tc-ctinfo(8) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | PARAMETERS | EXAMPLES | SEE ALSO | AUTHORS | COLOPHON

ctinfo action in tc(8)            Linux           ctinfo action in tc(8)

NAME         top

       ctinfo - tc connmark processing action

SYNOPSIS         top

       tc ... action ctinfo [ dscp MASK [STATEMASK] ] [ cpmark [MASK] ]
       [ zone ZONE ] [ CONTROL ] [ index <INDEX> ]

DESCRIPTION         top

       CTINFO (Conntrack Information) is a tc action for retrieving data
       from conntrack marks into various fields.  At present it has two
       independent processing modes which may be viewed as sub-
       functions.

       DSCP mode copies a DSCP stored in conntrack's connmark into the
       IPv4/v6 diffserv field.  The copying may conditionally occur
       based on a flag also stored in the connmark.  DSCP mode was
       designed to assist in restoring packet classifications on
       ingress, classifications which may then be used by qdiscs such as
       CAKE.  It may be used in any circumstance where ingress
       classification needs to be maintained across links that otherwise
       bleach or remap according to their own policies.

       CPMARK (copymark) mode copies the conntrack connmark into the
       packet's mark field.  Without additional parameters it is
       functionally completely equivalent to the existing connmark
       action.  An optional mask may be specified to mask which bits of
       the connmark are restored.  This may be useful when DSCP and
       CPMARK modes are combined.

       Simple statistics (tc -s) on DSCP restores and CPMARK copies are
       maintained where values for set indicate a count of packets
       altered for that mode.  DSCP includes an error count where the
       destination packet's diffserv field was unwriteable.

PARAMETERS         top

   DSCP mode parameters:
       mask   A mask of 6 contiguous bits indicating where the DSCP
              value is located in the 32 bit conntrack mark field.  A
              mask must be provided for this mode.  mask is a 32 bit
              unsigned value.

       statemask
              A mask of at least 1 bit indicating where a conditional
              restore flag is located in the 32 bit conntrack mark
              field.  The statemask bit/s must NOT overlap the mask
              bits.  The DSCP will be restored if the conntrack mark
              logically ANDed with the statemask yields a non-zero
              result.  statemask is an optional unsigned 32 bit value.

   CPMARK mode parameters:
       mask   Store the logically ANDed result of conntrack mark and
              mask into the packet's mark field.  Default is 0xffffffff
              i.e. the whole mark field.  mask is an optional unsigned
              32 bit value

   Overall action parameters:
       zone   Specify the conntrack zone when doing conntrack lookups
              for packets.  zone is a 16bit unsigned decimal value.
              Default is 0.

       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   Drop the packet.

              shot   synonym for drop

              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.

       index  Specify an index for this action in order to being able to
              identify it in later commands. index is a 32bit unsigned
              decimal value.

EXAMPLES         top

       Example showing conditional restoration of DSCP on ingress via an
       IFB

              #Set up the IFB interface
              tc qdisc add dev ifb4eth0 handle ffff: ingress

              #Put CAKE qdisc on it
              tc qdisc add dev ifb4eth0 root cake bandwidth 40mbit

              #Set interface UP
              ip link set dev ifb4eth0 up

              #Add 2 actions, ctinfo to restore dscp & mirred to redirect the packets to IFB
              tc filter add dev eth0 parent ffff: protocol all prio 10 u32 \
                  match u32 0 0 flowid 1:1 action    \
                  ctinfo dscp 0xfc000000 0x01000000  \
                  mirred egress redirect dev ifb4eth0

              tc -s qdisc show dev eth0 ingress

               filter parent ffff: protocol all pref 10 u32 chain 0
               filter parent ffff: protocol all pref 10 u32 chain 0 fh 800: ht divisor 1
               filter parent ffff: protocol all pref 10 u32 chain 0 fh 800::800 order 2048 key ht 800 bkt 0 flowid 1:1 not_in_hw
                match 00000000/00000000 at 0
                  action order 1: ctinfo zone 0 pipe
                  index 2 ref 1 bind 1 dscp 0xfc000000 0x01000000 installed 72 sec used 0 sec DSCP set 1333 error 0 CPMARK set 0
                  Action statistics:
                  Sent 658484 bytes 1833 pkt (dropped 0, overlimits 0 requeues 0)
                  backlog 0b 0p requeues 0

                  action order 2: mirred (Egress Redirect to device ifb4eth0) stolen
                  index 1 ref 1 bind 1 installed 72 sec used 0 sec
                  Action statistics:
                  Sent 658484 bytes 1833 pkt (dropped 0, overlimits 0 requeues 0)
                  backlog 0b 0p requeues 0

       Example showing conditional restoration of DSCP on egress

       This may appear nonsensical since iptables marking of egress
       packets is easy to achieve, however the iptables flow
       classification rules may be extensive and so some sort of set
       once and forget may be useful especially on cpu constrained
       devices.

              # Send unmarked connections to a marking chain which needs to store a DSCP
              and set statemask bit in the connmark
              iptables -t mangle -A POSTROUTING -o eth0 -m connmark \
                  --mark 0x00000000/0x01000000 -g CLASS_MARKING_CHAIN

              # Apply marked DSCP to the packets
              tc filter add dev eth0 protocol all prio 10 u32 \
                  match u32 0 0 flowid 1:1 action \
                  ctinfo dscp 0xfc000000 0x01000000

              tc -s filter show dev eth0
               filter parent 800e: protocol all pref 10 u32 chain 0
               filter parent 800e: protocol all pref 10 u32 chain 0 fh 800: ht divisor 1
               filter parent 800e: protocol all pref 10 u32 chain 0 fh 800::800 order 2048 key ht 800 bkt 0 flowid 1:1 not_in_hw
                match 00000000/00000000 at 0
                  action order 1: ctinfo zone 0 pipe
                  index 1 ref 1 bind 1 dscp 0xfc000000 0x01000000 installed 7414 sec used 0 sec DSCP set 53404 error 0 CPMARK set 0
                  Action statistics:
                  Sent 32890260 bytes 120441 pkt (dropped 0, overlimits 0 requeues 0)
                  backlog 0b 0p requeues 0

SEE ALSO         top

       tc(8), tc-cake(8) tc-connmark(8) tc-mirred(8)

AUTHORS         top

       ctinfo was written by Kevin Darbyshire-Bryant.

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
       ⟨https://git.kernel.org/pub/scm/network/iproute2/iproute2.git⟩ on
       2021-06-20.  (At that time, the date of the most recent commit
       that was found in the repository was 2021-06-17.)  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                       4 Jun 2019         ctinfo action in tc(8)