feat: implement autodiscovery.

README.md

@@ -55,6 +55,10 @@ Smee's DHCP functionality can operate in one of the following modes:
    Smee will not respond to DHCP requests from clients. This is useful when the network has an existing DHCP server that will provide both IP and next boot info and Smee's TFTP and HTTP functionality will be used. The IP address in the hardware record must be the same as the IP address of the client requesting the `auto.ipxe` script. See this [doc](docs/DHCP.md) for more details.  
    To enable this mode set `-dhcp-enabled=false`.
 
+### Auto discovery
+
+In proxy DHCP mode, Smee can optionally be configured to provide network boot options to all network boot clients. This is called auto-discovery or auto-enrollment. When set to true, all machines are treated as iPXE clients and boot from the network, and a new hardware entry is automatically created for each when Smee receives a DHCP request. This feature is useful for environments where hardware is frequently added or removed, as it allows for automatic tracking and management of hardware resources.
+
 ### Interoperability with other DHCP servers
 
 It is not recommended, but it is possible for Smee to be run in `reservation` mode in networks with another DHCP server(s). To get the intended behavior from Smee one of the following must be true.

cmd/smee/flag.go

@@ -113,6 +113,7 @@ func ipxeHTTPScriptFlags(c *config, fs *flag.FlagSet) {
 func dhcpFlags(c *config, fs *flag.FlagSet) {
 	fs.BoolVar(&c.dhcp.enabled, "dhcp-enabled", true, "[dhcp] enable DHCP server")
 	fs.StringVar(&c.dhcp.mode, "dhcp-mode", "reservation", "[dhcp] DHCP mode (reservation, proxy)")
+	fs.BoolVar(&c.dhcp.autoDiscovery, "dhcp-auto-discovery", false, "[dhcp] enable auto discovery mode (only available with -dhcp-mode=proxy)")
 	fs.StringVar(&c.dhcp.bindAddr, "dhcp-addr", "0.0.0.0:67", "[dhcp] local IP:Port to listen on for DHCP requests")
 	fs.StringVar(&c.dhcp.bindInterface, "dhcp-iface", "", "[dhcp] interface to bind to for DHCP requests")
 	fs.StringVar(&c.dhcp.ipForPacket, "dhcp-ip-for-packet", detectPublicIPv4(""), "[dhcp] IP address to use in DHCP packets (opt 54, etc)")

cmd/smee/main.go

@@ -90,6 +90,7 @@ type ipxeHTTPScript struct {
 type dhcpConfig struct {
 	enabled           bool
 	mode              string
+	autoDiscovery     bool
 	bindAddr          string
 	bindInterface     string
 	ipForPacket       string
@@ -344,7 +345,7 @@ func (c *config) dhcpHandler(ctx context.Context, log logr.Logger) (server.Handl
 		return dh, nil
 	case "proxy":
 		dh := &proxy.Handler{
-			Backend: backend,
+			Backend: backend.(handler.BackendReadWriter),
 			IPAddr:  pktIP,
 			Log:     log,
 			Netboot: proxy.Netboot{
@@ -353,7 +354,8 @@ func (c *config) dhcpHandler(ctx context.Context, log logr.Logger) (server.Handl
 				IPXEScriptURL:     ipxeScript,
 				Enabled:           true,
 			},
-			OTELEnabled: true,
+			OTELEnabled:          true,
+			AutoDiscoveryEnabled: c.dhcp.autoDiscovery,
 		}
 		return dh, nil
 	}

internal/backend/kube/error.go

@@ -5,3 +5,11 @@ type hardwareNotFoundError struct{}
 func (hardwareNotFoundError) NotFound() bool { return true }
 
 func (hardwareNotFoundError) Error() string { return "hardware not found" }
+
+func IsHardwareNotFoundError(err error) bool {
+	if err == nil {
+		return false
+	}
+	e, ok := err.(hardwareNotFoundError)
+	return ok && e.NotFound()
+}

internal/backend/kube/kube.go

@@ -8,19 +8,23 @@ import (
 	"net"
 	"net/netip"
 	"net/url"
+	"strings"
 
 	"github.com/tinkerbell/smee/internal/dhcp/data"
 	"github.com/tinkerbell/tink/api/v1alpha1"
 	"go.opentelemetry.io/otel"
 	"go.opentelemetry.io/otel/codes"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/client-go/kubernetes/scheme"
 	"k8s.io/client-go/rest"
+	"k8s.io/utils/ptr"
 	"sigs.k8s.io/controller-runtime/pkg/client"
 	"sigs.k8s.io/controller-runtime/pkg/cluster"
 )
 
 const tracerName = "github.com/tinkerbell/smee/dhcp"
+const tinkerbellNamespace = "tink-system"
 
 // Backend is a backend implementation that uses the Tinkerbell CRDs to get DHCP data.
 type Backend struct {
@@ -182,6 +186,42 @@ func (b *Backend) GetByIP(ctx context.Context, ip net.IP) (*data.DHCP, *data.Net
 	return d, n, nil
 }
 
