From 407136030e223ac8abaef6f9bb134df38f6406ae Mon Sep 17 00:00:00 2001
From: John Beisley <greatred@gmail.com>
Date: Sat, 28 Sep 2013 00:09:38 +0100
Subject: [PATCH] Separated various levels of protocol out.

Specifically:
* HTTPU
* SSDP
* UPNP

Also now supports multiple discoveries from a search.
---
 goupnp.go          | 153 ++++++++++++++++++++++++---------------------
 httpu.go           |  98 +++++++++++++++++++++++++++++
 ssdp.go            |  76 ++++++++++++++++++++++
 udproundtripper.go |  69 --------------------
 xml.go             |  48 +++++++-------
 5 files changed, 279 insertions(+), 165 deletions(-)
 create mode 100644 httpu.go
 create mode 100644 ssdp.go
 delete mode 100644 udproundtripper.go

diff --git a/goupnp.go b/goupnp.go
index 6bdc9ec..a489f4f 100644
--- a/goupnp.go
+++ b/goupnp.go
@@ -2,112 +2,121 @@ package goupnp
 
 import (
 	"encoding/xml"
-	"errors"
 	"fmt"
 	"log"
-	"io"
-	"os"
 	"net/http"
-	"net/url"
 )
 
 const (
-	ssdpUDP4Addr = "239.255.255.250:1900"
-
-	methodSearch = "M-SEARCH"
 	// Search Target for InternetGatewayDevice.
-	stIgd  = "urn:schemas-upnp-org:device:InternetGatewayDevice:1"
-	hdrMan = `"ssdp:discover"`
+	SearchTargetIGD = "urn:schemas-upnp-org:device:InternetGatewayDevice:1"
 )
 
 // DiscoverIGD attempts to find Internet Gateway Devices.
 //
 // TODO: Fix implementation to discover multiple. Currently it will find a
 // maximum of one.
-func DiscoverIGD() ([]IGD, error) {
-	hc := http.Client{
-		Transport: udpRoundTripper{},
-		CheckRedirect: func(r *http.Request, via []*http.Request) error {
-			return errors.New("goupnp: unexpected HTTP redirect")
-		},
-		Jar: nil,
-	}
-
-	request := http.Request{
-		Method: methodSearch,
-		// TODO: Support both IPv4 and IPv6.
-		Host: ssdpUDP4Addr,
-		URL:  &url.URL{Opaque: "*"},
-		Header: http.Header{
-			// Putting headers in here avoids them being title-cased.
-			// (The UPnP discovery protocol uses case-sensitive headers)
-			"HOST": []string{ssdpUDP4Addr},
-			"MX":   []string{"2"}, // TODO: Variable max wait time.
-			"MAN":  []string{hdrMan},
-			"ST":   []string{stIgd},
-		},
-	}
-
-	response, err := hc.Do(&request)
+func DiscoverIGD() ([]*IGD, error) {
+	httpu, err := NewHTTPUClient()
 	if err != nil {
 		return nil, err
 	}
+	responses, err := SSDPRawSearch(httpu, SearchTargetIGD, 2, 3)
 
-	// Any errors past this point are simply "no result found". We log the
-	// errors, but report no results. In a future version of this implementation,
-	// multiple *good* results can be returned.
-
-	if response.StatusCode != 200 {
-		log.Printf("goupnp: response code %d %q from UPnP discovery",
-			response.StatusCode, response.Status)
-		return nil, nil
-	}
-	if st := response.Header.Get("ST"); st != stIgd {
-		log.Printf("goupnp: got unexpected search target result %q", st)
-		return nil, nil
+	results := make([]*IGD, 0, len(responses))
+	for _, response := range responses {
+		loc, err := response.Location()
+		if err != nil {
+			log.Printf("goupnp: unexpected bad location from search: %v", err)
+			continue
+		}
+		igd, err := requestIgd(loc.String())
+		if err != nil {
+			log.Printf("goupnp: error requesting IGD: %v", err)
+			continue
+		}
+		results = append(results, igd)
 	}
 
