feat: recursive dnslink lookups (#1935)

Co-Authored-By: niinpatel <31539366+niinpatel@users.noreply.github.com>

README.md

@@ -639,6 +639,7 @@ The core API is grouped into several areas:
   - [`ipfs.stop([callback])`](https://github.com/ipfs/interface-ipfs-core/tree/master/SPEC/MISCELLANEOUS.md#stop)
   - `ipfs.isOnline()`
   - [`ipfs.resolve(name, [options], [callback])`](https://github.com/ipfs/interface-ipfs-core/tree/master/SPEC/MISCELLANEOUS.md#resolve)
+  - [`ipfs.dns(name, [options], [callback]`](https://github.com/ipfs/interface-js-ipfs-core/blob/master/SPEC/MISCELLANEOUS.md#dns)
 
 - [repo](https://github.com/ipfs/interface-ipfs-core/tree/master/SPEC/REPO.md)
   - `ipfs.repo.init`

src/cli/commands/dns.js

@@ -7,15 +7,21 @@ module.exports = {
   describe: 'Resolve DNS links',
 
   builder: {
+    recursive: {
+      type: 'boolean',
+      default: true,
+      alias: 'r',
+      desc: 'Resolve until the result is not a DNS link'
+    },
     format: {
       type: 'string'
     }
   },
 
-  handler ({ getIpfs, domain, resolve }) {
+  handler ({ getIpfs, domain, resolve, recursive, format }) {
     resolve((async () => {
       const ipfs = await getIpfs()
-      const path = await ipfs.dns(domain)
+      const path = await ipfs.dns(domain, { recursive, format })
       print(path)
     })())
   }

src/core/runtime/dns-nodejs.js

@@ -2,10 +2,29 @@
 
 const dns = require('dns')
 const _ = require('lodash')
+const isIPFS = require('is-ipfs')
 const errcode = require('err-code')
 
+const MAX_RECURSIVE_DEPTH = 32
+
 module.exports = (domain, opts, callback) => {
-  resolveDnslink(domain)
+  // recursive is true by default, it's set to false only if explicitly passed as argument in opts
+  const recursive = opts.recursive == null ? true : Boolean(opts.recursive)
+
+  let depth
+  if (recursive) {
+    depth = MAX_RECURSIVE_DEPTH
+  }
+
+  return recursiveResolveDnslink(domain, depth, callback)
+}
+
+function recursiveResolveDnslink (domain, depth, callback) {
+  if (depth === 0) {
+    return callback(errcode(`recursion limit exceeded`, 'ERR_DNSLINK_RECURSION_LIMIT'))
+  }
+
+  return resolveDnslink(domain)
     .catch(err => {
       // If the code is not ENOTFOUND or ERR_DNSLINK_NOT_FOUND or ENODATA then throw the error
       if (err.code !== 'ENOTFOUND' && err.code !== 'ERR_DNSLINK_NOT_FOUND' && err.code !== 'ENODATA') throw err
@@ -22,7 +41,14 @@ module.exports = (domain, opts, callback) => {
       return resolveDnslink(_dnslinkDomain)
     })
     .then(dnslinkRecord => {
-      callback(null, dnslinkRecord.replace('dnslink=', ''))
+      const result = dnslinkRecord.replace('dnslink=', '')
+      const domainOrCID = result.split('/')[2]
+      const isIPFSCID = isIPFS.cid(domainOrCID)
+
+      if (isIPFSCID || !depth) {
+        return callback(null, result)
+      }
+      return recursiveResolveDnslink(domainOrCID, depth - 1, callback)
     })
     .catch(callback)
 }

src/http/api/resources/dns.js

@@ -3,11 +3,19 @@
 const Boom = require('boom')
 
 module.exports = async (request, h) => {
-  if (!request.query.arg) {
+  const domain = request.query.arg
+
+  if (!domain) {
     throw Boom.badRequest("Argument 'domain' is required")
   }
 
-  const path = await request.server.app.ipfs.dns(request.query.arg)
+  const format = request.query.format
+
+  // query parameters are passed as strings and need to be parsed to expected type
+  let recursive = request.query.recursive || request.query.r
+  recursive = !(recursive && recursive === 'false')
+
+  const path = await request.server.app.ipfs.dns(domain, { recursive, format })
   return h.response({
     Path: path
   })

test/cli/dns.js

@@ -3,6 +3,7 @@
 
 const expect = require('chai').expect
 const runOnAndOff = require('../utils/on-and-off')
+const isIPFS = require('is-ipfs')
 
 describe('dns', () => runOnAndOff((thing) => {
   let ipfs
@@ -12,19 +13,33 @@ describe('dns', () => runOnAndOff((thing) => {
     ipfs = thing.ipfs
   })
 
-  it('resolve ipfs.io dns', function () {
+  it('recursively resolve ipfs.io dns', function () {
     this.timeout(60 * 1000)
 
     return ipfs('dns ipfs.io').then((res) => {
-      expect(res.substr(0, 6)).to.eql('/ipns/')
+      expect(res.substr(0, 6)).to.eql('/ipfs/')
+      const resultingDomainOrCid = res.split('/')[2].trim()
+      expect(isIPFS.cid(resultingDomainOrCid)).to.eql(true)
     })
   })
 
-  it('resolve _dnslink.ipfs.io dns', function () {
+  it('recursively resolve _dnslink.ipfs.io dns', function () {
     this.timeout(60 * 1000)
 
     return ipfs('dns _dnslink.ipfs.io').then((res) => {
+      expect(res.substr(0, 6)).to.eql('/ipfs/')
+      const resultingDomainOrCid = res.split('/')[2].trim()
+      expect(isIPFS.cid(resultingDomainOrCid)).to.eql(true)
+    })
+  })
+
+  it('non-recursive resolve ipfs.io', function () {
+    this.timeout(60 * 1000)
+
+    return ipfs('dns --recursive false ipfs.io').then((res) => {
       expect(res.substr(0, 6)).to.eql('/ipns/')
+      const resultingDomainOrCid = res.split('/')[2].trim()
+      expect(isIPFS.cid(resultingDomainOrCid)).to.eql(false)
     })
   })