telegraf/plugins/inputs/iptables/README.md

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# Iptables Plugin
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 telegraf to run iptables:
* Run telegraf as root. This is strongly discouraged.
* Configure systemd to run telegraf with CAP_NET_ADMIN and CAP_NET_RAW. This is the simplest and recommended option.
* Configure sudo to grant telegraf to run iptables. This is the most restrictive option, but require sudo setup.
### Using systemd capabilities
You may run `systemctl edit telegraf.service` and add the following:
```
[Service]
CapabilityBoundingSet=CAP_NET_RAW CAP_NET_ADMIN
AmbientCapabilities=CAP_NET_RAW CAP_NET_ADMIN
```
Since telegraf will fork a process to run iptables, `AmbientCapabilities` is required to transmit the capabilities bounding set to the forked process.
### Using sudo
You may edit your sudo configuration with the following:
```sudo
telegraf ALL=(root) NOPASSWD: /usr/bin/iptables -nvL *
```
### Using IPtables lock feature
Defining multiple instances of this plugin in telegraf.conf can lead to concurrent IPtables access resulting in "ERROR in input [inputs.iptables]: exit status 4" messages in telegraf.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:
```toml
# 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)
### Tags:
- All measurements have the following tags:
- table
- chain
- ruleid
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 */
```
```
$ ./telegraf --config telegraf.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
```