313 lines
7.3 KiB
Go
313 lines
7.3 KiB
Go
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package ssdp
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import (
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"fmt"
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"log"
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"net/http"
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"net/url"
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"regexp"
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"strconv"
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"sync"
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"time"
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"github.com/huin/goupnp/httpu"
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)
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const (
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maxExpiryTimeSeconds = 24 * 60 * 60
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)
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var (
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maxAgeRx = regexp.MustCompile("max-age=([0-9]+)")
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)
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const (
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EventAlive = EventType(iota)
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EventUpdate
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EventByeBye
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)
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type EventType int8
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func (et EventType) String() string {
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switch et {
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case EventAlive:
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return "EventAlive"
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case EventUpdate:
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return "EventUpdate"
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case EventByeBye:
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return "EventByeBye"
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default:
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return fmt.Sprintf("EventUnknown(%d)", int8(et))
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}
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}
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type Update struct {
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// The USN of the service.
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USN string
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// What happened.
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EventType EventType
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// The entry, which is nil if the service was not known and
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// EventType==EventByeBye. The contents of this must not be modified as it is
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// shared with the registry and other listeners. Once created, the Registry
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// does not modify the Entry value - any updates are replaced with a new
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// Entry value.
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Entry *Entry
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}
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type Entry struct {
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// The address that the entry data was actually received from.
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RemoteAddr string
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// Unique Service Name. Identifies a unique instance of a device or service.
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USN string
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// Notfication Type. The type of device or service being announced.
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NT string
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// Server's self-identifying string.
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Server string
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Host string
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// Location of the UPnP root device description.
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Location url.URL
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// Despite BOOTID,CONFIGID being required fields, apparently they are not
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// always set by devices. Set to -1 if not present.
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BootID int32
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ConfigID int32
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SearchPort uint16
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// When the last update was received for this entry identified by this USN.
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LastUpdate time.Time
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// When the last update's cached values are advised to expire.
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CacheExpiry time.Time
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}
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func newEntryFromRequest(r *http.Request) (*Entry, error) {
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now := time.Now()
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expiryDuration, err := parseCacheControlMaxAge(r.Header.Get("CACHE-CONTROL"))
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if err != nil {
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return nil, fmt.Errorf("ssdp: error parsing CACHE-CONTROL max age: %v", err)
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}
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loc, err := url.Parse(r.Header.Get("LOCATION"))
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if err != nil {
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return nil, fmt.Errorf("ssdp: error parsing entry Location URL: %v", err)
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}
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bootID, err := parseUpnpIntHeader(r.Header, "BOOTID.UPNP.ORG", -1)
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if err != nil {
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return nil, err
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}
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configID, err := parseUpnpIntHeader(r.Header, "CONFIGID.UPNP.ORG", -1)
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if err != nil {
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return nil, err
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}
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searchPort, err := parseUpnpIntHeader(r.Header, "SEARCHPORT.UPNP.ORG", ssdpSearchPort)
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if err != nil {
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return nil, err
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}
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if searchPort < 1 || searchPort > 65535 {
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return nil, fmt.Errorf("ssdp: search port %d is out of range", searchPort)
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}
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return &Entry{
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RemoteAddr: r.RemoteAddr,
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USN: r.Header.Get("USN"),
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NT: r.Header.Get("NT"),
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Server: r.Header.Get("SERVER"),
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Host: r.Header.Get("HOST"),
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Location: *loc,
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BootID: bootID,
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ConfigID: configID,
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SearchPort: uint16(searchPort),
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LastUpdate: now,
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CacheExpiry: now.Add(expiryDuration),
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}, nil
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}
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func parseCacheControlMaxAge(cc string) (time.Duration, error) {
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matches := maxAgeRx.FindStringSubmatch(cc)
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if len(matches) != 2 {
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return 0, fmt.Errorf("did not find exactly one max-age in cache control header: %q", cc)
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}
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expirySeconds, err := strconv.ParseInt(matches[1], 10, 16)
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if err != nil {
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return 0, err
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}
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if expirySeconds < 1 || expirySeconds > maxExpiryTimeSeconds {
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return 0, fmt.Errorf("rejecting bad expiry time of %d seconds", expirySeconds)
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}
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return time.Duration(expirySeconds) * time.Second, nil
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}
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// parseUpnpIntHeader is intended to parse the
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// {BOOT,CONFIGID,SEARCHPORT}.UPNP.ORG header fields. It returns the def if
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// the head is empty or missing.
