Red Hat Bugzilla – Bug 860829
Grub2 can't resolve names on F18
Last modified: 2012-10-30 16:30:43 EDT
Description of problem:
Grub2 on Fedora 18 has DNS support, however it does not work properly.
Going to the grub2's console I get the following:
grub> net_nslookup ibm.com
error: no DNS reply received.
grub> net_nslookup ibm.com 220.127.116.11
error: no DNS record found.
Version-Release number of selected component (if applicable):
Google's DNS server does resolve grub's queries, however I can't tell what DNS server they run. BIND is a largely used DNS server and should be supported.
grub> net_nslookup ibm.com 18.104.22.168
Created attachment 618761 [details]
Workaround to fix DNS lookup (ipv4 only)
------- Comment on attachment From firstname.lastname@example.org 2012-09-28 20:50 EDT-------
After some investigation I found that this issue is caused by GRUB2 assembling 2 questions (ipv4 and ipv6) on a single DNS packet.
BIND does not support it, and my tests suggest that dnsmasq also doesn't when resolving local domains.
The reason why BIND doesn't support multiple questions per query is due to potential ambiguity on partial results. You can find some discussions on the following links. These discussions are a bit old but I can confirm that latest stable release of BIND still doesn't support multiple questions per query.
As a proof of concept, I've written and tested the attached patch which basically drops ipv6 question from GRUB's DNS queries. This makes ipv4 DNS work fine, though drops ipv6 DNS support.
I've only tested on ppc64, but this issue probably affects all arches, since the code is not arch-specific.
I will work on a more appropriate patch to make GRUB send 2 separate queries for ipv4 and ipv6. I would appreciate any comments/suggestions.
Created attachment 628205 [details]
[PATCH] Issue separate DNS queries for ipv4 and ipv6
------- Comment on attachment From email@example.com 2012-10-16 14:59 EDT-------
Sorry, forgot to mention the bugz number in the patch.
grub2-2.00-10.fc18 has been submitted as an update for Fedora 18.
* should fix your issue,
* was pushed to the Fedora 18 testing repository,
* should be available at your local mirror within two days.
Update it with:
# su -c 'yum update --enablerepo=updates-testing grub2-2.00-10.fc18'
as soon as you are able to.
Please go to the following url:
then log in and leave karma (feedback).
grub2-2.00-11.fc18 has been submitted as an update for Fedora 18.
Tested grub2-2.00-11.fc18 and it works fine.