53 lines
1.3 KiB
Markdown
53 lines
1.3 KiB
Markdown
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# 使用 tcpdump 抓包与分析
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## 抓包基础
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```bash
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# 抓包内容实时显示到控制台
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tcpdump -i eth0 host 10.0.0.10 -nn -tttt
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tcpdump -i any host 10.0.0.10 -nn -tttt
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tcpdump -i any host 10.0.0.10 and port 8088 -nn -tttt
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# 抓包存到文件
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tcpdump -i eth0 -w test.pcap
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# 读取抓包内容
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tcpdump -r test.pcap -nn -tttt
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```
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常用参数:
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* `-r`: 指定包文件。
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* `-nn`: 显示数字ip和端口，不转换成名字。
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* `-tttt`: 显示时间戳格式: `2006-01-02 15:04:05.999999`。
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## 轮转抓包
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```bash
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# 每100M轮转一次，最多保留200个文件 (推荐，文件大小可控，可通过文件修改时间判断报文时间范围)
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tcpdump -i eth0 port 8880 -w cvm.pcap -C 100 -W 200
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# 每2分钟轮转一次，后缀带上时间
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tcpdump -i eth0 port 31780 -w node-10.70.10.101-%Y-%m%d-%H%M-%S.pcap -G 120
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```
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## 过滤连接超时的包(reset)
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一般如果有连接超时发生，一般 client 会发送 reset 包，可以过滤下:
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```bash
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tcpdump -r test.pcap 'tcp[tcpflags] & (tcp-rst) != 0' -nn -ttt
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```
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## 统计流量源IP
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```bash
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tcpdump -i eth0 dst port 60002 -c 10000|awk '{print $3}'|awk -F. -v OFS="." '{print $1,$2,$3,$4}'|sort |uniq -c|sort -k1 -n
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```
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统计效果：
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```txt
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321 169.254.128.100
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409 10.0.0.175
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2202 10.0.226.49
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```
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