+func (b *Backend) CreateByMac(ctx context.Context, mac net.HardwareAddr) error {
+	tracer := otel.Tracer(tracerName)
+	ctx, span := tracer.Start(ctx, "backend.kube.CreateByMac")
+	defer span.End()
+
+	hardware := &v1alpha1.Hardware{
+		ObjectMeta: metav1.ObjectMeta{
+			Name:      strings.Replace(mac.String(), ":", "-", -1),
+			Namespace: tinkerbellNamespace,
+			Labels: map[string]string{
+				"created-by": "autodiscovery",
+			},
+		},
+		Spec: v1alpha1.HardwareSpec{
+			Interfaces: []v1alpha1.Interface{
+				{
+					DHCP: &v1alpha1.DHCP{
+						MAC: mac.String(),
+					},
+					Netboot: &v1alpha1.Netboot{
+						AllowPXE:      ptr.To[bool](true),
+						AllowWorkflow: ptr.To[bool](true),
+					},
+				},
+			},
+		},
+	}
+
+	if err := b.cluster.GetClient().Create(ctx, hardware); err != nil {
+		span.SetStatus(codes.Error, err.Error())
+		return fmt.Errorf("failed to create hardware for (%v): %w", mac, err)
+	}
+
+	return nil
+}
+
 // toDHCPData converts a v1alpha1.DHCP to a data.DHCP data structure.
 // if required fields are missing, an error is returned.
 // Required fields: v1alpha1.Interface.DHCP.MAC, v1alpha1.Interface.DHCP.IP.Address, v1alpha1.Interface.DHCP.IP.Netmask.

internal/dhcp/handler/handler.go

@@ -17,3 +17,15 @@ type BackendReader interface {
 	GetByMac(context.Context, net.HardwareAddr) (*data.DHCP, *data.Netboot, error)
 	GetByIP(context.Context, net.IP) (*data.DHCP, *data.Netboot, error)
 }
+
+// BackendWriter is the interface for writing data to a backend.
+type BackendWriter interface {
+	// Write data (to a backend) based on a mac address for creating a new hardware.
+	CreateByMac(context.Context, net.HardwareAddr) error
+}
+
+// BackendReadWriter is the interface for getting and setting data from a backend.
+type BackendReadWriter interface {
+	BackendReader
+	BackendWriter
+}

internal/dhcp/handler/proxy/proxy.go

@@ -23,6 +23,7 @@ import (
 
 	"github.com/go-logr/logr"
 	"github.com/insomniacslk/dhcp/dhcpv4"
+	"github.com/tinkerbell/smee/internal/backend/kube"
 	"github.com/tinkerbell/smee/internal/dhcp"
 	"github.com/tinkerbell/smee/internal/dhcp/data"
 	"github.com/tinkerbell/smee/internal/dhcp/handler"
@@ -39,7 +40,7 @@ const tracerName = "github.com/tinkerbell/smee/internal/dhcp/handler/proxy"
 // Handler holds the configuration details for the running the DHCP server.
 type Handler struct {
 	// Backend is the backend to use for getting DHCP data.
-	Backend handler.BackendReader
+	Backend handler.BackendReadWriter
 
 	// IPAddr is the IP address to use in DHCP responses.
 	// Option 54 and the sname DHCP header.
@@ -58,6 +59,9 @@ type Handler struct {
 	// For example, the filename will be "snp.efi-00-23b1e307bb35484f535a1f772c06910e-d887dc3912240434-01".
 	// <original filename>-00-<trace id>-<span id>-<trace flags>
 	OTELEnabled bool
+
+	// AutoDiscoveryEnabled is a flag that determines whether a new hardware entry should be created upon receiving a DHCP request.
+	AutoDiscoveryEnabled bool
 }
 
 // Netboot holds the netboot configuration details used in running a DHCP server.
@@ -184,12 +188,16 @@ func (h *Handler) Handle(ctx context.Context, conn *ipv4.PacketConn, dp data.Pac
 	// set bootfile header
 	reply.BootFileName = i.Bootfile("", h.Netboot.IPXEScriptURL(dp.Pkt), h.Netboot.IPXEBinServerHTTP, h.Netboot.IPXEBinServerTFTP)
 
+	var notHardwareFound bool
 	// check the backend, if PXE is NOT allowed, set the boot file name to "/<mac address>/not-allowed"
 	_, n, err := h.Backend.GetByMac(ctx, dp.Pkt.ClientHWAddr)
-	if err != nil || (n != nil && !n.AllowNetboot) {
-		log.V(1).Info("Ignoring packet", "error", err.Error(), "netbootAllowed", n.AllowNetboot)
-		span.SetStatus(codes.Ok, "netboot not allowed")
-		return
+	if err != nil {
+		notHardwareFound = kube.IsHardwareNotFoundError(err)
+		if n != nil && !n.AllowNetboot {
+			log.V(1).Info("Ignoring packet", "error", err.Error(), "netbootAllowed", n.AllowNetboot)
+			span.SetStatus(codes.Ok, "netboot not allowed")
+			return
+		}
 	}
 	log.Info(
 		"received DHCP packet",
@@ -220,6 +228,16 @@ func (h *Handler) Handle(ctx context.Context, conn *ipv4.PacketConn, dp data.Pac
 	log.Info("Sent ProxyDHCP response")
 	span.SetAttributes(h.encodeToAttributes(reply, "reply")...)
 	span.SetStatus(codes.Ok, "sent DHCP response")
+
+	// Create a new hardware entry if AutoDiscoveryEnabled is set to true and a hardware entry does not already exist.
+	if notHardwareFound && h.AutoDiscoveryEnabled && reply.MessageType() == dhcpv4.MessageTypeAck {
+		log.Info("AutoDiscoveryEnabled - Creating a new hardware entry", "mac", dp.Pkt.ClientHWAddr.String())
+		if err := h.Backend.CreateByMac(ctx, dp.Pkt.ClientHWAddr); err != nil {
+			log.Error(err, "failed to create hardware entry")
+			span.SetStatus(codes.Error, err.Error())
+			return
+		}
+	}
 }
 
 // encodeToAttributes takes a DHCP packet and returns opentelemetry key/value attributes.

manifests/kustomize/base/rbac.yaml

@@ -19,6 +19,7 @@ rules:
       - get
       - list
       - watch
+      - create
   - apiGroups:
       - tinkerbell.org
     resources: