fix: only fetch machine uuid if it's not set

During boot sequence, if `talos.config`'s url has the uuid parameter, the uuid
value is retrieved via SMBIOS. However, at this part of the code it can happen
that the uuid is already set and valid. If this is the case, instead of
re-fetching the uuid, the one that is already set can be used.

closes siderolabs#3676

Signed-off-by: Kevin Hellemun <17928966+OGKevin@users.noreply.github.com>

internal/app/machined/pkg/runtime/v1alpha1/platform/metal/metal.go

@@ -7,6 +7,7 @@ package metal
 import (
 	"context"
 	"fmt"
+	"github.com/google/uuid"
 	"io/ioutil"
 	"log"
 	"net"
@@ -48,26 +49,25 @@ func (m *Metal) Configuration(ctx context.Context) ([]byte, error) {
 
 	u, err := url.Parse(*option)
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("failed to parse talos.config url: %w", err)
 	}
 
 	values := u.Query()
 
 	if len(values) > 0 {
-		for key := range values {
+		for key, qValues := range values {
 			switch key {
 			case "uuid":
-				s, err := smbios.New()
-				if err != nil {
-					return nil, err
-				}
-
-				uuid, err := s.SystemInformation().UUID()
-				if err != nil {
-					return nil, err
+				if len(qValues) != 1 {
+					uid, err := getSystemUUID()
+					if err != nil {
+						return nil, err
+					}
+					values.Set("uuid", uid.String())
+					break
 				}
 
-				values.Set("uuid", uuid.String())
+				values.Set("uuid", qValues[0])
 			default:
 				log.Printf("unsupported query parameter: %q", key)
 			}
@@ -86,6 +86,20 @@ func (m *Metal) Configuration(ctx context.Context) ([]byte, error) {
 	}
 }
 
+func getSystemUUID() (uuid.UUID, error) {
+	s, err := smbios.New()
+	if err != nil {
+		return uuid.Nil, err
+	}
+
+	id, err := s.SystemInformation().UUID()
+	if err != nil {
+		return uuid.Nil, err
+	}
+
+	return id, nil
+}
+
 // Hostname implements the platform.Platform interface.
 func (m *Metal) Hostname(context.Context) (hostname []byte, err error) {
 	return nil, nil