autodetect interfaces on private networks

netutil/netutil.go

@@ -0,0 +1,48 @@
+package netutil
+
+import (
+	"net"
+
+	"github.com/go-kit/log"
+	"github.com/go-kit/log/level"
+)
+
+var (
+	getInterfaceAddrs = (*net.Interface).Addrs
+)
+
+// PrivateNetworkInterfaces lists network interfaces and returns those having an address conformant to RFC1918
+func PrivateNetworkInterfaces(logger log.Logger) []string {
+	ints, err := net.Interfaces()
+	if err != nil {
+		level.Warn(logger).Log("msg", "error getting network interfaces", "err", err)
+	}
+	return privateNetworkInterfaces(ints, logger)
+}
+
+// private testable function that checks each given interface
+func privateNetworkInterfaces(all []net.Interface, logger log.Logger) []string {
+	var privInts []string
+	for _, i := range all {
+		addrs, err := getInterfaceAddrs(&i)
+		if err != nil {
+			level.Warn(logger).Log("msg", "error getting addresses from network interface", "interface", i.Name, "err", err)
+		}
+		for _, a := range addrs {
+			s := a.String()
+			ip, _, err := net.ParseCIDR(s)
+			if err != nil {
+				level.Warn(logger).Log("msg", "error parsing network interface IP address", "inf", i.Name, "addr", s, "err", err)
+			}
+			if ip.IsPrivate() {
+				privInts = append(privInts, i.Name)
+				break
+			}
+		}
+	}
+	if len(privInts) == 0 {
+		return []string{"eth0", "en0"}
+	}
+	level.Debug(logger).Log("msg", "found network interfaces with private IP addresses assigned", "interfaces", privInts)
+	return privInts
+}

netutil/netutil_test.go

@@ -0,0 +1,126 @@
+package netutil
+
+import (
+	"net"
+	"os"
+	"testing"
+
+	"github.com/go-kit/log"
+	"github.com/stretchr/testify/assert"
+)
+
+// A type that implements the net.Addr interface
+// Only String() is called by netutil logic
+type mockAddr struct {
+	netAddr string
+}
+
+func (ma mockAddr) Network() string {
+	return "tcp"
+}
+
+func (ma mockAddr) String() string {
+	return ma.netAddr
+}
+
+// Helper function to test a list of interfaces
+func generateTestInterfaces(names []string) []net.Interface {
+	testInts := []net.Interface{}
+	for i, j := range names {
+		k := net.Interface{
+			Index:        i + 1,
+			MTU:          1500,
+			Name:         j,
+			HardwareAddr: []byte{},
+			Flags:        0,
+		}
+		testInts = append(testInts, k)
+	}
+	return testInts
+}
+
+func TestPrivateInterface(t *testing.T) {
+	testIntsAddrs := map[string][]string{
+		"privNetA":  {"10.6.19.34/8"},
+		"privNetB":  {"172.16.0.7/12"},
+		"privNetC":  {"192.168.3.29/24"},
+		"pubNet":    {"34.120.177.193/24"},
+		"multiPriv": {"10.6.19.34/8", "172.16.0.7/12"},
+		"multiMix":  {"1.1.1.1/24", "192.168.0.42/24"},
+		"multiPub":  {"1.1.1.1/24", "34.120.177.193/24"},
+	}
+	defaultOutput := []string{"eth0", "en0"}
+	type testCases struct {
+		description    string
+		interfaces     []string
+		expectedOutput []string
+	}
+	for _, scenario := range []testCases{
+		{
+			description:    "empty interface list",
+			interfaces:     []string{},
+			expectedOutput: defaultOutput,
+		},
+		{
+			description:    "single private interface",
+			interfaces:     []string{"privNetA"},
+			expectedOutput: []string{"privNetA"},
+		},
+		{
+			description:    "single public interface",
+			interfaces:     []string{"pubNet"},
+			expectedOutput: defaultOutput,
+		},
+		{
+			description:    "single interface multi address private",
+			interfaces:     []string{"multiPriv"},
+			expectedOutput: []string{"multiPriv"},
+		},
+		{
+			description:    "single interface multi address mix",
+			interfaces:     []string{"multiMix"},
+			expectedOutput: []string{"multiMix"},
+		},
+		{
+			description:    "single interface multi address public",
+			interfaces:     []string{"multiPub"},
+			expectedOutput: defaultOutput,
+		},
+		{
+			description:    "all private interfaces",
+			interfaces:     []string{"privNetA", "privNetB", "privNetC"},
+			expectedOutput: []string{"privNetA", "privNetB", "privNetC"},
+		},
+		{
+			description:    "mix of public and private interfaces",
+			interfaces:     []string{"pubNet", "privNetA", "privNetB", "privNetC", "multiPriv", "multiMix", "multiPub"},
+			expectedOutput: []string{"privNetA", "privNetB", "privNetC", "multiPriv", "multiMix"},
+		},
+	} {
+		getInterfaceAddrs = func(i *net.Interface) ([]net.Addr, error) {
+			addrs := []net.Addr{}
+			for _, ip := range testIntsAddrs[i.Name] {
+				addrs = append(addrs, mockAddr{netAddr: ip})
+			}
+			return addrs, nil
+		}
+		t.Run(scenario.description, func(t *testing.T) {
+			privInts := privateNetworkInterfaces(
+				generateTestInterfaces(scenario.interfaces),
+				log.NewNopLogger(),
+			)
+			assert.Equal(t, privInts, scenario.expectedOutput)
+		})
+	}
+}
+
+func TestPrivateInterfaceError(t *testing.T) {
+	interfaces := generateTestInterfaces([]string{"eth9"})
+	ipaddr := "not_a_parseable_ip_string"
+	getInterfaceAddrs = func(i *net.Interface) ([]net.Addr, error) {
+		return []net.Addr{mockAddr{netAddr: ipaddr}}, nil
+	}
+	logger := log.NewLogfmtLogger(os.Stdout)
+	privInts := privateNetworkInterfaces(interfaces, logger)
+	assert.Equal(t, privInts, []string{"eth0", "en0"})
+}

ring/lifecycler.go

@@ -19,6 +19,7 @@ import (
 
 	"github.com/grafana/dskit/flagext"
 	"github.com/grafana/dskit/kv"
+	"github.com/grafana/dskit/netutil"
 	"github.com/grafana/dskit/services"
 )
 
@@ -81,7 +82,7 @@ func (cfg *LifecyclerConfig) RegisterFlagsWithPrefix(prefix string, f *flag.Flag
 		panic(fmt.Errorf("failed to get hostname %s", err))
 	}
 
-	cfg.InfNames = []string{"eth0", "en0"}
+	cfg.InfNames = netutil.PrivateNetworkInterfaces(log.NewLogfmtLogger(os.Stdout))
 	f.Var((*flagext.StringSlice)(&cfg.InfNames), prefix+"lifecycler.interface", "Name of network interface to read address from.")
 	f.StringVar(&cfg.Addr, prefix+"lifecycler.addr", "", "IP address to advertise in the ring.")
 	f.IntVar(&cfg.Port, prefix+"lifecycler.port", 0, "port to advertise in consul (defaults to server.grpc-listen-port).")