icmp6

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icmp6

Amena El Homsi
Hi,

When we receive an echo request using IPv6, LwIP copies the request to new pbuf to send the reply.
Why LwIP doesn't use the echo request pbuf, instead of allocating a new one (as what LwIP does when replying to IPv4 echo requests)?

Thanks in advance.

--

Amena El-Homsi
Computer & Communication Engineer
Dipl. Eng,  M.S.

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Re: icmp6

goldsimon@gmx.de
On 14.08.2018 14:49, Amena El Homsi wrote:
> When we receive an echo request using IPv6, LwIP copies the request to
> new pbuf to send the reply.
> Why LwIP doesn't use the echo request pbuf, instead of allocating a
> new one (as what LwIP does when replying to IPv4 echo requests)?

Ehrm, I don't know really. But the code for IPv4 has been there a really
long time and has cause some problems in the past. Also, using an RX
buffer for TX can be a problem because it can starve RX when all the
buffers get queued for TX and TX somehow stalls for some time (e.g.
oending ARP request or something like that).

Is there a problem with copying the request for IPv6?

Simon

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Re: icmp6

Amena El Homsi
Hi, thanks for your reply.

Actually it is not a problem, I just want to avoid copying since it consumes power. However, since LwIP does copying for IPv6 I have no choice.

But does what you said mean that we will be facing issues with ICMP v4?

On Tue, Aug 14, 2018 at 4:03 PM, [hidden email] <[hidden email]> wrote:
On 14.08.2018 14:49, Amena El Homsi wrote:
When we receive an echo request using IPv6, LwIP copies the request to new pbuf to send the reply.
Why LwIP doesn't use the echo request pbuf, instead of allocating a new one (as what LwIP does when replying to IPv4 echo requests)?

Ehrm, I don't know really. But the code for IPv4 has been there a really long time and has cause some problems in the past. Also, using an RX buffer for TX can be a problem because it can starve RX when all the buffers get queued for TX and TX somehow stalls for some time (e.g. oending ARP request or something like that).

Is there a problem with copying the request for IPv6?

Simon

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Amena El-Homsi
Computer & Communication Engineer
Dipl. Eng,  M.S.

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Re: icmp6

Ivan Delamer-2
In reply to this post by Amena El Homsi
Hi Amena,

I don't remember the exact details for the copy, but it may have been
related to:

- the input/output pbufs are sometimes allocated from different sources
- it's possible the output pbuf needs to be buffered (e.g. if neighbor
discovery is required before the response)
- I believe there could be different IPv6 option headers in req and resp
and bring alignment issues

I know I tested no-copy at the time it was developed and run into some
problem. Hope this gives you a hint if you're investigating.

Regards,
Ivan


On 2018-08-14 10:00, [hidden email] wrote:

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> Today's Topics:
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>    1. icmp6 (Amena El Homsi)
>    2. Re: icmp6 ([hidden email])
>    3. Re: LwIP RAW + Zynq - Unresponsive Tx path when Rx is active
>       (Nenad Pekez)
>    4. Re: icmp6 (Amena El Homsi)
>
>
> ----------------------------------------------------------------------
>
> Date: Tue, 14 Aug 2018 15:49:57 +0300
> From: Amena El Homsi <[hidden email]>
> To: Mailing list for lwIP users <[hidden email]>
> Subject: [lwip-users] icmp6
> Message-ID:
> <CALEf8F3jNo=[hidden email]>
> Content-Type: text/plain; charset="utf-8"
>
> Hi,
>
> When we receive an echo request using IPv6, LwIP copies the request to
> new
> pbuf to send the reply.
> Why LwIP doesn't use the echo request pbuf, instead of allocating a new
> one
> (as what LwIP does when replying to IPv4 echo requests)?
>
> Thanks in advance.
>
> --
>
> Amena El-Homsi
> Computer & Communication Engineer
> Dipl. Eng,  M.S.

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Re: icmp6

Amena El Homsi
Yes thanks a lot

Sent from my iPhone

> On Aug 14, 2018, at 8:27 PM, [hidden email] wrote:
>
> Hi Amena,
>
> I don't remember the exact details for the copy, but it may have been related to:
>
> - the input/output pbufs are sometimes allocated from different sources
> - it's possible the output pbuf needs to be buffered (e.g. if neighbor discovery is required before the response)
> - I believe there could be different IPv6 option headers in req and resp and bring alignment issues
>
> I know I tested no-copy at the time it was developed and run into some problem. Hope this gives you a hint if you're investigating.
>
> Regards,
> Ivan
>
>
>> On 2018-08-14 10:00, [hidden email] wrote:
>> Send lwip-users mailing list submissions to
>>    [hidden email]
>> To subscribe or unsubscribe via the World Wide Web, visit
>>    https://lists.nongnu.org/mailman/listinfo/lwip-users
>> or, via email, send a message with subject or body 'help' to
>>    [hidden email]
>> You can reach the person managing the list at
>>    [hidden email]
>> When replying, please edit your Subject line so it is more specific
>> than "Re: Contents of lwip-users digest..."
>> Today's Topics:
>>   1. icmp6 (Amena El Homsi)
>>   2. Re: icmp6 ([hidden email])
>>   3. Re: LwIP RAW + Zynq - Unresponsive Tx path when Rx is active
>>      (Nenad Pekez)
>>   4. Re: icmp6 (Amena El Homsi)
>> ----------------------------------------------------------------------
>> Date: Tue, 14 Aug 2018 15:49:57 +0300
>> From: Amena El Homsi <[hidden email]>
>> To: Mailing list for lwIP users <[hidden email]>
>> Subject: [lwip-users] icmp6
>> Message-ID:
>>    <CALEf8F3jNo=[hidden email]>
>> Content-Type: text/plain; charset="utf-8"
>> Hi,
>> When we receive an echo request using IPv6, LwIP copies the request to new
>> pbuf to send the reply.
>> Why LwIP doesn't use the echo request pbuf, instead of allocating a new one
>> (as what LwIP does when replying to IPv4 echo requests)?
>> Thanks in advance.
>> --
>> Amena El-Homsi
>> Computer & Communication Engineer
>> Dipl. Eng,  M.S.
>
> _______________________________________________
> lwip-users mailing list
> [hidden email]
> https://lists.nongnu.org/mailman/listinfo/lwip-users

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