interfaces: added package with interface facilities

2 files changed, 120 insertions, 0 deletions

diff --git a/interfaces/interfaces.go b/interfaces/interfaces.go
new file mode 100644
index 0000000..5761669
--- /dev/null
+++ b/interfaces/interfaces.go
@@ -0,0 +1,41 @@
+package interfaces
+
+import "net"
+
+// InterfaceMatcher is a function type used to match the interfaces we want. See
+// GetInterfacesFunc below for usage.
+type InterfaceMatcher func(net.Interface) bool
+
+// interfaceGetter is used for testing purposes
+var interfaceGetter = net.Interfaces
+
+// GetInterfacesFunc loops through the available network interfaces, and returns
+// a list of interfaces for which the passed InterfaceMatcher function returns
+// true.
+func GetInterfacesFunc(matcher InterfaceMatcher) ([]net.Interface, error) {
+	ifaces, err := interfaceGetter()
+	if err != nil {
+		return nil, err
+	}
+	ret := make([]net.Interface, 0)
+	for _, iface := range ifaces {
+		if matcher(iface) {
+			ret = append(ret, iface)
+		}
+	}
+	return ret, nil
+}
+
+// GetLoopbackInterfaces returns a list of loopback interfaces.
+func GetLoopbackInterfaces() ([]net.Interface, error) {
+	return GetInterfacesFunc(func(iface net.Interface) bool {
+		return iface.Flags&net.FlagLoopback != 0
+	})
+}
+
+// GetNonLoopbackInterfaces returns a list of non-loopback interfaces.
+func GetNonLoopbackInterfaces() ([]net.Interface, error) {
+	return GetInterfacesFunc(func(iface net.Interface) bool {
+		return iface.Flags&net.FlagLoopback == 0
+	})
+}
diff --git a/interfaces/interfaces_test.go b/interfaces/interfaces_test.go
new file mode 100644
index 0000000..7633d5e
--- /dev/null
+++ b/interfaces/interfaces_test.go
@@ -0,0 +1,79 @@
+package interfaces
+
+import (
+	"errors"
+	"net"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func fakeIface(idx int, name string, loopback bool) net.Interface {
+	var flags net.Flags
+	if loopback {
+		flags |= net.FlagLoopback
+	}
+	return net.Interface{
+		Index:        idx,
+		MTU:          1500,
+		Name:         name,
+		HardwareAddr: []byte{0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff},
+		Flags:        flags,
+	}
+}
+
+func TestGetLoopbackInterfaces(t *testing.T) {
+	interfaceGetter = func() ([]net.Interface, error) {
+		return []net.Interface{
+			fakeIface(0, "lo", true),
+			fakeIface(1, "eth0", false),
+			fakeIface(2, "eth1", false),
+		}, nil
+	}
+	ifaces, err := GetLoopbackInterfaces()
+	// this has to be reassigned before any require.* call
+	interfaceGetter = net.Interfaces
+
+	require.NoError(t, err)
+	require.Equal(t, 1, len(ifaces))
+}
+
+func TestGetLoopbackInterfacesError(t *testing.T) {
+	interfaceGetter = func() ([]net.Interface, error) {
+		return nil, errors.New("expected error")
+
+	}
+	_, err := GetLoopbackInterfaces()
+	// this has to be reassigned before any require.* call
+	interfaceGetter = net.Interfaces
+
+	require.Error(t, err)
+}
+
+func TestGetNonLoopbackInterfaces(t *testing.T) {
+	interfaceGetter = func() ([]net.Interface, error) {
+		return []net.Interface{
+			fakeIface(0, "lo", true),
+			fakeIface(1, "eth0", false),
+			fakeIface(2, "eth1", false),
+		}, nil
+	}
+	ifaces, err := GetNonLoopbackInterfaces()
+	// this has to be reassigned before any require.* call
+	interfaceGetter = net.Interfaces
+
+	require.NoError(t, err)
+	require.Equal(t, 2, len(ifaces))
+}
+
+func TestGetNonLoopbackInterfacesError(t *testing.T) {
+	interfaceGetter = func() ([]net.Interface, error) {
+		return nil, errors.New("expected error")
+
+	}
+	_, err := GetNonLoopbackInterfaces()
+	// this has to be reassigned before any require.* call
+	interfaceGetter = net.Interfaces
+
+	require.Error(t, err)
+}