Added getting of external IP address

dyndns/external.go

@@ -0,0 +1,38 @@
+package dyndns
+
+import (
+	"errors"
+	"io/ioutil"
+	"net/http"
+)
+
+var (
+	Urls = []string{"http://myexternalip.com/raw"}
+)
+
+func tryMirror(url string) (string, error) {
+	resp, err := http.Get(url)
+	if err != nil {
+		return "", err
+	}
+
+	defer resp.Body.Close()
+	contents, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return "", err
+	}
+
+	return string(contents), nil
+}
+
+// Retrieves the external facing IP Address
+func GetExternalIP() (string, error) {
+	for _, url := range Urls {
+		resp, err := tryMirror(url)
+		if err == nil {
+			return resp, err
+		}
+	}
+
+	return "", errors.New("Could not retreive external IP")
+}

dyndns/external_test.go

@@ -0,0 +1,49 @@
+package dyndns
+
+import (
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+)
+
+func testServerHandler(w http.ResponseWriter, r *http.Request) {
+	if r.URL.String() == "/correct" {
+		w.Write([]byte("Correct"))
+	} else {
+		w.Write([]byte("Incorrect"))
+	}
+}
+
+func TestGetExternalIP(t *testing.T) {
+	// Setup local HTTP server to emulate external IP services.
+	server := httptest.NewServer(http.HandlerFunc(testServerHandler))
+	defer server.Close()
+
+	// In order to test the failover, we
+	// provide 2 bad IPs, and 2 correct ones,
+	// in that order.
+	Urls = make([]string, 4)
+	Urls[0] = ""
+	Urls[1] = "1.4.5.6"
+	Urls[2] = fmt.Sprintf("%s/%s", server.URL, "correct")
+	Urls[3] = fmt.Sprintf("%s/%s", server.URL, "incorrect")
+
+	resp, err := GetExternalIP()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if resp != "Correct" {
+		t.Fatal("Incorrect result returned:", resp)
+	}
+}
+
+func TestGetExternalIPFailure(t *testing.T) {
+	Urls = make([]string, 1)
+	Urls[0] = ""
+
+	_, err := GetExternalIP()
+	if err == nil {
+		t.Fatal("Should have returned error when no service can be reached")
+	}
+}