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use libp2p/zeroconf for mDNS discovery
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,218 @@ | ||
| package discovery | ||
|
|
||
| import ( | ||
| "context" | ||
| "errors" | ||
| "io" | ||
| "net" | ||
| "strings" | ||
| "sync" | ||
|
|
||
| logging "github.com/ipfs/go-log/v2" | ||
| "github.com/libp2p/go-libp2p-core/host" | ||
| "github.com/libp2p/go-libp2p-core/peer" | ||
| "github.com/libp2p/zeroconf/v2" | ||
|
|
||
| ma "github.com/multiformats/go-multiaddr" | ||
| manet "github.com/multiformats/go-multiaddr/net" | ||
| ) | ||
|
|
||
| const ( | ||
| ServiceName = "_p2p._udp" | ||
| mdnsDomain = "local" | ||
| dnsaddrPrefix = "dnsaddr=" | ||
| ) | ||
|
|
||
| var log = logging.Logger("mdns") | ||
|
|
||
| type Service interface { | ||
| io.Closer | ||
| RegisterNotifee(Notifee) | ||
| UnregisterNotifee(Notifee) | ||
| } | ||
|
|
||
| type Notifee interface { | ||
| HandlePeerFound(peer.AddrInfo) | ||
| } | ||
|
|
||
| type mdnsService struct { | ||
| host host.Host | ||
| serviceName string | ||
|
|
||
| // This ctx is passed to the resolver. | ||
| // It is closed when Close() is called. | ||
| ctx context.Context | ||
| ctxCancel context.CancelFunc | ||
|
|
||
| resolverRunning chan struct{} | ||
| server *zeroconf.Server | ||
|
|
||
| mutex sync.Mutex | ||
| notifees []Notifee | ||
| } | ||
|
|
||
| func NewMdnsService(host host.Host, serviceName string) *mdnsService { | ||
| ctx, cancel := context.WithCancel(context.Background()) | ||
| if serviceName == "" { | ||
| serviceName = ServiceName | ||
| } | ||
| s := &mdnsService{ | ||
| ctx: ctx, | ||
| ctxCancel: cancel, | ||
| resolverRunning: make(chan struct{}), | ||
| host: host, | ||
| serviceName: serviceName, | ||
| } | ||
| s.startServer() | ||
| s.startResolver() | ||
| return s | ||
| } | ||
|
|
||
| func (s *mdnsService) Close() error { | ||
| s.ctxCancel() | ||
| if s.server != nil { | ||
| s.server.Shutdown() | ||
| } | ||
| <-s.resolverRunning | ||
| return nil | ||
| } | ||
|
|
||
| // We don't really care about the IP addresses, but the spec (and various routers / firewalls) require us | ||
| // to send A and AAAA records. | ||
| func (s *mdnsService) getIPs(addrs []ma.Multiaddr) ([]string, error) { | ||
| var ip4, ip6 string | ||
| for _, addr := range addrs { | ||
| network, hostport, err := manet.DialArgs(addr) | ||
| if err != nil { | ||
| continue | ||
| } | ||
| host, _, err := net.SplitHostPort(hostport) | ||
| if err != nil { | ||
| continue | ||
| } | ||
| if ip4 == "" && (network == "udp4" || network == "tcp4") { | ||
| ip4 = host | ||
| } else if ip6 == "" && (network == "udp6" || network == "tcp6") { | ||
| ip6 = host | ||
| } | ||
| } | ||
| ips := make([]string, 0, 2) | ||
| if ip4 != "" { | ||
| ips = append(ips, ip4) | ||
| } | ||
| if ip6 != "" { | ||
| ips = append(ips, ip6) | ||
| } | ||
| if len(ips) == 0 { | ||
| return nil, errors.New("didn't find any IP addresses") | ||
| } | ||
| return ips, nil | ||
| } | ||
