feat: add strategy flag

Ref https://github.com/mr-karan/doggo/issues/35

TODO.md

@@ -62,5 +62,8 @@
 - [ ] Add tests for CLI Output.
 - [ ] Homebrew - Goreleaser
 - [ ] Add support for `dig +trace` like functionality.
+- [ ] Add `dig +x` short output
+- [x] Add `--strategy` for picking nameservers.
+- [ ] Explore `dig.rc` kinda file
 - [x] Separate Authority/Answer in JSON output.
 - [x] Error on NXDomain (Related upstream [bug](https://github.com/miekg/dns/issues/1198))

^

@@ -0,0 +1 @@
+nameserver 127.0.w0.1

cmd/doggo/cli.go

@@ -45,6 +45,7 @@ func main() {
 	f.Int("ndots", -1, "Specify the ndots parameter. Default value is taken from resolv.conf and fallbacks to 1 if ndots statement is missing in resolv.conf")
 	f.BoolP("ipv4", "4", false, "Use IPv4 only")
 	f.BoolP("ipv6", "6", false, "Use IPv6 only")
+	f.String("strategy", "all", "Strategy to query nameservers in resolv.conf file (`all`, `random`, `first`)")
 
 	// Output Options
 	f.BoolP("json", "J", false, "Set the output format as JSON")
@@ -126,6 +127,7 @@ func main() {
 		Ndots:       app.ResolverOpts.Ndots,
 		Timeout:     app.QueryFlags.Timeout * time.Second,
 		Logger:      app.Logger,
+		Strategy:    app.QueryFlags.Strategy,
 	})
 	if err != nil {
 		app.Logger.WithError(err).Error("error loading resolver")

cmd/doggo/help.go

@@ -47,6 +47,7 @@ var appHelpTextTemplate = `{{ "NAME" | color "" "heading" }}:
   {{"-x, --reverse" | color "yellow" ""}}               Performs a DNS Lookup for an IPv4 or IPv6 address. Sets the query type and class to PTR and IN respectively.
 
 {{ "Resolver Options" | color "" "heading" }}:
+  {{"--strategy=STRATEGY" | color "yellow" ""}}      Specify strategy to query nameserver listed in etc/resolv.conf. ({{"all, random, first" | color "cyan" ""}}).
   {{"--ndots=INT" | color "yellow" ""}}              Specify ndots parameter. Takes value from /etc/resolv.conf if using the system namesever or 1 otherwise.
   {{"--search" | color "yellow" ""}}                 Use the search list defined in resolv.conf. Defaults to true. Set --search=false to disable search list.
   {{"--timeout" | color "yellow" ""}}                Specify timeout (in seconds) for the resolver to return a response.

internal/app/nameservers.go

@@ -2,8 +2,10 @@ package app
 
 import (
 	"fmt"
+	"math/rand"
 	"net"
 	"net/url"
+	"time"
 
 	"github.com/ameshkov/dnsstamps"
 	"github.com/mr-karan/doggo/pkg/config"
@@ -29,7 +31,7 @@ func (app *App) LoadNameservers() error {
 	// fallback to system nameserver
 	// in case no nameserver is specified by user.
 	if len(app.Nameservers) == 0 {
-		ns, ndots, search, err := getDefaultServers()
+		ns, ndots, search, err := getDefaultServers(app.QueryFlags.Strategy)
 		if err != nil {
 			return fmt.Errorf("error fetching system default nameserver")
 		}
@@ -117,12 +119,36 @@ func initNameserver(n string) (models.Nameserver, error) {
 	return ns, nil
 }
 
-func getDefaultServers() ([]models.Nameserver, int, []string, error) {
+func getDefaultServers(strategy string) ([]models.Nameserver, int, []string, error) {
+	// Load nameservers from `/etc/resolv.conf`.
 	dnsServers, ndots, search, err := config.GetDefaultServers()
 	if err != nil {
 		return nil, 0, nil, err
 	}
 	servers := make([]models.Nameserver, 0, len(dnsServers))
+
+	switch strategy {
+	case "random":
+		// Choose a random server from the list.
+		rand.Seed(time.Now().Unix())
+		srv := dnsServers[rand.Intn(len(dnsServers))]
+		ns := models.Nameserver{
+			Type:    models.UDPResolver,
+			Address: net.JoinHostPort(srv, models.DefaultUDPPort),
+		}
+		servers = append(servers, ns)
+
+	case "first":
+		// Choose the first from the list, always.
+		srv := dnsServers[0]
+		ns := models.Nameserver{
+			Type:    models.UDPResolver,
+			Address: net.JoinHostPort(srv, models.DefaultUDPPort),
+		}
+		servers = append(servers, ns)
+
+	default:
+		// Default behaviour is to load all nameservers.
 		for _, s := range dnsServers {
 			ns := models.Nameserver{
 				Type:    models.UDPResolver,
@@ -130,5 +156,7 @@ func getDefaultServers() ([]models.Nameserver, int, []string, error) {
 			}
 			servers = append(servers, ns)
 		}
+	}
+
 	return servers, ndots, search, nil
 }

pkg/models/models.go

@@ -35,6 +35,7 @@ type QueryFlags struct {
 	ShowJSON         bool          `koanf:"json" json:"-"`
 	UseSearchList    bool          `koanf:"search" json:"-"`
 	ReverseLookup    bool          `koanf:"reverse" reverse:"-"`
+	Strategy         string        `koanf:"strategy" strategy:"-"`
 }
 
 // Nameserver represents the type of Nameserver

pkg/resolvers/resolver.go

@@ -18,6 +18,7 @@ type Options struct {
 	Ndots       int
 	Timeout     time.Duration
 	Logger      *logrus.Logger
+	Strategy    string
 }
 
 // Resolver implements the configuration for a DNS