Initial work on maintaining a registry of discovered devices.

ssdp/registry.go

@@ -0,0 +1,202 @@
+package ssdp
+
+import (
+	"fmt"
+	"log"
+	"net/http"
+	"net/url"
+	"regexp"
+	"strconv"
+	"sync"
+	"time"
+
+	"github.com/huin/goupnp/httpu"
+)
+
+const (
+	maxExpiryTimeSeconds = 24 * 60 * 60
+)
+
+var (
+	maxAgeRx = regexp.MustCompile("max-age=([0-9]+)")
+)
+
+type Entry struct {
+	// The address that the entry data was actually received from.
+	RemoteAddr string
+	// Unique Service Name. Identifies a unique instance of a device or service.
+	USN string
+	// Notfication Type. The type of device or service being announced.
+	NT string
+	// Server's self-identifying string.
+	Server string
+	Host   string
+	// Location of the UPnP root device description.
+	Location *url.URL
+
+	// Despite BOOTID,CONFIGID being required fields, apparently they are not
+	// always set by devices. Set to -1 if not present.
+
+	BootID   int32
+	ConfigID int32
+
+	SearchPort uint16
+
+	// When the last update was received for this entry identified by this USN.
+	LastUpdate time.Time
+	// When the last update's cached values are advised to expire.
+	CacheExpiry time.Time
+}
+
+func newEntryFromRequest(r *http.Request) (*Entry, error) {
+	now := time.Now()
+	expiryDuration, err := parseCacheControlMaxAge(r.Header.Get("CACHE-CONTROL"))
+	if err != nil {
+		return nil, fmt.Errorf("ssdp: error parsing CACHE-CONTROL max age: %v", err)
+	}
+
+	loc, err := url.Parse(r.Header.Get("LOCATION"))
+	if err != nil {
+		return nil, fmt.Errorf("ssdp: error parsing entry Location URL: %v", err)
+	}
+
+	bootID, err := parseUpnpIntHeader(r.Header, "BOOTID.UPNP.ORG", -1)
+	if err != nil {
+		return nil, err
+	}
+	configID, err := parseUpnpIntHeader(r.Header, "CONFIGID.UPNP.ORG", -1)
+	if err != nil {
+		return nil, err
+	}
+	searchPort, err := parseUpnpIntHeader(r.Header, "SEARCHPORT.UPNP.ORG", ssdpSearchPort)
+	if err != nil {
+		return nil, err
+	}
+
+	if searchPort < 1 || searchPort > 65535 {
+		return nil, fmt.Errorf("ssdp: search port %d is out of range", searchPort)
+	}
+
+	return &Entry{
+		RemoteAddr:  r.RemoteAddr,
+		USN:         r.Header.Get("USN"),
+		NT:          r.Header.Get("NT"),
+		Server:      r.Header.Get("SERVER"),
+		Host:        r.Header.Get("HOST"),
+		Location:    loc,
+		BootID:      bootID,
+		ConfigID:    configID,
+		SearchPort:  uint16(searchPort),
+		LastUpdate:  now,
+		CacheExpiry: now.Add(expiryDuration),
+	}, nil
+}
+
+func parseCacheControlMaxAge(cc string) (time.Duration, error) {
+	matches := maxAgeRx.FindStringSubmatch(cc)
+	if len(matches) != 2 {
+		return 0, fmt.Errorf("did not find exactly one max-age in cache control header: %q", cc)
+	}
+	expirySeconds, err := strconv.ParseInt(matches[1], 10, 16)
+	if err != nil {
+		return 0, err
+	}
+	if expirySeconds < 1 || expirySeconds > maxExpiryTimeSeconds {
+		return 0, fmt.Errorf("rejecting bad expiry time of %d seconds", expirySeconds)
+	}
+	return time.Duration(expirySeconds) * time.Second, nil
+}
+
+// parseUpnpIntHeader is intended to parse the
+// {BOOT,CONFIGID,SEARCHPORT}.UPNP.ORG header fields. It returns the def if
+// the head is empty or missing.
+func parseUpnpIntHeader(headers http.Header, headerName string, def int32) (int32, error) {
+	s := headers.Get(headerName)
+	if s == "" {
+		return def, nil
+	}
+	v, err := strconv.ParseInt(s, 10, 32)
+	if err != nil {
+		return 0, fmt.Errorf("ssdp: could not parse header %s: %v", headerName, err)
+	}
+	return int32(v), nil
+}
+
+var _ httpu.Handler = new(Registry)
+
+// Registry maintains knowledge of discovered devices and services.
+type Registry struct {
+	lock  sync.Mutex
+	byUSN map[string]*Entry
+}
+
+func NewRegistry() *Registry {
+	return &Registry{
+		byUSN: make(map[string]*Entry),
+	}
+}
+
+// ServeMessage implements httpu.Handler, and uses SSDP NOTIFY requests to
+// maintain the registry of devices and services.
+func (reg *Registry) ServeMessage(r *http.Request) {
+	if r.Method != methodNotify {
+		return
+	}
+
+	nts := r.Header.Get("nts")
+
+	var err error
+	switch nts {
+	case ntsAlive:
+		err = reg.handleNTSAlive(r)
+	case ntsUpdate:
+		err = reg.handleNTSUpdate(r)
+	case ntsByebye:
+		err = reg.handleNTSByebye(r)
+	default:
+		err = fmt.Errorf("unknown NTS value: %q", nts)
+	}
+	log.Printf("In %s request from %s: %v", nts, r.RemoteAddr, err)
+}
+
+func (reg *Registry) handleNTSAlive(r *http.Request) error {
+	entry, err := newEntryFromRequest(r)
+	if err != nil {
+		return err
+	}
+
+	reg.lock.Lock()
+	defer reg.lock.Unlock()
+
+	reg.byUSN[entry.USN] = entry
+
+	return nil
+}
+
+func (reg *Registry) handleNTSUpdate(r *http.Request) error {
+	entry, err := newEntryFromRequest(r)
+	if err != nil {
+		return err
+	}
+	nextBootID, err := parseUpnpIntHeader(r.Header, "NEXTBOOTID.UPNP.ORG", -1)
+	if err != nil {
+		return err
+	}
+	entry.BootID = nextBootID
+
+	reg.lock.Lock()
+	defer reg.lock.Unlock()
+
+	reg.byUSN[entry.USN] = entry
+
+	return nil
+}
+
+func (reg *Registry) handleNTSByebye(r *http.Request) error {
+	reg.lock.Lock()
+	defer reg.lock.Unlock()
+
+	delete(reg.byUSN, r.Header.Get("USN"))
+
+	return nil
+}

ssdp/ssdp.go

@@ -12,9 +12,14 @@ import (
 )
 
 const (
-	ssdpDiscover = `"ssdp:discover"`
-	methodSearch = "M-SEARCH"
-	ssdpUDP4Addr = "239.255.255.250:1900"
+	ssdpDiscover   = `"ssdp:discover"`
+	ntsAlive       = `ssdp:alive`
+	ntsByebye      = `ssdp:byebye`
+	ntsUpdate      = `ssdp:update`
+	ssdpUDP4Addr   = "239.255.255.250:1900"
+	ssdpSearchPort = 1900
+	methodSearch   = "M-SEARCH"
+	methodNotify   = "NOTIFY"
 )
 
 // SSDPRawSearch performs a fairly raw SSDP search request, and returns the