我正在做DHCP中继POC . 我的设置如下 .
DHCP Client(VX-works) ----------- DHCP Relay----------- DHCP Server (VXworks)
在此设置中，DHCP客户端正在发送DICOVER数据包，但中继代理未收到数据包 . 我查看了代码，发现Berkeley Packet Filtering（BPF）已应用于套接字 . DHCP Relay只是丢弃数据包而不是将其转发到服务器 .
为了在调试中进一步移动，我从代码中删除了BPF过滤器和校验和验证部分 .
现在，DHCP Relay正在转发数据包，但数据包不是DHCP服务器所期望的 . DHCP Relay正在将数据包从广播更改为单播 . 在服务器端接收的帧，以太网头，IP头和UDP头是正确的（我在Wireshark日志中检查过），但是bootstrap协议选项字段不正确 .
我还在客户端捕获了Wireshark日志 . 客户端按预期发送DICOVER数据包 .
如果您需要更多信息，请发表评论 .
Realy：基于ISC dhcrelay（4.3.1P1）Linux（3.14内核）
提前致谢 .
编辑：下面是在DHCP客户端捕获的单个数据包的十六进制转储 .
ff ff ff ff ff ff 00 20 61 1e 9e 14 08 00 45 00 01 1a 4f fe 40 00 20 11 09 d6 00 00 00 00 ff ff ff ff 00 44 00 43 01 06 fd 9b 01 01 06 00 00 ae af 53 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 20 61 1e 9e 14 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 63 82 53 63 35 01 01 39 02 02 4e 37 04 0f 06 03 01 ff
1 回答
BPF过滤器在common/bpf.c中定义 . 它检查数据包是否是具有单个片段（没有分段）的IP / UDP数据包并且发往端口67，否则它将丢弃它 .
你提到你的数据包是一个IP / UDP数据包，但是你确定它没有碎片并且有正确的端口吗？