Re: RFC: XenSock brainstorming

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 06/06/16 10:33, Stefano Stabellini wrote:
> Hi all,
>
> a couple of months ago I started working on a new PV protocol for
> virtualizing syscalls. I named it XenSock, as its main purpose is to
> allow the implementation of the POSIX socket API in a domain other than
> the one of the caller. It allows connect, accept, recvmsg, sendmsg, etc
> to be implemented directly in Dom0. In a way this is conceptually
> similar to virtio-9pfs, but for sockets rather than filesystem APIs.
> See this diagram as reference:
>
> https://docs.google.com/presentation/d/1z4AICTY2ejAjZ-Ul15GTL3i_wcmhKQJA7tcXwhI3dys/edit?usp=sharing
>
> The frontends and backends could live either in userspace or kernel
> space, with different trade-offs. My current prototype is based on Linux
> kernel drivers but it would be nice to have userspace drivers too.
> Discussing where the drivers could be implemented it's beyond the scope
> of this email.

Just to confirm, you are intending to create a cross-domain transport
for all AF_ socket types, or just some?

>
>
> # Goals
>
> The goal of the protocol is to provide networking capabilities to any
> guests, with the following added benefits:

Throughout, s/Dom0/the backend/

I expect running the backend in dom0 will be the overwhelmingly common
configuration, but you should avoid designing the protocol for just this
usecase.

>
> * guest networking should work out of the box with VPNs, wireless
>   networks and any other complex network configurations in Dom0
>
> * guest services should listen on ports bound directly to Dom0 IP
>   addresses, fitting naturally in a Docker based workflow, where guests
>   are Docker containers
>
> * Dom0 should have full visibility on the guest behavior and should be
>   able to perform inexpensive filtering and manipulation of guest calls
>
> * XenSock should provide excellent performance. Unoptimized early code
>   reaches 22 Gbit/sec TCP single stream and scales to 60 Gbit/sec with 3
>   streams.

What happens if domU tries to open an AF_INET socket, and the domain has
both sockfront and netfront ?  What happens if a domain has multiple
sockfronts?

~Andrew

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