Move multicasting into yggdrasil package

src/yggdrasil/multicast.go

@@ -0,0 +1,160 @@
+package yggdrasil
+
+import "net"
+import "time"
+import "fmt"
+
+import "golang.org/x/net/ipv6"
+
+type multicast struct {
+	core      *Core
+	sock      *ipv6.PacketConn
+	groupAddr string
+  interfaces []net.Interface
+}
+
+func (m *multicast) init(core *Core) {
+	m.core = core
+	m.groupAddr = "[ff02::114]:9001"
+  // Ask the system for network interfaces
+  allifaces, err := net.Interfaces()
+  if err != nil {
+    panic(err)
+  }
+  // Work out which interfaces to announce on
+  for _, iface := range allifaces {
+    if iface.Flags & net.FlagUp == 0 {
+      // Ignore interfaces that are down
+      continue
+    }
+    if iface.Flags & net.FlagMulticast == 0 {
+      // Ignore non-multicast interfaces
+      continue
+    }
+    if iface.Flags & net.FlagPointToPoint != 0 {
+      // Ignore point-to-point interfaces
+      continue
+    }
+    for _, expr := range m.core.ifceExpr {
+      m.core.log.Println(expr)
+      if expr.MatchString(iface.Name) {
+        m.core.log.Println(iface.Name, "matched", expr)
+        m.interfaces = append(m.interfaces, iface)
+      }
+    }
+  }
+  m.core.log.Println("Found", len(m.interfaces), "multicast interfaces")
+}
+
+func (m *multicast) Start() {
+	if len(m.core.ifceExpr) == 0 {
+		m.core.log.Println("Not starting multicast discovery")
+	} else {
+    m.core.log.Println("Starting multicast discovery...")
+  	addr, err := net.ResolveUDPAddr("udp", m.groupAddr)
+  	if err != nil {
+  		panic(err)
+  	}
+  	listenString := fmt.Sprintf("[::]:%v", addr.Port)
+  	conn, err := net.ListenPacket("udp6", listenString)
+  	if err != nil {
+  		panic(err)
+  	}
+  	//defer conn.Close() // Let it close on its own when the application exits
+  	m.sock = ipv6.NewPacketConn(conn)
+  	if err = m.sock.SetControlMessage(ipv6.FlagDst, true); err != nil {
+  		// Windows can't set this flag, so we need to handle it in other ways
+  		//panic(err)
+  	}
+
+  	go m.listen()
+  	go m.announce()
+  }
+}
+
+func (m *multicast) announce() {
+	groupAddr, err := net.ResolveUDPAddr("udp6", m.groupAddr)
+	if err != nil {
+		panic(err)
+	}
+	var anAddr net.TCPAddr
+	myAddr := m.core.DEBUG_getGlobalTCPAddr()
+	anAddr.Port = myAddr.Port
+	destAddr, err := net.ResolveUDPAddr("udp6", m.groupAddr)
+	if err != nil {
+		panic(err)
+	}
+	for {
+		for _, iface := range m.interfaces {
+
+			m.sock.JoinGroup(&iface, groupAddr)
+			//err := n.sock.JoinGroup(&iface, groupAddr)
+			//if err != nil { panic(err) }
+			addrs, err := iface.Addrs()
+			if err != nil {
+				panic(err)
+			}
+			for _, addr := range addrs {
+				addrIP, _, _ := net.ParseCIDR(addr.String())
+				if addrIP.To4() != nil {
+					continue
+				} // IPv6 only
+				if !addrIP.IsLinkLocalUnicast() {
+					continue
+				}
+				anAddr.IP = addrIP
+				anAddr.Zone = iface.Name
+				destAddr.Zone = iface.Name
+				msg := []byte(anAddr.String())
+				m.sock.WriteTo(msg, nil, destAddr)
+				break
+			}
+			time.Sleep(time.Second)
+		}
+		time.Sleep(time.Second)
+	}
+}
+
+func (m *multicast) listen() {
+	groupAddr, err := net.ResolveUDPAddr("udp6", m.groupAddr)
+	if err != nil {
+		panic(err)
+	}
+	bs := make([]byte, 2048)
+	for {
+		nBytes, rcm, fromAddr, err := m.sock.ReadFrom(bs)
+		if err != nil {
+			panic(err)
+		}
+		//if rcm == nil { continue } // wat
+		//fmt.Println("DEBUG:", "packet from:", fromAddr.String())
+		if rcm != nil {
+			// Windows can't set the flag needed to return a non-nil value here
+			// So only make these checks if we get something useful back
+			// TODO? Skip them always, I'm not sure if they're really needed...
+			if !rcm.Dst.IsLinkLocalMulticast() {
+				continue
+			}
+			if !rcm.Dst.Equal(groupAddr.IP) {
+				continue
+			}
+		}
+		anAddr := string(bs[:nBytes])
+		addr, err := net.ResolveTCPAddr("tcp6", anAddr)
+		if err != nil {
+			panic(err)
+			continue
+		} // Panic for testing, remove later
+		from := fromAddr.(*net.UDPAddr)
+		//fmt.Println("DEBUG:", "heard:", addr.IP.String(), "from:", from.IP.String())
+		if addr.IP.String() != from.IP.String() {
+			continue
+		}
+		addr.Zone = from.Zone
+		saddr := addr.String()
+		//if _, isIn := n.peers[saddr]; isIn { continue }
+		//n.peers[saddr] = struct{}{}
+		m.core.DEBUG_addTCPConn(saddr)
+		//fmt.Println("DEBUG:", "added multicast peer:", saddr)
+	}
+}