[Ns-developers] gsoc summary reports[quagga-porting]
liujatp at gmail.com
Mon Aug 18 07:02:54 PDT 2008
my Gsoc project is porting quagga routes to ns-3 and summarize some
experience about how to integrate real world application with ns-3.
During this three months of period, i learnd a lot, increase my code read
/write experience. (more details about my project process at:
1, netlink sockets implementation
Before step into porting, netlink socket was needed, since quagga rely
on it. my repo at http://code.nsnam.org/lj/ns-3-netlink.
netlink files at src/node/netlink-xxx.h/cc.
NetlinkSocket is subclass of Socket, and has the similar strcture and implementation.
The 2 main points of the NetlinkSocket implementation were
a)netlink message serilize and desirilize
b)netlink message handling.
For a): NetlinkMessage body has different payload due to different message type,
when do this, learn some experience from Header class, adopt simliar interface
functions to implement.
For b): To simulate how the linux kernel handle the netlink messages, I learn
from linux kernel code and just simply implement the part of the netlink
mechanism. how the linux do is: user socket send an request to kernel,
the kernel netlink socket recv it and handle it, then send ack back to
user-space socket. where in my NetlinkSocket, there was no kernel socket
exist, when user NetlinkSocket call send() to transfer an message, NetlinkSocket
::HandleMessage do it directly as kernel, then send the ack/response message
back to its own recv-queue, and it can be got when recv() called.
Netlink was big and complicated, here i just implemented what the quagga used.
Focusing on netlink route protocol: interface address dump/add/del, route entry
dump/add/del/get, link dump. To show how the netlink message be built in ns-3,
and to test the socket running, testing codes is at netlink-socket-test.cc.
2,porting(repo at http://code.nsnam.org/lj/quagga-porting.)
the porting is based on ns-3-simu, using the process model. There are two way which
i do the porting. Before the elfloader, the simu_xxx funtion mapping method is what
i use to port libnl/quagga. at that time, libnl run successfully on ns-3-simu.
when i was focusing porting zebra, mathieu implement the elfloader, which is genius.
it make porting much easier, just compile real-world program with -fpie, -pie option
and fill the actually function simu_xxx. now i have run libnl successfully on ns-test/
quagga-porting. In the next few days,i will try to run quagga.
>From the porting process, i tested the netlink socket with the realworld application,
and studied some skills from the great code. For code wrriting. i just wrote a few
code:some simu_xx function and definition for porting.
my test at ns-test:/lj/quagga-porting, it run as:
./build/debug/example/process-libnl nl-addr-dump xml
Before merge the NetlinkSocket, code review/clean is needed, which will also be done
next days. i wish my code will be some useful to ns-3.
>From this gsoc exprience, i rally learned a lot about code writing and technique, which
will be my great fortune in the future. At the end of the Gsoc project, i want to thank
ns-3 community give me the chance to do the project, and i would appreciate mathieu for
helping me a lot and fixing me many problem and explaining me many boring questions.
Also i will thanks tomh,gjc,joe,fw,etc. they all gave me many good suggestions when
i met difficulty.
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