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126 lines
3.1 KiB
Groff
126 lines
3.1 KiB
Groff
.TH "Packet sample action in tc" 8 "31 Jan 2017" "iproute2" "Linux"
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.SH NAME
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sample - packet sampling tc action
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.SH SYNOPSIS
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.in +8
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.ti -8
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.BR tc " ... " "action sample rate"
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.I RATE
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.BR "group"
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.I GROUP
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.RB "[ " trunc
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.IR SIZE " ] "
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.RB "[ " index
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.IR INDEX " ] "
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.ti -8
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.BR tc " ... " "action sample index "
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.I INDEX
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.ti -8
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.SH DESCRIPTION
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The
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.B sample
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action allows sampling packets matching classifier.
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The packets are chosen randomly according to the
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.B rate
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parameter, and are sampled using the
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.B psample
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generic netlink channel. The user can also specify packet truncation to save
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user-kernel traffic. Each sample includes some informative metadata about the
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original packet, which is sent using netlink attributes, alongside the original
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packet data.
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The user can either specify the sample action parameters as presented in the
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first form above, or use an existing sample action using its index, as presented
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in the second form.
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.SH SAMPLED PACKETS METADATA FIELDS
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The metadata are delivered to userspace applications using the
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.B psample
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generic netlink channel, where each sample includes the following netlink
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attributes:
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.TP
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.BI PSAMPLE_ATTR_IIFINDEX
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The input interface index of the packet, if there is one.
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.TP
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.BI PSAMPLE_ATTR_OIFINDEX
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The output interface index of the packet. This field is not relevant on ingress
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sampling
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.TP
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.BI PSAMPLE_ATTR_ORIGSIZE
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The size of the original packet (before truncation)
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.TP
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.BI PSAMPLE_ATTR_SAMPLE_GROUP
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The
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.B psample
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group the packet was sent to
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.TP
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.BI PSAMPLE_ATTR_GROUP_SEQ
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A sequence number of the sampled packet. This number is incremented with each
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sampled packet of the current
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.B psample
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group
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.TP
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.BI PSAMPLE_ATTR_SAMPLE_RATE
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The rate the packet was sampled with
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.RE
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.SH OPTIONS
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.TP
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.BI rate " RATE"
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The packet sample rate.
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.I "RATE"
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is the expected ratio between observed packets and sampled packets. For example,
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.I "RATE"
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of 100 will lead to an average of one sampled packet out of every 100 observed.
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.TP
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.BI trunc " SIZE"
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Upon set, defines the maximum size of the sampled packets, and causes truncation
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if needed
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.TP
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.BI group " GROUP"
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The
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.B psample
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group the packet will be sent to. The
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.B psample
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module defines the concept of groups, which allows the user to match specific
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sampled packets in the case of multiple sampling rules, thus identify only the
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packets that came from a specific rule.
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.TP
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.BI index " INDEX"
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Is a unique ID for an action. When creating new action instance, this parameter
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allows to set the new action index. When using existing action, this parameter
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allows to specify the existing action index. The index must 32bit unsigned
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integer greater than zero.
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.SH EXAMPLES
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Sample one of every 100 packets flowing into interface eth0 to psample group 12:
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.RS
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.EX
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tc qdisc add dev eth0 handle ffff: ingress
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tc filter add dev eth0 parent ffff: matchall \\
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action sample rate 100 group 12 index 19
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.EE
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.RE
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Use the same action instance to sample eth1 too:
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.RS
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.EX
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tc qdisc add dev eth1 handle ffff: ingress
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tc filter add dev eth1 parent ffff: matchall \\
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action sample index 19
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.EE
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.RE
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.EE
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.RE
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.SH SEE ALSO
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.BR tc (8),
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.BR tc-matchall (8)
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.BR psample (1)
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