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網絡抓包 tcpdump 使用指南

        在網絡問題的調試中，tcpdump應該說是一個必不可少的工具，和大部分linux下優秀工具一樣，它的特點就是簡單而強大。它是基于Unix系統的指令行式的資料包嗅探工具，可以抓取流動在網卡上的資料包。

網絡抓包 tcpdump 使用指南

監聽所有網卡所有包

tcpdump

監聽指定網卡的包

tcpdump -i ens18

監聽指定IP的包

tcpdump host 192.168.1.11

監聽指定來源IP

tcpdump src host 192.168.1.11

監聽目标位址IP

tcpdump dst host 192.168.1.11

監聽指定端口

tcpdump port 80

監聽TCP

tcpdump tcp

監聽UDP

tcpdump udp

監聽192.168.1.11的tcp協定的80端口的資料包

tcpdump tcp port 80 and src host 192.168.1.11


11:59:07.836563 IP 192.168.1.11.39680 > hello.http: Flags [.], ack 867022485, win 502, length 0
11:59:07.836711 IP 192.168.1.11.39680 > hello.http: Flags [P.], seq 0:77, ack 1, win 502, length 77: HTTP: HEAD / HTTP/1.1
11:59:07.838462 IP 192.168.1.11.39680 > hello.http: Flags [.], ack 248, win 501, length 0
11:59:07.838848 IP 192.168.1.11.39680 > hello.http: Flags [F.], seq 77, ack 248, win 501, length 0
11:59:07.839192 IP 192.168.1.11.39680 > hello.http: Flags [.], ack 249, win 501, length 0

監聽IP之間的包

tcpdump ip host 192.168.1.11 and 192.168.1.60


11:57:52.742468 IP 192.168.1.11.38978 > hello.http: Flags [S], seq 3437424457, win 64240, options [mss 1460,sackOK,TS val 2166810854 ecr 0,nop,wscale 7], length 0
11:57:52.742606 IP hello.http > 192.168.1.11.38978: Flags [S.], seq 3541873211, ack 3437424458, win 64240, options [mss 1460,nop,nop,sackOK,nop,wscale 7], length 0
11:57:52.742841 IP 192.168.1.11.38978 > hello.http: Flags [.], ack 1, win 502, length 0
11:57:52.742927 IP 192.168.1.11.38978 > hello.http: Flags [P.], seq 1:78, ack 1, win 502, length 77: HTTP: HEAD / HTTP/1.1
11:57:52.742943 IP hello.http > 192.168.1.11.38978: Flags [.], ack 78, win 502, length 0
11:57:52.744407 IP hello.http > 192.168.1.11.38978: Flags [P.], seq 1:248, ack 78, win 502, length 247: HTTP: HTTP/1.1 200 OK
11:57:52.744613 IP 192.168.1.11.38978 > hello.http: Flags [.], ack 248, win 501, length 0
11:57:52.744845 IP 192.168.1.11.38978 > hello.http: Flags [F.], seq 78, ack 248, win 501, length 0
11:57:52.745614 IP hello.http > 192.168.1.11.38978: Flags [F.], seq 248, ack 79, win 502, length 0
11:57:52.745772 IP 192.168.1.11.38978 > hello.http: Flags [.], ack 249, win 501, length 0

監聽除了與192.168.1.4之外的資料包

tcpdump ip host 192.168.1.60 and ! 192.168.1.4


11:57:20.862575 IP 192.168.1.9.47190 > hello.9200: Flags [P.], seq 3233461117:3233461356, ack 1301434191, win 9399, length 239
11:57:20.878165 IP hello.9200 > 192.168.1.9.47190: Flags [P.], seq 1:4097, ack 239, win 3081, length 4096
11:57:20.878340 IP hello.9200 > 192.168.1.9.47190: Flags [P.], seq 4097:8193, ack 239, win 3081, length 4096
11:57:20.878417 IP 192.168.1.9.47190 > hello.9200: Flags [.], ack 4097, win 9384, length 0