|
|
||
| func (s *mdnsService) mdnsInstance() string { | ||
| return string(s.host.ID()) | ||
| } | ||
|
|
||
| func (s *mdnsService) startServer() error { | ||
| interfaceAddrs, err := s.host.Network().InterfaceListenAddresses() | ||
| if err != nil { | ||
| return err | ||
| } | ||
| addrs, err := peer.AddrInfoToP2pAddrs(&peer.AddrInfo{ | ||
| ID: s.host.ID(), | ||
| Addrs: interfaceAddrs, | ||
| }) | ||
| if err != nil { | ||
| return err | ||
| } | ||
| var txts []string | ||
| for _, addr := range addrs { | ||
| if manet.IsThinWaist(addr) { // don't announce circuit addresses | ||
| txts = append(txts, dnsaddrPrefix+addr.String()) | ||
| } | ||
| } | ||
|
|
||
| ips, err := s.getIPs(addrs) | ||
| if err != nil { | ||
| return err | ||
| } | ||
|
|
||
| server, err := zeroconf.RegisterProxy( | ||
| s.mdnsInstance(), | ||
| s.serviceName, | ||
| mdnsDomain, | ||
| 4001, | ||
| s.host.ID().Pretty(), // TODO: deals with peer IDs longer than 63 characters | ||
| ips, | ||
| txts, | ||
| nil, | ||
| ) | ||
| if err != nil { | ||
| return err | ||
| } | ||
| s.server = server | ||
| return nil | ||
| } | ||
|
|
||
| func (s *mdnsService) startResolver() { | ||
| entryChan := make(chan *zeroconf.ServiceEntry, 1000) | ||
| go func() { | ||
| for entry := range entryChan { | ||
| // We only care about the TXT records. | ||
| // Ignore A, AAAA and PTR. | ||
| addrs := make([]ma.Multiaddr, 0, len(entry.Text)) // assume that all TXT records are dnsaddrs | ||
| for _, s := range entry.Text { | ||
| if !strings.HasPrefix(s, dnsaddrPrefix) { | ||
| log.Debug("missing dnsaddr prefix") | ||
| continue | ||
| } | ||
| addr, err := ma.NewMultiaddr(s[len(dnsaddrPrefix):]) | ||
| if err != nil { | ||
| log.Debugf("failed to parse multiaddr: %s", err) | ||
| continue | ||
| } | ||
| addrs = append(addrs, addr) | ||
| } | ||
| infos, err := peer.AddrInfosFromP2pAddrs(addrs...) | ||
| if err != nil { | ||
| log.Debugf("failed to get peer info: %s", err) | ||
| continue | ||
| } | ||
| s.mutex.Lock() | ||
| for _, info := range infos { | ||
| for _, notif := range s.notifees { | ||
| go notif.HandlePeerFound(info) | ||
| } | ||
| } | ||
| s.mutex.Unlock() | ||
| } | ||
| }() | ||
| go func() { | ||
| defer close(s.resolverRunning) | ||
| if err := zeroconf.Browse(s.ctx, s.serviceName, mdnsDomain, entryChan); err != nil { | ||
| log.Debugf("zeroconf browsing failed: %s", err) | ||
| } | ||
| }() | ||
| } | ||
|
|
||
| func (s *mdnsService) RegisterNotifee(n Notifee) { | ||
| s.mutex.Lock() | ||
| s.notifees = append(s.notifees, n) | ||
| s.mutex.Unlock() | ||
| } | ||
|
|
||
| func (s *mdnsService) UnregisterNotifee(n Notifee) { | ||
| s.mutex.Lock() | ||
| defer s.mutex.Unlock() | ||
|
|
||
| found := -1 | ||
| for i, notif := range s.notifees { | ||
| if notif == n { | ||
| found = i | ||
| break | ||
| } | ||
| } | ||
| if found != -1 { | ||
| s.notifees = append(s.notifees[:found], s.notifees[found+1:]...) | ||
| } | ||
| } |
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