[dns] try empty search scope

because in some configurations
it is possible to have "naked" domain
like in docker when linking containers

so it is necessary to query for "redis."
not for "redis"

Author: mikz

apicast/src/resty/resolver.lua

@@ -31,7 +31,7 @@ local default_resolver_port = 53
 local _M = {
   _VERSION = '0.1',
   _nameservers = {},
-  search = {}
+  search = { '' }
 }
 
 local mt = { __index = _M }
@@ -67,7 +67,7 @@ function _M.parse_nameservers(path)
 
   ngx.log(ngx.DEBUG, '/etc/resolv.conf:\n', resolv_conf)
 
-  local search = {}
+  local search = { '' }
   local nameservers = { search = search }
   local resolver = getenv('RESOLVER')
   local domains = match(resolv_conf, 'search%s+([^\n]+)')
@@ -185,14 +185,6 @@ local function is_ip(address)
   end
 end
 
-local function has_tld(qname)
-  return match(qname, '%.')
-end
-
-local function have_addresses(answers)
-  return answers and next(answers.addresses or {}) and #answers > 0 and not answers.errcode
-end
-
 local function convert_answers(answers, port)
   local servers = {}
 
@@ -216,18 +208,13 @@ local function lookup(dns, qname, search, options)
     ngx.log(ngx.DEBUG, 'host is ip address: ', qname)
     answers = { new_answer(qname) }
   else
-    answers, err = dns:query(qname, options)
+    for i=1, #search do
+      local query = qname .. '.' .. search[i]
+      ngx.log(ngx.DEBUG, 'resolver query: ', qname, ' search: ', search[i], ' query: ', query)
+      answers, err = dns:query(query, options)
 
-    if not has_tld(qname) and not have_addresses(answers) then
-      for i=1, #search do
-
-        local query = qname .. '.' .. search[i]
-        ngx.log(ngx.DEBUG, 'resolver query: ', qname, ' search: ', search[i], ' query: ', query)
-        answers, err = dns:query(query, options)
-
-        if answers and not answers.errcode and #answers > 0 then
-          break
-        end
+      if answers and not answers.errcode and #answers > 0 then
+        break
       end
     end
   end
@@ -249,8 +236,7 @@ function _M.get_servers(self, qname, opts)
   end
 
   local cache = self.cache
-  local search = self.search or {}
-
+  local search = self.search or _M.search
 
   -- TODO: pass proper options to dns resolver (like SRV query type)
 

docker-compose.yml

@@ -21,12 +21,16 @@ services:
     environment:
       TEST_NGINX_BINARY: openresty
       TEST_NGINX_REDIS_HOST: redis
+    dns_search:
+      - example.com
   test:
     image: ${IMAGE_NAME}
     depends_on:
       - gateway
     entrypoint: ""
     dns: 127.0.0.1
+    dns_search:
+      - example.com
   prove:
     image: ${IMAGE_NAME}
     user: root
@@ -35,6 +39,8 @@ services:
       TEST_NGINX_APICAST_PATH: /opt/app
       TEST_NGINX_REDIS_HOST: redis
     command: prove
+    dns_search:
+      - example.com
     depends_on:
       - redis
     volumes:

spec/resty/resolver_spec.lua

@@ -48,7 +48,7 @@ describe('resty.resolver', function()
 
       assert.falsy(err)
       assert.equal(1, #servers)
-      assert.spy(dns.query).was.called_with(dns, '3scale.net', { qtype = 'A' })
+      assert.spy(dns.query).was.called_with(dns, '3scale.net.', { qtype = 'A' })
     end)
 
     it('skips answers with no address', function()
@@ -63,7 +63,7 @@ describe('resty.resolver', function()
 
       assert.falsy(err)
       assert.equal(1, #servers)
-      assert.spy(dns.query).was.called_with(dns, 'www.3scale.net', {})
+      assert.spy(dns.query).was.called_with(dns, 'www.3scale.net.', {})
     end)
 
     it('searches domains', function()
@@ -77,13 +77,13 @@ describe('resty.resolver', function()
         end
       end)
       resolver.options = { qtype = 'A' }
-      resolver.search = { 'example.com', 'net' }
+      resolver.search = { '', 'example.com', 'net' }
 
       local servers, err = resolver:get_servers('3scale')
 
       assert.falsy(err)
       assert.equal(1, #servers)
-      assert.spy(dns.query).was.called_with(dns, '3scale', resolver.options)
+      assert.spy(dns.query).was.called_with(dns, '3scale.', resolver.options)
       assert.spy(dns.query).was.called_with(dns, '3scale.example.com', resolver.options)
       assert.spy(dns.query).was.called_with(dns, '3scale.net', resolver.options)
     end)
@@ -139,8 +139,8 @@ describe('resty.resolver', function()
     it('returns search domains', function()
       local search = resty_resolver.parse_nameservers(tmpname).search
 
-      assert.equal(2, #search)
-      assert.same({ 'localdomain.example.com', 'local' },  search)
+      assert.equal(3, #search)
+      assert.same({ '', 'localdomain.example.com', 'local' },  search)
     end)
 
   end)