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ct action in tc(8)                   Linux                  ct action in tc(8)
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 config-
       uring a 32bit mark, 128bit label, and src/dst nat.
       Send the packet to conntrack, which will mark the packet with the  con-
       nection's  state and configured metadata (mark/label), and execute pre-
       vious 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  connec-
              tions, so that current direction will become the original direc-
              tion (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 AT mellanox.com>
       Marcelo Ricardo Leitner <marcelo.leitner AT gmail.com>
       Yossi Kuperman <yossiku AT mellanox.com>
iproute2                          14 May 2020               ct action in tc(8)