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+COLO-proxy
+----------
+Copyright (c) 2016 Intel Corporation
+Copyright (c) 2016 HUAWEI TECHNOLOGIES CO., LTD.
+Copyright (c) 2016 Fujitsu, Corp.
+
+This work is licensed under the terms of the GNU GPL, version 2 or later.
+See the COPYING file in the top-level directory.
+
+This document gives an overview of COLO proxy's design.
+
+== Background ==
+COLO-proxy is a part of COLO project. It is used
+to compare the network package to help COLO decide
+whether to do checkpoint. With COLO-proxy's help,
+COLO greatly improves the performance.
+
+The filter-redirector, filter-mirror, colo-compare
+and filter-rewriter compose the COLO-proxy.
+
+== Architecture ==
+
+COLO-Proxy is based on qemu netfilter and it's a plugin for qemu netfilter
+(except colo-compare). It keep Secondary VM connect normally to
+client and compare packets sent by PVM with sent by SVM.
+If the packet difference, notify COLO-frame to do checkpoint and send
+all primary packet has queued. Otherwise just send the queued primary
+packet and drop the queued secondary packet.
+
+Below is a COLO proxy ascii figure:
+
+ Primary qemu Secondary qemu
++--------------------------------------------------------------+ +----------------------------------------------------------------+
+| +----------------------------------------------------------+ | | +-----------------------------------------------------------+ |
+| | | | | | | |
+| | guest | | | | guest | |
+| | | | | | | |
+| +-------^--------------------------+-----------------------+ | | +---------------------+--------+----------------------------+ |
+| | | | | ^ | |
+| | | | | | | |
+| | +------------------------------------------------------+ | | | |
+|netfilter| | | | | | netfilter | | |
+| +----------+ +----------------------------+ | | | +-----------------------------------------------------------+ |
+| | | | | | out | | | | | | filter excute order | |
+| | | | +-----------------------------+ | | | | | | +-------------------> | |
+| | | | | | | | | | | | | | TCP | |
+| | +-----+--+-+ +-----v----+ +-----v----+ |pri +----+----+sec| | | | +------------+ +---+----+---v+rewriter++ +------------+ | |
+| | | | | | | | |in | |in | | | | | | | | | | | | |
+| | | filter | | filter | | filter +------> colo <------+ +--------> filter +--> adjust | adjust +--> filter | | |
+| | | mirror | |redirector| |redirector| | | compare | | | | | | redirector | | ack | seq | | redirector | | |
+| | | | | | | | | | | | | | | | | | | | | | | |
+| | +----^-----+ +----+-----+ +----------+ | +---------+ | | | | +------------+ +--------+--------------+ +---+--------+ | |
+| | | tx | rx rx | | | | | tx all | rx | |
+| | | | | | | | +-----------------------------------------------------------+ |
+| | | +--------------+ | | | | | |
+| | | filter excute order | | | | | | |
+| | | +----------------> | | | +--------------------------------------------------------+ |
+| +-----------------------------------------+ | | |
+| | | | | |
++--------------------------------------------------------------+ +----------------------------------------------------------------+
+ |guest receive | guest send
+ | |
++--------+----------------------------v------------------------+
+| | NOTE: filter direction is rx/tx/all
+| tap | rx:receive packets sent to the netdev
+| | tx:receive packets sent by the netdev
++--------------------------------------------------------------+
+
+1.Guest receive packet route:
+
+Primary:
+
+Tap --> Mirror Client Filter
+Mirror client will send packet to guest,at the
+same time, copy and forward packet to secondary
+mirror server.
+
+Secondary:
+
+Mirror Server Filter --> TCP Rewriter
+If receive packet is TCP packet,we will adjust ack
+and update TCP checksum, then send to secondary
+guest. Otherwise directly send to guest.
+
+2.Guest send packet route:
+
+Primary:
+
+Guest --> Redirect Server Filter
+Redirect server filter receive primary guest packet
+but do nothing, just pass to next filter.
+
+Redirect Server Filter --> COLO-Compare
+COLO-compare receive primary guest packet then
+waiting scondary redirect packet to compare it.
