Odd network behaviors with an Intel Wireless 7260

Odd network behaviors with an Intel Wireless 7260

[Pierre Bourdon]

Hi linux-wireless folks,

I have been getting some weird network behaviors with my Intel
Wireless 7260 adapter that I cannot explain by anything else than a
driver/firmware bug. I'm out of ideas on how to debug this issue.

My network configuration is fairly basic: IPv4 over 802.11n,
AP/default gateway is 192.168.0.1, my Intel 7260 STA is 192.168.0.2.
Several AP/gateway hardware and software have been tested and have
shown the same problem.

On 192.168.0.2 I am constantly running some ICMP pings to 192.168.0.1
and 8.8.8.8. Randomly, the pings from 192.168.0.2 to 8.8.8.8 start
failing (responses never received) while the pings to 192.168.0.1
continue to succeed without any trouble. When tcpdumping on the
gateway, I see the pings to 8.8.8.8 being successfully forwarded and
responses being sent back to the STA (so this is not a routing issue
on the gateway - and again, I've tested several combinations of hw/sw
on the gateway).

Another example: my TCP sessions on the Intel 7260 STA to the internet
will start randomly freezing, but my TCP sessions going through
tunnels on another LAN host (let's say, 192.168.0.3) to the internet
will work fine.

After 30s-1min30 the problem fixes itself and packets start being
received by the STA again.

I only see this from the Intel 7260 host and not from any other WLAN
device connected to the AP, which is another strong evidence that the
issue is on the STA side.

I've shared this with some other people using an Intel 7260 adapter on
Linux and found someone having a similar issue. I'm not sure how
widespread it is and could not find an existing bug report.

What are the next steps to get useful debugging information out of
this issue? I unfortunately do not have the required hardware to do
monitor-mode sniffing of what's happening at the L2 level.

Thanks,

-- 
Pierre "delroth" Bourdon <delroth@gmail.com>
Software Engineer @ Zürich, Switzerland
http://code.delroth.net/

Re: Odd network behaviors with an Intel Wireless 7260

[Emmanuel Grumbach]

Hi,


On 04/25/2014 02:03 AM, Pierre Bourdon wrote:
> Hi linux-wireless folks,
> 
> I have been getting some weird network behaviors with my Intel
> Wireless 7260 adapter that I cannot explain by anything else than a
> driver/firmware bug. I'm out of ideas on how to debug this issue.
> 
> My network configuration is fairly basic: IPv4 over 802.11n,
> AP/default gateway is 192.168.0.1, my Intel 7260 STA is 192.168.0.2.
> Several AP/gateway hardware and software have been tested and have
> shown the same problem.
> 
> On 192.168.0.2 I am constantly running some ICMP pings to 192.168.0.1
> and 8.8.8.8. Randomly, the pings from 192.168.0.2 to 8.8.8.8 start
> failing (responses never received) while the pings to 192.168.0.1
> continue to succeed without any trouble. When tcpdumping on the
> gateway, I see the pings to 8.8.8.8 being successfully forwarded and
> responses being sent back to the STA (so this is not a routing issue
> on the gateway - and again, I've tested several combinations of hw/sw
> on the gateway).
> 
> Another example: my TCP sessions on the Intel 7260 STA to the internet
> will start randomly freezing, but my TCP sessions going through
> tunnels on another LAN host (let's say, 192.168.0.3) to the internet
> will work fine.
> 
> After 30s-1min30 the problem fixes itself and packets start being
> received by the STA again.
> 
> I only see this from the Intel 7260 host and not from any other WLAN
> device connected to the AP, which is another strong evidence that the
> issue is on the STA side.
> 
> I've shared this with some other people using an Intel 7260 adapter on
> Linux and found someone having a similar issue. I'm not sure how
> widespread it is and could not find an existing bug report.
> 
> What are the next steps to get useful debugging information out of
> this issue? I unfortunately do not have the required hardware to do
> monitor-mode sniffing of what's happening at the L2 level.
> 

Thank you very much for this very detailed report.
1) can you try with power save disabled?
   sudo iw wlan0 set power_save off
2) if 1) helps, can you try https://git.kernel.org/cgit/linux/kernel/git/iwlwifi/iwlwifi-fixes.git/commit/?id=a82dda6cd492b8c88952be6f6527f3656f7ac585.

