https://joekuan.wordpress.com/2017/05/30/behaviour-of-identifier-field-in-icmp-ping-as-udp-between-linux-and-osx/ https://lwn.net/Articles/443051/ https: //github.com/apache/incubator-nuttx-apps/blob/master/netutils/ping/icmp_ping.c#L298 Signed-off-by: chao.an <anchao@xiaomi.com>