[Nagiosplug-devel] check_dns: DNS WARNING - nslookup returned error status

[Ton Voon]

On 2 Sep 2005, at 13:40, sean finney wrote:

> so what, redhat is now defaulting to having that set?  i think i see a
> way around this, but i'm not sure:
>
> - set a signal handler for SIGCHLD
> - when SIGCHLD is thrown, we do exactly the opposite from the  
> above, and
>   *not* call any wait functions.
>
> i think that should leave the child as a zombie, for our later call to
> waitpid.

Tried this patch to popen.c:


--- popen.c.original    2005-09-02 14:02:33.760495184 +0100
+++ popen.c     2005-09-02 14:30:08.322963456 +0100
@@ -67,6 +67,8 @@
/*extern pid_t *childpid = NULL; *//* ptr to array allocated at run- 
time */
static int  
maxfd;                                                              / 
* from our open_max(), {Prog openmax} */
+void sigchld_handler(int signo) { printf( "Caught sigchld\n");  
return; }   /* Do nothing */
+
FILE *
spopen (const char *cmdstring)
{
@@ -171,6 +173,7 @@
         if (pipe (pfderr) < 0)
                 return  
(NULL);                                                  /* errno set  
by pipe() */
+       signal(SIGCHLD, &sigchld_handler);
         if ((pid = fork ()) < 0)
                 return  
(NULL);                                                  /* errno set  
by fork() */
         else if (pid == 0) {                                    /*  
child */

While this works consistently on debian and MacOSX (with output of:

Caught sigchld
DNS OK: 0.099 seconds response time altinity.com returns  
216.68.81.208|time=0.098571s;;;0.000000

wrapped in a 'while true; do ./check_dns -H altinity.com || break ;  
done' loop), I still get the occasional error on Red Hat. Amazingly,  
there is no Caught sigchld for the failing scenario, which I find  
hard to understand. Any other suggestions from anyone?

Ton


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