noise: add documentation for the Prologue option

p2p/security/noise/session_transport.go

@@ -12,6 +12,16 @@ import (
 
 type SessionOption = func(*SessionTransport) error
 
+// Prologue sets a prologue for the Noise session.
+// The handshake will only complete successfully if both parties set the same prologue.
+// See https://noiseprotocol.org/noise.html#prologue for details.
+func Prologue(prologue []byte) SessionOption {
+	return func(s *SessionTransport) error {
+		s.prologue = prologue
+		return nil
+	}
+}
+
 var _ sec.SecureTransport = &SessionTransport{}
 
 // SessionTransport can be used
@@ -39,20 +49,3 @@ func (i *SessionTransport) SecureInbound(ctx context.Context, insecure net.Conn,
 func (i *SessionTransport) SecureOutbound(ctx context.Context, insecure net.Conn, p peer.ID) (sec.SecureConn, error) {
 	return newSecureSession(i.t, ctx, insecure, p, i.prologue, true)
 }
-
-func (t *Transport) WithSessionOptions(opts ...SessionOption) (sec.SecureTransport, error) {
-	st := &SessionTransport{t: t}
-	for _, opt := range opts {
-		if err := opt(st); err != nil {
-			return nil, err
-		}
-	}
-	return st, nil
-}
-
-func Prologue(prologue []byte) SessionOption {
-	return func(s *SessionTransport) error {
-		s.prologue = prologue
-		return nil
-	}
-}

p2p/security/noise/transport.go

@@ -55,3 +55,13 @@ func (t *Transport) SecureInbound(ctx context.Context, insecure net.Conn, p peer
 func (t *Transport) SecureOutbound(ctx context.Context, insecure net.Conn, p peer.ID) (sec.SecureConn, error) {
 	return newSecureSession(t, ctx, insecure, p, nil, true)
 }
+
+func (t *Transport) WithSessionOptions(opts ...SessionOption) (sec.SecureTransport, error) {
+	st := &SessionTransport{t: t}
+	for _, opt := range opts {
+		if err := opt(st); err != nil {
+			return nil, err
+		}
+	}
+	return st, nil
+}