Use alternative DNS resolver for initial setup

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## main
 
+FEATURES:
+
+- The plugin now supports the setting of `client_dns_resolver` to override the DNS resolver used for DNSimple API endpoints. This is useful when running CoreDNS as the DNS resolver for the host. Format is `ADDRESS:PORT`. (#25)
+
 ## 1.0.0-rc.1
 
 FEATURES:

README.md

@@ -16,6 +16,7 @@ dnsimple ZONE[:REGION ZONE ...] {
     account_id            DNSIMPLE_ACCOUNT_ID
     base_url              STRING
     custom_dns_resolver   ADDRESS
+    client_dns_resolver   ADDRESS
     fallthrough           [ZONES...]
     identifier            STRING
     max_retries           MAX_RETRIES
@@ -28,8 +29,9 @@ dnsimple ZONE[:REGION ZONE ...] {
 - `account_id`: The account ID containing the configured zones. If it's not provided, the environment variable `DNSIMPLE_ACCOUNT_ID` will be used.
 - `base_url`: The base url for interacting with the DNSimple API. If no value is provided the production environment is used. See [DNSimple Sandbox API](https://support.dnsimple.com/articles/sandbox/) for sandbox environment testing.
 - `custom_dns_resolver`: Optionally override the DNS resolver to use for resolving ALIAS records. By default, the system resolver is used. See the [ALIAS records](#alias-records) section for more details.
+- `client_dns_resolver`: Optionally provide a DNS resolver to use for resolving DNSimple API endpoints. By default, the system resolver is used. This is useful when running CoreDNS as the DNS resolver for the host. Format is `ADDRESS:PORT`.
 - `fallthrough`: If a query matches the zone(s) but no response message can be generated, the query will be passed to the next plugin in the chain. To restrict passing only for specific zones, list them here; all other zone queries will **not** "fall through".
-- `identifer`: Optionally set the CoreDNS instance identifer string. This is used to report the sync status of the zone to the DNSimple application. If no identifier is provided, "default" is used.
+- `identifier`: Optionally set the CoreDNS instance identifier string. This is used to report the sync status of the zone to the DNSimple application. If no identifier is provided, "default" is used.
 - `max_retries`: Maximum retry attempts to fetch zones using the DNSimple API. Must be greater than zero. Defaults to 3.
 - `refresh`: The interval to refresh zones at. It must be a valid duration, and defaults to `1m`.
 

dnsimple.go

@@ -83,17 +83,23 @@ func (g *nameGraph) insertName(name string, value string) {
 
 type DNSimpleApiCaller func(path string, body []byte) error
 
-func createDNSimpleApiCaller(baseUrl string, accessToken string, userAgent string) DNSimpleApiCaller {
+func createDNSimpleAPICaller(options Options, baseURL string, accessToken string, userAgent string) DNSimpleApiCaller {
 	return func(path string, body []byte) error {
-		url := fmt.Sprintf("%s%s", baseUrl, path)
+		url := fmt.Sprintf("%s%s", baseURL, path)
 		req, err := http.NewRequest("POST", url, bytes.NewBuffer(body))
 		if err != nil {
 			return err
 		}
+
+		client := http.Client{}
+		if options.clientDNSResolver != "" {
+			client.Transport.(*http.Transport).DialContext = options.customHTTPDialer
+		}
+
 		req.Header.Set("authorization", fmt.Sprintf("Bearer %s", accessToken))
 		req.Header.Set("content-type", "application/json")
 		req.Header.Set("user-agent", userAgent)
-		res, err := http.DefaultClient.Do(req)
+		res, err := client.Do(req)
 		if err != nil {
 			return err
 		}
@@ -160,14 +166,14 @@ func New(ctx context.Context, client dnsimpleService, keys map[string][]string,
 		}
 	}
 	dnsResolver := net.DefaultResolver
-	if opts.customDnsResolver != "" {
+	if opts.customDNSResolver != "" {
 		dnsResolver = &net.Resolver{
 			PreferGo: true,
 			Dial: func(ctx context.Context, network, address string) (net.Conn, error) {
 				d := net.Dialer{
 					Timeout: time.Second * 10,
 				}
-				return d.DialContext(ctx, network, opts.customDnsResolver)
+				return d.DialContext(ctx, network, opts.customDNSResolver)
 			},
 		}
 	}

go.mod

@@ -6,8 +6,9 @@ require (
 	github.com/coredns/caddy v1.1.1
 	github.com/coredns/coredns v1.11.1
 	github.com/dnsimple/dnsimple-go v1.5.1
-	github.com/miekg/dns v1.1.57
+	github.com/miekg/dns v1.1.58
 	github.com/stretchr/testify v1.8.4
+	golang.org/x/oauth2 v0.14.0
 )
 