組合示例

tcpdump tcp -i ens18 -v -nn -t -A -s 0 -c 50 and dst port ! 22 and src net 192.168.1.0/24 -w ./cby.cap


(1)tcp: ip icmp arp rarp 和 tcp、udp、icmp這些選項等都要放到第一個參數的位置，用來過濾資料報的類型
(2)-i eth1 : 隻抓經過接口eth1的包
(3)-t : 不顯示時間戳
(4)-s 0 : 抓取資料包時預設抓取長度為68位元組。加上-S 0 後可以抓到完整的資料包
(5)-c 50 : 隻抓取50個資料包
(6)dst port ! 22 : 不抓取目标端口是22的資料包
(7)src net 192.168.1.0/24 : 資料包的源網絡位址為192.168.1.0/24
(8)-w ./cby.cap : 儲存成cap檔案，友善用ethereal(即wireshark)分析
(9)-v 使用 -v，-vv 和 -vvv 來顯示更多的詳細資訊，通常會顯示更多與特定協定相關的資訊。
(10)-nn 單個 n 表示不解析域名，直接顯示 IP；兩個 n 表示不解析域名和端口。
(11)-A 表示使用 ASCII 字元串列印封包的全部資料      
組合過濾器  《與/AND/&&》 《或/OR/||》 《非/not/!》
and or &&
or or ||
not or !

在HTTP中提取使用者頭

tcpdump -nn -A -s0 -l | grep "User-Agent:"


User-Agent: Prometheus/2.30.0
User-Agent: Microsoft-Delivery-Optimization/10.0

在HTTP中同時提取使用者頭和主機資訊

tcpdump -nn -A -s0 -l | egrep -i 'User-Agent:|Host:'


Host: 192.168.1.42:9200
User-Agent: Prometheus/2.30.0
HOST: 239.255.255.250:1900
USER-AGENT: Microsoft Edge/97.0.1072.55 Windows

抓取 HTTP GET 流量

tcpdump -s 0 -A -vv 'tcp[((tcp[12:1] & 0xf0) >> 2):4] = 0x47455420'


11:55:13.704801 IP (tos 0x0, ttl 64, id 14605, offset 0, flags [DF], proto TCP (6), length 291)
    localhost.35498 > localhost.9200: Flags [P.], cksum 0x849a (incorrect -> 0xd0b0), seq 3090925559:3090925798, ack 809492640, win 630, options [nop,nop,TS val 2076158003 ecr 842090965], length 239
E..#9.@.@.}C... ...+..#..;..0?.....v.......
{..321I.GET /metrics HTTP/1.1
Host: 192.168.1.43:9200
User-Agent: Prometheus/2.30.0
Accept: application/openmetrics-text; version=0.0.1,text/plain;version=0.0.4;q=0.5,*/*;q=0.1
Accept-Encoding: gzip
X-Prometheus-Scrape-Timeout-Seconds: 10

抓取 HTTP POST 請求流量

tcpdump -s 0 -A -vv 'tcp[((tcp[12:1] & 0xf0) >> 2):4] = 0x504f5354'


11:53:10.831855 IP (tos 0x0, ttl 63, id 0, offset 0, flags [none], proto TCP (6), length 643)
    localhost.47702 > dns50.online.tj.cn.http-alt: Flags [P.], cksum 0x1a41 (correct), seq 3331055769:3331056372, ack 799860501, win 4096, length 603: HTTP, length: 603
        POST /?tk=391f8956e632962ee9c1dc661a9b46779d86ca43fe252bddbfc09d2cc66bf875323f6e7f03b881db21133b1bf2ae5bc5 HTTP/1.1
        Host: 220.194.116.50:8080
        Accept: */*
        Accept-Language: zh-CN,zh-Hans;q=0.9
        Q-Guid: e54764008893a559b852b6e9f1c8ae268958471308f41a96fd42e477e26323b8
        Q-UA: 
        Accept-Encoding: gzip,deflate
        Q-UA2: QV=3&PL=IOS&RF=SDK&PR=IBS&PP=com.tencent.mqq&PPVN=3.8.0.1824&TBSVC=18500&DE=PHONE&VE=GA&CO=IMTT&RL=1170*2532&MO=iPhone14,2&CHID=50001&LCID=9751&OS=15.1.1
        Content-Length: 144
        User-Agent: 
        QQ-S-ZIP: gzip
        Connection: keep-alive
        Content-Type: application/multipart-formdata
        Q-Auth: 


