Re: [Qemu-devel] [RFC PATCH v2 00/10] Add colo-proxy based on netfilter

[Li Zhijian]

On 03/01/2016 04:04 AM, Dr. David Alan Gilbert wrote:
> * Zhang Chen (address@hidden) wrote:
> > From: zhangchen <address@hidden>
> >
> > Hi,all
> >
> > This patch add an colo-proxy object, COLO-Proxy is a part of COLO,
> > based on qemu netfilter and it's a plugin for qemu netfilter. the function
> > keep Secondary VM connect normal to Primary VM and compare packets
> > sent by PVM to sent by SVM.if the packet difference,notify COLO do
> > checkpoint and send all primary packet has queued.
>
> Hi Zhangchen,
>    How are you dealing with the IP 'identification' field?
> It's a very very random field, and not just the initial value in the connection.
> I can't see how the kernel colo-proxy dealt with it either; but I think it's
> comparison was after defragementation so probably ignored the identification
> field
You are right, most kernel colo-proxy code is working at mangle table (after 
defrag).
and colo proxy only compare the contents of L4(TCP/UDP) excluding IP 
identification.

>  - wouldn't that confuse a client at failover?
Err..., instersting question.

for example, a COLO including primay(PVM) adn secondary(SVM)
1. primay is sending a compared P_IP packet(identification=0x12345, split to 
IP_s1, IP_s2..IP_s100) to client
2. client is receiving the ip segment(but IP_s2, IP_s50, IP_s80..IP_s99 are 
missing)
   and primary host is down.
3. secondary VM takeover, and send a S_IP packet(ip contents is always same as 
at PVM)

in step 3,
if the S_IP identification isn't 0x12345, client will drop the ip segment at 
step 2 because of defrag timeout.
if the S_IP identification isn 0x12345, client may mix the segment from PVM or 
SVM(just like segment come
from different router), but that's Okay, because we have ensured the ip 
contents is identical.

so IMO, it will not confuse the client at failover.

> Dave
>
> > You can also get the series from:
> >
> > https://github.com/zhangckid/qemu/tree/colo-v2.2-periodic-mode-with-colo-proxyV2
> >
> > Usage:
> >
> > primary:
> > -netdev tap,id=bn0 -device e1000,netdev=bn0
> > -object colo-proxy,id=f0,netdev=bn0,queue=all,mode=primary,addr=host:port
> >
> > secondary:
> > -netdev tap,id=bn0 -device e1000,netdev=bn0
> > -object colo-proxy,id=f0,netdev=bn0,queue=all,mode=secondary,addr=host:port
> >
> > NOTE:
> > queue must set "all". See enum NetFilterDirection for detail.
> > colo-proxy need queue all packets
> > colo-proxy V2 just can compare ip packet
> >
> >
> > ## Background
> >
> > COLO FT/HA (COarse-grain LOck-stepping Virtual Machines for Non-stop Service)
> > project is a high availability solution. Both Primary VM (PVM) and Secondary VM
> > (SVM) run in parallel. They receive the same request from client, and generate
> > responses in parallel too. If the response packets from PVM and SVM are
> > identical, they are released immediately. Otherwise, a VM checkpoint (on
> > demand)is conducted.
> >
> > Paper:
> > http://www.socc2013.org/home/program/a3-dong.pdf?attredirects=0
> >
> > COLO on Xen:
> > http://wiki.xen.org/wiki/COLO_-_Coarse_Grain_Lock_Stepping
> >
> > COLO on Qemu/KVM:
> > http://wiki.qemu.org/Features/COLO
> >
> > By the needs of capturing response packets from PVM and SVM and finding out
> > whether they are identical, we introduce a new module to qemu networking
> > called colo-proxy.
> >
> > V2:
> >    rebase colo-proxy with qemu-colo-v2.2-periodic-mode
> >    fix dave's comments
> >    fix wency's comments
> >    fix zhanghailiang's comments
> >
> > v1:
> >    initial patch.
> >
> >
> >
> > zhangchen (10):
> >    Init colo-proxy object based on netfilter
> >    Jhash: add linux kernel jhashtable in qemu
> >    Colo-proxy: add colo-proxy framework
> >    Colo-proxy: add data structure and jhash func
> >    net/colo-proxy: Add colo interface to use proxy
> >    net/colo-proxy: add socket used by forward func
> >    net/colo-proxy: Add packet enqueue & handle func
> >    net/colo-proxy: Handle packet and connection
> >    net/colo-proxy: Compare pri pkt to sec pkt
> >    net/colo-proxy: Colo-proxy do checkpoint and clear
> >
> >   include/qemu/jhash.h |  61 ++++
> >   net/Makefile.objs    |   1 +
> >   net/colo-proxy.c     | 939 +++++++++++++++++++++++++++++++++++++++++++++++++++
> >   net/colo-proxy.h     |  24 ++
> >   qemu-options.hx      |   6 +
> >   trace-events         |   8 +
> >   vl.c                 |   3 +-
> >   7 files changed, 1041 insertions(+), 1 deletion(-)
> >   create mode 100644 include/qemu/jhash.h
> >   create mode 100644 net/colo-proxy.c
> >   create mode 100644 net/colo-proxy.h
> >
> > --
> > 1.9.1
> --
> Dr. David Alan Gilbert / address@hidden / Manchester, UK
>
>
> .

--
Best regards.
Li Zhijian (8555)