feat: Add support for multiple resolvers

pkg/resolvers/classic.go

@@ -1,94 +0,0 @@
-package resolvers
-
-import (
-	"net"
-
-	"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
-	servers []string
-}
-
-// ClassicResolverOpts holds options for setting up a Classic resolver.
-type ClassicResolverOpts struct {
-	UseIPv4 bool
-	UseIPv6 bool
-	UseTCP  bool
-	UseTLS  bool
-}
-
-// 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 {
-			// 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))
-			}
-		} else {
-			// use the port user specified.
-			nameservers = append(nameservers, srv)
-		}
-	}
-
-	client.Net = "udp"
-	if opts.UseIPv4 {
-		client.Net = "udp4"
-	}
-	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,
-	}, nil
-}
-
-// Lookup prepare a list of DNS messages to be sent to the server.
-// It's possible to send multiple question in one message
-// but some nameservers are not able to
-func (c *ClassicResolver) Lookup(questions []dns.Question) ([]Response, error) {
-	var (
-		messages  = prepareMessages(questions)
-		responses []Response
-	)
-
-	for _, msg := range messages {
-		for _, srv := range c.servers {
-			in, rtt, err := c.client.Exchange(&msg, srv)
-			if err != nil {
-				return nil, err
-			}
-			msg.Answer = in.Answer
-			rsp := Response{
-				Message:    msg,
-				RTT:        rtt,
-				Nameserver: srv,
-			}
-			responses = append(responses, rsp)
-		}
-	}
-	return responses, nil
-}