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HOWTO 0.2.0

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Javier Cardona edited this page Mar 6, 2012 · 2 revisions

This page explains how to set up a mesh network using open80211s and a "Airlink 101 USB wireless adapter, Model:AWLL3026":http://www.airlink101.com/products/awll3026.html.

Getting all the pieces

Each mesh node needs to be configured as follows:

The kernel

Get a kernel including the open80211s stack:


$ git clone git://o11s.org/open80211s.git

Configure the kernel including the mac80211 stack and zd1211-rw driver (CONFIG_ZD1211RW, CONFIG_MAC80211). Compile and install on your target.

Make sure /lib/modules/${KERNEL_VERSION}/build/include points to your kernel headers. This is necessary for pynl80211 to work (see #18 if you want to help us with this tool).

pynl80211

Get pynl80211:


$ git-clone http://git.sipsolutions.net/pynl80211.git

It is not necessary to compile it, but make sure that wificonf.py is in your target's $PATH. Alternatively, you can "use iw":/cozybit/open80211s/wiki/wiki:Using_iw.

iproute2

Get " iproute2-2.6.23":http://devresources.linux-foundation.org/dev/iproute2/download/iproute2-2.6.23.tar.bz2 and apply "the mesh support patch":http://o11s.org/patches/iproute2/iproute2-2.6.24-mesh-support-0.2.0.patch. Configure, compile, install on your target.

Testing

  • Boot several nodes with the compiled kernel and with wificonf.py'' and ''ip userspace tools properly installed.
  • Add a new mesh interface for the zd1211-rw device to each node with wificonf.sh:

# MESH_IFACE_TYPE=7
# wificonf.py new_interface 0 mesh $MESH_IFACE_TYPE

A new interface will be created:


# ifconfig -a | grep mesh
mesh      Link encap:Ethernet  HWaddr 00:18:39:14:48:B5
  • All mesh interfaces start by default in channel 1. The channel can be changed with

# iwconfig  channel
  • You can assign a mesh id. This mesh id will be used in the mesh node beacons when the interface is brought up. To do this with wificonf.sh, execute:

# wificonf.py set_mesh_cfg

mesh_id is max 32 characters long. If no mesh id is set, the zero-length wildcard mesh id will be used.

  • Assign a same-subnet IP to the mesh interface in each node.

# ifconfig

For this tutorial, let's assume that our mesh nodes are assigned addresses in the 192.168.3.80/28 subnet.


# ifconfig mesh 192.168.3.80
  • In the default configuration, mesh points will automatically attempt to creat peer links will all other mesh nodes with the same mesh ID. You can examine which peer links have been established with the ip mshplink command:

192-168-3.80:~# ip mshplink
00:11:a3:04:b1:0c ESTAB 65492 56250 mesh
00:11:a3:04:b1:06 ESTAB 1341 14415 mesh
00:11:a3:04:b0:85 ESTAB 48743 6007 mesh
00:11:a3:04:b2:33 ESTAB 16421 28630 mesh
  • You should now be able to ping any node in the mesh. After doing that you can use ip again to inspect the path table and see which path was used to reach the ping destination.

192-168-1-80:~# ping -c 2 192.168.3.87
PING 192.168.3.87 (192.168.3.87) 56(84) bytes of data.
64 bytes from 192.168.3.87: icmp_seq=1 ttl=64 time=36.6 ms
64 bytes from 192.168.3.87: icmp_seq=2 ttl=64 time=11.0 ms

192-168-1-80:~# arp 192.168.3.87
Address                  HWtype  HWaddress           Flags Mask            Iface
192.168.3.87             ether   00:11:A3:04:B0:85   C                     mesh

192-168-1-80:~# ip mshpath show
00:11:a3:04:b0:85 00:11:a3:04:b0:85 mesh 7 1 0x4 17642779 0 25 0
00:11:a3:04:b2:17 00:11:a3:04:b2:33 mesh 7 2 0x4 17642780 0 25 0
00:11:a3:04:b1:0c 00:11:a3:04:b1:0c mesh 0 1 0x20 17642779 0 0 0
00:11:a3:04:b1:06 00:11:a3:04:b1:06 mesh 0 1 0x20 17642780 0 0 0
00:11:a3:04:b2:33 00:11:a3:04:b2:33 mesh 0 1 0x20 17642780 0 0 0

In this example we can see that the destination was a single hop from the origin because the destination address (first column) matches the next hop address (second column). On the example table we can see a multi-hop path to destination 00:11:a3:04:b2:17.

