Hi,

do you see any remaining issue with the TCP MSS clamping plugin that has not 
been addressed yet?
The patch set has been hanging for quite some time and I am wondering how we 
could proceed further. https://gerrit.fd.io/r/c/vpp/+/15144

Thanks,
Miklos
________________________________
From: [email protected] <[email protected]> on behalf of Miklos Tirpak via 
lists.fd.io <[email protected]>
Sent: Sunday, May 31, 2020 6:37 PM
To: Paul Vinciguerra <[email protected]>
Cc: [email protected] <[email protected]>; Mohsin Kazmi (sykazmi) 
<[email protected]>; [email protected] <[email protected]>
Subject: Re: [vpp-dev] generic TCP MSS clamping


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Thanks lot, Paul. I have updated the patch set.

I would appreciate a second look at the checksum around tmc_node.c:124. The 
function updates the TCP checksum instead of recalculating that now. I just 
find the usage of ip_csum_update() a bit unclear, there are also comments about 
cheating in other plugins.

Thanks,
Miklos
________________________________
From: Paul Vinciguerra <[email protected]>
Sent: Sunday, May 31, 2020 12:05 PM
To: Miklós Tirpák <[email protected]>
Cc: [email protected] <[email protected]>; Mohsin Kazmi (sykazmi) 
<[email protected]>; [email protected] <[email protected]>
Subject: Re: [vpp-dev] generic TCP MSS clamping


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Yes, please do.  My changeset only freshens the api code to take advantage of 
the refactorings that have been put in place since that code was last submitted 
and fix the tests to work properly under python3 in anticipation of your 
changes.

Paul

On Sun, May 31, 2020 at 5:23 AM Miklós Tirpák 
<[email protected]<mailto:[email protected]>> wrote:
Hi Paul,

I just saw the updated patch from you in https://gerrit.fd.io/r/c/vpp/+/15144/2.
We discussed on the mailing list few days ago that I am working on updating 
this plugin, and your patch is a bit conflicting with my changes unfortunately.

If you do not mind I would still update the patch set in this code review with 
some more changes: RX support, bugfix in clamping (mss is changed even if it is 
low enough), some more tests, cli command updates. I hope I can do this quickly.

Thanks,
Miklos
________________________________
From: [email protected]<mailto:[email protected]> 
<[email protected]<mailto:[email protected]>> on behalf of Miklos Tirpak 
via lists.fd.io<http://lists.fd.io> 
<[email protected]<mailto:[email protected]>>
Sent: Thursday, May 28, 2020 4:51 PM
To: [email protected]<mailto:[email protected]> 
<[email protected]<mailto:[email protected]>>; Mohsin Kazmi (sykazmi) 
<[email protected]<mailto:[email protected]>>
Cc: [email protected]<mailto:[email protected]> 
<[email protected]<mailto:[email protected]>>
Subject: Re: [vpp-dev] generic TCP MSS clamping


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Thank you for the pointer, this is exactly what I was looking for. I will 
rebase the patch and add RX support.

Thanks,
Miklos
________________________________
From: [email protected]<mailto:[email protected]> 
<[email protected]<mailto:[email protected]>>
Sent: Thursday, May 28, 2020 12:43 PM
To: Mohsin Kazmi (sykazmi) <[email protected]<mailto:[email protected]>>
Cc: Miklós Tirpák <[email protected]<mailto:[email protected]>>; 
[email protected]<mailto:[email protected]> 
<[email protected]<mailto:[email protected]>>
Subject: Re: [vpp-dev] generic TCP MSS clamping

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Good find Mohsin. So it's only missing clamping on RX. I'm sure Miklos can add 
that.

Cheers,
Ole

> On 28 May 2020, at 12:23, Mohsin Kazmi (sykazmi) 
> <[email protected]<mailto:[email protected]>> wrote:
>
> Hi Miklos,
>
> May be, it will help https://gerrit.fd.io/r/c/vpp/+/15144
>
> -br
> Mohsin
> From: <[email protected]<mailto:[email protected]>> on behalf of Ole 
> Troan <[email protected]<mailto:[email protected]>>
> Date: Thursday, May 28, 2020 at 11:23 AM
> To: Miklos Tirpak <[email protected]<mailto:[email protected]>>
> Cc: "[email protected]<mailto:[email protected]>" 
> <[email protected]<mailto:[email protected]>>
> Subject: Re: [vpp-dev] generic TCP MSS clamping
>
> Hi Miklos,
>
> > I see the NAT plugin already supports TCP MSS clamping but it is 
> > implemented only in in2out direction.
> >
> > We have endpoints with wrong MTUs behind tunnels and not all the traffic is 
> > NATed. Hence, it would be very nice to have generic support for MSS 
> > clamping that could be enabled on the tunnel interface.
> >
> > Do you think implementing this as a feature arch would make sense? Then it 
> > would not be limited to NAT or to one kind of tunnel for example.
> > If so, what is the best place? A new plugin?
>
> A bidirectional TCP MSS adjust would be fine.
> Putting it in a plugin is likely the simplest.
>
> I'm unsure if it should be generic or not. E.g. the NAT also needs to adjust 
> the TCP checksum, and it's likely better to do it only once.
>
> Best regards,
> Ole
>

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