-	location, err := response.Location()
-	if err != nil {
-		log.Printf("goupnp: missing location in response")
-		return nil, nil
-	}
-
-	igd, err := requestIgd(location.String())
-	if err != nil {
-		log.Printf("goupnp: error requesting IGD: %v", err)
-		return nil, nil
-	}
-
-	return []IGD{igd}, nil
+	return results, nil
 }
 
 // IGD defines the interface for an Internet Gateway Device.
-type IGD interface {
+type IGD struct {
+	xml xmlRootDevice
 }
 
-type igd struct {
-	serviceUrl string
-}
-
-func requestIgd(serviceUrl string) (IGD, error) {
+func requestIgd(serviceUrl string) (*IGD, error) {
 	resp, err := http.Get(serviceUrl)
 	if err != nil {
 		return nil, err
 	}
 	defer resp.Body.Close()
 
-	decoder := xml.NewDecoder(io.TeeReader(resp.Body, os.Stdout))
+	if resp.StatusCode != 200 {
+		return nil, fmt.Errorf("goupnp: got response status %s from IGD at %q",
+			resp.Status, serviceUrl)
+	}
+
+	decoder := xml.NewDecoder(resp.Body)
 	decoder.DefaultSpace = deviceXmlNs
-	var root xmlRootDevice
-	if err = decoder.Decode(&root); err != nil {
+	var xml xmlRootDevice
+	if err = decoder.Decode(&xml); err != nil {
 		return nil, err
 	}
-	log.Printf("%+v", root)
+	log.Printf("%+v", xml)
 
