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主頁 > 知識庫 > 在Linux中使用tcpdump命令捕獲與分析數(shù)據(jù)包詳解

在Linux中使用tcpdump命令捕獲與分析數(shù)據(jù)包詳解

前言

tcpdump 是一個有名的命令行數(shù)據(jù)包分析工具。我們可以使用 tcpdump 命令捕獲實(shí)時 TCP/IP 數(shù)據(jù)包，這些數(shù)據(jù)包也可以保存到文件中。之后這些捕獲的數(shù)據(jù)包可以通過 tcpdump 命令進(jìn)行分析。tcpdump 命令在網(wǎng)絡(luò)層面進(jìn)行故障排除時變得非常方便。

tcpdump 在大多數(shù) Linux 發(fā)行版中都能用，對于基于 Debian 的Linux，可以使用 apt 命令安裝它。

# apt install tcpdump -y

在基于 RPM 的 Linux 操作系統(tǒng)上，可以使用下面的 yum 命令安裝 tcpdump。

# yum install tcpdump -y

當(dāng)我們在沒用任何選項(xiàng)的情況下運(yùn)行 tcpdump 命令時，它將捕獲所有接口的數(shù)據(jù)包。因此，要停止或取消 tcpdump 命令，請鍵入 ctrl+c。在本教程中，我們將使用不同的實(shí)例來討論如何捕獲和分析數(shù)據(jù)包。

示例：1）從特定接口捕獲數(shù)據(jù)包

當(dāng)我們在沒用任何選項(xiàng)的情況下運(yùn)行 tcpdump 命令時，它將捕獲所有接口上的數(shù)據(jù)包，因此，要從特定接口捕獲數(shù)據(jù)包，請使用選項(xiàng) -i，后跟接口名稱。

語法：

# tcpdump -i {接口名}

假設(shè)我想從接口 enp0s3 捕獲數(shù)據(jù)包。

輸出將如下所示，

tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on enp0s3, link-type EN10MB (Ethernet), capture size 262144 bytes
06:43:22.905890 IP compute-0-1.example.com.ssh > 169.144.0.1.39374: Flags [P.], seq 21952160:21952540, ack 13537, win 291, options [nop,nop,TS val 26164373 ecr 6580205], length 380
06:43:22.906045 IP compute-0-1.example.com.ssh > 169.144.0.1.39374: Flags [P.], seq 21952540:21952760, ack 13537, win 291, options [nop,nop,TS val 26164373 ecr 6580205], length 220
06:43:22.906150 IP compute-0-1.example.com.ssh > 169.144.0.1.39374: Flags [P.], seq 21952760:21952980, ack 13537, win 291, options [nop,nop,TS val 26164373 ecr 6580205], length 220
06:43:22.906291 IP 169.144.0.1.39374 > compute-0-1.example.com.ssh: Flags [.], ack 21952980, win 13094, options [nop,nop,TS val 6580205 ecr 26164373], length 0
06:43:22.906303 IP 169.144.0.1.39374 > compute-0-1.example.com.ssh: Flags [P.], seq 13537:13609, ack 21952980, win 13094, options [nop,nop,TS val 6580205 ecr 26164373], length 72
06:43:22.906322 IP compute-0-1.example.com.ssh > 169.144.0.1.39374: Flags [P.], seq 21952980:21953200, ack 13537, win 291, options [nop,nop,TS val 26164373 ecr 6580205], length 220
^C
109930 packets captured
110065 packets received by filter
133 packets dropped by kernel
[[email protected] ~]#

示例：2）從特定接口捕獲特定數(shù)量數(shù)據(jù)包

假設(shè)我們想從特定接口（如 enp0s3）捕獲 12 個數(shù)據(jù)包，這可以使用選項(xiàng) -c {數(shù)量} -I {接口名稱} 輕松實(shí)現(xiàn)。

root@compute-0-1 ~]# tcpdump -c 12 -i enp0s3

上面的命令將生成如下所示的輸出，

N-Number-Packsets-tcpdump-interface

示例：3）顯示 tcpdump 的所有可用接口

使用 -D 選項(xiàng)顯示 tcpdump 命令的所有可用接口，

[root@compute-0-1 ~]# tcpdump -D
1.enp0s3
2.enp0s8
3.ovs-system
4.br-int
5.br-tun
6.nflog (Linux netfilter log (NFLOG) interface)
7.nfqueue (Linux netfilter queue (NFQUEUE) interface)
8.usbmon1 (USB bus number 1)
9.usbmon2 (USB bus number 2)
10.qbra692e993-28
11.qvoa692e993-28
12.qvba692e993-28
13.tapa692e993-28
14.vxlan_sys_4789
15.any (Pseudo-device that captures on all interfaces)
16.lo [Loopback]
[[email protected] ~]#

