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+# nutils
+
+## Response
+
+Every request returns 5 lines of plain text:
+
+```
+203.0.113.42
+host-203-0-113-42.example.net
+proxy=NO, type=UNKNOWN, tor=NO
+North America, United States, Los Angeles
+Example ISP / AS12345
+```
+
+| Line | Field | Meaning |
+|------|-------|---------|
+| 1 | IP | Client public IP (from X-Forwarded-For, X-Real-IP, or remote addr) |
+| 2 | Reverse DNS | PTR record, or "Unknown" |
+| 3 | Classification | Abuse flags |
+| 4 | Location | Continent, country, city (GeoLite2-City) |
+| 5 | ASN | Organization and ASN number (GeoLite2-ASN) |
+
+## Modes
+
+**ip** (default)
+Returns both IPv4 and IPv6. Works as a catch-all.
+
+**ip4**
+IPv4 only. Rejects IPv6 clients with HTTP 400.
+
+**ip6**
+IPv6 only. Rejects IPv4 clients with HTTP 400.
+
+## Config
+
+```toml
+[server]
+listen = ":8080"
+
+[services.ip]
+enabled = true
+subdomains = ["ip.example.com"]
+directories = ["/"]
+
+[services.ip4]
+enabled = true
+subdomains = ["ip4.example.com"]
+
+[services.ip6]
+enabled = true
+subdomains = ["ip6.example.com"]
+
+[geo]
+asn_db = "GeoLite2-ASN.mmdb"
+city_db = "GeoLite2-City.mmdb"
+download_url_asn = "https://git.io/GeoLite2-ASN.mmdb"
+download_url_city = "https://git.io/GeoLite2-City.mmdb"
+cache_dir = "data"
+```
+
+Services can be toggled on/off with `enabled`. MMDBs are downloaded automatically on first run and cached in `cache_dir`.