TARGET EXTENSIONS
iptables can use extended target modules: the following are included in the standard distribution.
LOG
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 IP header fields) via the kernel log (where it
can be read with dmesg or syslogd().
--log-level level
Level of logging (numeric or see syslog.conf(5)).
--log-prefix prefix
Prefix log messages with the specified prefix; up to 29 letters long, and useful for distinguish?
ing messages in the logs.
--log-tcp-sequence
Log TCP sequence numbers. This is a security risk if the log is readable by users.
--log-tcp-options
Log options from the TCP packet header.
--log-ip-options
Log options from the IP packet header.