GetGlobalAddr utility function (#81)

1 files changed, 31 insertions, 17 deletions

diff --git a/dhcpv6/iputils.go b/dhcpv6/iputils.go
index c3ac3aa..2b9788c 100644
--- a/dhcpv6/iputils.go
+++ b/dhcpv6/iputils.go
@@ -5,26 +5,40 @@ import (
 	"net"
 )
 
-func GetLinkLocalAddr(ifname string) (*net.IP, error) {
-	ifaces, err := net.Interfaces()
+// InterfaceAddresses is used to fetch addresses of an interface with given name
+var InterfaceAddresses func(string) ([]net.Addr, error) = interfaceAddresses
+
+func interfaceAddresses(ifname string) ([]net.Addr, error) {
+	iface, err := net.InterfaceByName(ifname)
 	if err != nil {
 		return nil, err
 	}
-	for _, iface := range ifaces {
-		if iface.Name != ifname {
-			continue
-		}
-		ifaddrs, err := iface.Addrs()
-		if err != nil {
-			return nil, err
-		}
-		for _, ifaddr := range ifaddrs {
-			if ifaddr, ok := ifaddr.(*net.IPNet); ok {
-				if ifaddr.IP.To4() == nil && ifaddr.IP.IsLinkLocalUnicast() {
-					return &ifaddr.IP, nil
-				}
-			}
+	return iface.Addrs()
+}
+
+func getMatchingAddr(ifname string, matches func(net.IP) bool) (net.IP, error) {
+	ifaddrs, err := InterfaceAddresses(ifname)
+	if err != nil {
+		return nil, err
+	}
+	for _, ifaddr := range ifaddrs {
+		if ifaddr, ok := ifaddr.(*net.IPNet); ok && matches(ifaddr.IP) {
+			return ifaddr.IP, nil
 		}
 	}
-	return nil, fmt.Errorf("No link-local address found for interface %v", ifname)
+	return nil, fmt.Errorf("no matching address found for interface %s", ifname)
+}
+
+// GetLinkLocalAddr returns a link-local address for the interface
+func GetLinkLocalAddr(ifname string) (net.IP, error) {
+	return getMatchingAddr(ifname, func(ip net.IP) bool {
+		return ip.To4() == nil && ip.IsLinkLocalUnicast()
+	})
+}
+
+// GetGlobalAddr returns a global address for the interface
+func GetGlobalAddr(ifname string) (net.IP, error) {
+	return getMatchingAddr(ifname, func(ip net.IP) bool {
+		return ip.To4() == nil && ip.IsGlobalUnicast()
+	})
 }