tc-sample(8) — Linux manual page


Packet sample action in tc(8)       Linux      Packet sample action in tc(8)

NAME         top

       sample - packet sampling tc action

SYNOPSIS         top

       tc ... action sample rate RATE group GROUP [ trunc SIZE ] [ index
               INDEX ]

       tc ... action sample index INDEX

DESCRIPTION         top

       The sample action allows sampling packets matching classifier.

       The packets are chosen randomly according to the rate parameter, and
       are sampled using the psample generic netlink channel. The user can
       also specify packet truncation to save user-kernel traffic. Each
       sample includes some informative metadata about the original packet,
       which is sent using netlink attributes, alongside the original packet

       The user can either specify the sample action parameters as presented
       in the first form above, or use an existing sample action using its
       index, as presented in the second form.


       The metadata are delivered to userspace applications using the
       psample generic netlink channel, where each sample includes the
       following netlink attributes:

              The input interface index of the packet, if there is one.

              The output interface index of the packet. This field is not
              relevant on ingress sampling

              The size of the original packet (before truncation)

              The psample group the packet was sent to

              A sequence number of the sampled packet. This number is
              incremented with each sampled packet of the current psample

              The rate the packet was sampled with

OPTIONS         top

       rate RATE
              The packet sample rate.  RATE is the expected ratio between
              observed packets and sampled packets. For example, RATE of 100
              will lead to an average of one sampled packet out of every 100

       trunc SIZE
              Upon set, defines the maximum size of the sampled packets, and
              causes truncation if needed

       group GROUP
              The psample group the packet will be sent to. The psample
              module defines the concept of groups, which allows the user to
              match specific sampled packets in the case of multiple
              sampling rules, thus identify only the packets that came from
              a specific rule.

       index INDEX
              Is a unique ID for an action. When creating new action
              instance, this parameter allows to set the new action index.
              When using existing action, this parameter allows to specify
              the existing action index.  The index must 32bit unsigned
              integer greater than zero.

EXAMPLES         top

       Sample one of every 100 packets flowing into interface eth0 to
       psample group 12:

              tc qdisc add dev eth0 handle ffff: ingress
              tc filter add dev eth0 parent ffff: matchall \
                   action sample rate 100 group 12 index 19

       Use the same action instance to sample eth1 too:

              tc qdisc add dev eth1 handle ffff: ingress
              tc filter add dev eth1 parent ffff: matchall \
                   action sample index 19

SEE ALSO         top

       tc(8), tc-matchall(8) psample(1)

COLOPHON         top

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iproute2                         31 Jan 2017   Packet sample action in tc(8)