tcpdump小记

tcpdump的语法：
tcpdump [options] [Protocol] [Direction] [Host(s)] [Value] [Logical Operations] [Other expression]

常用选项：
-i any : Listen on all interfaces just to see if you're seeing any traffic.
-n : Don't resolve hostnames.
-nn : Don't resolve hostnames or port names.
-X : Show the packet's contents in both hex and ASCII.
-XX : Same as -X, but also shows the ethernet header.
-v, -vv, -vvv : Increase the amount of packet information you get back.
-c # : Only get x number of packets and then stop.
-s : Define the snaplength (size) of the capture in bytes. Use -s0 to get everything, unless you are intentionally capturing less.
-S : Print absolute sequence numbers.
-e : Get the ethernet header as well.
-q : Show less protocol information.
-E : Decrypt IPSEC traffic by providing an encryption key.
-A ：Display Captured Packets in ASCII
-w /path/to/some_file : Capture the packets and write into a file
-r /path/from/some_file : Reading the packets from a saved file
-tttt : Capture packets with proper readable timestamp

Protocol(协议):
Values(取值): ether, fddi, ip, arp, rarp, decnet, lat, sca, moprc, mopdl, tcp and udp.
If no protocol is specified, all the protocols are used.

Direction(流向):
Values(取值): src, dst, src and dst, src or dst
If no source or destination is specified, the "src or dst" keywords are applied. (默认是src or dst)
For example, "host 10.2.2.2" is equivalent to "src or dst host 10.2.2.2".

Host(s)(主机):
Values(替代关键字): net, port, host, portrange.
If no host(s) is specified, the "host" keyword is used. 默认如果此段没有指定关键字，默认即host。
For example, "src 10.1.1.1" is equivalent to "src host 10.1.1.1".

Logical Operations:
(1) AND
and or &&
(2) OR
or or ||
(3) EXCEPT
not or !