make DNS resolver pluggable, use new madns.BasicResolver interface

Author: vyzo

dns.go

@@ -4,19 +4,19 @@ import (
 	"context"
 	"errors"
 	"fmt"
-	"net"
 	"strings"
 
 	path "github.com/ipfs/go-path"
 	opts "github.com/ipfs/interface-go-ipfs-core/options/namesys"
 	isd "github.com/jbenet/go-is-domain"
+	madns "github.com/multiformats/go-multiaddr-dns"
 )
 
 const ethTLD = "eth"
 const linkTLD = "domains"
 
 // LookupTXTFunc is a generic type for a function that lookups TXT record values.
-type LookupTXTFunc func(name string) (txt []string, err error)
+type LookupTXTFunc func(ctx context.Context, name string) (txt []string, err error)
 
 // DNSResolver implements a Resolver on DNS domains
 type DNSResolver struct {
@@ -26,8 +26,8 @@ type DNSResolver struct {
 }
 
 // NewDNSResolver constructs a name resolver using DNS TXT records.
-func NewDNSResolver() *DNSResolver {
-	return &DNSResolver{lookupTXT: net.LookupTXT}
+func NewDNSResolver(rslv madns.BasicResolver) *DNSResolver {
+	return &DNSResolver{lookupTXT: rslv.LookupTXT}
 }
 
 // Resolve implements Resolver.
@@ -74,10 +74,10 @@ func (r *DNSResolver) resolveOnceAsync(ctx context.Context, name string, options
 	}
 
 	rootChan := make(chan lookupRes, 1)
-	go workDomain(r, fqdn, rootChan)
+	go workDomain(ctx, r, fqdn, rootChan)
 
 	subChan := make(chan lookupRes, 1)
-	go workDomain(r, "_dnslink."+fqdn, subChan)
+	go workDomain(ctx, r, "_dnslink."+fqdn, subChan)
 
 	appendPath := func(p path.Path) (path.Path, error) {
 		if len(segments) > 1 {
@@ -121,10 +121,10 @@ func (r *DNSResolver) resolveOnceAsync(ctx context.Context, name string, options
 	return out
 }
 
-func workDomain(r *DNSResolver, name string, res chan lookupRes) {
+func workDomain(ctx context.Context, r *DNSResolver, name string, res chan lookupRes) {
 	defer close(res)
 
-	txt, err := r.lookupTXT(name)
+	txt, err := r.lookupTXT(ctx, name)
 	if err != nil {
 		// Error is != nil
 		res <- lookupRes{"", err}

dns_test.go

@@ -1,6 +1,7 @@
 package namesys
 
 import (
+	"context"
 	"fmt"
 	"testing"
 
@@ -11,7 +12,7 @@ type mockDNS struct {
 	entries map[string][]string
 }
 
-func (m *mockDNS) lookupTXT(name string) (txt []string, err error) {
+func (m *mockDNS) lookupTXT(ctx context.Context, name string) (txt []string, err error) {
 	txt, ok := m.entries[name]
 	if !ok {
 		return nil, fmt.Errorf("no TXT entry for %s", name)

go.mod

@@ -22,6 +22,7 @@ require (
 	github.com/libp2p/go-libp2p-record v0.1.3
 	github.com/libp2p/go-libp2p-testing v0.4.0
 	github.com/multiformats/go-multiaddr v0.3.1
+	github.com/multiformats/go-multiaddr-dns v0.3.0
 	github.com/multiformats/go-multihash v0.0.14
 	github.com/whyrusleeping/base32 v0.0.0-20170828182744-c30ac30633cc
 )