More updates to networking tutorial

Fixes mirage#279.

tmpl/wiki/hello-world.md

@@ -422,38 +422,36 @@ directory in `mirage-skeleton`.
 ```
 open Mirage
 
-let handler = foreign "Unikernel.Main" (console @-> stackv4 @-> job)
+let main = foreign "Unikernel.Main" (console @-> stackv4 @-> job)
 
 let net =
   try match Sys.getenv "NET" with
     | "direct" -> `Direct
     | "socket" -> `Socket
-    | _ -> `Direct
+    | _        -> `Direct
   with Not_found -> `Direct
 
 let dhcp =
-  try match Sys.getenv "DHCP" with
-    | "" -> false
-    | _ -> true
-  with Not_found -> false
+  try match Sys.getenv "ADDR" with
+    | "dhcp"   -> `Dhcp
+    | "static" -> `Static
+  with Not_found -> `Dhcp
 
-let stack =
+let stack console =
   match net, dhcp with
-  | `Direct, true -> direct_stackv4_with_dhcp default_console tap0
-  | `Direct, false -> direct_stackv4_with_default_ipv4 default_console tap0
-  | `Socket, _ -> socket_stackv4 default_console [Ipaddr.V4.any]
+  | `Direct, `Dhcp   -> direct_stackv4_with_dhcp console tap0
+  | `Direct, `Static -> direct_stackv4_with_default_ipv4 console tap0
+  | `Socket, _       -> socket_stackv4 console [Ipaddr.V4.any]
 
 let () =
-  add_to_opam_packages ["mirage-http"];
-  add_to_ocamlfind_libraries ["mirage-http"];
-  register "stackv4" [
-    handler $ default_console $ stack;
+  register "network" [
+    main $ default_console $ stack default_console
   ]
 ```
 
 This configuration shows how composable the network stack subsystem is, by
 simultaneously listening on a socket port (using the Linux kernel) *and* 
-a direct tuntap for the same webcode.  The definition of `handler` just
+a direct tuntap for the same webcode.  The definition of `main` just
 adds a new `stackv4` device driver.  
 
 The `net` handler checks to see if it's building for a socket or direct network stack.  
@@ -472,11 +470,11 @@ The definition of `stack` then uses `dhcp` and `net` accordingly to set up the n
 <br />
 <div class="panel callout">
   <i class="fa fa-info fa-3x pull-left"> </i>
-  <p>You will have noticed by this stage that the `Makefile` generated by <code>mirage configure</code>
+  <p>You will have noticed by this stage that <code>mirage configure</code>
      invokes OPAM to install any libraries that it needs.  If your application
-     needs some extra packages, you can use the <code>add_to_opam_packages</code>
-     and <code>add_to_ocamlfind_libraries</code> functions to hook in the extra
-     packages and libraries.  The example above does this to add the HTTP library.</p>
+     needs some extra packages, you can use the optional <code>~packages</code>
+     and <code>~libraries</code> arguments to <code>foreign</code> to add the extra
+     OPAM packages and ocamlfind libraries.  For example, you could modify the code above to add an <a href='https://github.com/mirage/mirage-http'>HTTP library</a>.</p>
 </div>
 
 Let's get the network stack compiling on Unix first.  On a Mac, be sure
@@ -515,7 +513,7 @@ hello!
 
 The `ifconfig` call binds `10.0.0.1` as the gateway IP address to
 our unikernel.  We then test our userspace network stack by pinging
-it, and if that succeeds, the subsequent `telent` call now retrieves
+it, and if that succeeds, the subsequent `telnet` call now retrieves
 the request via the OCaml TCP/IP stack!
 
 At this point, recompiling a Xen unikernel is pretty straightforward.