resolver environment variables

[Joseph S D Yao]

On Wed, Mar 15, 2006 at 04:32:00PM -0800, David Carmean wrote:
> On Wed, Mar 15, 2006 at 04:49:22PM -0500, Joseph S D Yao wrote:
> > On Tue, Mar 14, 2006 at 01:52:54PM -0800, David Carmean wrote:
> > > Do the environment variables LOCALDOMAIN, RES_OPTIONS, and friends 
> > > actually work on any common/modern OS package?  I have so far been 
> > > unsuccessful in using RES_OPTIONS or LOCALDOMAIN in FreeBSD (4.x and 5.4), 
> > > Solaris (2.8, 2.9), and Linux (RedHat 8).
> > > 
> > > Thanks.
> > 
> > I double-checked the code and our local libc.* files, and I was wrong
> > yesterday.  They do appear to be compiled into the running versions of
> > the resolver library, on Red Hat Linux, at least..
> > 
> > How had you been trying to make them work?
> 
> By setting, for example, $LOCALDOMAIN to a subdomain not in the client's 
> search order and using ping to test the client's resolver.  
> 
> However, on Solaris and (RedHat) Linux it's starting to look like an nscd 
> issue.  

????  AFAIK, 'nscd' doesn't run on RHL.

!!ps -ef | grep 'nsc[d]'

Nope.

I also tried same here, and despite the strings being in the libc.so
[redirected], nothing changed when doing [e.g.] a 'ping':

	bash$ LOCALDOMAIN="somebody.else" ping ns1
	[get local "ns1" response]

I would have to trace this down a bit, but I suspect that many programs
don't actually use the BIND resolver routines.  This may be a legacy
thing.

I compiled the following program and ran it twice:

	bash$ ./gethost_test
	[shows local host]
	bash$ LOCALDOMAIN="somebody.else" ./gethost_test
	[shows "somebody else"'s host]

So it IS in there!

=========================== gethost_test.c ============================
#include <unistd.h>
#include <string.h>
#include <stdio.h>
#include <netdb.h>

#define NUL	'\0'
#define DIRC	'/'
#define FLAGC	'-'

char *myname	= "gethost_test";

static char default_host[]	= "ns1";

char *ip2str(unsigned char *addr);

int main(int argc, char **argv, char **envp)
{
	char *cp;
	extern int h_errno;
	struct hostent *gp;

	if (argc > 0) {
		cp = strrchr(*argv, DIRC);
		if (cp == (char *) NULL) {
			myname = *argv;
		} else {
			myname = ++cp;
		}
	}

	gp = gethostbyname(default_host);

	if (gp == (struct hostent *) NULL) {
		herror(myname);
		return(1);
	}

	if (gp->h_name == (char *) NULL) {
		fprintf(stderr, "%s: found no name matching \"%s\".\n",
			myname, default_host);
		return(1);
	}

	printf("%s == %s\n", gp->h_name, ip2str(gp->h_addr));

	return(0);
}

char *ip2str(unsigned char *addr)
{
	static char buffer[16];

	sprintf(buffer, "%u.%u.%u.%u",
		addr[0], addr[1], addr[2], addr[3]);

	return(buffer);
}
=======================================================================

-- 
Joe Yao
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