Improve mDNS package
This commit is contained in:
Alexey Khit
+216
-21
@@ -1,18 +1,19 @@
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package mdns
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import (
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"context"
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"errors"
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"fmt"
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"github.com/miekg/dns"
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"net"
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"strings"
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"syscall"
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"time"
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"github.com/miekg/dns" // awesome library for parsing mDNS records
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)
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const ServiceHAP = "_hap._tcp.local." // HomeKit Accessory Protocol
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const requestTimeout = time.Millisecond * 505
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const responseTimeout = time.Second * 2
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type ServiceEntry struct {
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Name string
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IP net.IP
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@@ -28,40 +29,191 @@ func (e *ServiceEntry) Addr() string {
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return fmt.Sprintf("%s:%d", e.IP, e.Port)
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}
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func Discovery(service string, onentry func(*ServiceEntry) bool) error {
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addr := &net.UDPAddr{
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IP: net.IP{224, 0, 0, 251},
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Port: 5353,
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}
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var MulticastAddr = &net.UDPAddr{
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IP: net.IP{224, 0, 0, 251},
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Port: 5353,
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}
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conn, err := net.ListenMulticastUDP("udp4", nil, addr)
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const sendTimeout = time.Millisecond * 505
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const respTimeout = time.Second * 3
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// BasicDiscovery - default golang Multicast UDP listener.
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// Does not work well with multiple interfaces.
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func BasicDiscovery(service string, onentry func(*ServiceEntry) bool) error {
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conn, err := net.ListenMulticastUDP("udp4", nil, MulticastAddr)
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if err != nil {
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return err
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}
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defer conn.Close()
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b := Browser{
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Service: service,
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Addr: MulticastAddr,
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Recv: conn,
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Sends: []net.PacketConn{conn},
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RecvTimeout: respTimeout,
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SendTimeout: sendTimeout,
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}
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if err = conn.SetDeadline(time.Now().Add(responseTimeout)); err != nil {
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defer b.Close()
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return b.Browse(onentry)
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}
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// Discovery - better discovery version. Works well with multiple interfaces.
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func Discovery(service string, onentry func(*ServiceEntry) bool) error {
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b := Browser{
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Service: service,
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Addr: MulticastAddr,
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RecvTimeout: respTimeout,
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SendTimeout: sendTimeout,
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}
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if err := b.ListenMulticastUDP(); err != nil {
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return err
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}
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msg := &dns.Msg{
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Question: []dns.Question{
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{service, dns.TypePTR, dns.ClassINET},
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defer b.Close()
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return b.Browse(onentry)
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}
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// Query - direct Discovery request on device IP-address. Works even over VPN.
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func Query(host, service string) (entry *ServiceEntry, err error) {
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conn, err := net.ListenPacket("udp4", ":0") // shouldn't use ":5353"
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if err != nil {
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return
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}
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br := Browser{
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Service: service,
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Addr: &net.UDPAddr{
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IP: net.ParseIP(host),
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Port: 5353,
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},
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Recv: conn,
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Sends: []net.PacketConn{conn},
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SendTimeout: time.Millisecond * 255,
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RecvTimeout: time.Second,
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}
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defer br.Close()
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err = br.Browse(func(en *ServiceEntry) bool {
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entry = en
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return true
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})
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return
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}
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func QueryOrDiscovery(host, service string, onentry func(*ServiceEntry) bool) error {
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entry, _ := Query(host, service)
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if entry != nil && onentry(entry) {
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return nil
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}
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return Discovery(service, onentry)
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}
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type Browser struct {
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Service string
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Addr net.Addr
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Recv net.PacketConn
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Sends []net.PacketConn
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RecvTimeout time.Duration
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SendTimeout time.Duration
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}
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// ListenMulticastUDP - creates multiple senders socket (each for IP4 interface).
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// And one receiver with multicast membership for each sender.
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// Receiver will get multicast responses on senders requests.
