Manpages - tc-ct.8

ct - tc connection tracking action

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

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.

*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).

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

*tc*(8), *tc-flower*(8) *tc-mirred*(8)

Paul Blakey <paulb@mellanox.com>

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

Yossi Kuperman <yossiku@mellanox.com>