The iptables plugin gathers packets and bytes counters for rules within a set of table and chain from the Linux's iptables firewall.
Rules are identified through associated comment. Rules without comment are ignored.
Indeed we need a unique ID for the rule and the rule number is not a constant: it may vary when rules are inserted/deleted at start-up or by automatic tools (interactive firewalls, fail2ban, ...).
Also when the rule set is becoming big (hundreds of lines) most people are interested in monitoring only a small part of the rule set.
Before using this plugin you must ensure that the rules you want to monitor are named with a unique comment. Comments are added using the -m comment --comment "my comment"
iptables options.
The iptables command requires CAP_NET_ADMIN and CAP_NET_RAW capabilities. You have several options to grant agent to run iptables:
- Run agent as root. This is strongly discouraged.
- Configure systemd to run agent with CAP_NET_ADMIN and CAP_NET_RAW. This is the simplest and recommended option.
- Configure sudo to grant agent to run iptables. This is the most restrictive option, but require sudo setup.
Using systemd capabilities
You may run systemctl edit circonus-unified-agent.service
and add the following:
[Service]
CapabilityBoundingSet=CAP_NET_RAW CAP_NET_ADMIN
AmbientCapabilities=CAP_NET_RAW CAP_NET_ADMIN
Since the agent will fork a process to run iptables, AmbientCapabilities
is required to transmit the capabilities bounding set to the forked process.
Using sudo
You will need the following in your config:
[[inputs.iptables]]
instance_id = "" # unique instance identifier (REQUIRED)
use_sudo = true
You will also need to update your sudoers file:
$ visudo
# Add the following line:
Cmnd_Alias IPTABLESSHOW = /usr/bin/iptables -nvL *
cua ALL=(root) NOPASSWD: IPTABLESSHOW
Defaults!IPTABLESSHOW !logfile, !syslog, !pam_session
Using IPtables lock feature
Defining multiple instances of this plugin in circonus-unified-agent.conf can lead to concurrent IPtables access resulting in "ERROR in input [inputs.iptables]: exit status 4" messages in the log and missing metrics. Setting 'use_lock = true' in the plugin configuration will run IPtables with the '-w' switch, allowing a lock usage to prevent this error.
Configuration
instance_id = "" # unique instance identifier (REQUIRED)
# use sudo to run iptables
use_sudo = false
# run iptables with the lock option
use_lock = false
# Define an alternate executable, such as "ip6tables". Default is "iptables".
# binary = "ip6tables"
# defines the table to monitor:
table = "filter"
# defines the chains to monitor:
chains = [ "INPUT" ]
Measurements & Fields
- iptables
- pkts (integer, count)
- bytes (integer, bytes)
- All measurements have the following tags:
The ruleid
is the comment associated to the rule.
Example Output
$ iptables -nvL INPUT
Chain INPUT (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
100 1024 ACCEPT tcp -- * * 192.168.0.0/24 0.0.0.0/0 tcp dpt:22 /* ssh */
42 2048 ACCEPT tcp -- * * 192.168.0.0/24 0.0.0.0/0 tcp dpt:80 /* httpd */
$ ./circonus-unified-agent --config circonus-unified-agent.conf --input-filter iptables --test
iptables,table=filter,chain=INPUT,ruleid=ssh pkts=100i,bytes=1024i 1453831884664956455
iptables,table=filter,chain=INPUT,ruleid=httpd pkts=42i,bytes=2048i 1453831884664956455