netdev - Re: Checksum offload queries

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Date:	Sat, 12 Dec 2015 09:24:42 -0800
From:	Tom Herbert <tom@...bertland.com>
To:	Sowmini Varadhan <sowmini.varadhan@...cle.com>
Cc:	Edward Cree <ecree@...arflare.com>,
	Linux Kernel Network Developers <netdev@...r.kernel.org>,
	David Miller <davem@...emloft.net>
Subject: Re: Checksum offload queries

On Sat, Dec 12, 2015 at 8:41 AM, Sowmini Varadhan
<sowmini.varadhan@...cle.com> wrote:
> On (12/11/15 15:50), Tom Herbert wrote:
>> layers of encapsulation. For example, suppose send a UDP packet in
>> VXLAN in VXLAN, where packet looks like:
>> IP|UDP|VXLAN|Eth|IP|UDP|VXLAN|Eth|IP|UDP. I believe the kernel can set
>
> Without detracting from the fact that you have probably found a bug
> for checksumming here..
>
> if you have multiple encapsulations above (vxlan over vxlan?)
> I think lot of other things like pmtu may also be broken?  (Each
> encaps layer lowers the actual application mtu till the thing starts
> to get absurd)
>
PMTU is going to be a headache with any encapsulation, multiple layers
just makes the headache worse. This is one of the reasons why ILA is
better for network virtualization-- no PMTU issue since there is no
encapsulation being done.

> --Sowmini
>
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