packet: add a metatable to the packet ctype

This makes the paket an object, and allows for example p:free() instead
of packet.free(p)

Add a new method `physical` to get the physical address of packet.data

src/core/packet.lua

@@ -94,6 +94,11 @@ end
 -- Return pointer to packet data.
 function data (p) return p.data end
 
+-- Return physical address of packet data
+function physical (p)
+   return memory.memory.virtual_to_physical(p.data)
+end
+
 -- Return packet data length.
 function length (p) return p.length end
 
@@ -109,3 +114,21 @@ function preallocate_step()
    packet_allocation_step = 2 * packet_allocation_step
 end
 
+function dump(p, w)
+   w = w or io.write
+   for i = 0, p.length-1 do
+      if i % 16 == 0 then w('\n', bit.tohex(i, -4), ': ') end
+      w(bit.tohex(p.data[i], -2), ' ')
+   end
+   w('\n')
+end
+
+ffi.metatype(packet_t, {__index = {
+   clone = clone,
+   append = append,
+   prepend = prepend,
+   shiftleft = shiftleft,
+   free = free,
+   physical = physical,
+   dump = dump,
+}})