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This page describes software that has been developed for L4Env and is no longer supported with L4Re.


In L4-based systems it is quite common to have multiple applications trying to use the same resource in parallel. One might for instance imagine a setup where multiple L4Linux servers run and try to use the computer's physical network interface. In such cases, the physical resource needs to be multiplexed (or virtualized in new-age termini).

ORe (short for Oshkosh Resurrection) is a best-effort ethernet multiplexer for L4. It provides an abstract send/receive interface for network packets and makes sure that every client gets only those packets it wants to receive. This is achieved by assigning each client a virtual MAC address and filtering packets accordingly.

Running ORe

Arping client

The most fundamental ORe example is a client listening for and replying to ARP-based ping packets (such as those sent by the arping tool). To do so in Qemu, you need a menu.lst such as this:

title ORe
kernel /bootstrap -serial -modaddr 0x2000000
module /fiasco -serial_esc -comspeed 115200 -comport 1 -nokdb -jdb_cmd=JH
module /sigma0
module /roottask
module /names
module /dm_phys
module /log
module /l4io
module /ore
module /ore_test_arping

Then we run Qemu with a tun/tap network setup:

$> qemu -cdrom image.iso -serial stdio -net nic,model=rtl8139,vlan=0 -net tap,vlan=0 -m 200

image.iso is the image containing your L4 binaries, the net options say that we want to emulate a RealTek RTL8139 network card and connect it to VLAN0, which is also connected to the TAP device. Qemu starts running and we get some output, in the end the arping client comes up:

ore     | main(): initialized DDELinux2.6
ore     | main(): loopback: 0
ore     | <6>device lo entered promiscuous mode
ore     | <6>device eth0 entered promiscuous mode
ore     | <6>eth0: link up, 100Mbps, full-duplex, lpa 0x05E1
ore     | main(): Initialized 2 network devices.
ore     | Device =   lo, IRQ =  0, MAC = 00:00:00:00:00:00
ore     | Device = eth0, IRQ = 11, MAC = 52:54:00:12:34:56
ore     | main(): Registering 'ORe' at names...
ore     | main(): Ready for service.
arping  | ore_lookup_server(): ORe server ORe = 9.02
arping  | ore_do_open(): called
ore     | __init_mac(): MAC =  04:EA:43:01:96:09
arping  | ore_do_open(): opened. worker = 9.08
arping  | main(): opened eth0: 0 for 04:EA:43:01:96:09
arping  | main(): ORe handle = 0
arping  | main(): got send area: 0x00600008

The initial messages from ORe show devices being initialized (loopback lo and the NIC eth0). Arping then finds the ORe server and establishes a connection. The interesting part is the bold one - ORe assigns arping a pseudo-MAC-address 04:EA:43:01:96:09 - this is the one we are going to use now. In another shell, we start arping and tell it to use the tap interface tap0 to ping above MAC:

./arping -i tap0 04:EA:43:01:96:09 -w 100 -c 10000
60 bytes from (04:ea:43:01:96:09): icmp_seq=9914 time=823.021 usec
60 bytes from (04:ea:43:01:96:09): icmp_seq=9915 time=851.154 usec
60 bytes from (04:ea:43:01:96:09): icmp_seq=9916 time=771.046 usec

Using ORe from your application


To successfully establish a network connection with ORe, you need the following applications running in addition to the basic L4 stuff you'll be running anyway:

  • the ORe server
  • L4IO

Optionally you might want to run the Events server so that ORe can obtain termination messages from its clients and can cleanly close connections in that case.

Connecting to the server

Connection configuration

Sending and receiving packets

ORe and L4Linux

There is an ORe stub driver for L4Linux.