我正在我的一個 openstack 計算節(jié)點(diǎn)上運(yùn)行 tcpdump 命令，這就是為什么在輸出中你會看到數(shù)字接口、標(biāo)簽接口、網(wǎng)橋和 vxlan 接口。

示例：4）捕獲帶有可讀時間戳的數(shù)據(jù)包（-tttt 選項(xiàng)）

默認(rèn)情況下，在 tcpdump 命令輸出中，不顯示可讀性好的時間戳，如果您想將可讀性好的時間戳與每個捕獲的數(shù)據(jù)包相關(guān)聯(lián)，那么使用 -tttt 選項(xiàng)，示例如下所示，

[[email protected] ~]# tcpdump -c 8 -tttt -i enp0s3
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on enp0s3, link-type EN10MB (Ethernet), capture size 262144 bytes
2018-08-25 23:23:36.954883 IP compute-0-1.example.com.ssh > 169.144.0.1.39406: Flags [P.], seq 1449206247:1449206435, ack 3062020950, win 291, options [nop,nop,TS val 86178422 ecr 21583714], length 188
2018-08-25 23:23:36.955046 IP 169.144.0.1.39406 > compute-0-1.example.com.ssh: Flags [.], ack 188, win 13585, options [nop,nop,TS val 21583717 ecr 86178422], length 0
2018-08-25 23:23:37.140097 IP controller0.example.com.amqp > compute-0-1.example.com.57818: Flags [P.], seq 814607956:814607964, ack 2387094506, win 252, options [nop,nop,TS val 86172228 ecr 86176695], length 8
2018-08-25 23:23:37.140175 IP compute-0-1.example.com.57818 > controller0.example.com.amqp: Flags [.], ack 8, win 237, options [nop,nop,TS val 86178607 ecr 86172228], length 0
2018-08-25 23:23:37.355238 IP compute-0-1.example.com.57836 > controller0.example.com.amqp: Flags [P.], seq 1080415080:1080417400, ack 1690909362, win 237, options [nop,nop,TS val 86178822 ecr 86163054], length 2320
2018-08-25 23:23:37.357119 IP controller0.example.com.amqp > compute-0-1.example.com.57836: Flags [.], ack 2320, win 1432, options [nop,nop,TS val 86172448 ecr 86178822], length 0
2018-08-25 23:23:37.357545 IP controller0.example.com.amqp > compute-0-1.example.com.57836: Flags [P.], seq 1:22, ack 2320, win 1432, options [nop,nop,TS val 86172449 ecr 86178822], length 21
2018-08-25 23:23:37.357572 IP compute-0-1.example.com.57836 > controller0.example.com.amqp: Flags [.], ack 22, win 237, options [nop,nop,TS val 86178825 ecr 86172449], length 0
8 packets captured
134 packets received by filter
69 packets dropped by kernel
[[email protected] ~]#

示例：5）捕獲數(shù)據(jù)包并將其保存到文件（-w 選項(xiàng)）

使用 tcpdump 命令中的 -w 選項(xiàng)將捕獲的 TCP/IP 數(shù)據(jù)包保存到一個文件中，以便我們可以在將來分析這些數(shù)據(jù)包以供進(jìn)一步分析。

語法：

# tcpdump -w 文件名.pcap -i {接口名}

注意：文件擴(kuò)展名必須為 .pcap。

假設(shè)我要把 enp0s3 接口捕獲到的包保存到文件名為 enp0s3-26082018.pcap。

[root@compute-0-1 ~]# tcpdump -w enp0s3-26082018.pcap -i enp0s3

上述命令將生成如下所示的輸出，

[root@compute-0-1 ~]# tcpdump -w enp0s3-26082018.pcap -i enp0s3
tcpdump: listening on enp0s3, link-type EN10MB (Ethernet), capture size 262144 bytes
^C841 packets captured
845 packets received by filter
0 packets dropped by kernel
[root@compute-0-1 ~]# ls
anaconda-ks.cfg enp0s3-26082018.pcap
[root@compute-0-1 ~]#

