Properly handle absolute URLs when parsing UPnP service control URLs

Fixes #1187

internal/upnp/upnp.go

@@ -448,6 +448,13 @@ func getIGDServices(rootURL string, device upnpDevice, wanDeviceURN string, wanC
 }
 
 func replaceRawPath(u *url.URL, rp string) {
+	asURL, err := url.Parse(rp)
+	if err != nil {
+		return
+	} else if asURL.IsAbs() {
+		u.Path = asURL.Path
+		u.RawQuery = asURL.RawQuery
+	} else {
 		var p, q string
 		fs := strings.Split(rp, "?")
 		p = fs[0]
@@ -462,6 +469,7 @@ func replaceRawPath(u *url.URL, rp string) {
 		}
 		u.RawQuery = q
 	}
+}
 
 func soapRequest(url, service, function, message string) ([]byte, error) {
 	tpl := `<?xml version="1.0" ?>

internal/upnp/upnp_test.go

@@ -17,6 +17,7 @@ package upnp
 
 import (
 	"encoding/xml"
+	"net/url"
 	"testing"
 )
 
@@ -40,3 +41,25 @@ func TestExternalIPParsing(t *testing.T) {
 		t.Error("Parse of SOAP request failed.")
 	}
 }
+
+func TestControlURLParsing(t *testing.T) {
+	rootURL := "http://192.168.243.1:80/igd.xml"
+
+	u, _ := url.Parse(rootURL)
+	subject := "/upnp?control=WANCommonIFC1"
+	expected := "http://192.168.243.1:80/upnp?control=WANCommonIFC1"
+	replaceRawPath(u, subject)
+
+	if u.String() != expected {
+		t.Error("URL normalization of", subject, "failed; expected", expected, "got", u.String())
+	}
+
+	u, _ = url.Parse(rootURL)
+	subject = "http://192.168.243.1:80/upnp?control=WANCommonIFC1"
+	expected = "http://192.168.243.1:80/upnp?control=WANCommonIFC1"
+	replaceRawPath(u, subject)
+
+	if u.String() != expected {
+		t.Error("URL normalization of", subject, "failed; expected", expected, "got", u.String())
+	}
+}