不是很理解的ICMP
14:36:20.622293 IP 118.115.138.203 > 202.98.131.189: ICMP host 118.115.138.203 unreachable - admin prohibited, length 80
14:37:33.574297 IP 118.115.138.203 > 202.98.131.189: ICMP host 118.115.138.203 unreachable - admin prohibited, length 80
14:37:43.148297 IP 118.115.138.203 > 202.98.131.189: ICMP host 118.115.138.203 unreachable - admin prohibited, length 80
这个在ftp时抓到的, 感觉很奇怪, 自己怎么会告诉别人自己不可达呢? 望高手解惑