feat: add human-friendly entry point

* Added /start as entry point, for humans and iPXE

The '/poll/1/${netX/mac:hexhyp}' is fairly iPXE internal, not something
that invites curious people to look better at shoelaces. Neither it is
looking nice in DHCP server configuration.

This change adds a HTTP handler for '/start'. And '/start' points
to '/poll/1/${netX/mac:hexhyp}'. The benefit of it is that human visible
documentation can replace the "voodoo" '/poll/1/${netX/mac:hexhyp}'
with "friendly" '/start'.

Because it is an addition are the existing HTTP handlers not effected,
neither the installed deployments effected.

Signed-off-by: Geert Stappers <stappers@stappers.it>

6 files changed, 48 insertions, 5 deletions

diff --git a/README.md b/README.md
index 18d8e64..fec8e04 100644
--- a/README.md
+++ b/README.md
@@ -141,7 +141,7 @@ with your TFTP and Shoelaces server addresses.
 # dhcp.conf
 next-server <your-tftp-server>;
 if exists user-class and option user-class = "iPXE" {
-  filename "http://<shoelaces-server>/poll/1/${netX/mac:hexhyp}";
+  filename "http://<shoelaces-server>/start";
 } else {
   filename "undionly.kpxe";
 }
@@ -153,7 +153,7 @@ putting it in `dnsmasq.d/ipxe.conf`:
 ```txt
 dhcp-match=set:ipxe,175 # iPXE sends a 175 option.
 dhcp-boot=tag:!ipxe,undionly.kpxe
-dhcp-boot=http://<shoelaces-server>/poll/1/${netX/mac:hexhyp}
+dhcp-boot=http://<shoelaces-server>/start
 ```
 
 The **${netX/mac:hexhyp}** strings represents the MAC address of the booting
diff --git a/docs/shoelaces.8.scd b/docs/shoelaces.8.scd
index 445994c..f803dd3 100644
--- a/docs/shoelaces.8.scd
+++ b/docs/shoelaces.8.scd
@@ -88,7 +88,7 @@ debug=true
 # dhcp.conf
 next-server <your-tftp-server>;
 if exists user-class and option user-class = "iPXE" {
-  filename "http://<shoelaces-server>/poll/1/${netX/mac:hexhyp}";
+  filename "http://<shoelaces-server>/start";
 } else {
   filename "undionly.kpxe";
 }
@@ -100,7 +100,7 @@ the following snippet:
 ```
 dhcp-match=set:ipxe,175 # iPXE sends a 175 option.
 dhcp-boot=tag:!ipxe,undionly.kpxe
-dhcp-boot=http://<shoelaces-server>/poll/1/${netX/mac:hexhyp}
+dhcp-boot=http://<shoelaces-server>/start
 ```
 
 A TFTP server such as *tftpd*(8) must be configured to serve the iPXE executable,
diff --git a/internal/handlers/polling.go b/internal/handlers/polling.go
index 12f36e2..51fd8ad 100644
--- a/internal/handlers/polling.go
+++ b/internal/handlers/polling.go
@@ -28,6 +28,16 @@ import (
 	"github.com/thousandeyes/shoelaces/internal/utils"
 )
 
+// StartPollingHandler is called by iPXE boot agents. It returns the poll script.
+func StartPollingHandler(w http.ResponseWriter, r *http.Request) {
+	env := envFromRequest(r)
+
+	script := polling.GenStartScript(env.Logger,  env.BaseURL)
+
+	w.Write([]byte(script))
+}
+
+
 // PollHandler is called by iPXE boot agents. It returns the boot script
 // specified on the configuration or, if the host is unknown, it makes it
 // retry for a while until the user specifies alternative IPXE boot script.
diff --git a/internal/polling/polling.go b/internal/polling/polling.go
index 853a751..cfd489f 100644
--- a/internal/polling/polling.go
+++ b/internal/polling/polling.go
@@ -34,6 +34,16 @@ import (
 type ManualAction int
 
 const (
+	startScript = "#!ipxe\n" +
+		"echo Shoelaces starts polling\n" +
+		"chain --autofree --replace \\\n" +
+		"    http://{{.baseURL}}/poll/1/${netX/mac:hexhyp}\n" +
+		"#\n" +
+		"#\n" +
+		"# Do\n" +
+		"#    curl http://{{.baseURL}}/poll/1/06-66-de-ad-be-ef\n" +
+		"# to get an idea about what iPXE will receive.\n"
+
 	maxRetry = 10
 
 	retryScript = "#!ipxe\n" +
@@ -226,6 +236,26 @@ func setHostName(params map[string]interface{}, mac string) {
 	}
 }
 
+func GenStartScript(logger log.Logger, baseURL string) string {
+	variablesMap := map[string]interface{}{}
+	parsedTemplate := &bytes.Buffer{}
+
+	tmpl, err := template.New("retry").Parse(startScript)
+	if err != nil {
+		logger.Info("component", "polling", "msg", "Error parsing start template")
+		panic(err)
+	}
+
+	variablesMap["baseURL"] = baseURL
+	err = tmpl.Execute(parsedTemplate, variablesMap)
+	if err != nil {
+		logger.Info("component", "polling", "msg", "Error executing start template")
+		panic(err)
+	}
+
+	return parsedTemplate.String()
+}
+
 func genBootScript(logger log.Logger, templateRenderer *templates.ShoelacesTemplates, baseURL string, script *mappings.Script) string {
 	script.Params["baseURL"] = utils.BaseURLforEnvName(baseURL, script.Environment)
 	text, err := templateRenderer.RenderTemplate(logger, script.Name, script.Params, script.Environment)
diff --git a/internal/router/router.go b/internal/router/router.go
index d729d16..1313705 100644
--- a/internal/router/router.go
+++ b/internal/router/router.go
@@ -53,6 +53,9 @@ func ShoelacesRouter(env *environment.Environment) http.Handler {
 	r.PathPrefix("/configs/").Handler(http.StripPrefix("/configs/",
 		handlers.TemplateServer()))
 
+	// Starting point for iPXE boot agents, usualy defined by DHCP server.
+	// Gets the iPXE boot agents into the polling loop.
+	r.HandleFunc("/start", handlers.StartPollingHandler).Methods("GET")
 	// Called by iPXE boot agents, returns boot script specified on the configuration
 	// or if the host is unknown makes it retry for a while until the user specifies
 	// alternative ipxe boot script
diff --git a/web/templates/html/index.html b/web/templates/html/index.html
index 4f09ba9..ea93c01 100644
--- a/web/templates/html/index.html
+++ b/web/templates/html/index.html
@@ -31,7 +31,7 @@
         <div class="center-block col-md-6">
             <div class="card">
                 <div class="card-body">
-                    <p class="text-center">Shoelaces is waiting for a server to boot. Using iPXE, your server should reach the following endpoint:  <br /> <b class="text-primary-custom">http://{{ .BaseURL }}/poll/1/&#60;MAC&#62;</b> </p>
+                    <p class="text-center">Shoelaces is waiting for a server to boot. Using iPXE, your server should reach the following endpoint:  <br /> <b class="text-primary-custom">http://{{ .BaseURL }}/start</b> </p>
                     <p class="text-center">You can automate this process by setting up a DHCP server.</p>
                 </div>
             </div>