rxtxcpu captures packets in per-cpu streams, optionally writing to per-cpu pcap files. On exit, it reports per-cpu packet counts.
rxtxcpu can assist with behavior validation, configuration comparisons, and providing additional data points on packet steering. It also can be used simply for learning purposes across several topics, including the following.
- RSS (Receive-Side Scaling)
- RPS (Receive Packet Steering)
- RFS (Receive Flow Steering)
- RX Flow Hash Algorithm
- RX Flow Hash Indirection Table
rxtxcpu requires PACKET_FANOUT_CPU (added to the linux kernel in v3.1).
rxtxcpu has build time dependencies on gcc, libpcap-devel, and make. It also has a run time dependency on libpcap. libpcap installation is not explicitly included in the following steps since libpcap is a dependency of libpcap-devel. However, please take this into account when building and installing on separate hosts. These package names may vary slightly between distros.
Install build time dependencies on CentOS.
sudo yum install gcc libpcap-devel make
Install build time dependencies on Ubuntu.
sudo apt-get install gcc libpcap-dev make
sudo make install
The most basic invocation of rxtxcpu will capture packets until receiving a SIGINT signal (e.g. via Ctrl-C) or SIGTERM signal. Upon SIGINT initiated exit, it will display per-cpu packet counts.
rxtxcpu # packets from any interface rxtxcpu eth0
Capture rx only
rxtxcpu -d rx eth0
Capture tx only
rxtxcpu -d tx eth0
Capture N packets
Supply a count and rxtxcpu will display per-cpu packet counts and exit after receiving that number of packets.
rxtxcpu -c100 eth0
Write to per-cpu pcap files
The supplied pcap filename will be used as a template for per-cpu pcap filenames ("-<cpu>" is injected just before the .pcap extension when present, otherwise appended to the end).
rxtxcpu -w test.pcap eth0
Capture on a subset of cpus
Both of these will capture only on cpus 0, 2, 3, 4, and 6.
rxtxcpu -l 0,2-4,6 eth0
rxtxcpu -m 5d eth0
Pipe pcap data to tcpdump
When capturing on a single cpu the pcap data can be written to stdout and piped to other pcap capable utils. Using packet buffered output is recommended for this usage.
rxtxcpu -l2 -w - -U eth0 | tcpdump -c100 -Snnr -
Bug reports and pull requests are welcome. Please see our contributing guide.
Vagrant is used for consistent test environments.
To spin up the CentOS 7 enviroment, build, and run the tests use the following. This will clean up the vm.
If developing new tests, it can be convenient to keep the environment around for several runs. This will leave the vm in place.
Testing against alternate distros is also available. See the Vagrantfile for available machine names (distros).
This project adheres to Semantic Versioning.
rxtxcpu is available as open source under the terms of the MIT license.
rxtxcpu has been tested on the following distros.
- CentOS 7
- Ubuntu 14.04
- Ubuntu 16.04
- Ubuntu 18.04