ips-le-mcp

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What it does

An allow-list review asks whether 2001:0db8::0001 is already on the list. The list says 2001:db8::1. A diff of the raw text calls them two addresses; they are one.

Open a document, run IPs-LE: Extract Addresses, and every IPv4 and IPv6 address, CIDR block and MAC address in it is listed by kind with its line and column, the key it sits under, its canonical form and what it is for — loopback, private, link-local, documentation and the rest. A CIDR block comes with its network, its last address and how many addresses it holds. The report opens beside the editor. Works in VS Code and in VS Code–based editors like Cursor and VSCodium (installable from Open VSX).

• Reviewing a config or an allow-list — one spelling per address, and the private ones named as private

• Reading a log — every peer and upstream, even inside a URL or a [host]:port

• Before trusting 010.1.1.1 — which is two different hosts depending on who reads it

• Across a project — every file that holds an address, and how many, in one table

Text it cannot read unambiguously is reported with the reason, never guessed at. It resolves nothing, looks nothing up and rewrites nothing.

Related MCP server: IPMentor

Install

What it answers

One address, one form. IPv6 is normalized per RFC 5952 — 2001:0db8:0000:0000:0000:0000:0000:0001, 2001:db8:0:0:0:0:0:1, 2001:0db8::0001 and 2001:DB8::1 all come back as 2001:db8::1. Sorting the raw text gives four addresses; sorting the normalized form gives one.

Four kinds. ipv4, ipv6, cidr, mac.

Ten classes, closed. A class this cannot name is a class it does not claim.

An IPv4-mapped IPv6 address takes the IPv4 class, so ::ffff:127.0.0.1 is loopback rather than global — which is the miss an allow-list review is looking for.

Where it is. Line, column, and the key it sits under: JSON, YAML, TOML, INI, dotenv, CSV and logs all supply one. Everything else is still scanned — the search runs over the bytes, so a .tf, a .rules or a rotated access.log.1 yields its addresses and only loses the key path.

Blocks, with their arithmetic. A CIDR finding carries prefix, network, broadcast (IPv4 only — IPv6 has none), last and hosts. hosts is a decimal string, because ::/0 holds 2^128 addresses, which is one more than a u128 and far more than a JSON number.

{
  "kind": "cidr",
  "text": "10.0.0.0/8",
  "normalized": "10.0.0.0/8",
  "class": "private",
  "cidr": {
    "prefix": 8,
    "network": "10.0.0.0",
    "broadcast": "10.255.255.255",
    "last": "10.255.255.255",
    "hosts": "16777216"
  }
}

What it refuses

Where the text supports more than one reading, ips-le reports the text, names the ambiguity, and stops.

Six reasons, each a place where two answers are equally defensible:

The two that matter most:

• 010.1.1.1 is not resolved. A leading-zero octet is octal to some resolvers and decimal to others, so that text names two different hosts. Neither reading appears anywhere in the output — a tool that picked one would be the thing hiding the bug.

• 2130706433 is decoded only next to the flag. Under an address key it is reported as integer_form, with 127.0.0.1 inside the refusal message. What you never get is a loopback address quietly appearing in a list of addresses with the flag gone.

A refusal is a finding, not a failure. It does not move the exit code, and no filter can hide it — filtering to private still shows you the octal hazard, because that is the finding a filtered report would most regret dropping. --strict is there for the pipeline that wants an unresolved ambiguity to stop the build.

crate/SPEC.md says exactly when each reason fires.

It never touches a network

No DNS, no geolocation, no ASN, no WHOIS, no reachability check, no telemetry. Not behind a flag, not once. Classification is arithmetic over the bits and the IANA registries; a lookup would make the answer depend on the network the auditor happened to be sitting on.

It also never rewrites a file, and it never gives a verdict. It says what an address is, never whether it should be there.

Across a folder or a workspace

Extract reads the document you have open. A scan reads many files from disk and gives one report.

• The whole workspace: run IPs-LE: Scan Workspace for Addresses from the command palette.

• One folder: right-click it in the Explorer and choose Scan Folder for Addresses, or run IPs-LE: Scan Folder for Addresses and pick one.

The report opens with a table of every file that holds something, then has a section per file:

# IPs-LE workspace report

`my-project` · 113 file(s) read · 2 address(es), 1 could not be read

| File | Addresses | Could not be read |
|---|---|---|
| `deploy/config.json` | 2 | 1 |

## `deploy/config.json` · json (2)

- **3:14** · `2001:0db8:0000:0000:0000:0000:0000:0001` · ipv6 · → `2001:db8::1` · documentation · key `upstream.host`
- **5:12** · `192.0.2.10` · ipv4 · documentation · key `peer`

> 2 file(s) larger than the safety limit were not read.

