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
       configured 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
              commit).

              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
              direction 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 ingress
       $ tc qdisc add dev eth1 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), tc-flower(8) tc-mirred(8)

AUTHORS

       Paul Blakey <paulb@mellanox.com>

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

       Yossi Kuperman <yossiku@mellanox.com>