Testing v6 workarounds

If v6 attempt fails, attempts to turn off v6 stack by clearing
netX/dns6 var which should cause stack to fallback to v4.

This should attempt to load the menu in multiple scenarios where DNS
miget be getting set when there's no actual support for v6 on the local
network.

roles/netbootxyz/templates/disks/netboot.xyz.j2

@@ -7,12 +7,14 @@ set fg_cya ${esc:string}[36m
 set fg_whi ${esc:string}[37m
 set VARS_ERR Local vars file not found... attempting TFTP boot...
 set TFTP_ERR Local TFTP failed... attempting remote HTTPS
+set V6_ERR IPv6 appears to have failed... attempting IPv4...
 set HTTPS_ERR HTTPS appears to have failed... attempting HTTP
 set HTTP_ERR HTTP has failed, localbooting...
 set site_name {{ site_name }}
 set boot_domain {{ boot_domain }}
 set ipxe_version ${version}
 set version {{ boot_version }}
+set conn_type https
 
 :start
 echo ${bold}${fg_gre}${site_name} - ${fg_whi}v${version}${boldoff}
@@ -101,15 +103,29 @@ chain --autofree tftp://${tftp-server}/menu.ipxe || echo ${TFTP_ERR} && goto men
 
 :menu
 {% if bootloader_https_enabled | bool %}
+:menu_https
 set conn_type https
-chain --autofree https://${boot_domain}/menu.ipxe || echo ${HTTPS_ERR}
-sleep 5
+goto menu_start
 {% endif %}
+
 {% if bootloader_http_enabled | bool %}
+:menu_http
 set conn_type http
-chain --autofree http://${boot_domain}/menu.ipxe || echo ${HTTP_ERR}
+goto menu_start
 {% endif %}
-goto localboot
+
+:menu_start
+isset netX/dns6 && goto menu_v6 || goto menu_v4
+:menu_v6
+isset netX/dns6_bak && set netX/dns6 ${netX/dns6_bak} ||
+set netX/dns6_bak ${netX/dns6}
+echo Attempting ${conn_type} boot over IPv6...
+chain --autofree ${conn_type}://${boot_domain}/menu.ipxe || echo ${conn_type} IPv6 failed... attempting IPv4...
+clear netX/dns6
+:menu_v4
+echo Attempting ${conn_type} boot over IPv4...
+chain --autofree ${conn_type}://${boot_domain}/menu.ipxe || echo ${conn_type} IPv4 failed...
+iseq ${conn_type} https && goto menu_http || goto localboot
 
 :localboot
 exit