feat: add support for tcp, dot

pkg/resolvers/classic.go

@@ -7,6 +7,15 @@ import (
 	"github.com/miekg/dns"
 )
 
+const (
+	// DefaultUDPPort specifies the default port for a DNS server connecting over UDP
+	DefaultUDPPort = "53"
+	// DefaultTLSPort specifies the default port for a DNS server connecting over TCP over TLS
+	DefaultTLSPort = "853"
+	//DefaultResolvConfPath specifies path to default resolv config file on UNIX.
+	DefaultResolvConfPath = "/etc/resolv.conf"
+)
+
 // ClassicResolver represents the config options for setting up a Resolver.
 type ClassicResolver struct {
 	client  *dns.Client
@@ -18,24 +27,24 @@ type ClassicResolverOpts struct {
 	UseIPv4 bool
 	UseIPv6 bool
 	UseTCP  bool
+	UseTLS  bool
 }
 
-//DefaultResolvConfPath specifies path to default resolv config file on UNIX.
-const DefaultResolvConfPath = "/etc/resolv.conf"
-
 // NewClassicResolver accepts a list of nameservers and configures a DNS resolver.
 func NewClassicResolver(servers []string, opts ClassicResolverOpts) (Resolver, error) {
 	client := &dns.Client{}
 	var nameservers []string
 	for _, srv := range servers {
 		if i := net.ParseIP(srv); i != nil {
-			nameservers = append(nameservers, net.JoinHostPort(srv, "53"))
-		} else {
-			host, port, err := net.SplitHostPort(srv)
-			if err != nil {
-				return nil, err
+			// if no port specified in nameserver, append defaults.
+			if opts.UseTLS == true {
+				nameservers = append(nameservers, net.JoinHostPort(srv, DefaultTLSPort))
+			} else {
+				nameservers = append(nameservers, net.JoinHostPort(srv, DefaultUDPPort))
 			}
-			nameservers = append(nameservers, fmt.Sprintf("%s:%s", host, port))
+		} else {
+			// use the port user specified.
+			nameservers = append(nameservers, srv)
 		}
 	}
 	client.Net = "udp"
@@ -45,6 +54,12 @@ func NewClassicResolver(servers []string, opts ClassicResolverOpts) (Resolver, e
 	if opts.UseIPv6 {
 		client.Net = "udp6"
 	}
+	if opts.UseTCP {
+		client.Net = "tcp"
+	}
+	if opts.UseTLS {
+		client.Net = "tcp-tls"
+	}
 	return &ClassicResolver{
 		client:  client,
 		servers: nameservers,

pkg/resolvers/dot.go

@@ -1 +0,0 @@
-package resolvers