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138 lines
3.0 KiB
138 lines
3.0 KiB
4 months ago
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.TH "skbmod action in tc" 8 "21 Sep 2016" "iproute2" "Linux"
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.SH NAME
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skbmod - user-friendly packet editor 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 skbmod " "{ [ " "set "
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.IR SETTABLE " ] [ "
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.BI swap " SWAPPABLE"
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.RI " ] [ " CONTROL " ] [ "
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.BI index " INDEX "
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] }
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.ti -8
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.IR SETTABLE " := "
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.RB " [ " dmac
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.IR DMAC " ] "
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.RB " [ " smac
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.IR SMAC " ] "
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.RB " [ " etype
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.IR ETYPE " ] "
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.ti -8
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.IR SWAPPABLE " := "
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.B mac
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.ti -8
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.IR CONTROL " := {"
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.BR reclassify " | " pipe " | " drop " | " shot " | " continue " | " pass " }"
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.SH DESCRIPTION
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The
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.B skbmod
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action is intended as a usability upgrade to the existing
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.B pedit
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action. Instead of having to manually edit 8-, 16-, or 32-bit chunks of an
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ethernet header,
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.B skbmod
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allows complete substitution of supported elements.
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.SH OPTIONS
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.TP
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.BI dmac " DMAC"
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Change the destination mac to the specified address.
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.TP
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.BI smac " SMAC"
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Change the source mac to the specified address.
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.TP
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.BI etype " ETYPE"
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Change the ethertype to the specified value.
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.TP
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.BI mac
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Used to swap mac addresses. The
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.B swap mac
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directive is performed
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after any outstanding D/SMAC changes.
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.TP
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.I CONTROL
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The following keywords allow to control how the tree of qdisc, classes,
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filters and actions is further traversed after this action.
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.RS
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.TP
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.B reclassify
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Restart with the first filter in the current list.
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.TP
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.B pipe
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Continue with the next action attached to the same filter.
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.TP
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.B drop
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.TQ
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.B shot
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Drop the packet.
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.TP
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.B continue
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Continue classification with the next filter in line.
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.TP
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.B pass
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Finish classification process and return to calling qdisc for further packet
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processing. This is the default.
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.SH EXAMPLES
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To start, observe the following filter with a pedit action:
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.RS
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.EX
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tc filter add dev eth1 parent 1: protocol ip prio 10 \\
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u32 match ip protocol 1 0xff flowid 1:2 \\
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action pedit munge offset -14 u8 set 0x02 \\
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munge offset -13 u8 set 0x15 \\
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munge offset -12 u8 set 0x15 \\
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munge offset -11 u8 set 0x15 \\
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munge offset -10 u16 set 0x1515 \\
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pipe
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.EE
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.RE
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Using the skbmod action, this command can be simplified to:
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.RS
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.EX
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tc filter add dev eth1 parent 1: protocol ip prio 10 \\
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u32 match ip protocol 1 0xff flowid 1:2 \\
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action skbmod set dmac 02:15:15:15:15:15 \\
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pipe
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.EE
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.RE
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Complexity will increase if source mac and ethertype are also being edited
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as part of the action. If all three fields are to be changed with skbmod:
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.RS
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.EX
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tc filter add dev eth5 parent 1: protocol ip prio 10 \\
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u32 match ip protocol 1 0xff flowid 1:2 \\
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action skbmod \\
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set etype 0xBEEF \\
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set dmac 02:12:13:14:15:16 \\
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set smac 02:22:23:24:25:26
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.EE
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.RE
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Finally, swap the destination and source mac addresses in the header:
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.RS
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.EX
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tc filter add dev eth3 parent 1: protocol ip prio 10 \\
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u32 match ip protocol 1 0xff flowid 1:2 \\
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action skbmod \\
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swap mac
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.EE
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.RE
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As mentioned above, the swap action will occur after any
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.B " smac/dmac "
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substitutions are executed, if they are present.
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.SH SEE ALSO
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.BR tc (8),
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.BR tc-u32 (8),
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.BR tc-pedit (8)
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