捕獲并保存大小大于 N 字節(jié)的數(shù)據(jù)包。

[root@compute-0-1 ~]# tcpdump -w enp0s3-26082018-2.pcap greater 1024

捕獲并保存大小小于 N 字節(jié)的數(shù)據(jù)包。

[root@compute-0-1 ~]# tcpdump -w enp0s3-26082018-3.pcap less 1024

示例：6）從保存的文件中讀取數(shù)據(jù)包（-r 選項(xiàng)）

在上面的例子中，我們已經(jīng)將捕獲的數(shù)據(jù)包保存到文件中，我們可以使用選項(xiàng) -r 從文件中讀取這些數(shù)據(jù)包，例子如下所示，

[root@compute-0-1 ~]# tcpdump -r enp0s3-26082018.pcap

用可讀性高的時間戳讀取包內(nèi)容，

[root@compute-0-1 ~]# tcpdump -tttt -r enp0s3-26082018.pcap
reading from file enp0s3-26082018.pcap, link-type EN10MB (Ethernet)
2018-08-25 22:03:17.249648 IP compute-0-1.example.com.ssh > 169.144.0.1.39406: Flags [P.], seq 1426167803:1426167927, ack 3061962134, win 291, options
[nop,nop,TS val 81358717 ecr 20378789], length 124
2018-08-25 22:03:17.249840 IP 169.144.0.1.39406 > compute-0-1.example.com.ssh: Flags [.], ack 124, win 564, options [nop,nop,TS val 20378791 ecr 81358
717], length 0
2018-08-25 22:03:17.454559 IP controller0.example.com.amqp > compute-0-1.example.com.57836: Flags [.], ack 1079416895, win 1432, options [nop,nop,TS v
al 81352560 ecr 81353913], length 0
2018-08-25 22:03:17.454642 IP compute-0-1.example.com.57836 > controller0.example.com.amqp: Flags [.], ack 1, win 237, options [nop,nop,TS val 8135892
2 ecr 81317504], length 0
2018-08-25 22:03:17.646945 IP compute-0-1.example.com.57788 > controller0.example.com.amqp: Flags [.], seq 106760587:106762035, ack 688390730, win 237
, options [nop,nop,TS val 81359114 ecr 81350901], length 1448
2018-08-25 22:03:17.647043 IP compute-0-1.example.com.57788 > controller0.example.com.amqp: Flags [P.], seq 1448:1956, ack 1, win 237, options [nop,no
p,TS val 81359114 ecr 81350901], length 508
2018-08-25 22:03:17.647502 IP controller0.example.com.amqp > compute-0-1.example.com.57788: Flags [.], ack 1956, win 1432, options [nop,nop,TS val 813
52753 ecr 81359114], length 0
.........................................................................................................................