-	return igd{serviceUrl}, nil
+	return &IGD{xml}, nil
 }
 
-func (device *igd) String() string {
-	return fmt.Sprintf("goupnp.IGD @ %s", device.serviceUrl)
+func (igd *IGD) Device() *Device {
+	return &Device{
+		igd.xml.URLBase,
+		igd.xml.Device,
+	}
+}
+
+func (igd *IGD) String() string {
+	return fmt.Sprintf("IGD{UDN: %q friendlyName: %q}",
+		igd.xml.Device.UDN, igd.xml.Device.FriendlyName)
+}
+
+type Device struct {
+	urlBase string
+	xml     xmlDevice
+}
+
+func (device *Device) String() string {
+	return fmt.Sprintf("Device{friendlyName: %q}", device.xml.FriendlyName)
+}
+
+func (device *Device) Devices() []*Device {
+	devices := make([]*Device, len(device.xml.Devices))
+	for i, childXml := range device.xml.Devices {
+		devices[i] = &Device{
+			device.urlBase,
+			childXml,
+		}
+	}
+	return devices
+}
+
+func (device *Device) Services() []*Service {
+	srvs := make([]*Service, len(device.xml.Services))
+	for i, childXml := range device.xml.Services {
+		srvs[i] = &Service{
+			device.urlBase,
+			childXml,
+		}
+	}
+	return srvs
+}
+
+type Service struct {
+	urlBase string
+	xml     xmlService
+}
+
+func (srv *Service) String() string {
+	return fmt.Sprintf("Service{serviceType: %q}", srv.xml.ServiceType)
 }
diff --git a/httpu.go b/httpu.go
new file mode 100644
index 0000000..cd332c9
--- /dev/null
+++ b/httpu.go
@@ -0,0 +1,98 @@
+package goupnp
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"log"
+	"net"
+	"net/http"
+	"sync"
+	"time"
+)
+
+// HTTPUClient is a client for dealing with HTTPU (HTTP over UDP). Its typical
+// function is for HTTPMU, and particularly SSDP.
+type HTTPUClient struct {
+	connLock sync.Mutex // Protects use of conn.
+	conn     net.PacketConn
+}
+
+// NewHTTPUClient creates a new HTTPUClient, opening up a new UDP socket for the
+// purpose.
+func NewHTTPUClient() (*HTTPUClient, error) {
+	conn, err := net.ListenPacket("udp", ":0")
+	if err != nil {
+		return nil, err
+	}
+	return &HTTPUClient{conn: conn}, nil
+}
+
+// Close shuts down the client. The client will no longer be useful following
+// this.
+func (httpu *HTTPUClient) Close() error {
+	httpu.connLock.Lock()
+	defer httpu.connLock.Unlock()
+	return httpu.conn.Close()
+}
+
+// Do performs a request. The timeout is how long to wait for before returning
+// the responses that were received. An error is only returned for failing to
+// send the request. Failures in receipt simply do not add to the resulting
+// responses.
+//
+// Note that at present only one concurrent connection will happen per
+// HTTPUClient.
+func (httpu *HTTPUClient) Do(req *http.Request, timeout time.Duration, numSends int) ([]*http.Response, error) {
+	httpu.connLock.Lock()
+	defer httpu.connLock.Unlock()
+
+	var requestBuf bytes.Buffer
+	if err := req.Write(&requestBuf); err != nil {
+		return nil, err
+	}
+	destAddr, err := net.ResolveUDPAddr("udp", req.Host)
+	if err != nil {
+		return nil, err
+	}
+	if err = httpu.conn.SetDeadline(time.Now().Add(timeout)); err != nil {
+		return nil, err
+	}
+
+	// Send request.
+	for i := 0; i < numSends; i++ {
+		if n, err := httpu.conn.WriteTo(requestBuf.Bytes(), destAddr); err != nil {
+			return nil, err
+		} else if n < len(requestBuf.Bytes()) {
+			return nil, fmt.Errorf("httpu: wrote %d bytes rather than full %d in request",
+				n, len(requestBuf.Bytes()))
+		}
+	}
+
+	// Await responses until timeout.
+	var responses []*http.Response
+	responseBytes := make([]byte, 2048)
+	for {
+		// 2048 bytes should be sufficient for most networks.
+		n, _, err := httpu.conn.ReadFrom(responseBytes)
+		if err != nil {
+			if err, ok := err.(net.Error); ok && err.Timeout() {
+				break
+			}
+			log.Print("httpu: error while receiving response: %v", err)
+			// Sleep in case this is a persistent error to avoid pegging CPU until deadline.
+			time.Sleep(10 * time.Millisecond)
+			continue
+		}
+
+		// Parse response.
+		response, err := http.ReadResponse(bufio.NewReader(bytes.NewBuffer(responseBytes[:n])), req)
+		if err != nil {
+			log.Print("httpu: error while parsing response: %v", err)
+			continue
+		}
+
+		responses = append(responses, response)
+	}
+	return responses, err
+}
diff --git a/ssdp.go b/ssdp.go
new file mode 100644
index 0000000..9e0fe05
--- /dev/null
+++ b/ssdp.go
@@ -0,0 +1,76 @@
+package goupnp
