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-----------------------------------------------------------------------------
-- TFTP support for the Lua language
-- LuaSocket toolkit.
-- Author: Diego Nehab
-- Conforming to: RFC 783, LTN7
-- RCS ID: $Id$
-----------------------------------------------------------------------------
local Public, Private = {}, {}
local socket = _G[LUASOCKET_LIBNAME] -- get LuaSocket namespace
socket.tftp = Public -- create tftp sub namespace
-----------------------------------------------------------------------------
-- Program constants
-----------------------------------------------------------------------------
local char = string.char
local byte = string.byte
Public.PORT = 69
Private.OP_RRQ = 1
Private.OP_WRQ = 2
Private.OP_DATA = 3
Private.OP_ACK = 4
Private.OP_ERROR = 5
Private.OP_INV = {"RRQ", "WRQ", "DATA", "ACK", "ERROR"}
-----------------------------------------------------------------------------
-- Packet creation functions
-----------------------------------------------------------------------------
function Private.RRQ(source, mode)
return char(0, Private.OP_RRQ) .. source .. char(0) .. mode .. char(0)
end
function Private.WRQ(source, mode)
return char(0, Private.OP_RRQ) .. source .. char(0) .. mode .. char(0)
end
function Private.ACK(block)
local low, high
low = math.mod(block, 256)
high = (block - low)/256
return char(0, Private.OP_ACK, high, low)
end
function Private.get_OP(dgram)
local op = byte(dgram, 1)*256 + byte(dgram, 2)
return op
end
-----------------------------------------------------------------------------
-- Packet analysis functions
-----------------------------------------------------------------------------
function Private.split_DATA(dgram)
local block = byte(dgram, 3)*256 + byte(dgram, 4)
local data = string.sub(dgram, 5)
return block, data
end
function Private.get_ERROR(dgram)
local code = byte(dgram, 3)*256 + byte(dgram, 4)
local msg
_,_, msg = string.find(dgram, "(.*)\000", 5)
return string.format("error code %d: %s", code, msg)
end
-----------------------------------------------------------------------------
-- Downloads and returns a file pointed to by url
-----------------------------------------------------------------------------
function Public.get(url)
local parsed = socket.url.parse(url, {
host = "",
port = Public.PORT,
path ="/",
scheme = "tftp"
})
if parsed.scheme ~= "tftp" then
return nil, string.format("unknown scheme '%s'", parsed.scheme)
end
local retries, dgram, sent, datahost, dataport, code
local cat = socket.concat.create()
local last = 0
local udp, err = socket.udp()
if not udp then return nil, err end
-- convert from name to ip if needed
parsed.host = socket.toip(parsed.host)
udp:timeout(1)
-- first packet gives data host/port to be used for data transfers
retries = 0
repeat
sent, err = udp:sendto(Private.RRQ(parsed.path, "octet"),
parsed.host, parsed.port)
if err then return nil, err end
dgram, datahost, dataport = udp:receivefrom()
retries = retries + 1
until dgram or datahost ~= "timeout" or retries > 5
if not dgram then return nil, datahost end
-- associate socket with data host/port
udp:setpeername(datahost, dataport)
-- process all data packets
while 1 do
-- decode packet
code = Private.get_OP(dgram)
if code == Private.OP_ERROR then
return nil, Private.get_ERROR(dgram)
end
if code ~= Private.OP_DATA then
return nil, "unhandled opcode " .. code
end
-- get data packet parts
local block, data = Private.split_DATA(dgram)
-- if not repeated, write
if block == last+1 then
cat:addstring(data)
last = block
end
-- last packet brings less than 512 bytes of data
if string.len(data) < 512 then
sent, err = udp:send(Private.ACK(block))
return cat:getresult()
end
-- get the next packet
retries = 0
repeat
sent, err = udp:send(Private.ACK(last))
if err then return err end
dgram, err = udp:receive()
retries = retries + 1
until dgram or err ~= "timeout" or retries > 5
if not dgram then return err end
end
end
|