E.......?.f.......t2.V....../...P....A..POST /?tk=391f8956e632962ee9c1dc661a9b46779d86ca43fe252bddbfc09d2cc66bf875323f6e7f03b881db21133b1bf2ae5bc5 HTTP/1.1
Host: 220.194.116.50:8080
Accept: */*
Accept-Language: zh-CN,zh-Hans;q=0.9
Q-Guid: e54764008893a559b852b6e9f1c8ae268958471308f41a96fd42e477e26323b8
Q-UA: 
Accept-Encoding: gzip,deflate
Q-UA2: QV=3&PL=IOS&RF=SDK&PR=IBS&PP=com.tencent.mqq&PPVN=3.8.0.1824&TBSVC=18500&DE=PHONE&VE=GA&CO=IMTT&RL=1170*2532&MO=iPhone14,2&CHID=50001&LCID=9751&OS=15.1.1
Content-Length: 144
User-Agent: 
QQ-S-ZIP: gzip
Connection: keep-alive
Content-Type: application/multipart-formdata
Q-Auth:

注意：一個 POST 請求會被分割為多個 TCP 資料包

提取 HTTP 請求的主機名和路徑

root@pve:~# tcpdump -s 0 -v -n -l | egrep -i "POST /|GET /|Host:"


tcpdump: listening on eno1, link-type EN10MB (Ethernet), snapshot length 262144 bytes
        GET /gchatpic_new/2779153238/851197814-3116860870-F4902AF1432FE48B812982F082A31097/0?term=255&pictype=0 HTTP/1.1
        Host: 112.80.128.33
        GET /gchatpic_new/2779153238/851197814-3116860870-F4902AF1432FE48B812982F082A31097/0?term=255&pictype=0 HTTP/1.1
        Host: 112.80.128.33
        POST /mmtls/74ce36ed HTTP/1.1
        Host: extshort.weixin.qq.com
        POST /mmtls/74ce36ed HTTP/1.1
        Host: extshort.weixin.qq.com

從 HTTP 請求中提取密碼和主機名

tcpdump -s 0 -v -n -l | egrep -i "POST /|GET /|pwd=|passwd=|password=|Host:"


        POST /index.php/action/login?_=b395d487431320461e9a6741e3828918 HTTP/1.1
        Host: x.oiox.cn
        name=cby&password=Cby****&referer=http%3A%2F%2Fx.oiox.cn%2Fadmin%2Fwelcome.php [|http]
        POST /index.php/action/login?_=b395d487431320461e9a6741e3828918 HTTP/1.1
        Host: x.oiox.cn
        name=cby&password=Cby****&referer=http%3A%2F%2Fx.oiox.cn%2Fadmin%2Fwelcome.php [|http]
        GET /admin/welcome.php HTTP/1.1
        Host: x.oiox.cn

從 HTTP 請求中提取Cookie資訊

tcpdump -nn -A -s0 -l -v | egrep -i 'Set-Cookie|Host:|Cookie:'


Host: x.oiox.cn
Cookie: 8bf110c223e1a04b7b63ca5aa97c9f61__typecho_uid=1; 8bf110cxxxxxxxb7b63ca5aa97c9f61__typecho_authCode=%24T%24W3hV7B9vRfefa6593049ba02c33b3c4796a7cfa35; PHPSESSID=bq67s1n0cb9ml6dq254qpdvfec

通過排除 echo 和 reply 類型的資料包使抓取到的資料包不包括标準的 ping 包

tcpdump 'icmp[icmptype] != icmp-echo and icmp[icmptype] != icmp-echoreply'


