From 61ded1b1d57409d57465820e705491b41847aa2b Mon Sep 17 00:00:00 2001
From: Diptanu Choudhury <diptanuc@gmail.com>
Date: Tue, 27 Oct 2015 14:14:25 -0700
Subject: [PATCH] Using the Go stdlib APIs to detect IP Address of a device

---
 client/fingerprint/network_unix.go | 118 ++++++-----------------------
 1 file changed, 25 insertions(+), 93 deletions(-)

diff --git a/client/fingerprint/network_unix.go b/client/fingerprint/network_unix.go
index 020c99516..de06191e3 100644
--- a/client/fingerprint/network_unix.go
+++ b/client/fingerprint/network_unix.go
@@ -10,7 +10,6 @@ import (
 	"net"
 	"os/exec"
 	"regexp"
-	"runtime"
 	"strconv"
 	"strings"
 
@@ -46,10 +45,10 @@ func (f *NetworkFingerprint) Fingerprint(cfg *config.Config, node *structs.Node)
 			return false, err
 		}
 
-		for _, i := range intfs {
-			if (i.Flags&net.FlagUp != 0) && (i.Flags&(net.FlagLoopback|net.FlagPointToPoint) == 0) {
-				if ip := f.ipAddress(i.Name); ip != "" {
-					defaultDevice = i.Name
+		for _, intf := range intfs {
+			if f.isDeviceEnabled(&intf) && f.isDeviceLoopBackOrPointToPoint(&intf) && f.deviceHasIpAddress(&intf) {
+				if ip, err := f.ipAddress(&intf); err == nil {
+					defaultDevice = intf.Name
 					node.Attributes["network.ip-address"] = ip
 					newNetwork.IP = ip
 					newNetwork.CIDR = newNetwork.IP + "/32"
@@ -150,99 +149,32 @@ func (f *NetworkFingerprint) linkSpeedEthtool(path, device string) int {
 	return mbs
 }
 
-// ipAddress returns the first IPv4 address on the configured default interface
-// Tries Golang native functions and falls back onto ifconfig
-func (f *NetworkFingerprint) ipAddress(device string) string {
-	if ip, err := f.nativeIpAddress(device); err == nil {
-		return ip
+func (f *NetworkFingerprint) ipAddress(intf *net.Interface) (string, error) {
+	var (
+		addrs []net.Addr
+		err   error
+	)
+	if addrs, err = intf.Addrs(); err != nil {
+		return "", err
 	}
 
-	return f.ifConfig(device)
+	if len(addrs) == 0 {
+		return "", errors.New(fmt.Sprintf("Interface %s has no IP address", intf.Name))
+	}
+	return addrs[0].String(), nil
 }
 
-func (f *NetworkFingerprint) nativeIpAddress(device string) (string, error) {
-	// Find IP address on configured interface
-	var ip string
-	ifaces, err := net.Interfaces()
-	if err != nil {
-		return "", errors.New("could not retrieve interface list")
-	}
-
-	// TODO: should we handle IPv6 here? How do we determine precedence?
-	for _, i := range ifaces {
-		if i.Name != device {
-			continue
-		}
-
-		addrs, err := i.Addrs()
-		if err != nil {
-			return "", errors.New("could not retrieve interface IP addresses")
-		}
-
-		for _, a := range addrs {
-			switch v := a.(type) {
-			case *net.IPNet:
-				if v.IP.To4() != nil {
-					ip = v.IP.String()
-				}
-			case *net.IPAddr:
-				if v.IP.To4() != nil {
-					ip = v.IP.String()
-				}
-			}
-		}
-	}
-
-	if net.ParseIP(ip) == nil {
-		return "", errors.New(fmt.Sprintf("could not parse IP address `%s`", ip))
-	}
-
-	return ip, nil
+func (f *NetworkFingerprint) isDeviceEnabled(intf *net.Interface) bool {
+	return intf.Flags&net.FlagUp != 0
 }
 
-// ifConfig returns the IP Address for this node according to ifConfig, for the
-// specified device.
-func (f *NetworkFingerprint) ifConfig(device string) string {
-	ifConfigPath, _ := exec.LookPath("ifconfig")
-	if ifConfigPath == "" {
-		f.logger.Println("[WARN] fingerprint.network: ifconfig not found")
-		return ""
+func (f *NetworkFingerprint) deviceHasIpAddress(intf *net.Interface) bool {
+	if addrs, err := intf.Addrs(); err == nil {
+		return len(addrs) > 0
 	}
-
-	outBytes, err := exec.Command(ifConfigPath, device).Output()
-	if err != nil {
-		f.logger.Printf("[WARN] fingerprint.network: Error calling ifconfig (%s %s): %v", ifConfigPath, device, err)
-		return ""
-	}
-
-	// Parse out the IP address returned from ifconfig for this device
-	// Tested on Ubuntu, the matching part of ifconfig output for eth0 is like
-	// so:
-	//   inet addr:10.0.2.15  Bcast:10.0.2.255  Mask:255.255.255.0
-	// For OS X and en0, we have:
-	//  inet 192.168.0.7 netmask 0xffffff00 broadcast 192.168.0.255
-	output := strings.TrimSpace(string(outBytes))
-
-	// re is a regular expression, which can vary based on the OS
-	var re *regexp.Regexp
-
-	if "darwin" == runtime.GOOS {
-		re = regexp.MustCompile("inet [0-9].+")
-	} else {
-		re = regexp.MustCompile("inet addr:[0-9].+")
-	}
-	args := strings.Split(re.FindString(output), " ")
-
-	var ip string
-	if len(args) > 1 {
-		ip = strings.TrimPrefix(args[1], "addr:")
-	}
-
-	// validate what we've sliced out is a valid IP
-	if net.ParseIP(ip) == nil {
-		f.logger.Printf("[WARN] fingerprint.network: Unable to parse IP in output of '%s %s'", ifConfigPath, device)
-		return ""
-	}
-
-	return ip
+	return false
+}
+
+func (n *NetworkFingerprint) isDeviceLoopBackOrPointToPoint(intf *net.Interface) bool {
+	return intf.Flags&(net.FlagLoopback|net.FlagPointToPoint) == 0
 }