NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | SEE ALSO | COLOPHON

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

NAME         top

       skbmod - user-friendly packet editor action

SYNOPSIS         top

       tc ... action skbmod { [ set SETTABLE ] [ swap SWAPPABLE  ] [ CONTROL
               ] [ index INDEX ] }

       SETTABLE :=  [ dmac DMAC ]  [ smac SMAC ]  [ etype ETYPE ]

       SWAPPABLE := mac
       CONTROL := { reclassify | pipe | drop | shot | continue | pass }

DESCRIPTION         top

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

OPTIONS         top

       dmac DMAC
              Change the destination mac to the specified address.

       smac SMAC
              Change the source mac to the specified address.

       etype ETYPE
              Change the ethertype to the specified value.

       mac    Used to swap mac addresses. The swap mac directive is
              performed after any outstanding D/SMAC changes.

       CONTROL
              The following keywords allow to control how the tree of qdisc,
              classes, filters and actions is further traversed after this
              action.

              reclassify
                     Restart with the first filter in the current list.

              pipe   Continue with the next action attached to the same
                     filter.

              drop
              shot   Drop the packet.

              continue
                     Continue classification with the next filter in line.

              pass   Finish classification process and return to calling
                     qdisc for further packet processing. This is the
                     default.

EXAMPLES         top

       To start, observe the following filter with a pedit action:

              tc filter add dev eth1 parent 1: protocol ip prio 10 \
                   u32 match ip protocol 1 0xff flowid 1:2 \
                   action pedit munge offset -14 u8 set 0x02 \
                   munge offset -13 u8 set 0x15 \
                   munge offset -12 u8 set 0x15 \
                   munge offset -11 u8 set 0x15 \
                   munge offset -10 u16 set 0x1515 \
                   pipe

       Using the skbmod action, this command can be simplified to:

              tc filter add dev eth1 parent 1: protocol ip prio 10 \
                   u32 match ip protocol 1 0xff flowid 1:2 \
                   action skbmod set dmac 02:15:15:15:15:15 \
                   pipe

       Complexity will increase if source mac and ethertype are also being
       edited as part of the action. If all three fields are to be changed
       with skbmod:

              tc filter add dev eth5 parent 1: protocol ip prio 10 \
                   u32 match ip protocol 1 0xff flowid 1:2 \
                   action skbmod \
                   set etype 0xBEEF \
                   set dmac 02:12:13:14:15:16 \
                   set smac 02:22:23:24:25:26

       Finally, swap the destination and source mac addresses in the header:

              tc filter add dev eth3 parent 1: protocol ip prio 10 \
                   u32 match ip protocol 1 0xff flowid 1:2 \
                   action skbmod \
                   swap mac

       As mentioned above, the swap action will occur after any  smac/dmac
       substitutions are executed, if they are present.

SEE ALSO         top

       tc(8), tc-u32(8), tc-pedit(8)

COLOPHON         top

       This page is part of the iproute2 (utilities for controlling TCP/IP
       networking and traffic) project.  Information about the project can
       be found at 
       ⟨http://www.linuxfoundation.org/collaborate/workgroups/networking/iproute2⟩.
       If you have a bug report for this manual page, send it to
       netdev@vger.kernel.org, shemminger@osdl.org.  This page was obtained
       from the project's upstream Git repository 
       ⟨git://git.kernel.org/pub/scm/linux/kernel/git/shemminger/iproute2.git⟩
       on 2017-07-05.  If you discover any rendering problems in this HTML
       version of the page, or you believe there is a better or more up-to-
       date source for the page, or you have corrections or improvements to
       the information in this COLOPHON (which is not part of the original
       manual page), send a mail to man-pages@man7.org

iproute2                         21 Sep 2016          skbmod action in tc(8)