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一种用于AD HOC 无线自组网络上的动态路由的源代码

Introduction
============

This is an AODV implementation developed at Uppsala University,
Sweden, with some funding from Ericsson AB. It has been developed
mainly for use in the APE testbed, http://apetestbed.sourceforge.net.
The code is released under the GNU General Public License (GPL). See
the GPL document for more information.

This release is based on AODV draft version 13. There are no
guarantees that it implements all features correctly, although this is
the goal. The code is provided as is. See the CHANGELOG for updates
and changes between releases.

This AODV implementation runs as a user-space daemon, maintaining the
kernel routing table. Netfilter is used to capture data
packets. Filtering is done in user-space, so there may be some
performance penalties, although coding is much simplified. Stable
operation has higher priority than performance.

The code has been successfully tested in a real ad-hoc environment
using up to 5 nodes (4 hops) without problems. It has been debugged in
ns-2 by running extensive simulations. The performance is usually on
par or better than the AODV version in ns-2. It has also been interop
tested with great results. If you happen to experience less successful
operation of this implementation, please contact the author(s) and
describe your problems.

Requirements
============

Real world:
* Linux OS (2.4.x, 2.6.x).
* Kernel with Netfilter support.
  Most Red Hat/Fedora kernels have this support.
* Wireless LAN cards in ad-hoc mode (alternatively a wired setup can
  be used).

ns-2:
* See README.ns

Installation
============

If you are running AODV-UU in NS-2, then you should read README.ns for
install instructions.

Make sure you have the kernel source (or at least headers) of the
kernel you are compiling against installed. Otherwise the kernel
modules might not compile. See the troubleshooting section if there
are problems.

Compile with "make":

> make

Install (as "root"):

> make install

Run (as "root" with recommended options for debugging):

> aodvd -l -r 3

For command line options, run:

> aodvd --help

The following module must be loaded when running (or compiled into
the kernel):
* kaodv.{o,ko}

Module loading should happen automatically if AODV is installed and
the module loading system (modprobe) is properly configured.

Compiling for ARM (iPAQ, Zaurus)
================================

AODV-UU now easily compiles for the ARM platform, which makes it
suitable for use on many PDAs, including the Compaq/HP iPAQ and the
Sharp Zaurus. However, since cross-platform compiling is necessary,
this process requires some extra steps. This is what I did to get it
working with the Familiar distribution on a H3800 iPAQ:

1. First download the cross-compiler, for example:

> wget ftp://ftp.handhelds.org/pub/linux/arm/toolchain/arm-linux-toolchain-current.tar.gz

2. Unpack the cross-compiler according to instructions in
ftp://ftp.handhelds.org/pub/linux/arm/toolchain/README, usually:

> cd /; tar zxvf /path/to/arm-linux-toolchain-current.tar.gz

3. Retrieve the kernel source code matching the kernel used on the ARM
device.You may check the URL below for binary pre-compiled kernel
packages, installable via ipkg. There are no guarantees that these are
always available or up to date...

http://www.docs.uu.se/docs/research/projects/ape/familiar/

Otherwise, for the Familiar distribution, the kernel source code can
be retrieved via anonymous cvs:

> export CVSROOT=:pserver:[e-mail]:/cvs

> cvs login
Password=anoncvs

Get the matching version with "-r":

> cvs export -r K2-4-18-rmk3-hh6 linux/kernel

4. Re-link the "asm" and "linux" include directories in arm
cross-compiler tree to point to those in the ARM kernel source tree:

> ln -s /path/to/arm-kernel-source/include/linux /skiff/local/arm-linux/include/linux
> ln -s /path/to/arm-kernel-source/include/asm /skiff/local/arm-linux/include/asm

5. Make sure the arm compiler is in the PATH and that /usr/src/linux
points to the ARM kernel source.

> export PATH=$PATH:/skiff/local/arm-linux/bin
> ln -s /path/to/arm-kernel-source /usr/src/linux

6. Since the default Familiar kernel do not have the proper netfilter
support for AODV-UU (CONFIG_IP_NF_QUEUE) it is necessary to compile a
new kernel. Follow the instructions at
http://www.handhelds.org/handhelds-faq/development.html. Build
ipkg-packages for easy installation. Then install kernel using ipkg. It
may be possible to transfer only the ip_queue.o module so that
installing a new kernel can be avoided.

6. Compile AODV-UU for ARM:

> make arm

To install, copy kaodv.o and aodvd to the ARM device.


Debug output
============

To get debug output, make sure the daemon is compiled with the -DDEBUG
option set (check Makefile). Debug information is written to
/var/log/aodvd.log if the AODV is run with the "-l" flag:

> aodvd -l

This is the same output as written to STDOUT if running the daemon in
the foreground. To get printouts of the AODV internal routing table,
run AODV with:

> aodvd -r 2.5

where the number is the interval between routing table printing, in seconds.
The routing table is written to /var/log/aodvd.rtlog.

