Link refactoring, admin socket changes

src/multicast/advertisement.go

@@ -0,0 +1,28 @@
+package multicast
+
+import (
+	"crypto/ed25519"
+	"encoding/binary"
+	"fmt"
+)
+
+type multicastAdvertisement struct {
+	PublicKey ed25519.PublicKey
+	Port      uint16
+}
+
+func (m *multicastAdvertisement) MarshalBinary() ([]byte, error) {
+	b := make([]byte, 0, ed25519.PublicKeySize+2)
+	b = append(b, m.PublicKey...)
+	b = binary.BigEndian.AppendUint16(b, m.Port)
+	return b, nil
+}
+
+func (m *multicastAdvertisement) UnmarshalBinary(b []byte) error {
+	if len(b) < ed25519.PublicKeySize+2 {
+		return fmt.Errorf("invalid multicast beacon")
+	}
+	m.PublicKey = b[:ed25519.PublicKeySize]
+	m.Port = binary.BigEndian.Uint16(b[ed25519.PublicKeySize:])
+	return nil
+}