示例：7）僅捕獲特定接口上的 IP 地址數(shù)據(jù)包（-n 選項(xiàng)）

使用 tcpdump 命令中的 -n 選項(xiàng)，我們能只捕獲特定接口上的 IP 地址數(shù)據(jù)包，示例如下所示，

[root@compute-0-1 ~]# tcpdump -n -i enp0s3

上述命令輸出如下，

tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on enp0s3, link-type EN10MB (Ethernet), capture size 262144 bytes
22:22:28.537904 IP 169.144.0.20.ssh > 169.144.0.1.39406: Flags [P.], seq 1433301395:1433301583, ack 3061976250, win 291, options [nop,nop,TS val 82510005 ecr 20666610], length 188
22:22:28.538173 IP 169.144.0.1.39406 > 169.144.0.20.ssh: Flags [.], ack 188, win 9086, options [nop,nop,TS val 20666613 ecr 82510005], length 0
22:22:28.538573 IP 169.144.0.20.ssh > 169.144.0.1.39406: Flags [P.], seq 188:552, ack 1, win 291, options [nop,nop,TS val 82510006 ecr 20666613], length 364
22:22:28.538736 IP 169.144.0.1.39406 > 169.144.0.20.ssh: Flags [.], ack 552, win 9086, options [nop,nop,TS val 20666613 ecr 82510006], length 0
22:22:28.538874 IP 169.144.0.20.ssh > 169.144.0.1.39406: Flags [P.], seq 552:892, ack 1, win 291, options [nop,nop,TS val 82510006 ecr 20666613], length 340
22:22:28.539042 IP 169.144.0.1.39406 > 169.144.0.20.ssh: Flags [.], ack 892, win 9086, options [nop,nop,TS val 20666613 ecr 82510006], length 0
22:22:28.539178 IP 169.144.0.20.ssh > 169.144.0.1.39406: Flags [P.], seq 892:1232, ack 1, win 291, options [nop,nop,TS val 82510006 ecr 20666613], length 340
22:22:28.539282 IP 169.144.0.1.39406 > 169.144.0.20.ssh: Flags [.], ack 1232, win 9086, options [nop,nop,TS val 20666614 ecr 82510006], length 0
22:22:28.539479 IP 169.144.0.20.ssh > 169.144.0.1.39406: Flags [P.], seq 1232:1572, ack 1, win 291, options [nop,nop,TS val 82510006 ecr 20666614], length 340
22:22:28.539595 IP 169.144.0.1.39406 > 169.144.0.20.ssh: Flags [.], ack 1572, win 9086, options [nop,nop,TS val 20666614 ecr 82510006], length 0
22:22:28.539760 IP 169.144.0.20.ssh > 169.144.0.1.39406: Flags [P.], seq 1572:1912, ack 1, win 291, options [nop,nop,TS val 82510007 ecr 20666614], length 340
.........................................................................

您還可以使用 tcpdump 命令中的 -c 和 -N 選項(xiàng)捕獲 N 個 IP 地址包，

[root@compute-0-1 ~]# tcpdump -c 25 -n -i enp0s3

示例：8）僅捕獲特定接口上的 TCP 數(shù)據(jù)包

在 tcpdump 命令中，我們能使用 tcp 選項(xiàng)來只捕獲 TCP 數(shù)據(jù)包，

[root@compute-0-1 ~]# tcpdump -i enp0s3 tcp
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on enp0s3, link-type EN10MB (Ethernet), capture size 262144 bytes
22:36:54.521053 IP 169.144.0.20.ssh > 169.144.0.1.39406: Flags [P.], seq 1433336467:1433336655, ack 3061986618, win 291, options [nop,nop,TS val 83375988 ecr 20883106], length 188
22:36:54.521474 IP 169.144.0.1.39406 > 169.144.0.20.ssh: Flags [.], ack 188, win 9086, options [nop,nop,TS val 20883109 ecr 83375988], length 0
22:36:54.522214 IP 169.144.0.20.ssh > 169.144.0.1.39406: Flags [P.], seq 188:552, ack 1, win 291, options [nop,nop,TS val 83375989 ecr 20883109], length 364
22:36:54.522508 IP 169.144.0.1.39406 > 169.144.0.20.ssh: Flags [.], ack 552, win 9086, options [nop,nop,TS val 20883109 ecr 83375989], length 0
22:36:54.522867 IP 169.144.0.20.ssh > 169.144.0.1.39406: Flags [P.], seq 552:892, ack 1, win 291, options [nop,nop,TS val 83375990 ecr 20883109], length 340
22:36:54.523006 IP 169.144.0.1.39406 > 169.144.0.20.ssh: Flags [.], ack 892, win 9086, options [nop,nop,TS val 20883109 ecr 83375990], length 0
22:36:54.523304 IP 169.144.0.20.ssh > 169.144.0.1.39406: Flags [P.], seq 892:1232, ack 1, win 291, options [nop,nop,TS val 83375990 ecr 20883109], length 340
22:36:54.523461 IP 169.144.0.1.39406 > 169.144.0.20.ssh: Flags [.], ack 1232, win 9086, options [nop,nop,TS val 20883110 ecr 83375990], length 0
22:36:54.523604 IP 169.144.0.20.ssh > 169.144.0.1.39406: Flags [P.], seq 1232:1572, ack 1, win 291, options [nop,nop,TS val 83375991 ecr 20883110], length 340
...................................................................................................................................................

