This target allows you to mark that connection with an arbitrary walue.  This
value can later be matched via the 
.B connmark
match.
.TP
.BI "--set-mark " "mark"
Set the conntrack mark,
.TP
.BI "--save-mark"
Save the packet nfmark on the connection mark.
.TP
.BI "--restore-mark"
Restore the saved nfmark value from the connection mark.