+
+import (
+	"errors"
+	"log"
+	"net/http"
+	"net/url"
+	"strconv"
+	"time"
+)
+
+const (
+	ssdpDiscover = `"ssdp:discover"`
+	methodSearch = "M-SEARCH"
+	ssdpUDP4Addr = "239.255.255.250:1900"
+)
+
+// SSDPRawSearch performs a fairly raw SSDP search request, and returns the
+// unique response(s) that it receives. Each response has the requested
+// searchTarget, a USN, and a valid location. maxWaitSeconds states how long to
+// wait for responses in seconds, and must be a minimum of 1 (the
+// implementation waits an additional 100ms for responses to arrive), 2 is a
+// reasonable value for this. numSends is the number of requests to send - 3 is
+// a reasonable value for this.
+func SSDPRawSearch(httpu *HTTPUClient, searchTarget string, maxWaitSeconds int, numSends int) ([]*http.Response, error) {
+	if maxWaitSeconds < 1 {
+		return nil, errors.New("ssdp: maxWaitSeconds must be >= 1")
+	}
+
+	seenUsns := make(map[string]bool)
+	var responses []*http.Response
+	req := http.Request{
+		Method: methodSearch,
+		// TODO: Support both IPv4 and IPv6.
+		Host: ssdpUDP4Addr,
+		URL:  &url.URL{Opaque: "*"},
+		Header: http.Header{
+			// Putting headers in here avoids them being title-cased.
+			// (The UPnP discovery protocol uses case-sensitive headers)
+			"HOST": []string{ssdpUDP4Addr},
+			"MX":   []string{strconv.FormatInt(int64(maxWaitSeconds), 10)},
+			"MAN":  []string{ssdpDiscover},
+			"ST":   []string{searchTarget},
+		},
+	}
+	allResponses, err := httpu.Do(&req, time.Duration(maxWaitSeconds)*time.Second+100*time.Millisecond, numSends)
+	if err != nil {
+		return nil, err
+	}
+	for _, response := range allResponses {
+		if response.StatusCode != 200 {
+			log.Printf("ssdp: got response status code %q in search response", response.Status)
+			continue
+		}
+		if st := response.Header.Get("ST"); st != searchTarget {
+			log.Printf("ssdp: got unexpected search target result %q", st)
+			return nil, nil
+		}
+		location, err := response.Location()
+		if err != nil {
+			log.Printf("ssdp: no usable location in search response (discarding): %v", err)
+			continue
+		}
+		usn := response.Header.Get("USN")
+		if usn == "" {
+			log.Printf("ssdp: empty/missing USN in search response (using location instead): %v", err)
+			usn = location.String()
+		}
+		if _, alreadySeen := seenUsns[usn]; !alreadySeen {
+			seenUsns[usn] = true
+			responses = append(responses, response)
+		}
+	}
+
+	return responses, nil
+}
diff --git a/udproundtripper.go b/udproundtripper.go
deleted file mode 100644
index ceeeaa8..0000000
--- a/udproundtripper.go
+++ /dev/null
@@ -1,69 +0,0 @@
-package goupnp
-
-import (
-	"bufio"
-	"bytes"
-	"fmt"
-	"net"
-	"net/http"
-	"time"
-)
-
-// TODO: RoundTripper is probably the wrong interface, as there could be
-// multiple responses to a request.
-
-type udpRoundTripper struct {
-	// If zero, defaults to 3 second deadline (a zero deadline makes no sense).
-	Deadline       time.Duration
-	MaxWaitSeconds int
-}
-
-func (urt udpRoundTripper) RoundTrip(r *http.Request) (*http.Response, error) {
-	conn, err := net.ListenPacket("udp", ":0")
-	if err != nil {
-		return nil, err
-	}
-	defer conn.Close()
-
-	var requestBuf bytes.Buffer
-	if err := r.Write(&requestBuf); err != nil {
-		return nil, err
-	}
-	destAddr, err := net.ResolveUDPAddr("udp", r.Host)
-	if err != nil {
-		return nil, err
-	}
-
-	deadline := urt.Deadline
-	if urt.Deadline == 0 {
-		deadline = 3 * time.Second
-	}
-
-	if err = conn.SetDeadline(time.Now().Add(deadline)); err != nil {
-		return nil, err
-	}
-
-	// Send request.
-	if n, err := conn.WriteTo(requestBuf.Bytes(), destAddr); err != nil {
-		return nil, err
-	} else if n < len(requestBuf.Bytes()) {
-		return nil, fmt.Errorf("goupnp: wrote %d bytes rather than full %d in request",
-			n, len(requestBuf.Bytes()))
-	}
-
-	// Await response.
-	responseBytes := make([]byte, 2048)
-	n, _, err := conn.ReadFrom(responseBytes)
-	if err != nil {
-		return nil, err
-	}
-	responseBytes = responseBytes[:n]
-
-	// Parse response.
-	response, err := http.ReadResponse(bufio.NewReader(bytes.NewBuffer(responseBytes)), r)
-	if err != nil {
-		return nil, err
-	}
-
-	return response, err
-}
diff --git a/xml.go b/xml.go
index 5300a78..1403f26 100644
--- a/xml.go
+++ b/xml.go
@@ -11,10 +11,10 @@ const (
 )
 