示例：9）從特定接口上的特定端口捕獲數(shù)據(jù)包

使用 tcpdump 命令，我們可以從特定接口 enp0s3 上的特定端口（例如 22）捕獲數(shù)據(jù)包。

語法：

# tcpdump -i {interface-name} port {Port_Number}

[root@compute-0-1 ~]# tcpdump -i enp0s3 port 22
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on enp0s3, link-type EN10MB (Ethernet), capture size 262144 bytes
22:54:45.032412 IP compute-0-1.example.com.ssh > 169.144.0.1.39406: Flags [P.], seq 1435010787:1435010975, ack 3061993834, win 291, options [nop,nop,TS val 84446499 ecr 21150734], length 188
22:54:45.032631 IP 169.144.0.1.39406 > compute-0-1.example.com.ssh: Flags [.], ack 188, win 9131, options [nop,nop,TS val 21150737 ecr 84446499], length 0
22:54:55.037926 IP compute-0-1.example.com.ssh > 169.144.0.1.39406: Flags [P.], seq 188:576, ack 1, win 291, options [nop,nop,TS val 84456505 ecr 21150737], length 388
22:54:55.038106 IP 169.144.0.1.39406 > compute-0-1.example.com.ssh: Flags [.], ack 576, win 9154, options [nop,nop,TS val 21153238 ecr 84456505], length 0
22:54:55.038286 IP compute-0-1.example.com.ssh > 169.144.0.1.39406: Flags [P.], seq 576:940, ack 1, win 291, options [nop,nop,TS val 84456505 ecr 21153238], length 364
22:54:55.038564 IP 169.144.0.1.39406 > compute-0-1.example.com.ssh: Flags [.], ack 940, win 9177, options [nop,nop,TS val 21153238 ecr 84456505], length 0
22:54:55.038708 IP compute-0-1.example.com.ssh > 169.144.0.1.39406: Flags [P.], seq 940:1304, ack 1, win 291, options [nop,nop,TS val 84456506 ecr 21153238], length 364
............................................................................................................................

示例：10）在特定接口上捕獲來自特定來源 IP 的數(shù)據(jù)包

在 tcpdump 命令中，使用 src 關(guān)鍵字后跟 IP 地址，我們可以捕獲來自特定來源 IP 的數(shù)據(jù)包，

語法：

# tcpdump -n -i {接口名} src {IP 地址}

例子如下，

[root@compute-0-1 ~]# tcpdump -n -i enp0s3 src 169.144.0.10
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on enp0s3, link-type EN10MB (Ethernet), capture size 262144 bytes
23:03:45.912733 IP 169.144.0.10.amqp > 169.144.0.20.57800: Flags [.], ack 526623844, win 243, options [nop,nop,TS val 84981008 ecr 84982372], length 0
23:03:46.136757 IP 169.144.0.10.amqp > 169.144.0.20.57796: Flags [.], ack 2535995970, win 252, options [nop,nop,TS val 84981232 ecr 84982596], length 0
23:03:46.153398 IP 169.144.0.10.amqp > 169.144.0.20.57798: Flags [.], ack 3623063621, win 243, options [nop,nop,TS val 84981248 ecr 84982612], length 0
23:03:46.361160 IP 169.144.0.10.amqp > 169.144.0.20.57802: Flags [.], ack 2140263945, win 252, options [nop,nop,TS val 84981456 ecr 84982821], length 0
23:03:46.376926 IP 169.144.0.10.amqp > 169.144.0.20.57808: Flags [.], ack 175946224, win 252, options [nop,nop,TS val 84981472 ecr 84982836], length 0
23:03:46.505242 IP 169.144.0.10.amqp > 169.144.0.20.57810: Flags [.], ack 1016089556, win 252, options [nop,nop,TS val 84981600 ecr 84982965], length 0
23:03:46.616994 IP 169.144.0.10.amqp > 169.144.0.20.57812: Flags [.], ack 832263835, win 252, options [nop,nop,TS val 84981712 ecr 84983076], length 0
23:03:46.809344 IP 169.144.0.10.amqp > 169.144.0.20.57814: Flags [.], ack 2781799939, win 252, options [nop,nop,TS val 84981904 ecr 84983268], length 0
23:03:46.809485 IP 169.144.0.10.amqp > 169.144.0.20.57816: Flags [.], ack 1662816815, win 252, options [nop,nop,TS val 84981904 ecr 84983268], length 0
23:03:47.033301 IP 169.144.0.10.amqp > 169.144.0.20.57818: Flags [.], ack 2387094362, win 252, options [nop,nop,TS val 84982128 ecr 84983492], length 0
^C
10 packets captured
12 packets received by filter
0 packets dropped by kernel

