Add support for ipxe load (nova, foc, fiasco)

This makes use of the iPXE sanboot command [1] which downloads and
boots an ISO image directly via HTTP. Therefore, your RUN_OPT needs
both

  --include image/iso   and
  --include load/ipxe

NOTE: The webserver serving the ISO image must support ranged requests,
      see [2].

[1] - http://ipxe.org/cmd/sanboot
[2] - http://forum.ipxe.org/showthread.php?tid=7295&pid=10482#pid10482

tool/run/boot_dir/fiasco

@@ -144,4 +144,10 @@ proc run_boot_dir {binaries} {
 
 		generate_tftp_config
 	}
+
+	if {[have_include "load/ipxe"]} {
+		create_ipxe_iso_config
+		update_ipxe_boot_dir
+		create_symlink_for_iso
+	}
 }

tool/run/boot_dir/foc

@@ -183,6 +183,12 @@ proc run_boot_dir_x86 {binaries} {
 
 		generate_tftp_config
 	}
+
+	if {[have_include "load/ipxe"]} {
+		create_ipxe_iso_config
+		update_ipxe_boot_dir
+		create_symlink_for_iso
+	}
 }
 
 

tool/run/boot_dir/nova

@@ -93,4 +93,10 @@ proc run_boot_dir {binaries} {
 
 		generate_tftp_config
 	}
+
+	if {[have_include "load/ipxe"]} {
+		create_ipxe_iso_config
+		update_ipxe_boot_dir
+		create_symlink_for_iso
+	}
 }

tool/run/load/ipxe

@@ -46,3 +46,23 @@ proc create_symlink_for_iso { } {
 proc update_ipxe_boot_dir { } {
 	exec ln -sfn [pwd]/[run_dir] [load_ipxe_base_dir]/[load_ipxe_boot_dir]
 }
+
+##
+# Create iPXE config file which directly boots an ISO file.
+#
+proc create_ipxe_iso_config { } {
+	if {[have_include "image/iso"]} {
+		set fh [open "[run_dir]/boot.cfg" "WRONLY CREAT TRUNC"]
+		puts $fh "#!ipxe"
+		puts $fh "sanboot [run_name].iso || goto failed"
+		puts $fh
+		puts $fh ":failed"
+		puts $fh "echo Booting failed, dropping to shell"
+		puts $fh "shell"
+		puts $fh "boot"
+		close $fh
+	} else {
+		puts "Warning, iPXE requires ISO image."
+		exit -1
+	}
+}