Note about Local Repair
=======================

As of version 0.6 of AODV-UU, local repair is fully implemented.
However, please be aware of the fact that local repair does not always
help performance, it may in fact hurt it. Consider turning local
repair off if this is not a feature you are interested in.

Note about HELLO messages
=========================

This implementation rely on HELLO messages. However, it has been
found, through real world testing, that HELLO messages are not a good
way to do neighbor sensing in a wireless environment (at least not
over 802.11). Therefore, you may experience bad performance when
running over wireless. There are several reasons for this:

* HELLO messages are broadcasted. In 802.11, broadcasting is done at a
lower bit rate than unicasting, thus HELLO messages travel further
than data.

* HELLO messages are small, thus less prone to bit errors than data
transmissions.

* Broadcast transmissions are not guaranteed to be bidirectional,
unlike unicast transmissions.

Running a test
==============

To test the basic functionality of AODV you need at least three
computers configured to run AODV. The nodes IP-address configuration
should be in the same subnet. Then try to place the computers so that
two of them are out of each others transmission range with the third
computer in the middle, as in the illustration below. It may also be
convenient to use a MAC-filter, like that part of the APE testbed,
http://apetestbed.sourceforge.net.

A <-> B <-> C

Run on either A or C:

> ping -R <IP A or C>

to ping the remote computer. The "-R" option will record the route
taken by ping packets, so that the actual route taken can be seen.

Unidirectional links
=====================

This AODV implementation can detect the presence of unidirectional
links, and avoid them if necessary. It is done by sending a RREP
extension along with the hello messages containing the neighbor set of
a node. This functionality is not part of the AODV draft as of version
10, but similar functionality may be in future
versions. Unidirectional link detection can be enabled with the "-u"
option. This feature is experimental and may be BROKEN in any release.

Internet gateway support
========================

As of v0.8, AODV-UU implements gateway support by tunneling packets to
gateway configured nodes. This is much more robust than a default
route solution or similar. 

AODV-UU must be compiled with "CONFIG_GATEWAY" defined (see
Makefile). Nodes that run "aodvd" with the -w flag will automatically
act as gateways - thus answering to RREQs according to an "address
locality" decision, i.e., RREQs for addresses that a gateway thinks
lie outside the ad hoc network will generate a (proxy) RREP. This RREP
contains a special extension that automatically sets up a tunnel
between the source node and the gateway. Gateways currently implement
"address locality" through a prefix check, thus the ad hoc network
must share a prefix (e.g., 192.168.0.0/16). Other "locality checks"
can easily be implemented in locality.c. Tunnels (i.e., routes to
gateways) are marked with a "G" flag in the routing table, while
tunnel entries (i.e., Internet destinations) are marked with and "I"
flag.

In case the ad hoc network does not use a globally valid prefix (or
runs Mobile IP or similar), gateways should also have NAT enabled:

> /sbin/iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

Change eth0 to the name of the interface connected to the Internet if
necessary.

On the ad hoc nodes it is also necessary to add a default route in the
kernel routing table, pointing to the ad hoc interface. For example, if
the wireless ad hoc interface is eth1:

> route add default dev eth1

Otherwise, it will not be possible to communicate with destinations
outside the ad hoc prefix.

Issues & Troubleshooting
========================

* If you run Fedora Core 1 and the kernel module "kaodv.o" fails to
compile, install the compatibility gcc compiler (gcc32 rpm). Then try
compiling with "make KCC=gcc32".

* If the kernel module compilation fails or the module does not load,
make sure that the kernel source code is installed and properly
configured. If you have a kernel config file (.config) matching your
running kernel, do a "make mrproper" (WARNING: this cleans up the tree
and removes the .config file. You might want to make a .config backup
first). Create a .config file (or use an existing one). Make sure that
the kernel version numbering in the kernel's top-level Makefile
matches your running kernel (Red Hat/Fedora sometimes add a
"custom"-string). Do "make oldconfig".  Dependending on whether you
have a 2.4 kernel or a 2.6 kernel, do "make dep" or "make prepare-all"
respectively. Your tree should now be configured.

* If a crash occurs, the kernel module "kaodv.o" may remain loaded and
can stop traffic from going through on the interface. Unload with
"/sbin/rmmod kaodv" (root permissions required).

* If the daemon refuse to start and complains about ipchains, make
sure that the "ipchains" compatibility kernel module is not loaded.
It will conflict with iptables. Do "ipchains -F" followed by "modprobe
-r ipchains" to unload it.

* For routing between nodes with arbitrary subnet addresses the
default gateway in the kernel routing table must point to the node
itself. Otherwise communication with addresses on a foreign subnet
will not be possible, since the kernel will complain that there is no
route available. Setting this gateway is typically done with the
command:

> route add default dev <wireless iface e.g., "eth1">

Notes about the source code
===========================

libipq.c and libipq.h are unmodified files from the netfilter
package which are included here for convenience.

Contact:
========

Source code and implementation questions:
Erik Nordstr鰉 <[e-mail]>

NS port questions:
Bj鰎n Wiberg <[e-mail]>

Misc. questions:
Henrik Lundgren <[e-mail]>