How do I run the snf_bridge example program?

snf_bridge is a simple Sniffer10G example program in the /bin/tests/ directory that receives packets on an interface and injects them on an interface. Its main purpose is to demonstrate how to use the Sniffer10G API to receive and inject. The source code of this example program can be found in the /share/examples/ directory in the software distribution.

Invoke the test program snf_bridge with the option --help to obtain the usage summary of the command-line arguments.

Usage Summary:

$ ./snf_bridge [args] -b <...> [ -b <...> ... ]

Command-line [args]:

[ -b <board_source>:<board_dest>:<num_rings>[:] 
     where
     <board_source> is the location to capture packets, 
     <board_dest> is the location to forward packets, 
     <num_rings> is the number of rings/workers to dedicate to capture, and 
      is an optional binding cpumask in hexadecimal.

[ -n <num_packets> ] Number of packets to forward before exiting.
[ -N <tx_try_again> ] Number of times to try injecting before dropping
packet.
[ -W <tx_wait_msecs> ] Number of milliseconds to wait in
snf_inject_send.
[ -R ] Reflect non UDP and TCP packets to network device.

Here is a simple test you can conduct with two machines (machine1 and machine2) with dual port network adapters connected point to point (switchless).

On machine2, the briding machine, run the command:

$ ./snf_bridge -n 1000 -b0:1:1

This command-line says to bridge all traffic between board 0 and board 1 using one receive ring. Because -n was specified, it will stop bridging once 1000 packets have been received.

And then on machine1, open two windows. In the first window run:

$ ./snf_simple_recv -v -n 1000 -b 1

And in the second window run:

$ ./snf_pktgen -p 0 -n 1000

The result is that snf_pktgen will send 1000 packets out of interface 0 on machine1, it will be received by machine2 on interface 0, which will then reinject them on interface 1, and machine0 will then receive them with snf_simple_recv on interface 1. At this point, since we sent 1000 packets, and we told snf_bridge and snf_simple_receive to end after 1000 packets, everything should terminate and you should see from the snf_bridge counters printed that it did in fact receive and transmit 1000 packets. If you run into packet loss (which would be unexpected in a short point-to-point connection) you may want to increase the number of packets snf_pktgen sends.

You could also do the test using a one port network adapter. You would just be injecting back onto the same interface you received from (by passing -b0:0:1 to snf_bridge and -b0 to snf_simple_receive), making the bridging machine look like a loopback connector.