Re: [Qemu-devel] [POC] colo-proxy in qemu

[zhanghailiang]

On 2015/7/20 18:32, Stefan Hajnoczi wrote:
> On Mon, Jul 20, 2015 at 02:42:33PM +0800, Li Zhijian wrote:
> > We are planning to implement colo-proxy in qemu to cache and compare packets.
>
> I thought there is a kernel module to do that?

Yes, but we decided to re-implement it in userspace (Here is in qemu),
there are mainly two reasons that we made this change. One is the colo-proxy in 
kernel is
narrowly used, which can only be used for COLO FT, besides, we have to modify 
iptables and nftables
to support this capability. IMHO, it is hardly been accepted by the kernel 
community.
The other reason is that the kernel proxy scenario can't been used in all 
situations, for example,
evs + vhost-user + dpdk, it can't work if VM's network packets don't go through 
host's network
stack. (For the new userspace colo proxy scheme, we also can't use it with 
vhost-net,
we have to use virtio-net instead).

> Why does the proxy need to be part of the QEMU process?  -netdev socket
> or host network stack features allow you to process packets in a
> separate process.
>
> Without details on what the proxy does it's hard to discuss this.  What
> happens in the non-TCP case?  What happens in the TCP case?
>
> Does the proxy need to perform privileged operations, create sockets,
> open files, etc?
>
> The slirp code is not actively developed or used much in production.  It
> might be a good idea to audit the code for bugs if you want to use it.

Agreed, besides, it is seemed that slirp is not supporting ipv6, we also
have to supplement it.

Thanks,
zhanghailiang