Bug 48741

Summary: ipv6 localhost connection times out since linux 3.6.0
Product: Networking Reporter: Jan Hinnerk Stosch (janhinnerk.stosch)
Component: IPV6Assignee: Hideaki YOSHIFUJI (yoshfuji)
Status: RESOLVED CODE_FIX    
Severity: low CC: alan
Priority: P1    
Hardware: All   
OS: Linux   
Kernel Version: 3.6.2 Subsystem:
Regression: Yes Bisected commit-id:
Attachments: strace output
tcpdump with -vvv option

Description Jan Hinnerk Stosch 2012-10-13 17:16:28 UTC
Created attachment 83401 [details]
strace output

By chance I detected a small regression that seems to be related to some changes in linux 3.6.0:
I have ntp-daemon running and usually could print a list of peers and some further sync information with the command "ntpq -p".
Since linux 3.6.0 this command times out ("localhost.localdomain: timed out, nothing received ***Request timed out"). As you can see in the attached strace output the program tries to connect to the ipv6 loopback interface and fails with that. If I explicitly use ipv4 (ntpq -4 -p) the command works fine.
If I downgrade my kernel to version 3.5.6 there are no timeouts.
I don't have any similar problems with other software.
One thing to add:
I first reported this bug to my distribution (https://bugs.archlinux.org/task/31775) and found at least one person having the same regression.

Please be patient with me, as I don't have any insight into the kernel and might be even wrong with my component classification (ipv6). I'd be glad to help though. Just tell me if you need any further information.
Comment 1 Alan 2012-10-14 12:14:29 UTC
Best place to ask if you are not sure is netdev@vger.kernel.org.

Give the detail you have here and a pointer to the bug report. A tcpdump may also be useful
Comment 2 Jan Hinnerk Stosch 2012-10-14 15:23:13 UTC
Created attachment 83431 [details]
tcpdump with -vvv option
Comment 3 Jan Hinnerk Stosch 2012-10-17 09:29:16 UTC
A patch has been sent to the mailing list:
http://marc.info/?l=linux-netdev&m=135040905619911&w=2
As it solves the issue for me and no one else is claiming problems this report can be closed, I think. Thank you.
Comment 4 Jan Hinnerk Stosch 2012-10-31 22:02:18 UTC
Fixed in kernel version 3.6.4.