TUN-8646: Allow experimental feature support for datagram v3

Closes TUN-8646

connection/quic_datagram_v3.go

@@ -0,0 +1,48 @@
+package connection
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"time"
+
+	"github.com/google/uuid"
+	"github.com/quic-go/quic-go"
+	"github.com/rs/zerolog"
+
+	cfdquic "github.com/cloudflare/cloudflared/quic/v3"
+	"github.com/cloudflare/cloudflared/tunnelrpc/pogs"
+)
+
+type datagramV3Connection struct {
+	conn quic.Connection
+	// datagramMuxer mux/demux datagrams from quic connection
+	datagramMuxer cfdquic.DatagramConn
+	logger        *zerolog.Logger
+}
+
+func NewDatagramV3Connection(ctx context.Context,
+	conn quic.Connection,
+	sessionManager cfdquic.SessionManager,
+	logger *zerolog.Logger,
+) DatagramSessionHandler {
+	datagramMuxer := cfdquic.NewDatagramConn(conn, sessionManager, logger)
+
+	return &datagramV3Connection{
+		conn,
+		datagramMuxer,
+		logger,
+	}
+}
+
+func (d *datagramV3Connection) Serve(ctx context.Context) error {
+	return d.datagramMuxer.Serve(ctx)
+}
+
+func (d *datagramV3Connection) RegisterUdpSession(ctx context.Context, sessionID uuid.UUID, dstIP net.IP, dstPort uint16, closeAfterIdleHint time.Duration, traceContext string) (*pogs.RegisterUdpSessionResponse, error) {
+	return nil, fmt.Errorf("datagram v3 does not support RegisterUdpSession RPC")
+}
+
+func (d *datagramV3Connection) UnregisterUdpSession(ctx context.Context, sessionID uuid.UUID, message string) error {
+	return fmt.Errorf("datagram v3 does not support UnregisterUdpSession RPC")
+}