Lua /etc/resolv.conf parser and some refactoring

rootfs/etc/nginx/lua/test/util/dns_test.lua

@@ -1,41 +1,51 @@
+local conf = [===[
+nameserver 1.2.3.4
+nameserver 4.5.6.7
+search ingress-nginx.svc.cluster.local svc.cluster.local cluster.local
+options ndots:5
+]===]
+
+helpers.with_resolv_conf(conf, function()
+  require("util.resolv_conf")
+end)
+
 describe("resolve", function()
   local dns = require("util.dns")
-  local dns_helper = require("test/dns_helper")
 
   it("sets correct nameservers", function()
-    dns_helper.mock_new(function(self, options)
+    helpers.mock_resty_dns_new(function(self, options)
       assert.are.same({ nameservers = { "1.2.3.4", "4.5.6.7" }, retrans = 5, timeout = 2000 }, options)
       return nil, ""
-    end, { "1.2.3.4", "4.5.6.7" })
+    end)
     dns.resolve("example.com")
   end)
 
   it("returns host when an error happens", function()
     local s_ngx_log = spy.on(ngx, "log")
 
-    dns_helper.mock_new(function(...) return nil, "an error" end)
+    helpers.mock_resty_dns_new(function(...) return nil, "an error" end)
     assert.are.same({ "example.com" }, dns.resolve("example.com"))
     assert.spy(s_ngx_log).was_called_with(ngx.ERR, "failed to instantiate the resolver: an error")
 
-    dns_helper.mock_dns_query(nil, "oops!")
+    helpers.mock_resty_dns_query(nil, "oops!")
     assert.are.same({ "example.com" }, dns.resolve("example.com"))    
     assert.spy(s_ngx_log).was_called_with(ngx.ERR, "failed to query the DNS server:\noops!\noops!")
 
-    dns_helper.mock_dns_query({ errcode = 1, errstr = "format error" })
+    helpers.mock_resty_dns_query({ errcode = 1, errstr = "format error" })
     assert.are.same({ "example.com" }, dns.resolve("example.com"))
     assert.spy(s_ngx_log).was_called_with(ngx.ERR, "failed to query the DNS server:\nserver returned error code: 1: format error\nserver returned error code: 1: format error")
 
-    dns_helper.mock_dns_query({})
+    helpers.mock_resty_dns_query({})
     assert.are.same({ "example.com" }, dns.resolve("example.com"))
     assert.spy(s_ngx_log).was_called_with(ngx.ERR, "failed to query the DNS server:\nno record resolved\nno record resolved")
 
-    dns_helper.mock_dns_query({ { name = "example.com", cname = "sub.example.com", ttl = 60 } })
+    helpers.mock_resty_dns_query({ { name = "example.com", cname = "sub.example.com", ttl = 60 } })
     assert.are.same({ "example.com" }, dns.resolve("example.com"))
     assert.spy(s_ngx_log).was_called_with(ngx.ERR, "failed to query the DNS server:\nno record resolved\nno record resolved")
   end)
 
   it("resolves all A records of given host, caches them with minimal ttl and returns from cache next time", function()
-    dns_helper.mock_dns_query({
+    helpers.mock_resty_dns_query({
       {
         name = "example.com",
         address = "192.168.1.1",
@@ -66,7 +76,7 @@ describe("resolve", function()
 
     assert.are.same({ "192.168.1.1", "1.2.3.4" }, dns.resolve("example.com"))
 
-    dns_helper.mock_new(function(...)
+    helpers.mock_resty_dns_new(function(...)
       error("expected to short-circuit and return response from cache")
     end)
     assert.are.same({ "192.168.1.1", "1.2.3.4" }, dns.resolve("example.com"))

rootfs/etc/nginx/lua/test/util/resolv_conf_test.lua

@@ -0,0 +1,64 @@
+local original_io_open = io.open
+
+describe("resolv_conf", function()
+  after_each(function()
+    package.loaded["util.resolv_conf"] = nil
+    io.open = original_io_open
+  end)
+
+  it("errors when file can not be opened", function()
+    io.open = function(...)
+      return nil, "file does not exist"
+    end
+
+    assert.has_error(function() require("util.resolv_conf") end, "could not open /etc/resolv.conf: file does not exist")
+  end)
+
+  it("opens '/etc/resolv.conf' with mode 'r'", function()
+    io.open = function(path, mode)
+      assert.are.same("/etc/resolv.conf", path)
+      assert.are.same("r", mode)
+
+      return original_io_open(path, mode)
+    end
+
+    assert.has_no.errors(function() require("util.resolv_conf") end)
+  end)
+
+  it("correctly parses resolv.conf", function()
+    local conf = [===[
+# This is a comment
+nameserver 10.96.0.10
+nameserver 10.96.0.99
+search ingress-nginx.svc.cluster.local svc.cluster.local cluster.local
+options ndots:5
+    ]===]
+
+    helpers.with_resolv_conf(conf, function()
+      local resolv_conf = require("util.resolv_conf")
+      assert.are.same({
+        nameservers = { "10.96.0.10", "10.96.0.99" },
+        search = { "ingress-nginx.svc.cluster.local", "svc.cluster.local", "cluster.local" },
+        ndots = 5,
+      }, resolv_conf)
+    end)
+  end)
+
+  it("ignores options that it does not understand", function()
+    local conf = [===[
+nameserver 10.96.0.10
+search example.com
+options debug
+options ndots:3
+    ]===]
+
+    helpers.with_resolv_conf(conf, function()
+      local resolv_conf = require("util.resolv_conf")
+      assert.are.same({
+        nameservers = { "10.96.0.10" },
+        search = { "example.com" },
+        ndots = 3,
+      }, resolv_conf)
+    end)
+  end)
+end)