Turn on kernel logging of matching packets.  When this option is set
for a rule, the Linux kernel will print some information on all
matching packets (like most IPv6 IPv6-header fields) via the kernel log
(where it can be read with
.I dmesg
or 
.IR syslogd (8)).
This is a "non-terminating target", i.e. rule traversal continues at
the next rule.  So if you want to LOG the packets you refuse, use two
separate rules with the same matching criteria, first using target LOG
then DROP (or REJECT).
.TP
.BI "--log-level " "level"
Level of logging (numeric or see \fIsyslog.conf\fP(5)).
.TP
.BI "--log-prefix " "prefix"
Prefix log messages with the specified prefix; up to 29 letters long,
and useful for distinguishing messages in the logs.
.TP
.B --log-tcp-sequence
Log TCP sequence numbers. This is a security risk if the log is
readable by users.
.TP
.B --log-tcp-options
Log options from the TCP packet header.
.TP
.B --log-ip-options
Log options from the IPv6 packet header.
.TP
.B --log-uid
Log the userid of the process which generated the packet.