util/addr: Fixes findIP to return the correct public IP

util/addr/addr.go

@@ -35,8 +35,8 @@ func IsLocal(addr string) bool {
 }
 
 // Extract returns a valid IP address. If the address provided is a valid
-// address, it will be returned directly. Otherwise the available interfaces
-// be itterated over to find an IP address, prefferably private.
+// address, it will be returned directly. Otherwise, the available interfaces
+// will be iterated over to find an IP address, preferably private.
 func Extract(addr string) (string, error) {
 	// if addr is already specified then it's directly returned
 	if len(addr) > 0 && (addr != "0.0.0.0" && addr != "[::]" && addr != "::") {
@@ -115,10 +115,12 @@ func IPs() []string {
 	return ipAddrs
 }
 
-// findIP will return the first private IP available in the list,
-// if no private IP is available it will return a public IP if present.
+// findIP will return the first private IP available in the list.
+// If no private IP is available it will return the first public IP, if present.
+// If no public IP is available, it will return the first loopback IP, if present.
 func findIP(addresses []net.Addr) (net.IP, error) {
 	var publicIP net.IP
+	var localIP net.IP
 
 	for _, rawAddr := range addresses {
 		var ip net.IP
@@ -131,8 +133,17 @@ func findIP(addresses []net.Addr) (net.IP, error) {
 			continue
 		}
 
+		if ip.IsLoopback() {
+			if localIP == nil {
+				localIP = ip
+			}
+			continue
+		}
+
 		if !ip.IsPrivate() {
-			publicIP = ip
+			if publicIP == nil {
+				publicIP = ip
+			}
 			continue
 		}
 
@@ -145,5 +156,10 @@ func findIP(addresses []net.Addr) (net.IP, error) {
 		return publicIP, nil
 	}
 
+	// Return local IP
+	if len(localIP) > 0 {
+		return localIP, nil
+	}
+
 	return nil, ErrIPNotFound
 }

util/addr/addr_test.go

@@ -1,6 +1,7 @@
 package addr
 
 import (
+	"github.com/stretchr/testify/assert"
 	"net"
 	"testing"
 )
@@ -54,3 +55,78 @@ func TestExtractor(t *testing.T) {
 		}
 	}
 }
+
+func TestFindIP(t *testing.T) {
+	localhost, _ := net.ResolveIPAddr("ip", "127.0.0.1")
+	localhostIPv6, _ := net.ResolveIPAddr("ip", "::1")
+	privateIP, _ := net.ResolveIPAddr("ip", "10.0.0.1")
+	publicIP, _ := net.ResolveIPAddr("ip", "100.0.0.1")
+	publicIPv6, _ := net.ResolveIPAddr("ip", "2001:0db8:85a3:0000:0000:8a2e:0370:7334")
+
+	testCases := []struct {
+		addrs  []net.Addr
+		ip     net.IP
+		errMsg string
+	}{
+		{
+			addrs:  []net.Addr{},
+			ip:     nil,
+			errMsg: ErrIPNotFound.Error(),
+		},
+		{
+			addrs: []net.Addr{localhost},
+			ip: localhost.IP,
+		},
+		{
+			addrs: []net.Addr{localhost, localhostIPv6},
+			ip: localhost.IP,
+		},
+		{
+			addrs: []net.Addr{localhostIPv6},
+			ip: localhostIPv6.IP,
+		},
+		{
+			addrs: []net.Addr{privateIP, localhost},
+			ip: privateIP.IP,
+		},
+		{
+			addrs: []net.Addr{privateIP, publicIP, localhost},
+			ip: privateIP.IP,
+		},
+		{
+			addrs: []net.Addr{publicIP, privateIP, localhost},
+			ip: privateIP.IP,
+		},
+		{
+			addrs: []net.Addr{publicIP, localhost},
+			ip: publicIP.IP,
+		},
+		{
+			addrs: []net.Addr{publicIP, localhostIPv6},
+			ip: publicIP.IP,
+		},
+		{
+			addrs: []net.Addr{localhostIPv6, publicIP},
+			ip: publicIP.IP,
+		},
+		{
+			addrs: []net.Addr{localhostIPv6, publicIPv6, publicIP},
+			ip: publicIPv6.IP,
+		},
+		{
+			addrs: []net.Addr{publicIP, publicIPv6},
+			ip: publicIP.IP,
+		},
+	}
+
+	for _, tc := range testCases {
+		ip, err := findIP(tc.addrs)
+		if tc.errMsg == "" {
+			assert.Nil(t, err)
+			assert.Equal(t, tc.ip.String(), ip.String())
+		} else {
+			assert.NotNil(t, err)
+			assert.Equal(t, tc.errMsg, err.Error())
+		}
+	}
+}