[ovs-dev] STT Implementation Thoughts

Jesse Gross jesse at nicira.com
Wed Mar 21 19:09:09 UTC 2012


On Wed, Mar 21, 2012 at 1:52 AM, Simon Horman <horms at verge.net.au> wrote:
> Hi Jesse, Hi all,
>
> I am currently investigating how STT[1] may be implemented for Open vSwtich.
> In the course of this it has struck me that a property particular
> to STT is that it uses the TCP IP protocol number but actually isn't TCP.
> Which makes me wonder how the receive-side it may be hooked into the Linux
> kernel.
>
> My thought so far is that some modifications may need to be made to
> tcp_v4_rcv() and/or tcp_v6_rcv() to skip TCP processing of packets
> for sockets that have been bound by STT. But I was wondering if you
> have any thoughts on this.

I agree it is an issue.  I think what we want is something analogous
to encap_rcv in the UDP stack, which is used for exactly this purpose
(for example, the OVS CAPWAP implementation uses it, as do L2TP and
UDP encapsulated IPsec upstream).  It's perhaps somewhat more likely
to be contentious since with UDP the packets are still processed by
the UDP stack just without the userspace termination part whereas this
takes the TCP state machine out of the picture but as least there is
precedent.



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