Bug 11161

Summary:	nslookup doesn't work in kubernetes
Product:	Busybox	Reporter:	sylvain.boily
Component:	Networking	Assignee:	unassigned
Status:	RESOLVED FIXED
Severity:	normal	CC:	admwiggin+busyboxbugs, busybox-cvs
Priority:	P5
Version:	1.29.x
Target Milestone:	---
Hardware:	All
OS:	Linux
Host:		Target:
Build:

Description sylvain.boily 2018-07-18 12:26:15 UTC

see the following github issue for details.

https://github.com/docker-library/busybox/issues/48

This started with version 1.29

Comment 1 Tianon Gravi 2018-07-20 21:05:13 UTC

I haven't dug into the code yet, but in testing it would appear that the new DNS code in "nslookup" for the 1.29 release doesn't support DNS search domains ("search" entry in /etc/resolv.conf) at all, which Kubernetes makes pretty heavy use of.

Comment 2 Tianon Gravi 2018-07-20 21:10:23 UTC

(For context, my previous comment was based on testing a build of 1.29.1 built against all three of uClibc via buildroot, musl via Alpine, and glibc via Debian.)

Looking in the code, it appears my hunch was correct; I think "parse_resolvconf" is the culprit? (https://git.busybox.net/busybox/tree/networking/nslookup.c?h=1_29_1#n664)

That doesn't appear to do anything with "search" values (except ignore them), which is a regression from the previous libc-based behavior.  Was ignoring these intentional in this new implementation, or simply an oversight? (should someone work on / is someone working on a patch?)

Comment 3 Denys Vlasenko 2018-07-24 09:49:01 UTC

No, it's not intentional.
I'm actually surprised there were users of "old" nslookup, it had severe problems working (and even compiling on some libc).

Your options:
(1) switch to old version (disable FEATURE_NSLOOKUP_BIG)
(2) send a patch to improve the new version
(3) wait for someone to do (2)

Comment 4 ghicken 2018-07-26 21:22:33 UTC

I'm seeing nslookup fail intermittently. If I specify -type=a then it succeeds reliably.

In my case it appears to be related to nslookup issuing A and AAAA queries concurrently; in this case there is no AAAA record - I have not tried a scenario where there is an AAAA record.

From the DNS side the two queries are using the same ID and as best I can determine the failure happens if the AAAA response returns first.

Hopefully that's helpful additional data.

Comment 5 Denys Vlasenko 2018-07-31 11:48:50 UTC

(In reply to ghicken from comment #4)
> I'm seeing nslookup fail intermittently. If I specify -type=a then it succeeds reliably.
> In my case it appears to be related to nslookup issuing A and AAAA queries concurrently; in this case there is no AAAA record - I have not tried a scenario where there is an AAAA record.
> From the DNS side the two queries are using the same ID and as best I can determine the failure happens if the AAAA response returns first.

Can you provide the error message and ideally, tcpdump of the resolution attempt?

Comment 6 Denys Vlasenko 2018-08-01 17:44:59 UTC

Hopefully fixed in git.