Profiling of Socket, PCAP and Fastnet to receive RAW packets in userspace

The code source I presented is available at :

http://gitlab.montefiore.ulg.ac.be/INFO0940/rcvtest

I’m willing to merge any pull request (called merge request on gitlab, so that they don’t copy github too much^^). Especially for parsing arguments, having options like “-b” to set the buffer size instead of recompiling, …

Since the presentation I added a “do_something” function called for each received packets of each methods, it will simply read bytes 12 and 13 of the ethernet header and check if it’s an IP packet, and sum up the amount of IP packets. As I said in class, this allows to effectively read the content of the packet and is a much better benchmarking, as nobody receive raw packets in userspace to do nothing with them… So you will hit memory for each packets. For nearly all method you just memcopied the content to userspace, but in mode 3 the NIC writes directly the packet to the buffer so when you’ll access the content you’ll loose ~300cpu cycles just to wait for the packet content to be bringed to cache, so it would be unfair to just get the packet length and not the data.

I also added a “socket” method, using the standard Linux socket which works like the fastnet read function. As you’ll probably find out, PCAP has already a big advantage using a special feature of the Kernel to receive much like what we do in Fastnet Step 7 : packet_mmap. I imagine you’ll be happy to see that you, humble student, can already do better than packet_mmap which is the best that Linux can offer to receive raw packets. Those doing the implementation for mode 3 will be able to see how much faster we can go.

If people are interested to change the mode 3 to make it work with packet_mmap and try to submit a patch to the linux networking team, they can contact me and we’ll do it together. It’s time to make Linux move regarding fast packet capture and if our patch is not accepted, it will at least piss of some people and make linux move in the right direction… I know you have a “personal project” course in master 1 that can surely credit this task.

Some of the commands I use in class :

sudo ip link add veth0 type veth peer name veth1

sudo ifconfig eth2 up

sudo tcpreplay -l 0 -q -i vboxnet0 –preload packet

sudo tcpreplay -l 0 –mbps=100.0 -q -i vboxnet0 –preload packet

The 64byte UDP packet I made is available at https://www.tombarbette.be/packet

If you use a bridge, update the packet to set its source and destination mac address to the mac address of the bridge on your host and the mac address of the ethernet port on your virtual machine.

Leave a Reply

Your email address will not be published. Required fields are marked *

Time limit is exhausted. Please reload the CAPTCHA.