The CT target allows to set parameters for a packet or its associated connection. The target attaches a "template" connection tracking entry to the packet, which is then used by the conntrack core when initializing a new ct entry. This target is thus only valid in the "raw" table.

--notrack
    Disables connection tracking for this packet.

--helper name
    Use the helper identified by name for the connection. This is more flexible than loading the conntrack helper modules with preset ports.

--ctevents event[,...]
    Only generate the specified conntrack events for this connection. Possible event types are: new, related, destroy, reply, assured, protoinfo, helper, mark (this refers to the ctmark, not nfmark), natseqinfo, secmark (ctsecmark).

--expevents event[,...]
    Only generate the specified expectation events for this connection. Possible event types are: new.

--zone-orig {id|mark}
    For traffic coming from ORIGINAL direction, assign this packet to zone id and only have lookups done in that zone. If mark is used instead of id, the zone is derived from the packet nfmark.

--zone-reply {id|mark}
    For traffic coming from REPLY direction, assign this packet to zone id and only have lookups done in that zone. If mark is used instead of id, the zone is derived from the packet nfmark.

--zone {id|mark}
    Assign this packet to zone id and only have lookups done in that zone. If mark is used instead of id, the zone is derived from the packet nfmark. By default, packets have zone 0. This option applies to both directions.

--timeout name
    Use the timeout policy identified by name for the connection. This is provides more flexible timeout policy definition than global timeout values available at /proc/sys/net/netfilter/nf_conntrack_*_timeout_*.