示例：11）在特定接口上捕獲來自特定目的 IP 的數(shù)據(jù)包

語法：

# tcpdump -n -i {接口名} dst {IP 地址}

[root@compute-0-1 ~]# tcpdump -n -i enp0s3 dst 169.144.0.1
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on enp0s3, link-type EN10MB (Ethernet), capture size 262144 bytes
23:10:43.520967 IP 169.144.0.20.ssh > 169.144.0.1.39406: Flags [P.], seq 1439564171:1439564359, ack 3062005550, win 291, options [nop,nop,TS val 85404988 ecr 21390356], length 188
23:10:43.521441 IP 169.144.0.20.ssh > 169.144.0.1.39406: Flags [P.], seq 188:408, ack 1, win 291, options [nop,nop,TS val 85404988 ecr 21390359], length 220
23:10:43.521719 IP 169.144.0.20.ssh > 169.144.0.1.39406: Flags [P.], seq 408:604, ack 1, win 291, options [nop,nop,TS val 85404989 ecr 21390359], length 196
23:10:43.521993 IP 169.144.0.20.ssh > 169.144.0.1.39406: Flags [P.], seq 604:800, ack 1, win 291, options [nop,nop,TS val 85404989 ecr 21390359], length 196
23:10:43.522157 IP 169.144.0.20.ssh > 169.144.0.1.39406: Flags [P.], seq 800:996, ack 1, win 291, options [nop,nop,TS val 85404989 ecr 21390359], length 196
23:10:43.522346 IP 169.144.0.20.ssh > 169.144.0.1.39406: Flags [P.], seq 996:1192, ack 1, win 291, options [nop,nop,TS val 85404989 ecr 21390359], length 196
.........................................................................................

示例：12）捕獲兩臺主機(jī)之間的 TCP 數(shù)據(jù)包通信

假設(shè)我想捕獲兩臺主機(jī) 169.144.0.1 和 169.144.0.20 之間的 TCP 數(shù)據(jù)包，示例如下所示，

[root@compute-0-1 ~]# tcpdump -w two-host-tcp-comm.pcap -i enp0s3 tcp and \(host 169.144.0.1 or host 169.144.0.20\)

使用 tcpdump 命令只捕獲兩臺主機(jī)之間的 SSH 數(shù)據(jù)包流，

[root@compute-0-1 ~]# tcpdump -w ssh-comm-two-hosts.pcap -i enp0s3 src 169.144.0.1 and port 22 and dst 169.144.0.20 and port 22

示例：13）捕獲兩臺主機(jī)之間（來回）的 UDP 網(wǎng)絡(luò)數(shù)據(jù)包

語法：

# tcpdump -w -s -i udp and \(host and host \)

[root@compute-0-1 ~]# tcpdump -w two-host-comm.pcap -s 1000 -i enp0s3 udp and \(host 169.144.0.10 and host 169.144.0.20\)

示例：14）捕獲十六進(jìn)制和 ASCII 格式的數(shù)據(jù)包

使用 tcpdump 命令，我們可以以 ASCII 和十六進(jìn)制格式捕獲 TCP/IP 數(shù)據(jù)包，

要使用 -A 選項(xiàng)捕獲 ASCII 格式的數(shù)據(jù)包，示例如下所示:

[root@compute-0-1 ~]# tcpdump -c 10 -A -i enp0s3
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on enp0s3, link-type EN10MB (Ethernet), capture size 262144 bytes
00:37:10.520060 IP compute-0-1.example.com.ssh > 169.144.0.1.39406: Flags [P.], seq 1452637331:1452637519, ack 3062125586, win 333, options [nop,nop,TS val 90591987 ecr 22687106], length 188
E...[root@compute-0-1 @...............V.|...T....MT......
.fR..Z-....b.:..Z5...{.'p....]."}...Z..9.?......."root@compute-0-1 <.....V..C.....{,...OKP.2.*...`..-sS..1S...........:.O[.....{G..%ze.Pn.T..N.... ....qB..5...n.....`...:=...[..0....k.....S.:..5!.9..G....!-..'..
00:37:10.520319 IP 169.144.0.1.39406 > compute-0-1.example.com.ssh: Flags [.], ack 188, win 13930, options [nop,nop,TS val 22687109 ecr 90591987], length 0
root@compute-0-1 @.|+..............T.V.}O..6j.d.....
.Z-..fR.
00:37:11.687543 IP controller0.example.com.amqp > compute-0-1.example.com.57800: Flags [.], ack 526624548, win 243, options [nop,nop,TS val 90586768 ecr 90588146], length 0
root@compute-0-1 @.!L...
.....(..g....c.$...........
.f>..fC.
00:37:11.687612 IP compute-0-1.example.com.57800 > controller0.example.com.amqp: Flags [.], ack 1, win 237, options [nop,nop,TS val 90593155 ecr 90551716], length 0
root@compute-0-1 @..........
...(.c.$g.......Se.....
.fW..e..
..................................................................................................................................................

