Re: [BUG] Kernel recieves DNS reply, but doesn't deliver it to a waiting application

Hello,

On Sat, 13 Oct 2012 15:44:20 +0200 Eric Dumazet wrote:

On Sat, 2012-10-13 at 16:36 +0400, Andrew Savchenko wrote:

quoted

On Wed, 3 Oct 2012 23:25:48 +0400 Andrew Savchenko wrote:

quoted

I encountered a very weird bug: after a while of uptime kernel stops to deliver
DNS reply to applications. Tcpdump shows that correct reply is recieved, but 
strace shows inquiring application never recieves it and ends with timeout,
epoll_wait() always returns 0:
a slice from: $ host kernel.org 8.8.8.8:

[...]

quoted

quoted

In a few days I'll try 3.4.12 (I need to rebuild kernel anyway due to unrelated
issue) and will report if this bug will occur again. But please note it may
take several weeks to check this.

I got this problem again with 3.4.12 kernel. System lasted less than
a week and reboot was the only option...

You should investigate and check where the incoming packet is lost

Tools :

netstat -s

drop_monitor module and dropwatch command

cat /proc/net/udp

Thank you for you reply; I updated my kernel to 3.4.14, enabled
CONFIG_NET_DROP_MONITOR, and installed dropwatch utility.

I will report back when the bug will struck again.
This may take a weak or two, however.

Best regards,
Andrew Savchenko