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func (b *Browser) ListenMulticastUDP() error {
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// 1. Collect IPv4 interfaces
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ip4s, err := InterfacesIP4()
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if err != nil {
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return err
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}
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ctx := context.Background()
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// 2. Create senders
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lc1 := net.ListenConfig{
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Control: func(network, address string, c syscall.RawConn) error {
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return c.Control(func(fd uintptr) {
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// 1. Allow multicast UDP to listen concurrently across multiple listeners
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_ = syscall.SetsockoptInt(syscall.Handle(fd), syscall.SOL_SOCKET, syscall.SO_REUSEADDR, 1)
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})
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},
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}
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b1, err := msg.Pack()
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for _, ip4 := range ip4s {
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conn, err := lc1.ListenPacket(ctx, "udp4", ip4.String()+":5353") // same port important
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if err != nil {
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continue
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}
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b.Sends = append(b.Sends, conn)
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}
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if b.Sends == nil {
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return errors.New("no interfaces for listen")
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}
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// 3. Create receiver
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lc2 := net.ListenConfig{
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Control: func(network, address string, c syscall.RawConn) error {
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return c.Control(func(fd uintptr) {
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// 1. Allow multicast UDP to listen concurrently across multiple listeners
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_ = syscall.SetsockoptInt(syscall.Handle(fd), syscall.SOL_SOCKET, syscall.SO_REUSEADDR, 1)
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// 2. Disable loop responses
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_ = syscall.SetsockoptInt(syscall.Handle(fd), syscall.IPPROTO_IP, syscall.IP_MULTICAST_LOOP, 0)
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// 3. Allow receive multicast responses on all this addresses
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mreq := &syscall.IPMreq{
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Multiaddr: [4]byte{224, 0, 0, 251},
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}
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_ = syscall.SetsockoptIPMreq(syscall.Handle(fd), syscall.IPPROTO_IP, syscall.IP_ADD_MEMBERSHIP, mreq)
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for _, send := range b.Sends {
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addr := send.LocalAddr().(*net.UDPAddr)
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mreq.Interface = [4]byte(addr.IP.To4())
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_ = syscall.SetsockoptIPMreq(syscall.Handle(fd), syscall.IPPROTO_IP, syscall.IP_ADD_MEMBERSHIP, mreq)
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}
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})
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},
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}
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b.Recv, err = lc2.ListenPacket(ctx, "udp4", "0.0.0.0:5353")
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return err
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}
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func (b *Browser) Browse(onentry func(*ServiceEntry) bool) error {
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msg := &dns.Msg{
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Question: []dns.Question{
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{b.Service, dns.TypePTR, dns.ClassINET},
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},
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}
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query, err := msg.Pack()
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if err != nil {
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return err
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}
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if err = b.Recv.SetDeadline(time.Now().Add(b.RecvTimeout)); err != nil {
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return err
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}
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go func() {
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for {
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if _, err := conn.WriteToUDP(b1, addr); err != nil {
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return
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for _, send := range b.Sends {
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if _, err := send.WriteTo(query, b.Addr); err != nil {
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return
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}
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}
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time.Sleep(requestTimeout)
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time.Sleep(b.SendTimeout)
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}
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}()
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@@ -71,7 +223,7 @@ func Discovery(service string, onentry func(*ServiceEntry) bool) error {
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loop:
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for {
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// in the Hass docker network can receive same msg from different address
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n, _, err := conn.ReadFromUDP(b2)
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n, _, err := b.Recv.ReadFrom(b2)
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if err != nil {
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break
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}
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@@ -82,7 +234,7 @@ loop:
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ptr := GetPTR(msg)
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if !strings.HasSuffix(ptr, service) {
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if !strings.HasSuffix(ptr, b.Service) {
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continue
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}
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@@ -102,6 +254,16 @@ loop:
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return nil
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}
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func (b *Browser) Close() error {
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if b.Recv != nil {
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_ = b.Recv.Close()
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}
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for _, send := range b.Sends {
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_ = send.Close()
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}
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return nil
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}
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func GetPTR(msg *dns.Msg) string {
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for _, rr := range msg.Answer {
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if rr, ok := rr.(*dns.PTR); ok {
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@@ -139,3 +301,36 @@ func NewServiceEntry(msg *dns.Msg) *ServiceEntry {
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return entry
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}
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func InterfacesIP4() ([]net.IP, error) {
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intfs, err := net.Interfaces()
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if err != nil {
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return nil, err
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}
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var ips []net.IP
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loop:
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for _, intf := range intfs {
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if intf.Flags&net.FlagUp == 0 || intf.Flags&net.FlagLoopback != 0 {
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continue
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}
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addrs, err := intf.Addrs()
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if err != nil {
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continue
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}
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for _, addr := range addrs {
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switch v := addr.(type) {
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case *net.IPNet:
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if ip := v.IP.To4(); ip != nil {
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ips = append(ips, ip)
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continue loop
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}
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}
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}
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}
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return ips, nil
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}
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