Synproxy Input Plugin

The synproxy plugin gathers the synproxy counters. Synproxy is a Linux netfilter module used for SYN attack mitigation. The use of synproxy is documented in man iptables-extensions under the SYNPROXY section.

Configuration

The synproxy plugin does not need any configuration

[[inputs.synproxy]]
  # no configuration

Metrics

The following synproxy counters are gathered

synproxy
- fields:
  - cookie_invalid (uint32, packets, counter) - Invalid cookies
  - cookie_retrans (uint32, packets, counter) - Cookies retransmitted
  - cookie_valid (uint32, packets, counter) - Valid cookies
  - entries (uint32, packets, counter) - Entries
  - syn_received (uint32, packets, counter) - SYN received
  - conn_reopened (uint32, packets, counter) - Connections reopened

Sample Queries

Get the number of packets per 5 minutes for the measurement in the last hour from InfluxDB:

SELECT difference(last("cookie_invalid")) AS "cookie_invalid", difference(last("cookie_retrans")) AS "cookie_retrans", difference(last("cookie_valid")) AS "cookie_valid", difference(last("entries")) AS "entries", difference(last("syn_received")) AS "syn_received", difference(last("conn_reopened")) AS "conn_reopened" FROM synproxy WHERE time > NOW() - 1h GROUP BY time(5m) FILL(null);

Troubleshooting

Execute the following CLI command in Linux to test the synproxy counters:

cat /proc/net/stat/synproxy

Example Output

This section shows example output in Line Protocol format.

synproxy,host=Filter-GW01,rack=filter-node1 conn_reopened=0i,cookie_invalid=235i,cookie_retrans=0i,cookie_valid=8814i,entries=0i,syn_received=8742i 1549550634000000000

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