt-acl/src/nwfilter/nwfilter_ebiptables_driver.c
@@ -104,6 +104,7 @@ static int ebiptablesDriverInit(void);
 static void ebiptablesDriverShutdown(void);
 static int ebtablesCleanAll(const char *ifname);

+static virMutex execCLIMutex;

 struct ushort_map {
     unsigned short attr;
@@ -2309,8 +2310,13 @@ ebiptablesExecCLI(virBufferPtr buf,
         return 1;

     argv[0] = filename;
+
+    virMutexLock(&execCLIMutex);
+
     rc = virRun(argv, status);

+    virMutexUnlock(&execCLIMutex);
+
     *status >>= 8;

     VIR_DEBUG("rc = %d, status = %d",rc, *status);
@@ -3163,8 +3169,9 @@ tear_down_tmpebchains:
     ebiptablesExecCLI(&buf, &cli_status);

     virNWFilterReportError(VIR_ERR_BUILD_FIREWALL,
-                           "%s",
-                           _("Some rules could not be created."));
+                           _("Some rules could not be created for "
+                             "interface %s."),
+                           ifname);

     return 1;
 }
@@ -3364,6 +3371,9 @@ ebiptablesDriverInit(void)
     virBuffer buf = VIR_BUFFER_INITIALIZER;
     int cli_status;

+    if (virMutexInit(&execCLIMutex))
+        return EINVAL;
+
     bash_cmd_path = virFindFileInPath("bash");
     gawk_cmd_path = virFindFileInPath("gawk");
     grep_cmd_path = virFindFileInPath("grep");

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