 require (
@@ -25,7 +26,6 @@ require (
 	github.com/kr/text v0.2.0 // indirect
 	github.com/matttproud/golang_protobuf_extensions v1.0.4 // indirect
 	github.com/onsi/ginkgo/v2 v2.11.0 // indirect
-	github.com/onsi/gomega v1.27.10 // indirect
 	github.com/opentracing/opentracing-go v1.2.0 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/prometheus/client_golang v1.16.0 // indirect
@@ -34,20 +34,18 @@ require (
 	github.com/prometheus/procfs v0.10.1 // indirect
 	github.com/quic-go/qtls-go1-20 v0.3.1 // indirect
 	github.com/quic-go/quic-go v0.37.4 // indirect
-	github.com/rogpeppe/go-internal v1.11.0 // indirect
 	github.com/shopspring/decimal v1.3.1 // indirect
 	github.com/stretchr/objx v0.5.0 // indirect
-	golang.org/x/crypto v0.17.0 // indirect
+	golang.org/x/crypto v0.18.0 // indirect
 	golang.org/x/exp v0.0.0-20221205204356-47842c84f3db // indirect
-	golang.org/x/mod v0.12.0 // indirect
-	golang.org/x/net v0.18.0 // indirect
-	golang.org/x/oauth2 v0.14.0 // indirect
-	golang.org/x/sys v0.15.0 // indirect
+	golang.org/x/mod v0.14.0 // indirect
+	golang.org/x/net v0.20.0 // indirect
+	golang.org/x/sys v0.16.0 // indirect
 	golang.org/x/text v0.14.0 // indirect
-	golang.org/x/tools v0.13.0 // indirect
+	golang.org/x/tools v0.17.0 // indirect
 	google.golang.org/appengine v1.6.7 // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20230807174057-1744710a1577 // indirect
-	google.golang.org/grpc v1.57.1 // indirect
+	google.golang.org/grpc v1.57.0 // indirect
 	google.golang.org/protobuf v1.31.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

setup.go

@@ -4,6 +4,8 @@ import (
 	"context"
 	"fmt"
 	"math/rand"
+	"net"
+	"net/http"
 	"os"
 	"strconv"
 	"strings"
@@ -15,6 +17,7 @@ import (
 	"github.com/coredns/coredns/plugin/pkg/fall"
 	clog "github.com/coredns/coredns/plugin/pkg/log"
 	"github.com/dnsimple/dnsimple-go/dnsimple"
+	"golang.org/x/oauth2"
 )
 
 var log = clog.NewWithPlugin("dnsimple")
@@ -27,15 +30,22 @@ type Options struct {
 	accountId         string
 	accessToken       string
 	apiCaller         DNSimpleApiCaller
-	customDnsResolver string
+	customDNSResolver string
+	clientDNSResolver string
 	identifier        string
 	maxRetries        int
 	refresh           time.Duration
+	customHTTPDialer  func(ctx context.Context, network, address string) (net.Conn, error)
 }
 
 // exposed for testing
-var newDnsimpleService = func(ctx context.Context, accessToken string, baseUrl string) (dnsimpleService, error) {
-	client := dnsimple.NewClient(dnsimple.StaticTokenHTTPClient(ctx, accessToken))
+var newDnsimpleService = func(ctx context.Context, options Options, accessToken string, baseUrl string) (dnsimpleService, error) {
+	httpClient := dnsimple.StaticTokenHTTPClient(ctx, accessToken)
+
+	if options.clientDNSResolver != "" {
+		httpClient.Transport.(*oauth2.Transport).Base.(*http.Transport).DialContext = options.customHTTPDialer
+	}
+	client := dnsimple.NewClient(httpClient)
 	client.BaseURL = baseUrl
 	client.SetUserAgent(defaultUserAgent + "/" + PluginVersion)
 	return dnsimpleClient{client}, nil
@@ -75,7 +85,6 @@ func setup(c *caddy.Controller) error {
 			keys[zone] = append(keys[zone], region)
 		}
 
-		// TODO: set to warn when no zones are defined
 		if len(keys) == 0 {
 			return plugin.Error("dnsimple", c.Errf("no zone(s) specified"))
 		}
@@ -104,7 +113,12 @@ func setup(c *caddy.Controller) error {
 				if !c.NextArg() {
 					return plugin.Error("dnsimple", c.ArgErr())
 				}
-				opts.customDnsResolver = c.Val()
+				opts.customDNSResolver = c.Val()
+			case "client_dns_resolver":
+				if !c.NextArg() {
+					return plugin.Error("dnsimple", c.ArgErr())
+				}
+				opts.clientDNSResolver = c.Val()
 			case "fallthrough":
 				fall.SetZonesFromArgs(c.RemainingArgs())
 			case "identifier":
@@ -168,10 +182,27 @@ func setup(c *caddy.Controller) error {
 			opts.refresh = time.Duration(1) * time.Minute
 		}
 
-		opts.apiCaller = createDNSimpleApiCaller(baseUrl, accessToken, defaultUserAgent+"/"+PluginVersion)
+		if opts.clientDNSResolver == "" {
+			dialer := &net.Dialer{
+				Resolver: &net.Resolver{
+					PreferGo: true,
+					Dial: func(ctx context.Context, network, address string) (net.Conn, error) {
+						d := net.Dialer{
+							Timeout: time.Second * 5,
+						}
+						return d.DialContext(ctx, network, opts.clientDNSResolver)
+					},
+				},
+			}
+			opts.customHTTPDialer = func(ctx context.Context, network, address string) (net.Conn, error) {
+				return dialer.DialContext(ctx, network, address)
+			}
+		}
+
+		opts.apiCaller = createDNSimpleAPICaller(opts, baseUrl, accessToken, defaultUserAgent+"/"+PluginVersion)
 
 		ctx, cancel := context.WithCancel(context.Background())
-		client, err := newDnsimpleService(ctx, accessToken, baseUrl)
+		client, err := newDnsimpleService(ctx, opts, accessToken, baseUrl)
 		if err != nil {
 			cancel()
 			return err

setup_test.go

@@ -10,7 +10,7 @@ import (
 
 func TestSetupDNSimple(t *testing.T) {
 	fakeClient := new(fakeDNSimpleClient)
-	newDnsimpleService = func(ctx context.Context, accessToken, baseUrl string) (dnsimpleService, error) {
+	newDnsimpleService = func(ctx context.Context, options Options, accessToken, baseUrl string) (dnsimpleService, error) {
 		return fakeClient, nil
 	}