Jigsaw Outline 是如何做到 proxy ICMP 包的？

[ImJoeHs]

最近试用了下 Outline 作为梯子，晚上惊奇地发现 google ping 得通了

打开 Outline 时

➜ ~ ping google.com PING google.com (74.125.204.101): 56 data bytes 64 bytes from 74.125.204.101: icmp_seq=0 ttl=255 time=0.170 ms 64 bytes from 74.125.204.101: icmp_seq=1 ttl=255 time=0.350 ms 64 bytes from 74.125.204.101: icmp_seq=2 ttl=255 time=0.352 ms 64 bytes from 74.125.204.101: icmp_seq=3 ttl=255 time=0.448 ms 64 bytes from 74.125.204.101: icmp_seq=4 ttl=255 time=0.401 ms ^C --- google.com ping statistics --- 5 packets transmitted, 5 packets received, 0.0% packet loss round-trip min/avg/max/stddev = 0.170/0.344/0.448/0.094 ms

随后关闭 Outline，直接 ping 这个 ip

➜ ~ ping 74.125.204.101 PING 74.125.204.101 (74.125.204.101): 56 data bytes Request timeout for icmp_seq 0 Request timeout for icmp_seq 1 Request timeout for icmp_seq 2 Request timeout for icmp_seq 3 Request timeout for icmp_seq 4 ^C --- 74.125.204.101 ping statistics --- 6 packets transmitted, 0 packets received, 100.0% packet loss

工作在上层的 proxy，是不可能作用到网络层的 ICMP 协议的，那么 Outline 是通过什么方式做到的呢？

[qyb]

ping 的时候去你的梯子那里抓一下包？能想到的是 outline 启动之后，改变了 default route，然后可能你的网络环境里有一个路由是能通 google 的 ICMP 的，也许是有个透明代理？