What a scan reads. Files come from disk, so an unsaved edit is not seen. A file over the safety size, or one that is not UTF-8 text, is left unread. It stops at 5,000 files or 10,000 listed addresses. The report ends with a line for each thing it left out, so a short report is never mistaken for a clean project.

What it skips, and how to change that. Three switches are on by default, and each can be turned off on its own in Settings:

Two lists adjust the result without turning a switch off. To skip more, add a pattern to scanExcludes. To read something a switch would skip, add it to scanAlwaysInclude:

{
	// Also skip the test fixtures.
	"ips-le.workspace.scanExcludes": ["**/fixtures/**"],
	// Read the vendored code, though the built-in list skips it.
	"ips-le.workspace.scanAlwaysInclude": ["**/vendor/**"]
}

IPs-LE: Open Settings opens all of these in the Settings editor.

Folders, wherever they appear:

.git, .hg, .svn, node_modules, bower_components, jspm_packages, .pnpm-store, .yarn, vendor, site-packages, Pods, Carthage, dist, build, out, target, _build, _site, dist-newstyle, zig-out, storybook-static, cdk.out, DerivedData, CMakeFiles, .next, .nuxt, .output, .svelte-kit, .angular, .astro, .docusaurus, .vuepress, .expo, .turbo, .parcel-cache, .cache, .sass-cache, .jekyll-cache, .dart_tool, .pub-cache, .gradle, .kotlin, .cxx, .externalNativeBuild, captures, ephemeral, .symlinks, .swiftpm, .build, .bundle, .stack-work, .zig-cache, .godot, elm-stuff, .vercel, .netlify, .serverless, .aws-sam, .terraform, .venv, venv, __pycache__, .tox, .nox, .mypy_cache, .pytest_cache, .ruff_cache, .ipynb_checkpoints, .eggs, coverage, htmlcov, .nyc_output, .vscode-test, .idea, .vs, xcuserdata, *.egg-info

Files, wherever they appear:

*.min.js, *.min.css, *.map, *.snap, *.lock, package-lock.json, pnpm-lock.yaml, npm-shrinkwrap.json, go.sum, *.pbxproj, *.iml, local.properties, output-metadata.json, .flutter-plugins, .flutter-plugins-dependencies, .packages, Generated.xcconfig, flutter_export_environment.sh, GeneratedPluginRegistrant.*, fastlane/report.xml, fastlane/test_output/**, doc/api/**

Not on the list, because they are ordinary folders in many projects: bin, obj, tmp, logs, public, generated. A project that generates those ignores them in git, and the scan reads .gitignore.

What it could not read. Across a project there can be many, and they crowd out the rest. So a scan counts them per file in the table and does not list them. ips-le.workspace.scanIncludeRefusals lists each one with its reason, and ips-le.workspace.scanProblemsEnabled also puts them in the Problems panel, where each is a line you can click.

The settings that shape a scan are under Settings.

Positions

Each row leads with the line and column of the address:

- **3:14** · `2001:0db8:0000:0000:0000:0000:0000:0001` · → `2001:db8::1` · documentation · key `upstream.host`

Turn ips-le.showPositions off and the same row is:

- `2001:0db8:0000:0000:0000:0000:0000:0001` · → `2001:db8::1` · documentation · key `upstream.host`

Nothing else changes: the same rows, the same counts. The copy on the clipboard is a separate choice, ips-le.clipboardIncludesPositions, so a report can show positions on screen and paste without them. Both apply to a scan as they do to Extract.

Use it from an AI agent

The same engine runs as an MCP server, so an agent can call it directly instead of deciding by eye whether two spellings are one address.

extract_ips(content, format?, filename?, kind?, class?, maxResults?)

It returns the findings the editor renders, refusals included, as data — capped at 500 by default with meta.truncated. It reads no files and makes no network requests. Published as ips-le-mcp on npm and as io.github.nolindnaidoo/ips-le in the MCP registry. It answers exactly as the Rust CLI's server does: one corpus runs against both, and a differential test feeds both thousands of generated documents in every format — broken JSON included, where both report the parser's own words and position — and compares every answer.

{
  "mcpServers": {
    "ips-le": {
      "command": "npx",
      "args": ["-y", "ips-le-mcp"]
    }
  }
}

Or install it once with npm install -g ips-le-mcp and point at ips-le-mcp. It needs no environment variables, no API key and no configuration of its own. To check it:

echo '{"jsonrpc":"2.0","id":1,"method":"tools/list"}' | npx -y ips-le-mcp

The CLI

The same extraction runs over a whole tree from a terminal or a CI step: a Rust CLI in crate/, sharing one corpus with the extension — crate/fixtures/ — so the two can never read an address differently. The same command line also ships on npm as ips-le, for a machine with Node and no Rust, and CI holds it to the crate byte for byte on three operating systems.

