feat: include client username and hostname in overlay messages

Added a new `HostInfo` struct to `overlayMessage` to encapsulate the
username and hostname of the connecting client. Updated the `Receive`
and `Send` handlers to utilize this information. Enhanced connection
logs to display the username and hostname, providing more context on
incoming connections. Refactored the `ListenOverlaySTUN` and
`ListenOverlayDERP` methods to use a new helper `newHelloPacket` for
constructing the initial packet with the client's host info.

Author: coadler

overlay/overlay.go

@@ -28,6 +28,12 @@ const (
 type overlayMessage struct {
 	Typ messageType
 
-	IP   netip.Addr
-	Node tailcfg.Node
+	HostInfo HostInfo
+	IP       netip.Addr
+	Node     tailcfg.Node
+}
+
+type HostInfo struct {
+	Username string
+	Hostname string
 }

overlay/receive.go

@@ -342,7 +342,15 @@ func (r *Receive) handleNextMessage(msg []byte, system string) (resRaw []byte, n
 	case messageTypeHello:
 		res.Typ = messageTypeHelloResponse
 		res.IP = r.assignNextIP()
-		fmt.Println(cliui.Timestamp(time.Now()), "Received connection request over", system)
+		username := "unknown"
+		if u := ovMsg.HostInfo.Username; u != "" {
+			username = u
+		}
+		hostname := "unknown"
+		if h := ovMsg.HostInfo.Hostname; h != "" {
+			hostname = h
+		}
+		fmt.Println(cliui.Timestamp(time.Now()), "Received connection request over", system, "from", cliui.Keyword(fmt.Sprintf("%s@%s", username, hostname)))
 	case messageTypeNodeUpdate:
 		fmt.Println(cliui.Timestamp(time.Now()), "Received updated node from", cliui.Code(ovMsg.Node.Key.String()))
 		r.in <- &ovMsg.Node

overlay/send.go

@@ -8,6 +8,8 @@ import (
 	"log/slog"
 	"net"
 	"net/netip"
+	"os"
+	"os/user"
 	"sync"
 	"time"
 
@@ -68,19 +70,12 @@ func (s *Send) ListenOverlaySTUN(ctx context.Context) error {
 		_ = conn.Close()
 	}()
 
-	raw, err := json.Marshal(overlayMessage{
-		Typ: messageTypeHello,
-	})
-	if err != nil {
-		panic("marshal node: " + err.Error())
-	}
-
+	sealed := s.newHelloPacket()
 	receiverAddr := s.Auth.ReceiverStunAddr
 	if s.STUNIPOverride.IsValid() {
 		receiverAddr = netip.AddrPortFrom(s.STUNIPOverride, s.Auth.ReceiverStunAddr.Port())
 	}
 
-	sealed := s.Auth.OverlayPrivateKey.SealTo(s.Auth.ReceiverPublicKey, raw)
 	_, err = conn.WriteToUDPAddrPort(sealed, receiverAddr)
 	if err != nil {
 		return fmt.Errorf("send overlay hello over STUN: %w", err)
@@ -168,14 +163,7 @@ func (s *Send) ListenOverlayDERP(ctx context.Context) error {
 		return err
 	}
 
-	raw, err := json.Marshal(overlayMessage{
-		Typ: messageTypeHello,
-	})
-	if err != nil {
-		panic("marshal node: " + err.Error())
-	}
-
-	sealed := s.Auth.OverlayPrivateKey.SealTo(s.Auth.ReceiverPublicKey, raw)
+	sealed := s.newHelloPacket()
 	err = c.Send(s.Auth.ReceiverPublicKey, sealed)
 	if err != nil {
 		return fmt.Errorf("send overlay hello over derp: %w", err)
@@ -236,6 +224,34 @@ func (s *Send) ListenOverlayDERP(ctx context.Context) error {
 	}
 }
 
+func (s *Send) newHelloPacket() []byte {
+	var (
+		username,
+		hostname string
+	)
+
+	cu, _ := user.Current()
+	if cu != nil {
+		username = cu.Username
+	}
+	hostname, _ = os.Hostname()
+
+	raw, err := json.Marshal(overlayMessage{
+		Typ: messageTypeHello,
+		HostInfo: HostInfo{
+			Username: username,
+			Hostname: hostname,
+		},
+	})
+	if err != nil {
+		panic("marshal node: " + err.Error())
+	}
+
+	fmt.Println("sending", string(raw))
+	sealed := s.Auth.OverlayPrivateKey.SealTo(s.Auth.ReceiverPublicKey, raw)
+	return sealed
+}
+
 func (s *Send) handleNextMessage(msg []byte) (resRaw []byte, _ error) {
 	cleartext, ok := s.Auth.OverlayPrivateKey.OpenFrom(s.Auth.ReceiverPublicKey, msg)
 	if !ok {