qemu: allow to use live iso without cache

Signed-off-by: Vasiliy Tolstov <v.tolstov@selfip.ru>

builder/qemu/builder.go

@@ -83,6 +83,7 @@ type Config struct {
 	common.ISOConfig    `mapstructure:",squash"`
 	Comm                communicator.Config `mapstructure:",squash"`
 
+	ISOSkipCache    bool       `mapstructure:"iso_skip_cache"`
 	Accelerator     string     `mapstructure:"accelerator"`
 	BootCommand     []string   `mapstructure:"boot_command"`
 	DiskInterface   string     `mapstructure:"disk_interface"`
@@ -221,6 +222,10 @@ func (b *Builder) Prepare(raws ...interface{}) ([]string, error) {
 	var errs *packer.MultiError
 	warnings := make([]string, 0)
 
+	if b.config.ISOSkipCache {
+		b.config.ISOChecksumType = "none"
+	}
+
 	isoWarnings, isoErrs := b.config.ISOConfig.Prepare(&b.config.ctx)
 	warnings = append(warnings, isoWarnings...)
 	errs = packer.MultiErrorAppend(errs, isoErrs...)
@@ -326,8 +331,9 @@ func (b *Builder) Run(ui packer.Ui, hook packer.Hook, cache packer.Cache) (packe
 		steprun.Message = "Starting VM, booting disk image"
 	}
 
-	steps := []multistep.Step{
+	steps := []multistep.Step{}
-		&common.StepDownload{
+	if !b.config.ISOSkipCache {
+		steps = append(steps, &common.StepDownload{
 			Checksum:     b.config.ISOChecksum,
 			ChecksumType: b.config.ISOChecksumType,
 			Description:  "ISO",
@@ -336,7 +342,16 @@ func (b *Builder) Run(ui packer.Ui, hook packer.Hook, cache packer.Cache) (packe
 			TargetPath:   b.config.TargetPath,
 			Url:          b.config.ISOUrls,
 		},
-		new(stepPrepareOutputDir),
+		)
+	} else {
+		steps = append(steps, &stepSetISO{
+			ResultKey: "iso_path",
+			Url:       b.config.ISOUrls,
+		},
+		)
+	}
+
+	steps = append(steps, new(stepPrepareOutputDir),
 		&common.StepCreateFloppy{
 			Files: b.config.FloppyFiles,
 		},
@@ -362,7 +377,7 @@ func (b *Builder) Run(ui packer.Ui, hook packer.Hook, cache packer.Cache) (packe
 		new(common.StepProvision),
 		new(stepShutdown),
 		new(stepConvertDisk),
-	}
+	)
 
 	// Setup the state bag
 	state := new(multistep.BasicStateBag)

builder/qemu/step_set_iso.go

@@ -0,0 +1,56 @@
+package qemu
+
+import (
+	"fmt"
+	"net/http"
+
+	"github.com/mitchellh/multistep"
+	"github.com/mitchellh/packer/packer"
+)
+
+// This step set iso_patch to available url
+type stepSetISO struct {
+	ResultKey string
+	Url       []string
+}
+
+func (s *stepSetISO) Run(state multistep.StateBag) multistep.StepAction {
+	ui := state.Get("ui").(packer.Ui)
+
+	iso_path := ""
+
+	for _, url := range s.Url {
+		req, err := http.NewRequest("HEAD", url, nil)
+		if err != nil {
+			continue
+		}
+
+		req.Header.Set("User-Agent", "Packer")
+
+		httpClient := &http.Client{
+			Transport: &http.Transport{
+				Proxy: http.ProxyFromEnvironment,
+			},
+		}
+
+		res, err := httpClient.Do(req)
+		if err == nil && (res.StatusCode >= 200 && res.StatusCode < 300) {
+			if res.Header.Get("Accept-Ranges") == "bytes" {
+				iso_path = url
+			}
+		}
+	}
+
+	if iso_path == "" {
+		err := fmt.Errorf("No byte serving support. The HTTP server must support Accept-Ranges=bytes")
+		state.Put("error", err)
+		ui.Error(err.Error())
+		return multistep.ActionHalt
+	}
+
+	state.Put(s.ResultKey, iso_path)
+
+	return multistep.ActionContinue
+}
+
+func (s *stepSetISO) Cleanup(state multistep.StateBag) {}

website/source/docs/builders/qemu.html.markdown

@@ -173,10 +173,13 @@ builder.
     to force the HTTP server to be on one port, make this minimum and maximum
     port the same. By default the values are 8000 and 9000, respectively.
 
+-   `iso_skip_cache` (boolean) - Use iso from provided url. Qemu must support
+    curl block device.
+
 -   `iso_target_path` (string) - The path where the iso should be saved after
     download. By default will go in the packer cache, with a hash of the
     original filename as its name.
-      
+
 -   `iso_urls` (array of strings) - Multiple URLs for the ISO to download.
     Packer will try these in order. If anything goes wrong attempting to
     download or while downloading a single URL, it will move on to the next. All