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golib/net/iplist/README.md
AJ ONeal c41ac3732d
feat(iplist): load and validate IP policy entries from TSV/CSV sources 
Add net/iplist for shared IP-policy source loading.

- Accept local TSV/CSV file paths or HTTP(S) URLs (including Google Sheets).
- Auto-detect TSV vs CSV format from file content.
- Send Accept: text/tab-separated-values header for content negotiation.
- Parse the first column and ignore comments (#) and optional "network" header.
- Expand nested list URLs up to MaxNestedSources (2) levels.
- Support Basic Auth from URL userinfo without sending credentials in the URL.
- Persist cached URL responses across restarts via httpcache.
- Refresh periodically and preserve the known-good cache on fetch or parse failure.
- Validate entries as IP address, CIDR range, or domain name (Validate()).
- Use golib/https.NewInternalClient() through httpcache.NewWith.
- Add README with usage examples and entry format documentation.
2026-09-08 22:46:17 -06:00

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net/iplist

Load and validate IP policy entries from local TSV/CSV files, cached HTTP(S) URLs, and Google Sheets.

Features

  • Local files: TSV or CSV, auto-detected by content.
  • HTTP(S) URLs: fetched with conditional GET (ETag / Last-Modified), cached to disk, and refreshed periodically. The cache survives process restarts.
  • Google Sheets: edit/share URLs are recognised and fetched as CSV exports automatically.
  • Nested sources: entries that are themselves HTTP(S) URLs are recursively expanded up to MaxNestedSources (2) levels deep.
  • Basic Auth: credentials embedded in URL userinfo (https://user:pass@host/path) are extracted and sent via the Authorization header. The URL is stripped of credentials before being used as a cache key or included in error messages.
  • Content negotiation: sends Accept: text/tab-separated-values, text/csv;q=0.5 so well-behaved servers return TSV. Format is auto-detected from the response content (TSV if the first data line contains a tab, otherwise CSV).
  • Entry validation: each non-URL entry must be an IP address, CIDR range, or domain name. Invalid entries cause an error.

Usage

import "github.com/therootcompany/golib/net/iplist"

// Load from a local TSV file.
entries, err := iplist.Load(ctx, "/etc/policy/allowlist.tsv", "/var/cache/iplist")

// Load from an HTTPS URL with Basic Auth.
entries, err := iplist.Load(ctx, "https://user:pass@policy.example.com/allowlist.tsv", "/var/cache/iplist")

// Load from a Google Sheet.
entries, err := iplist.Load(ctx, "https://docs.google.com/spreadsheets/d/1AbC.../edit?gid=123#gid=123", "/var/cache/iplist")

Entry format

Each row in a TSV or CSV source contributes its first column as an entry. Blank lines, comments (#), and an optional network header on the first line are ignored. Other columns are treated as labels and discarded.

# Allowlist
network              note
192.0.2.1            primary
10.0.0.0/8           internal
example.com          partner
https://other.example.com/more-entries.tsv

In this example the URL on the last line will be fetched and its entries expanded inline (counted as one nesting level).

Validation

Entries must be one of:

Type Examples
IP address 192.0.2.1, 2001:db8::1
CIDR range 10.0.0.0/8, 2001:db8::/32
Domain example.com, sub.example.com
Source URL https://host/path.tsv (expanded)

Use iplist.Validate(s) to check a single entry without loading a file.

Cache resilience

On fetch failure the previous cache file is still used. If a fetch succeeds but the new content fails to parse, the previous cache is restored and the .meta sidecar is removed so the next call retries from scratch.

Dependencies