根据目的ip抓取ipip单向报文
tcpdump -i p6p1 "ip proto 4 and (ip[20+16:1]=10 and ip[20+17:1]=184 and ip[20+18:1]=243 and ip[20+19:1]=62)"
双向报文
tcpdump -i p5p2 "ip proto 4 and ( (ip[20+12:1]=10 and ip[20+13:1]=184 and ip[20+14:1]=243 and ip[20+15:1]=62) or (ip[20+16:1]=10 and ip[20+17:1]=184 and ip[20+18:1]=243 and ip[20+19:1]=62) )" -s 0 -w /dev/shm/p5p2-jl.cap
