core: provide optional curl downloader.

cmd/start.go

@@ -22,6 +22,7 @@ import (
 	"github.com/abiosoft/colima/environment/container/incus"
 	"github.com/abiosoft/colima/environment/container/kubernetes"
 	"github.com/abiosoft/colima/util"
+	"github.com/abiosoft/colima/util/downloader"
 	"github.com/abiosoft/colima/util/osutil"
 	log "github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
@@ -106,6 +107,15 @@ Run 'colima template' to set the default configurations or 'colima start --edit'
 			}
 		}
 
+		// validate and set downloader if flag is specified (takes precedence over env var)
+		if cmd.Flag("downloader").Changed {
+			normalized, err := downloader.ValidateDownloader(startCmdArgs.Flags.Downloader)
+			if err != nil {
+				return err
+			}
+			downloader.SetDownloader(normalized)
+		}
+
 		return nil
 	},
 }
@@ -141,8 +151,9 @@ var startCmdArgs struct {
 		DNSHosts                []string
 		Foreground              bool
 		SaveConfig              bool
-		LegacyCPU               int // for backward compatibility
+		LegacyCPU               int    // for backward compatibility
 		Template                bool
+		Downloader              string // downloader to use (native, curl)
 	}
 }
 
@@ -255,6 +266,9 @@ func init() {
 	// dns
 	startCmd.Flags().IPSliceVarP(&startCmdArgs.Network.DNSResolvers, "dns", "n", nil, "DNS resolvers for the VM")
 	startCmd.Flags().StringSliceVar(&startCmdArgs.Flags.DNSHosts, "dns-host", nil, "custom DNS names to provide to resolver")
+
+	// download options
+	startCmd.Flags().StringVar(&startCmdArgs.Flags.Downloader, "downloader", downloader.DownloaderNative, "downloader to use (native, curl)")
 }
 
 func dnsHostsFromFlag(hosts []string) map[string]string {

util/downloader/curl.go

@@ -0,0 +1,93 @@
+package downloader
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"path"
+	"strings"
+
+	"github.com/abiosoft/colima/util/osutil"
+	"github.com/abiosoft/colima/util/terminal"
+)
+
+const (
+	// DownloaderNative uses Go's native HTTP client
+	DownloaderNative = "native"
+	// DownloaderCurl uses the curl command (honors .curlrc)
+	DownloaderCurl = "curl"
+
+	envDownloader = "COLIMA_DOWNLOADER"
+)
+
+// ValidateDownloader validates the downloader value (case-insensitive).
+// Returns the normalized value or an error if invalid.
+func ValidateDownloader(v string) (string, error) {
+	switch strings.ToLower(v) {
+	case DownloaderNative:
+		return DownloaderNative, nil
+	case DownloaderCurl:
+		return DownloaderCurl, nil
+	default:
+		return "", fmt.Errorf("invalid downloader %q: must be one of %s, %s", v, DownloaderNative, DownloaderCurl)
+	}
+}
+
+// Downloader returns the configured downloader type.
+// Flag takes precedence over environment variable when explicitly set.
+func Downloader() string {
+	if downloaderOverride != nil {
+		return *downloaderOverride
+	}
+	if v := osutil.EnvVar(envDownloader).Val(); v != "" {
+		// normalize env var value
+		if normalized, err := ValidateDownloader(v); err == nil {
+			return normalized
+		}
+	}
+	return DownloaderNative
+}
+
+// UseCurl returns true if curl should be used for downloads.
+func UseCurl() bool {
+	return Downloader() == DownloaderCurl
+}
+
+// downloaderOverride is set by the --downloader flag (nil means not set)
+var downloaderOverride *string
+
+// SetDownloader sets the downloader override (called from start command when flag is explicitly set).
+// The value should be validated before calling this function.
+func SetDownloader(v string) {
+	downloaderOverride = &v
+}
+
+// curlDownloader handles downloads using the curl command
+type curlDownloader struct{}
+
+// downloadFile downloads a file using curl
+func (c curlDownloader) downloadFile(r Request, destPath string) error {
+	// check if curl is available
+	if _, err := exec.LookPath("curl"); err != nil {
+		return fmt.Errorf("curl not found in PATH: %w", err)
+	}
+
+	args := []string{
+		"-fSL",    // fail on HTTP errors, show errors, follow redirects
+		"-C", "-", // resume if possible (auto-detect offset)
+		"--progress-bar", // show progress bar
+		"-o", destPath,   // output file
+		r.URL,
+	}
+
+	cmd := exec.Command("curl", args...)
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+
+	if err := cmd.Run(); err != nil {
+		return fmt.Errorf("curl download failed for '%s': %w", path.Base(r.URL), err)
+	}
+
+	terminal.ClearLine()
+	return nil
+}