 type xmlRootDevice struct {
-	Name xml.Name `xml:"root`
+	Name        xml.Name       `xml:"root`
 	SpecVersion xmlSpecVersion `xml:"specVersion"`
-	URLBase string `xml:"URLBase"`
-	Device xmlDevice `xml:"device"`
+	URLBase     string         `xml:"URLBase"`
+	Device      xmlDevice      `xml:"device"`
 }
 
 type xmlSpecVersion struct {
@@ -23,20 +23,20 @@ type xmlSpecVersion struct {
 }
 
 type xmlDevice struct {
-	DeviceType string `xml:"deviceType"`
-	FriendlyName string `xml:"friendlyName"`
-	Manufacturer string `xml:"manufacturer"`
-	ManufacturerURL string `xml:"manufacturerURL"`
-	ModelDescription string `xml:"modelDescription"`
-	ModelName string `xml:"modelName"`
-	ModelNumber string `xml:"modelNumber"`
-	ModelURL string `xml:"modelURL"`
-	SerialNumber string `xml:"serialNumber"`
-	UDN string `xml:"UDN"`
-	UPC string `xml:"UPC,omitempty"`
-	Icons []xmlIcon `xml:"iconList>icon,omitempty"`
-	Services []xmlService `xml:"serviceList>service,omitempty"`
-	Devices []xmlDevice `xml:"deviceList>device,omitempty"`
+	DeviceType       string       `xml:"deviceType"`
+	FriendlyName     string       `xml:"friendlyName"`
+	Manufacturer     string       `xml:"manufacturer"`
+	ManufacturerURL  string       `xml:"manufacturerURL"`
+	ModelDescription string       `xml:"modelDescription"`
+	ModelName        string       `xml:"modelName"`
+	ModelNumber      string       `xml:"modelNumber"`
+	ModelURL         string       `xml:"modelURL"`
+	SerialNumber     string       `xml:"serialNumber"`
+	UDN              string       `xml:"UDN"`
+	UPC              string       `xml:"UPC,omitempty"`
+	Icons            []xmlIcon    `xml:"iconList>icon,omitempty"`
+	Services         []xmlService `xml:"serviceList>service,omitempty"`
+	Devices          []xmlDevice  `xml:"deviceList>device,omitempty"`
 
 	// Extra observed elements:
 	PresentationURL string `xml:"presentationURL"`
@@ -44,16 +44,16 @@ type xmlDevice struct {
 
 type xmlIcon struct {
 	Mimetype string `xml:"mimetype"`
-	Width int32 `xml:"width"`
-	Height int32 `xml:"height"`
-	Depth int32 `xml:"depth"`
-	URL string `xml:"url"`
+	Width    int32  `xml:"width"`
+	Height   int32  `xml:"height"`
+	Depth    int32  `xml:"depth"`
+	URL      string `xml:"url"`
 }
 
 type xmlService struct {
 	ServiceType string `xml:"serviceType"`
-	ServiceId string `xml:"serviceId"`
-	SCPDURL string `xml:"SCPDURL"`
-	ControlURL string `xml:"controlURL"`
+	ServiceId   string `xml:"serviceId"`
+	SCPDURL     string `xml:"SCPDURL"`
+	ControlURL  string `xml:"controlURL"`
 	EventSubURL string `xml:"eventSubURL"`
 }