Thanks

Re: Odd network behaviors with an Intel Wireless 7260

[Pierre Bourdon]

[+ another user who reported similar issues]

On Fri, Apr 25, 2014 at 9:51 AM, Emmanuel Grumbach <egrumbach@gmail.com> wrote:
> Thank you very much for this very detailed report.
> 1) can you try with power save disabled?
>    sudo iw wlan0 set power_save off

Thanks for the suggestion. I will be testing this over the week-end.
Since this is a random issue (happens every few hours) I will not be
able to be fully certain how much it helps, but I will definitely
notice large improvements / complete mitigations.

FWIW, I've had this issue happen with several 7260 fw versions. Was
uAPSD always advertised as supported or is it an addition of newer
firmwares?

-- 
Pierre "delroth" Bourdon <delroth@gmail.com>
Software Engineer @ Zürich, Switzerland
http://code.delroth.net/

Re: Odd network behaviors with an Intel Wireless 7260

[Emmanuel Grumbach]

On 04/25/2014 11:08 AM, Pierre Bourdon wrote:
> [+ another user who reported similar issues]
> 
> On Fri, Apr 25, 2014 at 9:51 AM, Emmanuel Grumbach <egrumbach@gmail.com> wrote:
>> Thank you very much for this very detailed report.
>> 1) can you try with power save disabled?
>>    sudo iw wlan0 set power_save off
> 
> Thanks for the suggestion. I will be testing this over the week-end.
> Since this is a random issue (happens every few hours) I will not be
> able to be fully certain how much it helps, but I will definitely
> notice large improvements / complete mitigations.
> 
> FWIW, I've had this issue happen with several 7260 fw versions. Was
> uAPSD always advertised as supported or is it an addition of newer
> firmwares?
> 

Hmm... What kernel are you using?
IIRC 22.1.7.0 doesn't have uAPSD support - so if it the problem exists with this firmware, then we should look for something else.

Re: Odd network behaviors with an Intel Wireless 7260

[Pierre Bourdon]

On Fri, Apr 25, 2014 at 11:49 AM, Emmanuel Grumbach <egrumbach@gmail.com> wrote:
> Hmm... What kernel are you using?
> IIRC 22.1.7.0 doesn't have uAPSD support - so if it the problem exists with this firmware, then we should look for something else.

Currently using Linux 3.13.8 and firmware 22.24.8.0. I don't remember
precisely what fw versions I tried before and I cannot really try
several mitigations at once so let's wait and see if disabling
power_save changes anything.

-- 
Pierre "delroth" Bourdon <delroth@gmail.com>
Software Engineer @ Zürich, Switzerland
http://code.delroth.net/

Re: Odd network behaviors with an Intel Wireless 7260

[Pierre Bourdon]

On Fri, Apr 25, 2014 at 9:51 AM, Emmanuel Grumbach <egrumbach@gmail.com> wrote:
> Thank you very much for this very detailed report.
> 1) can you try with power save disabled?
>    sudo iw wlan0 set power_save off
> 2) if 1) helps, can you try https://git.kernel.org/cgit/linux/kernel/git/iwlwifi/iwlwifi-fixes.git/commit/?id=a82dda6cd492b8c88952be6f6527f3656f7ac585.

Unfortunately I have to report that this does not solve the issue. I
was able to reproduce the random non-local drops several times with
power saving disabled on the interface.

-- 
Pierre "delroth" Bourdon <delroth@gmail.com>
Software Engineer @ Zürich, Switzerland
http://code.delroth.net/