我正在尝试从结构if_data64读取字段ifi_ibytes/ifi_obytes，如本头文件所述。我已经让ctype工作，我可以进行sysctl调用，并且从中获得了似乎可用的信息。然而，我从非零整数中获得了似乎完全是垃圾的东西。例如，我有一个接口，接收了0个字节，传输了~850万个字节。然而，我的python代码说接收了0个字节，传输了3,590,592,659,456个字节。

我从这个已知的工作程序中复制了这个方法，我从Python得到的字节计数与上面看到的MenuMeter数字没有任何相似之处。我使用了一个稍微不同的sysctl（NET_RT_IFLIST2），它提供了64位整数，我在代码中考虑到了这一点。

这是我的代码：

from ctypes import *
from ctypes.util import find_library
from ctypes import sizeof as c_sizeof
import errno

libc = CDLL(find_library('c'), use_errno=True)

# hardcoded macosx constants!
CTL_NET = 4
PF_ROUTE = 17
NET_RT_IFLIST2 = 6

RTM_IFINFO2 = 0x12
IFF_LOOPBACK = 0x8
AF_LINK = 18

class if_data64(Structure):
   _pack_ = 4
   _fields_ = [('ifi_type', c_ubyte),
               ('ifi_typelen', c_ubyte),
               ('ifi_physical', c_ubyte),
               ('ifi_addrlen', c_ubyte),
               ('ifi_hdrlen', c_ubyte),
               ('ifi_recvquota', c_ubyte),
               ('ifi_xmitquota', c_ubyte),
               ('ifi_unused1', c_ubyte),
               ('ifi_mtu', c_uint32),
               ('ifi_metric', c_uint32),
               ('ifi_baudrate', c_uint32),
               ('ifi_ipackets', c_uint64),
               ('ifi_ierrors', c_uint64),
               ('ifi_opackets', c_uint64),
               ('ifi_oerrors', c_uint64),
               ('ifi_collisions', c_uint64),
               ('ifi_ibytes', c_uint64),
               ('ifi_obytes', c_uint64),
               ('ifi_imcasts', c_uint64),
               ('ifi_omcasts', c_uint64),
               ('ifi_iqdrops', c_uint64),
               ('ifi_noproto', c_uint64),
               ('ifi_recvtiming', c_uint32),
               ('ifi_xmittiming', c_uint32)]

class if_msghdr2(Structure):
   _fields_ = [('ifm_msglen', c_ushort),
               ('ifm_version', c_ubyte),
               ('ifm_type', c_ubyte),
               ('ifm_addrs', c_int),
               ('ifm_flags', c_int),
               ('ifm_index', c_ushort),
               ('ifm_snd_len', c_int),
               ('ifm_snd_maxlen', c_int),
               ('ifm_snd_drops', c_int),
               ('ifm_timer', c_int),
               ('ifm_data', if_data64)]

class sockaddr_dl(Structure):
   _fields_ = [('sdl_len', c_ubyte),
               ('sdl_family', c_ubyte),
               ('sdl_index', c_ushort),
               ('sdl_type', c_ubyte),
               ('sdl_nlen', c_ubyte),
               ('sdl_alen', c_ubyte),
               ('sdl_slen', c_ubyte),
               ('sdl_data', c_char * 12)] # for now

MIB_TYPE = c_int * 6
mib = MIB_TYPE(CTL_NET, PF_ROUTE, 0, 0, NET_RT_IFLIST2, 0)

sysctl_buf_len = c_uint(0)

rval = libc.sysctl(mib, 6, None, byref(sysctl_buf_len), None, 0)
if rval != 0:
   raise Exception(errno.errorcode[get_errno()])

sysctl_buf = create_string_buffer(sysctl_buf_len.value)
rval = libc.sysctl(mib, 6, sysctl_buf, byref(sysctl_buf_len), None, 0)
if rval != 0:
   raise Exception(errno.errorcode[get_errno()])

# walk the structure.  you need to know the length from ifm_msglen
idx = addressof(sysctl_buf)
end = idx + sysctl_buf_len.value
while idx < end:
   batch_off = idx - addressof(sysctl_buf)
   ifmsg = cast(c_void_p(idx), POINTER(if_msghdr2))
   if ifmsg.contents.ifm_type != RTM_IFINFO2:
      idx += ifmsg.contents.ifm_msglen
      continue
   if ifmsg.contents.ifm_flags & IFF_LOOPBACK:
      idx += ifmsg.contents.ifm_msglen
      continue
   # 12 bytes to compensate for 32 bit alignment
   sdl = cast(c_void_p(idx + c_sizeof(if_msghdr2) + 12), POINTER(sockaddr_dl))
   if sdl.contents.sdl_family != AF_LINK:
      idx += ifmsg.contents.ifm_msglen
      continue

   print sdl.contents.sdl_data[0:sdl.contents.sdl_nlen]
   print ifmsg.contents.ifm_data.ifi_ibytes, ifmsg.contents.ifm_data.ifi_obytes
   idx += ifmsg.contents.ifm_msglen