Re: Queries with less than `ndots` dots never lead to resolution using the global namespace if the `search` domains don't work

[Rich Felker <dalias@libc.org>]

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On Wed, Mar 15, 2017 at 12:58:02PM +0000, dominic.chambers@glencore.com wrote:
> HI Rich,
> 
> Thanks for the prompt response here. Apologies for any confusion I
> may have created, but I think the server is responding with an
> overall `NXDOMAIN` response. This is what I get from running `dig
> google.com.default.svc.cluster.local`:
> 
> ```
> ; <<>> DiG 9.10.3-P4-Ubuntu <<>> google.com.default.svc.cluster.local
> ;; global options: +cmd
> ;; Got answer:
> ;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 20863
> ;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0
> 
> ;; QUESTION SECTION:
> ;google.com.default.svc.cluster.local. IN A
> 
> ;; AUTHORITY SECTION:
> cluster.local.          60      IN      SOA     ns.dns.cluster.local. hostmaster
> .cluster.local. 1489579200 28800 7200 604800 60
> 
> ;; Query time: 0 msec
> ;; SERVER: 10.43.0.10#53(10.43.0.10)
> ;; WHEN: Wed Mar 15 12:49:14 UTC 2017
> ;; MSG SIZE  rcvd: 147
> ```
> 
> Although there's less information with nslookup, the response from
> running `nslookup google.com.default.svc.cluster.local` seems even
> more definitive:
> 
> ```
> Server:         10.43.0.10
> Address:        10.43.0.10#53
> 
> ** server can't find google.com.default.svc.cluster.local: NXDOMAIN
> ```
> 
> Maybe I was just reading too much into the output from dig regarding
> exactly what was being returned from the server. Any further
> thoughts?

Can you send an strace log of an affected lookup with musl's resolver
(rather than dig/nslookup which use bind's resolver) for me to look
at? Attached is source for a trivial sample utility to perform a
lookup.

Rich

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#include <stdio.h>
#include <netdb.h>
#include <netinet/in.h>

int main(int argc, char **argv)
{
	int r;
	char buf[256], buf2[32];
	struct addrinfo *ai, hints = { .ai_protocol = IPPROTO_TCP, .ai_flags = 0, .ai_family = AF_UNSPEC };
	char *name = argc>1 ? argv[1][0] ? argv[1] : 0 : 0;
	char *serv = argc>2 ? argv[2] : 0;

	r = getaddrinfo(name, serv, &hints, &ai);
	if (r<0)
		printf("%s: %s\n", name, gai_strerror(r));
	else for (; ai; ai = ai->ai_next)
		if (!getnameinfo(ai->ai_addr,
			ai->ai_addrlen, buf, sizeof buf,
			buf2, sizeof buf2, NI_NUMERICHOST|NI_NUMERICSERV))
			printf("%s: %s %s %s %s %s\n", name?name:"NULL",
				ai->ai_canonname, buf, buf2,
				ai->ai_protocol == IPPROTO_TCP ? "tcp" : "udp",
				ai->ai_socktype == SOCK_STREAM ? "stream" : "dgram");
	return 0;
}