Hi All,
I'm running snmpd on my CentOS5 systems for monitoring.
Every 3 seconds the prErrorFlags are checked from the configured procs.
But on some moments it falsely detects an error, which is gone during
the next check.
Investigating this we didn't notice any strange behavior on the
machines, the specific process did not restart.
I enabled debugging and noticed that whenever such false positive occurs
the list of running processes is much smaller.
The debugging output also showed the function that handles the process
counting and therefore I verified that piece of code.
As it was reading from /proc/*/status I wrote a bash script which did
exactly the same, but the problem never occurred.
I copied the sh_count_proc function out of snmpd code into a separate
program doing only the proc check.
And the problem occurred again.
Every time the specific proc isn't found the debug output "Could not
fgets for /proc/<pid>/status" is printed as last line.
In the code you can see that in the if block a break is used and no
continue.
Is there a reason why there is a break instead of a continue?
I attached my test script.
This function is copied from the latest stable snmp-5-5 from file:
agent/mibgroup/ucd-snmp/proc.c
Is this a bug, and is changing the break into a continue a correct fix?
Greetings,
Johan Huysmans
Newtecs MENOS system awarded IBC Innovation Award for Content Delivery & the
IBC Judges Award Newtecs FlexACM awarded 2009 Teleport Technology of the Year by
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#include <stdio.h>
#include <dirent.h>
char *
skip_white(char *ptr)
{
if (ptr == NULL)
return (NULL);
while (*ptr != 0 && isspace((unsigned char)*ptr))
ptr++;
if (*ptr == 0 || *ptr == '#')
return (NULL);
return (ptr);
}
char *
skip_not_white(char *ptr)
{
if (ptr == NULL)
return (NULL);
while (*ptr != 0 && !isspace((unsigned char)*ptr))
ptr++;
if (*ptr == 0 || *ptr == '#')
return (NULL);
return (ptr);
}
char *
skip_token(char *ptr)
{
ptr = skip_white(ptr);
ptr = skip_not_white(ptr);
ptr = skip_white(ptr);
return (ptr);
}
int
sh_count_procs(char *procname)
{
DIR *dir;
char cmdline[512], *tmpc;
char state[64];
struct dirent *ent;
int len,plen=strlen(procname),total = 0;
FILE *status;
if ((dir = opendir("/proc")) == NULL) return -1;
while (NULL != (ent = readdir(dir))) {
if(!(ent->d_name[0] >= '0' && ent->d_name[0] <= '9')) continue;
/* read /proc/XX/status */
sprintf(cmdline,"/proc/%s/status",ent->d_name);
if ((status = fopen(cmdline, "r")) == NULL) {
// DEBUG
printf("Could not fopen for %s\n", cmdline);
continue;
}
if (fgets(cmdline, sizeof(cmdline), status) == NULL) {
// DEBUG
printf("Could not fgets for %s\n", cmdline);
fclose(status);
// break;
continue;
}
/* Grab the state of the process as well
* (so we can ignore zombie processes)
* XXX: Assumes the second line is the status
*/
if (fgets(state, sizeof(state), status) == NULL) {
state[0]='\0';
}
fclose(status);
cmdline[sizeof(cmdline)-1] = '\0';
state[sizeof(state)-1] = '\0';
/* XXX: assumes Name: is first */
if (strncmp("Name:",cmdline, 5) != 0)
break;
tmpc = skip_token(cmdline);
if (!tmpc)
break;
for (len=0;; len++) {
if (tmpc[len] && isgraph(tmpc[len])) continue;
tmpc[len]='\0';
break;
}
// DEBUGMSGTL(("proc","Comparing wanted %s against %s\n",
// procname, tmpc));
// DEBUG
printf("Comparing wanted %s against %s\n",procname, tmpc);
if(len==plen && !strncmp(tmpc,procname,plen)) {
/* Do not count zombie process as they are not running processes */
if ( strstr(state, "zombie") == NULL ) {
total++;
// DEBUGMSGTL(("proc", " Matched. total count now=%d\n", total));
} else {
// DEBUGMSGTL(("proc", " Skipping zombie process.\n"));
}
}
}
closedir(dir);
return total;
}
int main() {
int result = sh_count_procs("sshd");
return result;
}
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