from: http://blog.csdn.net/wolfwind521/article/details/41629539
设备Macbook Air，系统Mac OS X 10.10
mac下抓包，要么用第三方软件wireshark，要么自己写python脚本用 pcap, dpkt 。
首先，都必须开启网卡：
sudo chmod 777 /dev/bpf*
否则，wireshark无法搜到设备，python脚本会报没有权限的Error：
pc=pcap.pcap('en0',immediate=True)
File "pcap.pyx", line 198, in pcap.pcap.__init__ (pcap.c:1778)
OSError: en0: You don't have permission to capture on that device ((cannot open BPF device) /dev/bpf0: Permission denied)
File "pcap.pyx", line 198, in pcap.pcap.__init__ (pcap.c:1778)
OSError: en0: You don't have permission to capture on that device ((cannot open BPF device) /dev/bpf0: Permission denied)
开启网卡之后，就可以顺利用wireshark，或者python import pcap, dpkt 抓包了
