On 2011-02-18 17:16, Derek J. Balling wrote:
> But also my complaint is: Why *isn't* puppet-agent noticing
> that resolv.conf has changed? This seems like something that
> would only be caused by not using the standard gethostbyname()
> calls and such, > since *those* should reflect the change in
> resolv.conf almost immediately.... :-/
Except that they don't... At least the GNU libc implementation does
not re-read resolv.conf unless you call res_init(). I'm attaching
a test program that you can use to verify it yourself. It will call
gethostbyname() twice, optionally re-initialize the resolver before
the second call. You are supposed to change your resolv.conf between
the two calls.
I *think* other Unix libc implementations does the same, but I don't
have any machine available where I can test this at the moment.
/Bellman
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#define _BSD_SOURCE
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <time.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <arpa/nameser.h>
#include <arpa/inet.h>
#include <resolv.h>
#include <netdb.h>
#include <sysexits.h>
void showhost(char *hostname)
{
struct hostent *he;
int i;
char buf[4096];
he = gethostbyname(hostname);
if (he == NULL)
printf("gethostbyname(%s) failed: %d\n", hostname, h_errno);
else
{
for (i = 0 ; he->h_addr_list[i] ; i++)
{
printf("gethostbyname(%s): %s\n",
hostname,
inet_ntop(he->h_addrtype, he->h_addr_list[i],
buf, sizeof buf));
}
}
}
void usage(char **argv)
{
fprintf(stderr, "Usage: %s [-r] hostname\n", argv[0]);
exit(EX_USAGE);
}
int main(int argc, char **argv)
{
char *host;
int reread_resolvconf = 0;
if (argc < 2)
usage(argv);
reread_resolvconf = !strcmp(argv[1], "-r");
if (argc != 2 + reread_resolvconf)
usage(argv);
host = argv[1 + reread_resolvconf];
showhost(host);
fputs("Press Return: ", stdout);
fflush(stdout);
getc(stdin);
if (reread_resolvconf) {
fputs("Re-initializing resolver\n", stdout);
res_init();
}
showhost(host);
return 0;
}