Install it from npm (ips-le) or from crates.io (ips-le). Both install the same ips-le command.

npm install -g ips-le   # or run it once: npx ips-le
cargo install ips-le

ips-le .                                   # every address in the tree; one JSON line per file on stdout when piped
ips-le --class private --class loopback .  # what should not be reachable
ips-le --kind cidr infra/                  # every block, with its arithmetic
ips-le --strict config/                    # exit 2 on any ambiguity
ips-le mcp                                 # extract_ips and ips_le_scan over MCP on stdio

Exit codes follow grep — 0 at least one address named, 1 none, 2 the question was malformed. A refusal does not move the exit code; --strict is how a pipeline turns one into a failure.

Commands

No command is bound to a key by default. Give any of them one under Keyboard Shortcuts in the editor.

Settings

Languages

Twelve languages besides English:

German · Spanish · French · Indonesian · Italian · Japanese · Korean · Portuguese (Brazil) · Russian · Ukrainian · Vietnamese · Chinese (Simplified)

Both halves are covered — the manifest (command titles, setting names and descriptions) and everything shown while the extension runs (notifications, the status bar and the report's headings). A refusal's detail is the engine's English, identical to the CLI's.

Privacy & security

• No network access. The extension never sends data anywhere: no DNS, no geolocation, no lookups of any kind. The telemetryEnabled setting only writes events to a local Output Channel you can inspect (IPs-LE).

• The MCP server holds the same line. It takes content as an argument and returns data: no filesystem access, no network calls, no telemetry.

• Error notifications redact home directories and credential-shaped fragments.

• One rating prompt, at most twice. On the 3rd successful use the extension asks once whether you would rate it, and once more on the 20th if you chose Later or dismissed it. Don't Ask Again ends it. Setting notificationsLevel to important or silent yourself turns it off. The counts are kept in VS Code's extension storage and nothing is sent anywhere; Rate opens the listing you installed from — the VS Code Marketplace or Open VSX — in your browser.

Documentation

Performance

Median of 7 runs after warmup, on Apple M5 Pro, 24 GB RAM, Node 24.3.0. Inputs are generated by scripts/benchmark.ts rather than checked in, so the sizes above are exactly what was measured. Reproduce with bun run benchmark.

These are machine-specific and are not asserted in CI — a benchmark that gates a build only tells you how busy the runner was.

Testing

242 test cases across 20 files, plus an integration suite that runs in a real VS Code extension host and an end-to-end test that installs the built .vsix into a clean profile.

Generated from a real run — coverage/coverage-summary.json and coverage/test-results.json — by scripts/coverage-readme.js, and bun run coverage:readme:check says whether it has drifted since. Reproduce with bun run test:coverage, and the case count is the one vitest prints.

More from the LE family

Sixteen single-purpose tools for the work in front of every model. Each ships a Rust CLI and an MCP server. One page: letools.dev

Get it out

• String-LE — Extract every string in a codebase, so a person can read them

• Numbers-LE — Extract every hardcoded number in a codebase, so a person can check them

• Units-LE — Extract every quantity with its unit, normalized, and refuse the ambiguous ones by name

• Dates-LE — Extract every date and timestamp, and the exact instant each one resolves to

• IDs-LE — Extract every UUID, ULID, NanoID, ObjectId and Snowflake, and decode the time inside

• IPs-LE — Extract every IP address, CIDR block and MAC, normalized and classified by scope

• URLs-LE — Extract every URL in a codebase, with its protocol and exact position

• Paths-LE — Extract every file path in a codebase, and say whether it still points at anything

• Colors-LE — Extract every color in a codebase, and say which ones are not in your palette

Check it

• Regex-LE — Find every regex in a codebase, and report which can be driven into catastrophic backtracking

• Versions-LE — Find where one dependency is constrained differently across a repository's manifests

• i18n-LE — Identify the i18n library a project uses, then audit its catalogs by that library's rules

• Scrape-LE — Check whether a page is scrapeable before the scraper is written, and say when it cannot tell

Guard it

• Secrets-LE — Find hardcoded credentials in a codebase, and never print one into the report

• EnvSync-LE — Compare the dotenv files in a tree, and say which keys are missing from which

• Unicode-LE — Find the Unicode that hides meaning — bidi controls, invisibles, homoglyphs, mixed scripts

Each stands on its own: no shared crate, no published core. Where two of them agree, it is because the same answer was right twice.

Contact — nolindnaidoo.com · GitHub · LinkedIn

Also by nolindnaidoo

Rust — pixelcoords and pixelactions are one loop: pixelcoords answers where, pixelactions acts there. Their own tools, their own voice — not part of the LE family.

• pixelcoords — Freeze your screen, mark regions, get pixel-exact coordinates and crops pixelcoords.dev · crates.io · docs.rs

• pixelactions — Consume human-verified coordinates, perform the interaction, confirm it landed pixelactions.dev · crates.io · docs.rs

License

MIT © nolindnaidoo