要同時以十六進(jìn)制和 ASCII 格式捕獲數(shù)據(jù)包，請使用 -XX 選項(xiàng)。

[root@compute-0-1 ~]# tcpdump -c 10 -XX -i enp0s3
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on enp0s3, link-type EN10MB (Ethernet), capture size 262144 bytes
00:39:15.124363 IP compute-0-1.example.com.ssh > 169.144.0.1.39406: Flags [P.], seq 1452640859:1452641047, ack 3062126346, win 333, options [nop,nop,TS val 90716591 ecr 22718257], length 188
0x0000: 0a00 2700 0000 0800 27f4 f935 0800 4510 ..'.....'..5..E.
0x0010: 00f0 5bc6 4000 4006 8afc a990 0014 a990 ..[root@compute-0-1 @.........
0x0020: 0001 0016 99ee 5695 8a5b b684 570a 8018 ......V..[..W...
0x0030: 014d 5418 0000 0101 080a 0568 39af 015a .MT........h9..Z
0x0040: a731 adb7 58b6 1a0f 2006 df67 c9b6 4479 .1..X......g..Dy
0x0050: 19fd 2c3d 2042 3313 35b9 a160 fa87 d42c ..,=.B3.5..`...,
0x0060: 89a9 3d7d dfbf 980d 2596 4f2a 99ba c92a ..=}....%.O*...*
0x0070: 3e1e 7bf7 3af2 a5cc ee4f 10bc 7dfc 630d >.{.:....O..}.c.
0x0080: 898a 0e16 6825 56c7 b683 1de4 3526 ff04 ....h%V.....5&..
0x0090: 68d1 4f7d babd 27ba 84ae c5d3 750b 01bd h.O}..'.....u...
0x00a0: 9c43 e10a 33a6 8df2 a9f0 c052 c7ed 2ff5 .C..3......R../.
0x00b0: bfb1 ce84 edfc c141 6dad fa19 0702 62a7 .......Am.....b.
0x00c0: 306c db6b 2eea 824e eea5 acd7 f92e 6de3 0l.k...N......m.
0x00d0: 85d0 222d f8bf 9051 2c37 93c8 506d 5cb5 .."-...Q,7..Pm\.
0x00e0: 3b4a 2a80 d027 49f2 c996 d2d9 a9eb c1c4 ;J*..'I.........
0x00f0: 7719 c615 8486 d84c e42d 0ba3 698c w......L.-..i.
00:39:15.124648 IP 169.144.0.1.39406 > compute-0-1.example.com.ssh: Flags [.], ack 188, win 13971, options [nop,nop,TS val 22718260 ecr 90716591], length 0
0x0000: 0800 27f4 f935 0a00 2700 0000 0800 4510 ..'..5..'.....E.
0x0010: 0034 6b70 4000 4006 7c0e a990 0001 a990 root@compute-0-1 @.|.......
0x0020: 0014 99ee 0016 b684 570a 5695 8b17 8010 ........W.V.....
0x0030: 3693 7c0e 0000 0101 080a 015a a734 0568 6.|........Z.4.h
0x0040: 39af
.......................................................................

這就是本文的全部內(nèi)容，我希望您能了解如何使用 tcpdump 命令捕獲和分析 TCP/IP 數(shù)據(jù)包。請分享你的反饋和評論。

via: https://www.linuxtechi.com/capture-analyze-packets-tcpdump-command-linux/

作者：Pradeep Kumar

選題：lujun9972

譯者：ypingcn

校對：wxy

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