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UNIX and Linux netstat logs: Reduce log size and convert to TSV format

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Use case

Reduce the size of Unix and Linux netstat logs by removing unnecessary fields, replacing invalid values, and optimizing log storage. Extract essential fields while maintaining compatibility with the Splunk Common Information Model (CIM).

Version 0.4.1

Version 0.4.1 of the UNIX and Linux netstat logs: Reduce log size and convert to TSV format template was released on March 19, 2025.

Template details

Compatibility

This template is compatible with Splunk Add-on for Unix and Linux v9.2.0 and v10.0.0.

Template description

This is a sample pipeline that reduces the size of netstat logs coming from the Splunk Add-on for Unix and Linux while preserving compatibility with the Splunk Common Information Model (CIM). This pipeline processes data with the netstat source type and performs the following:

  1. Replaces repeated space characters used as delimiters in the logs with a single tab character (\t) or a custom delimiter.
  2. Removes unnecessary data from the logs.
  3. Converts the logs into tab-separated values (TSV) format.
  4. Optionally updates the values of the source and sourcetype event fields.

Supported sourcetype

This pipeline only works on complete netstat events that include the header row and all subsequent rows.

Template outline

The template consists of several custom functions followed by a pipeline that uses these functions.

Functions

The following table shows all functions, including possible configuration options.

Function name Description Configuration options
replace_multiple_whitespaces Replaces repeated space characters in the logs with a single tab character (\t) or a custom delimiter. $delimiter: The replacement delimiter to use instead of repeated space characters (default: \t).
replace_hyphens Removes hyphens from the headers Recv-Q and Send-Q and replaces them with RecvQ and SendQ. No configuration options.
extract_split_rows Splits the logs into rows using the newline character (\n) as the delimiter and further splits the rows into columns using the tab character (\t) or a custom delimiter. $row_split_separator: The delimiter for splitting rows into columns (default: \t).
find_header_indexes Assigns a number to each log field. Other functions in this pipeline use these numbers as indexes for accessing the log contents. No configuration options.
filter_state Removes rows where the value of the State field is <n/a>. No configuration options.
filter_foreign_address Removes rows where the ForeignAddress field contains values such as 127.0.0.1, 0.0.0.0, [::], or *:*. No configuration options.
rows_to_delimiter_separated Transforms the logs from JSON array format to tab-separated key-value pair format. $delimiter: The delimiter to use between columns (default: \t).
apply_transformations Groups the previously defined custom functions together to apply transformations to the logs. No configuration options.
update_source_and_source_type Appends a suffix to the values in the source and sourcetype fields, if those fields exist in the event. $suffix: The suffix to append to the source and sourcetype values.

Pipeline

This pipeline has the following outline:

  1. Replaces repeated space characters with tabs using the replace_multiple_whitespaces function.
  2. Removes hyphens from headers using the replace_hyphens function.
  3. Splits the logs into rows and columns using the extract_split_rows function.
  4. Assigns indexes to the log fields using the find_header_indexes function.
  5. Removes rows where the State field has the value <n/a> using the filter_state function.
  6. Removes rows where the ForeignAddress field contains invalid values using the filter_foreign_address function.
  7. Transforms the logs into tab-separated key-value pair format using the rows_to_delimiter_separated function.
  8. Optionally updates the source and sourcetype fields using the update_source_and_source_type function.
  9. Sends the transformed logs to the destination.

Configuration instructions

For significant license savings, use the filter_state and filter_foreign_address functions to remove unnecessary rows and replace unnecessary values in specific fields. You can comment out any of these functions you do not want to apply by prefixing it with //, allowing you to retain specific data that might otherwise be removed or modified.

Optionally, use the update_source_and_source_type function to append a suffix to the source and sourcetype fields, helping to distinguish modified logs from unmodified ones.

Notes

  • Ensure that the netstat source type is properly configured in your Splunk deployment.
  • Customize the pipeline as needed to meet your specific requirements.
  • If using the update_source_and_source_type function, ensure that the suffixed source type is configured in your Splunk platform deployment with appropriate time extraction and line-breaking settings.