Use Resolver for dns resolution

plugins/inputs/ping/ping.go

@@ -23,6 +23,10 @@ import (
 // for unit test purposes (see ping_test.go)
 type HostPinger func(binary string, timeout float64, args ...string) (string, error)
 
+type HostResolver func(ctx context.Context, ipv6 bool, host string) (*net.IPAddr, error)
+
+type IsCorrectNetwork func(ip net.IPAddr) bool
+
 type Ping struct {
 	wg sync.WaitGroup
 
@@ -60,6 +64,9 @@ type Ping struct {
 	// host ping function
 	pingHost HostPinger
 
+	// resolve host function
+	resolveHost HostResolver
+
 	// listenAddr is the address associated with the interface defined.
 	listenAddr string
 }
@@ -187,37 +194,47 @@ func hostPinger(binary string, timeout float64, args ...string) (string, error)
 	return string(out), err
 }
 
-func ResolveIP(ctx context.Context, network string, destination string) (*net.IPAddr, error) {
-	success := make(chan *net.IPAddr)
-	error := make(chan error)
-
-	go func() {
-		addrs, err := net.ResolveIPAddr(network, destination)
-		if err == nil {
-			success <- addrs
-		} else {
-			error <- err
+func filterIPs(addrs []net.IPAddr, filterFunc IsCorrectNetwork) []net.IPAddr {
+	n := 0
+	for _, x := range addrs {
+		if filterFunc(x) {
+			addrs[n] = x
+			n++
 		}
-	}()
+	}
+	return addrs[:n]
+}
+
+func hostResolver(ctx context.Context, ipv6 bool, destination string) (*net.IPAddr, error) {
+	resolver := &net.Resolver{}
+	ips, err := resolver.LookupIPAddr(ctx, destination)
 
-	select {
-	case addrs := <-success:
-		return addrs, nil
-	case err := <-error:
+	if err != nil {
 		return nil, err
-	case <-ctx.Done():
-		return nil, errors.New("ResolveIp timeout")
 	}
-}
 
-func (p *Ping) pingToURLNative(destination string, acc telegraf.Accumulator) {
-	ctx := context.Background()
+	if ipv6 {
+		ips = filterIPs(ips, isV6)
+	} else {
+		ips = filterIPs(ips, isV4)
+	}
 
-	network := "ip4"
-	if p.IPv6 {
-		network = "ip6"
+	if len(ips) == 0 {
+		return nil, errors.New("Cannot resolve ip address")
 	}
+	return &ips[0], err
+}
+
+func isV4(ip net.IPAddr) bool {
+	return ip.IP.To4() != nil
+}
+
+func isV6(ip net.IPAddr) bool {
+	return !isV4(ip)
+}
 
+func (p *Ping) pingToURLNative(destination string, acc telegraf.Accumulator) {
+	ctx := context.Background()
 	interval := p.PingInterval
 	if interval < 0.2 {
 		interval = 0.2
@@ -237,7 +254,7 @@ func (p *Ping) pingToURLNative(destination string, acc telegraf.Accumulator) {
 		defer cancel()
 	}
 
-	host, err := ResolveIP(ctx, network, destination)
+	host, err := p.resolveHost(ctx, p.IPv6, destination)
 	if err != nil {
 		acc.AddFields(
 			"ping",
@@ -408,6 +425,7 @@ func init() {
 	inputs.Add("ping", func() telegraf.Input {
 		return &Ping{
 			pingHost:     hostPinger,
+			resolveHost:  hostResolver,
 			PingInterval: 1.0,
 			Count:        1,
 			Timeout:      1.0,

plugins/inputs/ping/ping_test.go

@@ -3,7 +3,9 @@
 package ping
 
 import (
+	"context"
 	"errors"
+	"net"
 	"reflect"
 	"sort"
 	"testing"
@@ -340,6 +342,12 @@ func TestPingBinary(t *testing.T) {
 	acc.GatherError(p.Gather)
 }
 
+func mockHostResolver(ctx context.Context, ipv6 bool, host string) (*net.IPAddr, error) {
+	ipaddr := net.IPAddr{}
+	ipaddr.IP = net.IPv4(127, 0, 0, 1)
+	return &ipaddr, nil
+}
+
 // Test that Gather function works using native ping
 func TestPingGatherNative(t *testing.T) {
 	if testing.Short() {
@@ -348,12 +356,35 @@ func TestPingGatherNative(t *testing.T) {
 
 	var acc testutil.Accumulator
 	p := Ping{
-		Urls:   []string{"localhost", "127.0.0.2"},
-		Method: "native",
-		Count:  5,
+		Urls:        []string{"localhost", "127.0.0.2"},
+		Method:      "native",
+		Count:       5,
+		resolveHost: mockHostResolver,
 	}
 
 	assert.NoError(t, acc.GatherError(p.Gather))
 	assert.True(t, acc.HasPoint("ping", map[string]string{"url": "localhost"}, "packets_transmitted", 5))
 	assert.True(t, acc.HasPoint("ping", map[string]string{"url": "localhost"}, "packets_received", 5))
 }
+
+func mockHostResolverError(ctx context.Context, ipv6 bool, host string) (*net.IPAddr, error) {
+	return nil, errors.New("myMock error")
+}
+
+// Test failed DNS resolutions
+func TestDNSLookupError(t *testing.T) {
+	if testing.Short() {
+		t.Skip("Skipping test due to permission requirements.")
+	}
+
+	var acc testutil.Accumulator
+	p := Ping{
+		Urls:        []string{"localhost"},
+		Method:      "native",
+		IPv6:        false,
+		resolveHost: mockHostResolverError,
+	}
+
+	acc.GatherError(p.Gather)
+	assert.True(t, len(acc.Errors) > 0)
+}