Refactor - now wireguard based. (#7)

peer/multicast/receiver.go

@@ -0,0 +1,61 @@
+package multicast
+
+import (
+	"bytes"
+	"fmt"
+	"log"
+	"net"
+	"net/netip"
+	"time"
+)
+
+func Receiver(vpnNet netip.Prefix, selfVPNIP netip.Addr, ch chan<- Packet) {
+	for {
+		if err := receiver(vpnNet, selfVPNIP, ch); err != nil {
+			log.Printf("[MCReader] %v", err)
+		}
+		time.Sleep(errorTimeout)
+	}
+}
+
+func receiver(vpnNet netip.Prefix, selfVPNIP netip.Addr, ch chan<- Packet) error {
+	selfIP := selfVPNIP.As4()[3]
+
+	conn, err := net.ListenMulticastUDP("udp", nil, addr)
+	if err != nil {
+		return fmt.Errorf("bind: %w", err)
+	}
+	defer conn.Close()
+
+	buf := make([]byte, BufferSize+1) // +1 to detect oversized packets
+
+	for {
+		conn.SetReadDeadline(time.Now().Add(32 * time.Second))
+		n, src, err := conn.ReadFromUDPAddrPort(buf)
+		if err != nil {
+			if ne, ok := err.(net.Error); ok && ne.Timeout() {
+				continue
+			}
+			return fmt.Errorf("read: %w", err)
+		}
+
+		if n != SignedPacketSize {
+			continue
+		}
+
+		packet := Unmarshal(buf[:n])
+
+		if packet.PeerIP == selfIP {
+			continue
+		}
+
+		age := time.Since(time.Unix(packet.Timestamp, 0))
+		if age > maxPacketAge || age < -maxPacketAge {
+			continue
+		}
+
+		packet.Signed = bytes.Clone(packet.Signed)
+		packet.Src = src.Addr().Unmap()
+		ch <- packet
+	}
+}