phpman > man > tc-ctinfo(8)

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



NAME
       ctinfo - tc connmark processing action

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


DESCRIPTION
       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 clas‐
       sification 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  ac‐
       tion.   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
   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 un‐
              signed 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  com‐
              mands. index is a 32bit unsigned decimal value.

EXAMPLES
       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, how‐
       ever 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
       tc(8), tc-cake(8) tc-connmark(8) tc-mirred(8)

AUTHORS
       ctinfo was written by Kevin Darbyshire-Bryant.



iproute2                                     4 Jun 2019                       ctinfo action in tc(8)