Re: [Tofoo] VXLAN (UDP tunnel protocols) and non-zero checksums

Joe Touch <touch@isi.edu> Thu, 01 May 2014 20:34 UTC

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Date: Thu, 01 May 2014 13:34:03 -0700
From: Joe Touch <touch@isi.edu>
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Subject: Re: [Tofoo] VXLAN (UDP tunnel protocols) and non-zero checksums
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On 5/1/2014 1:30 PM, Behcet Sarikaya wrote:
>
>
>
> On Thu, May 1, 2014 at 3:20 PM, Joe Touch <touch@isi.edu
> <mailto:touch@isi.edu>> wrote:
>
>
>
>     On 4/30/2014 2:23 PM, Behcet Sarikaya wrote:
>
>         Here is what VXLAN says on tunneled traffic:
>
>         Tunneled traffic over the IP network can be secured with traditional
>              security mechanisms like IPsec that authenticate and optionally
>              encrypt VXLAN traffic. This will, of course, need to be
>         coupled with
>              an authentication infrastructure for authorized endpoints
>         to obtain
>              and distribute credentials.
>
>         Based on this, UDP checksum text seems to be consistent, no?
>
>
>     No; the UDP checksum is not for authetication. It is an error check.
>
>     The only party that can decide to make the UDP checksum optional
>     when using IPv4 is the source - by inserting zero.
>
>     It's not the receiver's choice to ignore that checksum if it's not
>     zero. That's where this doc breaks the current standards.
>
> The important point in the above text that I quoted was encryption being
> optional not about authentication.
> So checksum would be zero if the payload is encrypted and non-zero if it
> is not not and both cases are possible.

Receiver processing is simple:

	- if the checksum is zero, ignore

	- if the checksum is NOT zero, it MUST match

No other part of the packet needs to be examined. If the *sender* wants 
to have the receiver ignore the checksum, it inserts zero. If not, the 
receiver MUST process and validate it.

Joe