[ath9k-devel] Capture all transmissions with monitor interface

[ath9k-devel] Capture all transmissions with monitor interface

[Julien Herzen]

Hello,

I'm sending traffic from a node A to a node B, and I'm capturing traffic
sent by node A, at node A itself, using a monitor interface. I'm doing this
on lossy links, where many re-transmissions occur. It seems, however, that
each packet sent by A is captured only once (with our without retry bit
set). Is there a way to capture _all_ transmissions done by A?

I'm using AR9220 on Alix boards with kernel 2.6.32.27.

Thanks!


Julien
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[ath9k-devel] Capture all transmissions with monitor interface

[Alex Hacker]

On Tue, Dec 04, 2012 at 07:43:40PM +0100, Julien Herzen wrote:
>    Hello,
> 
>    I'm sending traffic from a node A to a node B, and I'm capturing traffic
>    sent by node A, at node A itself, using a monitor interface. I'm doing
>    this on lossy links, where many re-transmissions occur. It seems, however,
>    that each packet sent by A is captured only once (with our without retry
>    bit set). Is there a way to capture _all_ transmissions done by A?

No, packets automatically generated by HW i.e. retries, acks, rts/cts is not
visible for the software. Only solution is to use node C in monitor mode next
to node A.

> 
>    I'm using AR9220 on Alix boards with kernel 2.6.32.27.
> 
>    Thanks!
> 
>    Julien

Best wishes,
Alex.

[ath9k-devel] Capture all transmissions with monitor interface

[Julien Herzen]

Alex,

Thanks a lot for your answer.

Best,
Julien



On Wed, Dec 5, 2012 at 6:45 AM, Alex Hacker <hacker@epn.ru> wrote:

> On Tue, Dec 04, 2012 at 07:43:40PM +0100, Julien Herzen wrote:
> >    Hello,
> >
> >    I'm sending traffic from a node A to a node B, and I'm capturing
> traffic
> >    sent by node A, at node A itself, using a monitor interface. I'm doing
> >    this on lossy links, where many re-transmissions occur. It seems,
> however,
> >    that each packet sent by A is captured only once (with our without
> retry
> >    bit set). Is there a way to capture _all_ transmissions done by A?
>
> No, packets automatically generated by HW i.e. retries, acks, rts/cts is
> not
> visible for the software. Only solution is to use node C in monitor mode
> next
> to node A.
>
> >
> >    I'm using AR9220 on Alix boards with kernel 2.6.32.27.
> >
> >    Thanks!
> >
> >    Julien
>
> Best wishes,
> Alex.
>
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[ath9k-devel] Capture all transmissions with monitor interface

[Julien Herzen]

Thanks for your reply,

Does this mean that a packet is passed to the monitor interface only once
it has been successfully ACK'd by the receiver? In this case, do you know
how to exactly interpret the retry bit of the packets received by the
monitor interface?
In particular, if the retry bit is set, does it mean that at least one
hardware (or software?) re-transmission occurred for this packet before it
has been successfully ACK'd ?

Thanks!
Best,

Julien


On Wed, Dec 5, 2012 at 6:45 AM, Alex Hacker <hacker@epn.ru> wrote:

> On Tue, Dec 04, 2012 at 07:43:40PM +0100, Julien Herzen wrote:
> >    Hello,
> >
> >    I'm sending traffic from a node A to a node B, and I'm capturing
> traffic
> >    sent by node A, at node A itself, using a monitor interface. I'm doing
> >    this on lossy links, where many re-transmissions occur. It seems,
> however,
> >    that each packet sent by A is captured only once (with our without
> retry
> >    bit set). Is there a way to capture _all_ transmissions done by A?
>
> No, packets automatically generated by HW i.e. retries, acks, rts/cts is
> not
> visible for the software. Only solution is to use node C in monitor mode
> next
> to node A.
>
> >
> >    I'm using AR9220 on Alix boards with kernel 2.6.32.27.
> >
> >    Thanks!
> >
> >    Julien
>
> Best wishes,
> Alex.
>
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[ath9k-devel] Capture all transmissions with monitor interface

[abhinav narain]

On Wed, Dec 5, 2012 at 5:29 AM, Julien Herzen <j.herzen@gmail.com> wrote:

> Thanks for your reply,
>
> Does this mean that a packet is passed to the monitor interface only once
> it has been successfully ACK'd by the receiver? In this case, do you know
> how to exactly interpret the retry bit of the packets received by the
> monitor interface?
>
Yes.

> In particular, if the retry bit is set, does it mean that at least one
> hardware (or software?) re-transmission occurred for this packet before it
> has been successfully ACK'd ?
>

Yes.

-Abhinav
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