我注意到ping（iputils)id每次执行时都会增加 ICMP 计数器。我试着看看平源代码扫了一眼却没有找到柜台。 AFAIK ping 不运行任何守护进程或其他系统全局状态，那么 Linux 内核本身是否保存此计数器的记录？
% ping -c 3 127.0.0.1
PING 127.0.0.1 (127.0.0.1) 56(84) bytes of data.
64 bytes from 127.0.0.1: icmp_seq=1 ttl=64 time=0.039 ms
64 bytes from 127.0.0.1: icmp_seq=2 ttl=64 time=0.039 ms
64 bytes from 127.0.0.1: icmp_seq=3 ttl=64 time=0.033 ms
Tshark（id = 0x0043）：
14267 196372.989831489 127.0.0.1 → 127.0.0.1 ICMP 98 Echo (ping) request id=0x0043, seq=1/256, ttl=64
14268 196372.989843064 127.0.0.1 → 127.0.0.1 ICMP 98 Echo (ping) reply id=0x0043, seq=1/256, ttl=64 (request in 14267)
14269 196374.001333266 127.0.0.1 → 127.0.0.1 ICMP 98 Echo (ping) request id=0x0043, seq=2/512, ttl=64
14270 196374.001345051 127.0.0.1 → 127.0.0.1 ICMP 98 Echo (ping) reply id=0x0043, seq=2/512, ttl=64 (request in 14269)
14271 196375.014707417 127.0.0.1 → 127.0.0.1 ICMP 98 Echo (ping) request id=0x0043, seq=3/768, ttl=64
14272 196375.014717838 127.0.0.1 → 127.0.0.1 ICMP 98 Echo (ping) reply id=0x0043, seq=3/768, ttl=64 (request in 14271)
再次平：
% ping -c 3 127.0.0.1
PING 127.0.0.1 (127.0.0.1) 56(84) bytes of data.
64 bytes from 127.0.0.1: icmp_seq=1 ttl=64 time=0.047 ms
64 bytes from 127.0.0.1: icmp_seq=2 ttl=64 time=0.062 ms
64 bytes from 127.0.0.1: icmp_seq=3 ttl=64 time=0.037 ms
Tshark（id = 0x0044）：
14273 196381.959906106 127.0.0.1 → 127.0.0.1 ICMP 98 Echo (ping) request id=0x0044, seq=1/256, ttl=64
14274 196381.959921324 127.0.0.1 → 127.0.0.1 ICMP 98 Echo (ping) reply id=0x0044, seq=1/256, ttl=64 (request in 14273)
14275 196382.961393309 127.0.0.1 → 127.0.0.1 ICMP 98 Echo (ping) request id=0x0044, seq=2/512, ttl=64
14276 196382.961404803 127.0.0.1 → 127.0.0.1 ICMP 98 Echo (ping) reply id=0x0044, seq=2/512, ttl=64 (request in 14275)
14277 196383.974709944 127.0.0.1 → 127.0.0.1 ICMP 98 Echo (ping) request id=0x0044, seq=3/768, ttl=64
14278 196383.974722217 127.0.0.1 → 127.0.0.1 ICMP 98 Echo (ping) reply id=0x0044, seq=3/768, ttl=64 (request in 14277)