Et voilà! But keep reading for...

Advanced Tinkering

  • You can modify the mesh path table with these commands:

    • ip mshpath delete dev $MESH_DEV dst $DST_ADDR to delete a mesh path entry.
    • ip mshpath add dev $MESH_DEV dst $DST_ADDR next_hop $NEXTHOP_ADDR to force a specific network topology.

  • You can modify the mesh peer links table with these commands:

    • show: same as no subcommand, list all the plinks.
    • add dev $MESH_DEV addr $HW_ADDR: adds the peer to the table and tries to establish a link if the node is auto_open_plinks is set (see below).
    • del dev $MESH_DEV addr $HW_ADDR: deletes a peer link from the peer table.
    • block dev $MESH_DEV addr $HW_ADDR: prevents a peer link from being established with a given peer. As a result, no traffic will be sent to or received from that peer.
    • open dev $MESH_DEV addr $HW_ADDR: tries to establish a peer link with a peer already in the table and in LISTEN state.

  • Mount the debug filesystem, debugfs, and you'll be able to examine mesh statistics and modify configuration parameters:


192-168-1-80:~# mount -t debugfs null /mnt

192-168-1-80:~# # find /mnt/debugfs/ieee80211/phy0/netdev\:mesh/mesh_config
/mnt/debugfs/ieee80211/phy0/netdev:mesh/mesh_config
/mnt/debugfs/ieee80211/phy0/netdev:mesh/mesh_config/min_discovery_timeout
/mnt/debugfs/ieee80211/phy0/netdev:mesh/mesh_config/path_refresh_time
/mnt/debugfs/ieee80211/phy0/netdev:mesh/mesh_config/dot11MeshHWMPmaxPREQretries
/mnt/debugfs/ieee80211/phy0/netdev:mesh/mesh_config/dot11MeshHWM[[PnetDiameterTraversalTime]]
/mnt/debugfs/ieee80211/phy0/netdev:mesh/mesh_config/dot11MeshHWM[[PpreqMinInterval]]
/mnt/debugfs/ieee80211/phy0/netdev:mesh/mesh_config/dot11MeshHWM[[PactivePathTimeout]]
/mnt/debugfs/ieee80211/phy0/netdev:mesh/mesh_config/dot11[[MeshMaxPeerLinks]]
/mnt/debugfs/ieee80211/phy0/netdev:mesh/mesh_config/auto_open_plinks
/mnt/debugfs/ieee80211/phy0/netdev:mesh/mesh_config/dot11MeshTTL
/mnt/debugfs/ieee80211/phy0/netdev:mesh/mesh_config/dot11[[MeshHoldingTimeout]]
/mnt/debugfs/ieee80211/phy0/netdev:mesh/mesh_config/dot11[[MeshConfirmTimeout]]
/mnt/debugfs/ieee80211/phy0/netdev:mesh/mesh_config/dot11[[MeshRetryTimeout]]
/mnt/debugfs/ieee80211/phy0/netdev:mesh/mesh_config/dot11[[MeshMaxRetries]]

192-168-1-80:~# find /mnt/debugfs/ieee80211/phy0/netdev\:mesh/mesh_stats
/mnt/debugfs/ieee80211/phy0/netdev:mesh/mesh_stats
/mnt/debugfs/ieee80211/phy0/netdev:mesh/mesh_stats/estab_plinks
/mnt/debugfs/ieee80211/phy0/netdev:mesh/mesh_stats/dropped_frames_no_route
/mnt/debugfs/ieee80211/phy0/netdev:mesh/mesh_stats/dropped_frames_ttl
/mnt/debugfs/ieee80211/phy0/netdev:mesh/mesh_stats/fwded_frames

For instance, to change the mesh TTL value for the interface (which currently defaults to 5) one would:


192-168-1-80:~# cat /mnt/debugfs/ieee80211/phy0/netdev:mesh/mesh_config/dot11MeshTTL
5
192-168-1-80:~# echo 3 > /mnt/debugfs/ieee80211/phy0/netdev:mesh/mesh_config/dot11MeshTTL
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