homebrew mdns implementation
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parent
1e69f37777
commit
684aae7bc7
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@ -1,12 +1,18 @@
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package main
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import (
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"container/list"
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"encoding/json"
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"flag"
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"fmt"
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"log"
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"net"
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"os"
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"os/user"
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"path/filepath"
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"strings"
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"sync"
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"time"
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)
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const help = `unnamed-project: WIP
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@ -53,7 +59,7 @@ func main() {
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debug: debugFlag,
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}
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fmt.Println(conf)
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serve(conf)
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}
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@ -74,3 +80,209 @@ type config struct {
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sharePath string
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debug bool
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}
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type announcer struct {
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conf *config
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}
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type nodeInfo struct {
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nodeID string `json:"nodeID"`
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addr string `json:"addr"`
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webPort int `json:"webPort"`
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lastMulticast int64 `json:"lastMulticast"`
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}
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var (
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nodeMutex sync.Mutex
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)
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func newAnnouncePacket(n *nodeInfo) (string, error) {
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jsonMessage, err := json.Marshal(n)
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if err != nil {
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return "", err
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}
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message := fmt.Sprintf("%s%s%s", header, nodeAnnounceCommand, jsonMessage)
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return message, nil
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}
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func announceNode(nodeInfo *nodeInfo) {
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address, err := net.ResolveUDPAddr("udp", multicastAddress)
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if err != nil {
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return
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}
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conn, err := net.DialUDP("udp", nil, address)
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if err != nil {
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return
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}
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for {
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fmt.Println("sending multicast info")
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message, err := newAnnouncePacket(nodeInfo)
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if err != nil {
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fmt.Println("Could not get announce package")
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fmt.Println(err)
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continue
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}
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conn.Write([]byte(message))
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time.Sleep(announceIntervalSec * time.Second)
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}
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}
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const (
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multicastAddress = "239.6.6.6:1337"
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multicastBufferSize = 4096
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nodeAnnounceCommand = "\x01"
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header = "\x60\x0D\xF0\x0D"
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minPackageSize = 6
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expireTimeoutSec = 50
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announceIntervalSec = 10
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)
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func announcedNodeHandler(ninfo *nodeInfo, nodeList *list.List) {
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nodeMutex.Lock()
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updateNodeList(ninfo, nodeList)
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nodeMutex.Unlock()
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fmt.Println("Printing nodes")
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fmt.Print("[")
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for el := nodeList.Front(); el != nil; el = el.Next() {
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fmt.Print(el.Value.(*nodeInfo).nodeID, " ")
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}
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fmt.Print("]\n\n")
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}
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func updateNodeList(ninfo *nodeInfo, nodeList *list.List) {
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nodeExists := false
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for el := nodeList.Front(); el != nil; el = el.Next() {
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tmp := el.Value.(*nodeInfo)
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// Already in list
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if tmp.nodeID == ninfo.nodeID {
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tmp.lastMulticast = time.Now().Unix()
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fmt.Printf("Updating node %s multicast\n", ninfo.nodeID)
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nodeExists = true
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break
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}
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}
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for el := nodeList.Front(); el != nil; el = el.Next() {
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tmp := el.Value.(*nodeInfo)
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if isNodeExpired(tmp, expireTimeoutSec) {
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fmt.Println("Node expired, removing: ", tmp.nodeID)
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nodeList.Remove(el)
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}
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}
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if !nodeExists {
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fmt.Printf("Adding new node! %p %s\n", ninfo, ninfo.nodeID)
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ninfo.lastMulticast = time.Now().Unix()
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nodeList.PushBack(ninfo)
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}
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}
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func isNodeExpired(nodeInfo *nodeInfo, timeout int) bool {
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diff := time.Now().Unix() - nodeInfo.lastMulticast
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return diff > int64(timeout)
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}
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func parseAnnouncePacket(size int, addr *net.UDPAddr, packet []byte) (*nodeInfo, error) {
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if size <= minPackageSize {
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return nil, fmt.Errorf("Invalid packet size")
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}
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if strings.Compare(string(packet[0:len(header)]), header) != 0 {
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return nil, fmt.Errorf("Invalid packet header")
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}
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if string(packet[len(header):len(header)+1]) != nodeAnnounceCommand[0:] {
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return nil, fmt.Errorf("Command different than NODE_ANNOUNCE_COMMAND")
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}
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fmt.Println("Packet command is nodeAnnounceCommand")
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payload := string(packet[len(header)+1:])
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payload = strings.Trim(payload, "\x00")
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nodeInfo := &nodeInfo{}
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err := json.Unmarshal([]byte(payload), nodeInfo)
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nodeInfo.addr = addr.IP.String()
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nodeInfo.nodeID = fmt.Sprintf("%s-%s", nodeInfo.nodeID, nodeInfo.addr)
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if err != nil {
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return nil, err
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}
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return nodeInfo, nil
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}
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func listenForNodes(nodeList *list.List) {
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address, err := net.ResolveUDPAddr("udp", multicastAddress)
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if err != nil {
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return
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}
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conn, err := net.ListenMulticastUDP("udp", nil, address)
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if err != nil {
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return
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}
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conn.SetReadBuffer(multicastBufferSize)
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for {
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packet := make([]byte, multicastBufferSize)
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size, udpAddr, err := conn.ReadFromUDP(packet)
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if err != nil {
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fmt.Println(err)
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continue
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}
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nodeInfo, err := parseAnnouncePacket(size, udpAddr, packet)
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if err != nil {
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fmt.Println(err)
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continue
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}
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fmt.Printf("Received multicast packet from %s Id: %s\n", udpAddr.String(), nodeInfo.nodeID)
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go announcedNodeHandler(nodeInfo, nodeList)
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}
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}
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func (a *announcer) Start(nodeList *list.List) {
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nodeInfo := &nodeInfo{
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nodeID: a.conf.nodeID,
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addr: "",
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webPort: a.conf.webPort,
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lastMulticast: 0,
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}
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go announceNode(nodeInfo)
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go listenForNodes(nodeList)
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}
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func startAnnouncer(conf *config, nodeList *list.List) {
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announcer := &announcer{conf: conf}
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announcer.Start(nodeList)
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}
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func serve(conf *config) {
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nodeList := list.New()
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go startAnnouncer(conf, nodeList)
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// TODO: next steps...
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// go fileServe(conf)
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// go dashboardServe(conf, nodeList)
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for {
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// TODO: do this context cancel trick to escape cleanly?
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time.Sleep(time.Minute * 15)
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}
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}
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