+If packet same,send queued primary packet and clear
+queued secondary packet, Otherwise send primary packet
+and do checkpoint.
+
+COLO-Compare --> Another Redirector Filter
+The redirector get packet from colo-compare by use
+chardev socket.
+
+Redirector Filter --> Tap
+Send the packet.
+
+Secondary:
+
+Guest --> TCP Rewriter Filter
+If the packet is TCP packet,we will adjust seq
+and update TCP checksum. Then send it to
+redirect client filter. Otherwise directly send to
+redirect client filter.
+
+Redirect Client Filter --> Redirect Server Filter
+Forward packet to primary.
+
+== Components introduction ==
+
+Filter-mirror is a netfilter plugin.
+It gives qemu the ability to mirror
+packets to a chardev.
+
+Filter-redirector is a netfilter plugin.
+It gives qemu the ability to redirect net packet.
+Redirector can redirect filter's net packet to outdev,
+and redirect indev's packet to filter.
+
+ filter
+ +
+ redirector |
+ +--------------+
+ | | |
+ | | |
+ | | |
+ indev +---------+ +----------> outdev
+ | | |
+ | | |
+ | | |
+ +--------------+
+ |
+ v
+ filter
+
+COLO-compare, we do packet comparing job.
+Packets coming from the primary char indev will be sent to outdev.
+Packets coming from the secondary char dev will be dropped after comparing.
+COLO-comapre need two input chardev and one output chardev:
+primary_in=chardev1-id (source: primary send packet)
+secondary_in=chardev2-id (source: secondary send packet)
+outdev=chardev3-id
+
+Filter-rewriter will rewrite some of secondary packet to make
+secondary guest's tcp connection established successfully.
+In this module we will rewrite tcp packet's ack to the secondary
+from primary,and rewrite tcp packet's seq to the primary from
+secondary.
+
+== Usage ==
+
+Here, we use demo ip and port discribe more clearly.
+Primary(ip:3.3.3.3):
+-netdev tap,id=hn0,vhost=off,script=/etc/qemu-ifup,downscript=/etc/qemu-ifdown
+-device e1000,id=e0,netdev=hn0,mac=52:a4:00:12:78:66
+-chardev socket,id=mirror0,host=3.3.3.3,port=9003,server,nowait
+-chardev socket,id=compare1,host=3.3.3.3,port=9004,server,nowait
+-chardev socket,id=compare0,host=3.3.3.3,port=9001,server,nowait
+-chardev socket,id=compare0-0,host=3.3.3.3,port=9001
+-chardev socket,id=compare_out,host=3.3.3.3,port=9005,server,nowait
+-chardev socket,id=compare_out0,host=3.3.3.3,port=9005
+-object filter-mirror,id=m0,netdev=hn0,queue=tx,outdev=mirror0
+-object filter-redirector,netdev=hn0,id=redire0,queue=rx,indev=compare_out
+-object filter-redirector,netdev=hn0,id=redire1,queue=rx,outdev=compare0
+-object colo-compare,id=comp0,primary_in=compare0-0,secondary_in=compare1,outdev=compare_out0
+
+Secondary(ip:3.3.3.8):
+-netdev tap,id=hn0,vhost=off,script=/etc/qemu-ifup,down script=/etc/qemu-ifdown
+-device e1000,netdev=hn0,mac=52:a4:00:12:78:66
+-chardev socket,id=red0,host=3.3.3.3,port=9003
+-chardev socket,id=red1,host=3.3.3.3,port=9004
+-object filter-redirector,id=f1,netdev=hn0,queue=tx,indev=red0
+-object filter-redirector,id=f2,netdev=hn0,queue=rx,outdev=red1
+
+Note:
+ a.COLO-proxy must work with COLO-frame and Block-replication.
+ b.Primary COLO must be started firstly, because COLO-proxy needs
+ chardev socket server running before secondary started.
+ c.Filter-rewriter only rewrite tcp packet.
Introduce the design of COLO-proxy, and how to use it. Signed-off-by: Zhang Chen <zhangchen.fnst@cn.fujitsu.com> --- docs/colo-proxy.txt | 188 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 188 insertions(+) create mode 100644 docs/colo-proxy.txt