1skbmod action in tc(8)               Linux              skbmod action in tc(8)
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NAME

6       skbmod - user-friendly packet editor action
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SYNOPSIS

9       tc ... action skbmod { [ set SETTABLE ] [ swap SWAPPABLE  ] [ CONTROL ]
10               [ index INDEX ] }
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12       SETTABLE :=  [ dmac DMAC ]  [ smac SMAC ]  [ etype ETYPE ]
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14       SWAPPABLE := mac
15       CONTROL := { reclassify | pipe | drop | shot | continue | pass }
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DESCRIPTION

18       The skbmod action is intended as a usability upgrade  to  the  existing
19       pedit  action.  Instead  of  having to manually edit 8-, 16-, or 32-bit
20       chunks of an ethernet header, skbmod allows  complete  substitution  of
21       supported elements.
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OPTIONS

24       dmac DMAC
25              Change the destination mac to the specified address.
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27       smac SMAC
28              Change the source mac to the specified address.
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30       etype ETYPE
31              Change the ethertype to the specified value.
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33       mac    Used  to swap mac addresses. The swap mac directive is performed
34              after any outstanding D/SMAC changes.
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36       CONTROL
37              The following keywords allow to control how the tree  of  qdisc,
38              classes,  filters  and  actions  is further traversed after this
39              action.
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41              reclassify
42                     Restart with the first filter in the current list.
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44              pipe   Continue with the next action attached to the  same  fil‐
45                     ter.
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47              drop
48              shot   Drop the packet.
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50              continue
51                     Continue classification with the next filter in line.
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53              pass   Finish classification process and return to calling qdisc
54                     for further packet processing. This is the default.
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EXAMPLES

57       To start, observe the following filter with a pedit action:
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59              tc filter add dev eth1 parent 1: protocol ip prio 10 \
60                   u32 match ip protocol 1 0xff flowid 1:2 \
61                   action pedit munge offset -14 u8 set 0x02 \
62                   munge offset -13 u8 set 0x15 \
63                   munge offset -12 u8 set 0x15 \
64                   munge offset -11 u8 set 0x15 \
65                   munge offset -10 u16 set 0x1515 \
66                   pipe
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68       Using the skbmod action, this command can be simplified to:
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70              tc filter add dev eth1 parent 1: protocol ip prio 10 \
71                   u32 match ip protocol 1 0xff flowid 1:2 \
72                   action skbmod set dmac 02:15:15:15:15:15 \
73                   pipe
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75       Complexity will increase if source mac and  ethertype  are  also  being
76       edited  as  part  of  the action. If all three fields are to be changed
77       with skbmod:
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79              tc filter add dev eth5 parent 1: protocol ip prio 10 \
80                   u32 match ip protocol 1 0xff flowid 1:2 \
81                   action skbmod \
82                   set etype 0xBEEF \
83                   set dmac 02:12:13:14:15:16 \
84                   set smac 02:22:23:24:25:26
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86       Finally, swap the destination and source mac addresses in the header:
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88              tc filter add dev eth3 parent 1: protocol ip prio 10 \
89                   u32 match ip protocol 1 0xff flowid 1:2 \
90                   action skbmod \
91                   swap mac
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93       As mentioned above, the swap action will occur  after  any    smac/dmac
94       substitutions are executed, if they are present.
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SEE ALSO

98       tc(8), tc-u32(8), tc-pedit(8)
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102iproute2                          21 Sep 2016           skbmod action in tc(8)
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