util/downloader/download.go

@@ -82,6 +82,40 @@ func (d downloader) downloadFile(r Request) (err error) {
 		return fmt.Errorf("error preparing cache dir: %w", err)
 	}
 
+	// use curl if enabled (supports .curlrc for proxy auth, SSPI, etc.)
+	if UseCurl() {
+		if err := d.downloadWithCurl(r, cacheDownloadingFilename); err != nil {
+			return err
+		}
+	} else {
+		if err := d.downloadWithHTTP(r, cacheDownloadingFilename); err != nil {
+			return err
+		}
+	}
+
+	// validate download if SHA is present
+	if r.SHA != nil {
+		if err := r.SHA.validateDownload(r.URL, cacheDownloadingFilename); err != nil {
+			// move file to allow subsequent re-download
+			_ = os.Rename(cacheDownloadingFilename, cacheDownloadingFilename+".invalid")
+			return fmt.Errorf("error validating SHA sum for '%s': %w", path.Base(r.URL), err)
+		}
+	}
+
+	// move completed download to final location
+	if err := os.Rename(cacheDownloadingFilename, CacheFilename(r.URL)); err != nil {
+		return fmt.Errorf("error finalizing download: %w", err)
+	}
+
+	return nil
+}
+
+func (d downloader) downloadWithCurl(r Request, destPath string) error {
+	curl := curlDownloader{}
+	return curl.downloadFile(r, destPath)
+}
+
+func (d downloader) downloadWithHTTP(r Request, destPath string) error {
 	// check for existing partial download and resume info
 	var resumeInfo ResumeInfo
 	resumeInfoPath := d.resumeInfoPath(r.URL)
@@ -91,7 +125,7 @@ func (d downloader) downloadFile(r Request) (err error) {
 
 	// get existing file size for resume
 	var existingSize int64
-	if stat, err := os.Stat(cacheDownloadingFilename); err == nil {
+	if stat, err := os.Stat(destPath); err == nil {
 		existingSize = stat.Size()
 	}
 
@@ -111,7 +145,7 @@ func (d downloader) downloadFile(r Request) (err error) {
 	// download the file
 	result, err := client.Download(ctx, DownloadOptions{
 		URL:            finalURL,
-		DestPath:       cacheDownloadingFilename,
+		DestPath:       destPath,
 		ExpectedETag:   resumeInfo.ETag,
 		ResumeFromByte: existingSize,
 		ShowProgress:   true,
@@ -127,20 +161,6 @@ func (d downloader) downloadFile(r Request) (err error) {
 	// clean up resume info on successful download
 	_ = os.Remove(resumeInfoPath)
 
-	// validate download if SHA is present
-	if r.SHA != nil {
-		if err := r.SHA.validateDownload(r.URL, cacheDownloadingFilename); err != nil {
-			// move file to allow subsequent re-download
-			_ = os.Rename(cacheDownloadingFilename, cacheDownloadingFilename+".invalid")
-			return fmt.Errorf("error validating SHA sum for '%s': %w", path.Base(r.URL), err)
-		}
-	}
-
-	// move completed download to final location
-	if err := os.Rename(cacheDownloadingFilename, CacheFilename(r.URL)); err != nil {
-		return fmt.Errorf("error finalizing download: %w", err)
-	}
-
 	return nil
 }