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From: Simon Wunderlich <sw@simonwunderlich.de>
Date: Mon, 14 Oct 2013 19:52:34 +0200
References: <525B189E.1080105@altermundi.net>
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Subject: Re: [B.A.T.M.A.N.] [PATCH 2/2] alfred: Bundle a lua script for
	autogenerating bat-hosts file
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> Provide a lua script that uses alfred to propagate and collect all
> interface mac + names, then generate a /tmp/bat-hosts file.
> If there's already a (probably hand-made) /etc/bat-hosts it won't overwrite
> it but if there's none, it will symlink /etc/bat-hosts -> /tmp/bat-hosts
> 
> Signed-off-by: Gui Iribarren <gui@altermundi.net>
> Thanks-to: Joshua Head <joshua.head@outlook.com>

Thanks a lot, this sounds like a really good idea! As this will be part of the 
openwrt package, I'd like to ask to make the bat-hosts.lua script optional and 
selectable (like you can turn on/off vis). I'll do the same for other 
(optional) services like gps.

Also, do you need any additional dependencies for lua?

Thanks,
   Simon
> ---
>  alfred/Makefile            |    2 +
>  alfred/files/bat-hosts.lua |  107
> ++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 109
> insertions(+)
>  create mode 100644 alfred/files/bat-hosts.lua
> 
> diff --git a/alfred/Makefile b/alfred/Makefile
> index db9c71f..7027192 100644
> --- a/alfred/Makefile
> +++ b/alfred/Makefile
> @@ -74,6 +74,8 @@ define Package/alfred/install
>  	$(INSTALL_BIN) ./files/alfred.init $(1)/etc/init.d/alfred
>  	$(INSTALL_DIR) $(1)/etc/config
>  	$(INSTALL_DATA) ./files/alfred.config $(1)/etc/config/alfred
> +	$(INSTALL_DIR) $(1)/etc/alfred
> +	$(INSTALL_BIN) ./files/bat-hosts.lua $(1)/etc/alfred/bat-hosts.lua
>  endef
> 
>  $(eval $(call BuildPackage,alfred))
> diff --git a/alfred/files/bat-hosts.lua b/alfred/files/bat-hosts.lua
> new file mode 100644
> index 0000000..19f2cad
> --- /dev/null
> +++ b/alfred/files/bat-hosts.lua
> @@ -0,0 +1,107 @@
> +#!/usr/bin/lua
> +
> +local type_id = 64 -- bat-hosts
> +
> +function get_hostname()
> +  local hostfile = io.open("/proc/sys/kernel/hostname", "r")
> +  local ret_string = hostfile:read("*a")
> +  ret_string = string.gsub(ret_string, "\n", "")
> +  hostfile:close()
> +  return ret_string
> +end
> +
> +function get_interfaces_names()
> +  local ret = {}
> +
> +  for name in io.popen("ls -1 /sys/class/net/"):lines() do
> +    table.insert(ret, name)
> +  end
> +
> +  return ret
> +end
> +
> +function get_interface_address(name)
> +  local addressfile = io.open("/sys/class/net/"..name.."/address", "r")
> +  local ret_string = addressfile:read("*a")
> +  ret_string = string.gsub(ret_string, "\n", "")
> +  addressfile:close()
> +  return ret_string
> +end
> +
> +
> +local function generate_bat_hosts()
> +-- get hostname and interface macs/names
> +-- then return a table containing valid bat-hosts lines
> +  local n, i
> +  local ifaces, ret = {}, {}
> +
> +  local hostname = get_hostname()
> +
> +  for n, i in ipairs(get_interfaces_names()) do
> +    local address = get_interface_address(i)
> +    ifaces[address] = i
> +  end
> +
> +  for mac, iname in pairs(ifaces) do
> +    if mac:match("^%x%x:%x%x:%x%x:%x%x:%x%x:%x%x$") and not
> mac:match("00:00:00:00:00:00") then +      table.insert(ret, mac.."
> "..hostname.."_"..iname.."\n")
> +    end
> +  end
> +
> +  return ret
> +end
> +
> +local function publish_bat_hosts()
> +-- pass a raw chunk of data to alfred
> +  local fd = io.popen("alfred -s " .. type_id, "w")
> +  if fd then
> +    local ret = generate_bat_hosts()
> +    if ret then
> +      fd:write(table.concat(ret))
> +    end
> +    fd:close()
> +  end
> +end
> +
> +local function receive_bat_hosts()
> +-- read raw chunks from alfred, convert them to a nested table and call
> write_bat_hosts +  local fd = io.popen("alfred -r " .. type_id)
> +    --[[ this command returns something like
> +    { "54:e6:fc:b9:cb:37", "00:11:22:33:44:55
> ham_wlan0\x0a00:22:33:22:33:22 ham_eth0\x0a" }, +    {
> "90:f6:52:bb:ec:57", "00:22:33:22:33:23 spam\x0a" },
> +    ]]--
> +
> +  if fd then
> +    local output = fd:read("*a")
> +    if output then
> +      assert(loadstring("rows = {" .. output .. "}"))()
> +      write_bat_hosts(rows)
> +    end
> +    fd:close()
> +  end
> +end
> +
> +local function write_bat_hosts(rows)
> +  local content = { "### File generated by alfred-bat-hosts\n" }
> +
> +  -- merge the chunks from all nodes, de-escaping newlines
> +  for _, row in ipairs(rows) do
> +    local node, value = unpack(row)
> +    table.insert(content, "# Node ".. node .. "\n")
> +    table.insert(content, value:gsub("\x0a", "\n") .. "\n")
> +  end
> +
> +  -- write parsed content down to disk
> +  local fd = io.open("/tmp/bat-hosts", "w")
> +  if fd then
> +    fd:write(table.concat(content))
> +    fd:close()
> +  end
> +
> +  -- try to make a symlink in /etc pointing to /tmp,
> +  -- if it exists, ln will do nothing.
> +  os.execute("ln -ns /tmp/bat-hosts /etc/bat-hosts 2>/dev/null")
> +end
> +
> +publish_bat_hosts()
> +receive_bat_hosts()