This library enables userspace programs to interact with the kernel psample module.
The library allows to:
- Get sampled packets.
- Parse sampled packets
- List current sample groups
In addition, the library contains an executable named 'psample' that provide those features in a command line executable.
psample is kernel module that allows sampling packets and transferring them to userspace programs. The psample module is not bound to any specific kernel subsystem and allows every driver to sample packets. Currently, the tc action 'sample' uses psample for its sampled packets.
The psample module defines sampling 'group', thus allowing several kernel modules to sample packets in their own channel. In addition, the sampled packets are sent as a netlink multicast packets, thus allowing several user programs to get the sampled packets of a certain group.
To configure sampling using tc, one may use the commands:
tc qdisc add dev $DEV handle ffff: ingress
tc filter add dev $DEV parent ffff: matchall skip_hw \
action sample rate 12 group 7
In addition to the library, the git contains the psample executable, which allows a command-line user to get information about the current sample groups and the sampled packets in those groups.
Basic usage:
# to monitor all sampled packets and config events
psample [-v]
# to filter sampled packets/config events by group
psample [-v] --group 6
# to monitor all sampled packets only
psample [-v] --no-config
# to monitor all config events only
psample [-v] --no-sample
# to show all current groups
psample --list-groups
An example for the library usage can be seen in the psample executable code,
under psample_tool/psample.c
- man tc-sample