如何通过mac地址评估BOOTP chaddr？答案

【问题标题】：How to evaluate BOOTP chaddr by mac address?如何通过mac地址评估BOOTP chaddr？
【发布时间】：2016-01-13 03:10:28
【问题描述】：

在dhcp数据包中，一个字段表示客户端硬件地址，但它与“fa:16:3e:6f:1a:9d”之类的mac地址不同。

如果我知道接口的mac地址“fa:16:3e:6f:1a:9d”，如何通过mac地址判断chaddr？

 0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     op (1)    |   htype (1)   |   hlen (1)    |   hops (1)    |
   +---------------+---------------+---------------+---------------+
   |                            xid (4)                            |
   +-------------------------------+-------------------------------+
   |           secs (2)            |           flags (2)           |
   +-------------------------------+-------------------------------+
   |                          ciaddr  (4)                          |
   +---------------------------------------------------------------+
   |                          yiaddr  (4)                          |
   +---------------------------------------------------------------+
   |                          siaddr  (4)                          |
   +---------------------------------------------------------------+
   |                          giaddr  (4)                          |
   +---------------------------------------------------------------+
   |                                                               |
   |                          chaddr  (16)                         |
   |                                                               |
   |                                                               |
   +---------------------------------------------------------------+
   |                                                               |
   |                          sname   (64)                         |
   +---------------------------------------------------------------+
   |                                                               |
   |                          file    (128)                        |
   +---------------------------------------------------------------+
   |                                                               |
   |                          options (variable)                   |
   +---------------------------------------------------------------+

【问题讨论】：

标签： networking mac-address dhcp

【解决方案1】：

见https://www.ietf.org/rfc/rfc2131.txt

4.4.1 Initialization and allocation of network address
...
The client MUST include its hardware address in the 'chaddr'
field, if necessary for delivery of DHCP reply messages.

前六个字节包含硬件地址，其余的都是零。可以检查 bootp/dhcp 数据包的内容，例如在 Linux 中使用 dhcpdump。

【讨论】：