ether-proto-1500.md

ether proto 1500

BPF

000: A = P[12:2]
001: if (A > 1500) goto 5 else goto 2
002: A = P[14:1]
003: if (A == 1500) goto 4 else goto 5
004: return 65535
005: return 0

BPF cross-compiled to Lua

return function (P, length)
   local A = 0
   if 14 > length then return false end
   A = bit.bor(bit.lshift(P[12], 8), P[12+1])
   if (runtime_u32(A)>1500) then goto L4 end
   if 15 > length then return false end
   A = P[14]
   if not (A==1500) then goto L4 end
   do return true end
   ::L4::
   do return false end
   error("end of bpf")
end

Direct pflang compilation

return function(P,length)
   return false
end

Native pflang compilation

7f2ba1387000  B000              mov al, 0x0
7f2ba1387002  C3                ret