# tc-ct(8) - man - phpman

ct action in [tc(8)](https://www.chedong.com/phpMan.php/man/tc/8/markdown)                              Linux                             ct action in [tc(8)](https://www.chedong.com/phpMan.php/man/tc/8/markdown)



## NAME
       ct - tc connection tracking action

## SYNOPSIS
       **tc** **...** **action** **ct** **commit** **[** **force** **]** **[** **zone** _ZONE_ **]** **[** **mark** _MASKED_MARK_ **]** **[** **label** _MASKED_LABEL_ **]** **[**
               **nat** _NAT_SPEC_ **]**

       **tc** **...** **action** **ct** **[** **nat** **]** **[** **zone** _ZONE_ **]**

### tc ... action ct clear


## DESCRIPTION
       The ct action is a tc action for sending packets and interacting with the netfilter conntrack
       module.

       It can (as shown in the synopsis, in order):

       Send  the  packet  to  conntrack,  and commit the connection, while configuring a 32bit mark,
       128bit label, and src/dst nat.

       Send the packet to conntrack, which will mark the packet with the connection's state and con‐
       figured metadata (mark/label), and execute previous configured nat.

       Clear the packet's of previous connection tracking state.


## OPTIONS
       **zone** _ZONE_
              Specify a conntrack zone number on which to send the packet to conntrack.

       **mark** _MASKED_MARK_
              Specify a masked 32bit mark to set for the connection (only valid with commit).

       **label** _MASKED_LABEL_
              Specify a masked 128bit label to set for the connection (only valid with commit).

       **nat** _NAT_SPEC_
              **Where** _NAT_SPEC_ **:=** **{src|dst}** **addr** _addr1_**[-**_addr2_**]** **[port** _port1_**[-**_port2_**]]**

              Specify src/dst and range of nat to configure for the connection (only valid with com‐
              mit).

              src/dst - configure src or dst nat

              _addr1_**/**_addr2_ **-** **IPv4/IPv6** **addresses**

              _port1_**/**_port2_ **-** **Port** **numbers**

       **nat**    Restore any previous configured nat.

       **clear**  Remove any conntrack state and metadata (mark/label) from the packet (must only option
              specified).

       **force**  Forces conntrack direction for a previously committed connections, so that current di‐
              rection will become the original direction (only valid with commit).


## EXAMPLES
       Example showing natted firewall in conntrack zone 2, and conntrack mark usage:

       #Add ingress qdisc on eth0 and eth1 interfaces
       $ tc qdisc add dev eth0 handle ingress
       $ tc qdisc add dev eth1 handle ingress

       #Setup filters on eth0, allowing opening new connections in zone 2, and doing src nat + mark for each new connection
       $ tc filter add dev eth0 ingress prio 1 chain 0 proto ip flower ip_proto tcp ct_state -trk \
       action ct zone 2 pipe action goto chain 2
       $ tc filter add dev eth0 ingress prio 1 chain 2 proto ip flower ct_state +trk+new \
       action ct zone 2 commit mark 0xbb nat src addr 5.5.5.7 pipe action mirred egress redirect dev eth1
       $ tc filter add dev eth0 ingress prio 1 chain 2 proto ip flower ct_zone 2 ct_mark 0xbb ct_state +trk+est \
       action ct nat pipe action mirred egress redirect dev eth1

       #Setup filters on eth1, allowing only established connections of zone 2 through, and reverse nat (dst nat in this case)
       $ tc filter add dev eth1 ingress prio 1 chain 0 proto ip flower ip_proto tcp ct_state -trk \
       action ct zone 2 pipe action goto chain 1
       $ tc filter add dev eth1 ingress prio 1 chain 1 proto ip flower ct_zone 2 ct_mark 0xbb ct_state +trk+est \
       action ct nat pipe action mirred egress redirect dev eth0



## SEE ALSO
       [**tc**(8)](https://www.chedong.com/phpMan.php/man/tc/8/markdown), [**tc-flower**(8)](https://www.chedong.com/phpMan.php/man/tc-flower/8/markdown) [**tc-mirred**(8)](https://www.chedong.com/phpMan.php/man/tc-mirred/8/markdown)

## AUTHORS
       Paul Blakey <<paulb@mellanox.com>>

       Marcelo Ricardo Leitner <<marcelo.leitner@gmail.com>>

       Yossi Kuperman <<yossiku@mellanox.com>>



iproute2                                     14 May 2020                          ct action in [tc(8)](https://www.chedong.com/phpMan.php/man/tc/8/markdown)