feat: Multiple resolvers continued

pkg/resolvers/doh.go

@@ -2,7 +2,6 @@ package resolvers
 
 import (
 	"bytes"
-	"errors"
 	"fmt"
 	"io/ioutil"
 	"net/http"
@@ -14,34 +13,30 @@ import (
 
 // DOHResolver represents the config options for setting up a DOH based resolver.
 type DOHResolver struct {
-	client  *http.Client
-	servers []string
+	client *http.Client
+	server string
 }
 
 type DOHResolverOpts struct {
 	Timeout time.Duration
 }
 
-// NewDOHResolver accepts a list of nameservers and configures a DOH based resolver.
-func NewDOHResolver(servers []string, opts DOHResolverOpts) (Resolver, error) {
-	if len(servers) == 0 {
-		return nil, errors.New(`no DOH server specified`)
+// NewDOHResolver accepts a nameserver address and configures a DOH based resolver.
+func NewDOHResolver(server string, opts DOHResolverOpts) (Resolver, error) {
+	// do basic validation
+	u, err := url.ParseRequestURI(server)
+	if err != nil {
+		return nil, fmt.Errorf("%s is not a valid HTTPS nameserver", server)
 	}
-	for _, s := range servers {
-		u, err := url.ParseRequestURI(s)
-		if err != nil {
-			return nil, fmt.Errorf("%s is not a valid HTTPS nameserver", s)
-		}
-		if u.Scheme != "https" {
-			return nil, fmt.Errorf("missing https in %s", s)
-		}
+	if u.Scheme != "https" {
+		return nil, fmt.Errorf("missing https in %s", server)
 	}
 	httpClient := &http.Client{
 		Timeout: opts.Timeout,
 	}
 	return &DOHResolver{
-		client:  httpClient,
-		servers: servers,
+		client: httpClient,
+		server: server,
 	}, nil
 }
 
@@ -57,34 +52,32 @@ func (d *DOHResolver) Lookup(questions []dns.Question) ([]Response, error) {
 		if err != nil {
 			return nil, err
 		}
-		for _, srv := range d.servers {
-			now := time.Now()
-			// Make an HTTP POST request to the DNS server with the DNS message as wire format bytes in the body.
-			resp, err := d.client.Post(srv, "application/dns-message", bytes.NewBuffer(b))
-			if err != nil {
-				return nil, err
-			}
-			if resp.StatusCode != http.StatusOK {
-				return nil, fmt.Errorf("error from nameserver %s", resp.Status)
-			}
-			rtt := time.Since(now)
-			// extract the binary response in DNS Message.
-			body, err := ioutil.ReadAll(resp.Body)
-			if err != nil {
-				return nil, err
-			}
-
-			err = msg.Unpack(body)
-			if err != nil {
-				return nil, err
-			}
-			rsp := Response{
-				Message:    msg,
-				RTT:        rtt,
-				Nameserver: srv,
-			}
-			responses = append(responses, rsp)
+		now := time.Now()
+		// Make an HTTP POST request to the DNS server with the DNS message as wire format bytes in the body.
+		resp, err := d.client.Post(d.server, "application/dns-message", bytes.NewBuffer(b))
+		if err != nil {
+			return nil, err
 		}
+		if resp.StatusCode != http.StatusOK {
+			return nil, fmt.Errorf("error from nameserver %s", resp.Status)
+		}
+		rtt := time.Since(now)
+		// extract the binary response in DNS Message.
+		body, err := ioutil.ReadAll(resp.Body)
+		if err != nil {
+			return nil, err
+		}
+
+		err = msg.Unpack(body)
+		if err != nil {
+			return nil, err
+		}
+		rsp := Response{
+			Message:    msg,
+			RTT:        rtt,
+			Nameserver: d.server,
+		}
+		responses = append(responses, rsp)
 	}
 	return responses, nil
 }