Adding upstream version 1.34.4.

Signed-off-by: Daniel Baumann <daniel@debian.org>

plugins/inputs/synproxy/README.md

@@ -0,0 +1,63 @@
+# 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.
+
+## Global configuration options <!-- @/docs/includes/plugin_config.md -->
+
+In addition to the plugin-specific configuration settings, plugins support
+additional global and plugin configuration settings. These settings are used to
+modify metrics, tags, and field or create aliases and configure ordering, etc.
+See the [CONFIGURATION.md][CONFIGURATION.md] for more details.
+
+[CONFIGURATION.md]: ../../../docs/CONFIGURATION.md#plugins
+
+## Configuration
+
+```toml @sample.conf
+# Get synproxy counter statistics from procfs
+# This plugin ONLY supports Linux
+[[inputs.synproxy]]
+  # no configuration
+```
+
+The synproxy plugin does not need any 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:
+
+```sql
+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:
+
+```sh
+cat /proc/net/stat/synproxy
+```
+
+## Example Output
+
+This section shows example output in Line Protocol format.
+
+```text
+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
+```