11:20:32.285428 IP localhost > localhost: ICMP localhost udp port 64594 unreachable, length 36
11:20:32.522061 IP localhost > localhost: ICMP localhost udp port 58617 unreachable, length 36
11:20:37.736249 IP localhost > localhost: ICMP redirect 204.79.197.219 to host localhost, length 48
11:20:44.379646 IP localhost > 111.206.187.34: ICMP localhost udp port 37643 unreachable, length 36
11:20:44.379778 IP localhost > 111.206.187.34: ICMP localhost udp port 37643 unreachable, length 36
11:20:46.351245 IP localhost > localhost: ICMP redirect lt-in-f188.1e100.net to host localhost, length 49

可以通過過濾器 ip6 來抓取 IPv6 流量，同時可以指定協定如 TCP

root@vm371841:~# tcpdump -nn ip6 proto 6 -v


tcpdump: listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
06:40:26.060313 IP6 (flowlabel 0xfe65e, hlim 64, next-header TCP (6) payload length: 40) 2a00:b700::e831:2aff:fe27:e9d9.44428 > 2001:2030:21:181::26e7.443: Flags [S], cksum 0x451c (incorrect -> 0x24cd), seq 3503520271, win 64800, options [mss 1440,sackOK,TS val 2504544710 ecr 0,nop,wscale 6], length 0
06:40:34.296847 IP6 (flowlabel 0xc9f9c, hlim 64, next-header TCP (6) payload length: 40) 2a00:b700::e831:2aff:fe27:e9d9.55082 > 2a00:1450:4010:c0e::84.443: Flags [S], cksum 0x6754 (incorrect -> 0x0813), seq 3899361154, win 64800, options [mss 1440,sackOK,TS val 2141524802 ecr 0,nop,wscale 6], length 0

發起的出站 DNS 請求和 A 記錄響應

tcpdump -i eth0 -s0 port 53


tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
06:44:10.499529 IP vm371841.37357 > dns.yandex.ru.domain: 34151+ [1au] A? czr12g1e.slt-dk.sched.tdnsv8.com. (61)
06:44:10.500992 IP vm371841.56195 > dns.yandex.ru.domain: 45667+ [1au] PTR? 219.3.144.45.in-addr.arpa. (54)
06:44:10.661142 IP dns.yandex.ru.domain > vm371841.56195: 45667 NXDomain 0/1/1 (112)
06:44:10.661438 IP vm371841.56195 > dns.yandex.ru.domain: 45667+ PTR? 219.3.144.45.in-addr.arpa. (43)
06:44:10.687147 IP dns.yandex.ru.domain > vm371841.56195: 45667 NXDomain 0/1/0 (101)
06:44:10.806349 IP dns.yandex.ru.domain > vm371841.37357: 34151 11/0/1 A 139.170.156.155, A 220.200.129.141, A 58.243.200.63, A 113.59.43.25, A 124.152.41.39, A 139.170.156.154, A 59.83.204.154, A 123.157.255.158, A 113.200.17.157, A 43.242.166.42, A 116.177.248.23 (237)

抓取 DHCP 服務的請求和響應封包

tcpdump -v -n port 67 or 68


11:50:28.939726 IP (tos 0x0, ttl 64, id 35862, offset 0, flags [DF], proto UDP (17), length 320)
    192.168.1.136.68 > 255.255.255.255.67: BOOTP/DHCP, Request from 70:3a:a6:cb:27:3c, length 292, xid 0x3ccba40c, secs 11529, Flags [none]
          Client-IP 192.168.1.136
          Client-Ethernet-Address 70:3a:a6:cb:27:3c
          Vendor-rfc1048 Extensions
            Magic Cookie 0x63825363
            DHCP-Message (53), length 1: Request
            Client-ID (61), length 7: ether 70:3a:a6:cb:27:3c
            Hostname (12), length 11: "S24G-U_273C"
            Vendor-Class (60), length 13: "CloudSwitch_1"
            MSZ (57), length 2: 800
            Parameter-Request (55), length 5: 
              Subnet-Mask (1), Default-Gateway (3), Hostname (12), Domain-Name-Server (6)
              Vendor-Class (60)
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