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func parseUpnpIntHeader(headers http.Header, headerName string, def int32) (int32, error) {
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s := headers.Get(headerName)
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if s == "" {
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return def, nil
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}
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v, err := strconv.ParseInt(s, 10, 32)
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if err != nil {
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return 0, fmt.Errorf("ssdp: could not parse header %s: %v", headerName, err)
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}
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return int32(v), nil
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}
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var _ httpu.Handler = new(Registry)
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// Registry maintains knowledge of discovered devices and services.
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//
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// NOTE: the interface for this is experimental and may change, or go away
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// entirely.
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type Registry struct {
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lock sync.Mutex
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byUSN map[string]*Entry
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listenersLock sync.RWMutex
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listeners map[chan<- Update]struct{}
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}
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func NewRegistry() *Registry {
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return &Registry{
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byUSN: make(map[string]*Entry),
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listeners: make(map[chan<- Update]struct{}),
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}
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}
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// NewServerAndRegistry is a convenience function to create a registry, and an
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// httpu server to pass it messages. Call ListenAndServe on the server for
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// messages to be processed.
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func NewServerAndRegistry() (*httpu.Server, *Registry) {
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reg := NewRegistry()
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srv := &httpu.Server{
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Addr: ssdpUDP4Addr,
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Multicast: true,
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Handler: reg,
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}
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return srv, reg
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}
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func (reg *Registry) AddListener(c chan<- Update) {
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reg.listenersLock.Lock()
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defer reg.listenersLock.Unlock()
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reg.listeners[c] = struct{}{}
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}
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func (reg *Registry) RemoveListener(c chan<- Update) {
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reg.listenersLock.Lock()
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defer reg.listenersLock.Unlock()
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delete(reg.listeners, c)
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}
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func (reg *Registry) sendUpdate(u Update) {
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reg.listenersLock.RLock()
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defer reg.listenersLock.RUnlock()
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for c := range reg.listeners {
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c <- u
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}
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}
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// GetService returns known service (or device) entries for the given service
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// URN.
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func (reg *Registry) GetService(serviceURN string) []*Entry {
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// Currently assumes that the map is small, so we do a linear search rather
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// than indexed to avoid maintaining two maps.
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var results []*Entry
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reg.lock.Lock()
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defer reg.lock.Unlock()
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for _, entry := range reg.byUSN {
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if entry.NT == serviceURN {
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results = append(results, entry)
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}
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}
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return results
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}
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// ServeMessage implements httpu.Handler, and uses SSDP NOTIFY requests to
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// maintain the registry of devices and services.
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func (reg *Registry) ServeMessage(r *http.Request) {
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if r.Method != methodNotify {
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return
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}
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nts := r.Header.Get("nts")
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var err error
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switch nts {
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case ntsAlive:
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err = reg.handleNTSAlive(r)
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case ntsUpdate:
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err = reg.handleNTSUpdate(r)
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case ntsByebye:
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err = reg.handleNTSByebye(r)
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default:
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err = fmt.Errorf("unknown NTS value: %q", nts)
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}
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if err != nil {
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log.Printf("goupnp/ssdp: failed to handle %s message from %s: %v", nts, r.RemoteAddr, err)
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}
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}
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func (reg *Registry) handleNTSAlive(r *http.Request) error {
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entry, err := newEntryFromRequest(r)
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if err != nil {
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return err
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}
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reg.lock.Lock()
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reg.byUSN[entry.USN] = entry
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reg.lock.Unlock()
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reg.sendUpdate(Update{
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USN: entry.USN,
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EventType: EventAlive,
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Entry: entry,
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})
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return nil
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}
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func (reg *Registry) handleNTSUpdate(r *http.Request) error {
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entry, err := newEntryFromRequest(r)
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if err != nil {
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return err
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}
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nextBootID, err := parseUpnpIntHeader(r.Header, "NEXTBOOTID.UPNP.ORG", -1)
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if err != nil {
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return err
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}
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entry.BootID = nextBootID
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reg.lock.Lock()
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reg.byUSN[entry.USN] = entry
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reg.lock.Unlock()
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reg.sendUpdate(Update{
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USN: entry.USN,
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EventType: EventUpdate,
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Entry: entry,
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})
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return nil
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}
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func (reg *Registry) handleNTSByebye(r *http.Request) error {
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usn := r.Header.Get("USN")
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reg.lock.Lock()
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entry := reg.byUSN[usn]
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delete(reg.byUSN, usn)
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reg.lock.Unlock()
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reg.sendUpdate(Update{
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USN: usn,
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EventType: EventByeBye,
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Entry: entry,
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})
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return nil
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}
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