Section 8 · System administration
tc-ct.8
Package: iproute-tc
ct action in tc
NAME
SYNOPSIS
DESCRIPTION
OPTIONS
EXAMPLES
SEE ALSO
AUTHORS
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>