Pixelblaster_v6 by @HIlse

flut.lua

--[[
Pixelblaster_v6 by @hilse
Needs LuaJIT & ljsyscall (syscall.lua & syscall/...)
and lodepng

This is a perfect example on how to not do things correctly while still using Lua.

Run this with enough rights to send raw packets
Usage:

24bpp RGB from stdin (optionally, a continuous stream):
  luajit flut.lua <interface> <our MAC> <our IPv6> <target/router MAC> <target IPv6> <xoffs> <yoffs> <width> <height> [cont]
PNG (alpha aware):
  luajit flut.lua <interface> <our MAC> <our IPv6> <target/router MAC> <target IPv6> <xoffs> <yoffs> image.png

License: WAGTD 1.0
§1: We're all going to die.

Changelog:
- now supports PNG & Alpha
- IPv6 now without any payload at all: 54 byte on ethernet layer - a whopping 12% increase in productivity!
--]]
local ffi=require"ffi"
local bit=require"bit"
local S=require"syscall"

ffi.cdef"unsigned int lodepng_decode32_file(unsigned char **, unsigned int *, unsigned int *, const char *);"
-- compile lodepng: gcc -shared -fPIC -o lodepng.so -c lodepng.c
local lodepng=ffi.load("./lodepng.so")

-- mwahahahahaha!
local s = S.socket(S.c.AF.PACKET,S.c.SOCK.RAW,S.c.IPPROTO.RAW)

-- interface index
local if_idx = S.util.if_nametoindex(arg[1],s)

local sll_dest = S.t.sockaddr_ll{ifindex=if_idx, addr=S.t.macaddr(arg[4])}

-- we build ourselves a nice and shiny package
local sbuf_l = 54
local sbuf = ffi.new("uint8_t[?]", sbuf_l)

ffi.copy(sbuf, sll_dest.addr, 6)
ffi.copy(sbuf + 6, S.t.macaddr(arg[2]), 6)
sbuf[12]=0x86
sbuf[13]=0xDD
sbuf[14]=0x60
sbuf[15]=0
sbuf[16]=0x48 -- H
sbuf[17]=0x57 -- W
sbuf[18]=0 -- packet length
sbuf[19]=0 -- packet length
sbuf[20]=59 -- next header: UDP
sbuf[21]=0xFF -- hop limit
ffi.copy(sbuf+22, S.t.in6_addr(arg[3]), 16)
ffi.copy(sbuf+38, S.t.in6_addr(arg[5]), 16)

local function set_px(x, y, r, g, b, a)
    sbuf[46] = bit.rshift(x, 8)
    sbuf[47] = bit.band(x, 255)
    sbuf[48] = bit.rshift(y, 8)
    sbuf[49] = bit.band(y, 255)
    sbuf[50] = r
    sbuf[51] = g
    sbuf[52] = b
    sbuf[53] = a
    S.sendto(s, sbuf, sbuf_l, 0, sll_dest, ffi.sizeof(sll_dest))
end

local dx=arg[6]
local dy=arg[7]
local w, h
local pic
local lframe = function() end
local bpp = 24
if tonumber(arg[8]) and tonumber(arg[8]) > 0 then
  w=arg[8]
  h=arg[9]
  -- read data from... stdin
  pic=ffi.new("uint8_t[?]", w*h*3)
  -- read one frame:
  lframe = function()
    local r = w*h*3
    local d = 0
    while true do
      if(d == r) then return end
      local res = S.read(0, pic+d, r-d)
      if(res > 0) then
        d = d + res
      end
    end
  end
  lframe()
else
  bpp=32
  pic=ffi.new("uint8_t*[1]")
  w = ffi.new("unsigned int[1]")
  h = ffi.new("unsigned int[1]")
  local err=lodepng.lodepng_decode32_file(pic, w, h, arg[8])
  if err>0 then
    print("error opening file:", err)
    os.exit(1)
  end
  w = w[0]
  h = h[0]
  pic = pic[0]
end

local function get_px(x, y)
  local c
  local a
  if bpp==24 then
    c = (y*w+x)*3
    a = 255
  elseif bpp==32 then
    c = (y*w+x)*4
    a = pic[c+3]
  end
  return pic[c], pic[c+1], pic[c+2], a
end

local t=ffi.new("uint32_t[?]", w*h)
local act_px = w*h
local c=0
for y=0,h-1 do
  for x=0,w-1 do
    local r,g,b,a = get_px(x, y)
    if a==0 then
      act_px = act_px - 1
    else
      t[c]=bit.bor(bit.lshift(y, 16), x)
      c=c+1
    end
  end
end

-- Fisher - Yates shuffle:
math.randomseed(os.time())
for i=act_px, 1, -1 do
  local j=math.random(i)
  t[i], t[j] = t[j], t[i]
end

-- one loop:
local function play()
  -- send pic
  for p=0,act_px-1 do
    local x = bit.band(t[p], 0xffff)
    local y = bit.rshift(t[p], 16)
    local r,g,b,a = get_px(x, y)
    if a > 0 then
      set_px(dx+x, dy+y, r,g,b,a)
    end
  end
  if arg[10] == "cont" then
    -- continuous reading (e.g. from ffmpeg)
    lframe()
  end
end

while true do
  play()
end