<!--
  libdhcp/notes.md - Description of sbc-harness

  Copyright (C) 2024  Luke T. Shumaker <lukeshu@lukeshu.com>
  SPDX-License-Identifier: AGPL-3.0-or-later
-->

|           <c>           |   |           <c>           |
| In the message from the |   | ... then the server ... |
|     client the ...      |   |                         |
|                         |   |                         |
|      and       and      |   |                         |

|   <c>   |   <c>    |  <c>  |   |    <c>     |         <c>         |             <c>             |
| giaddr  |  ciaddr  | bcast |   |            |                     |                             |
| (relay) | (cur ip) |  bit  |   |   verbs    |    message types    |             to              |
|   is    |    is    |  is   |   |            |                     |                             |
|---------+----------+-------+---+------------+---------------------+-----------------------------|
| nonzero |    *     |   *   |   |   sends    |        (all)        | 'giaddr' BOOTP relay agent  |
|         |          |       |   |            |                     |                             |
|---------+----------+-------+---+------------+---------------------+-----------------------------|
|  zero   | nonzero  |   *   |   |  unicasts  | DHCPOFFER & DHCPACK |       'ciaddr' client       |
|         |          |       |   | broadcasts |      DHCPNACK       |         0xffffffff          |
|---------+----------+-------+---+------------+---------------------+-----------------------------|
|  zero   |   zero   |   1   |   | broadcasts | DHCPOFFER & DHCPACK |         0xffffffff          |
|         |          |       |   | broadcasts |      DHCPNACK       |         0xffffffff          |
|---------+----------+-------+---+------------+---------------------+-----------------------------|
|  zero   |   zero   |   0   |   |  unicasts  | DHCPOFFER & DHCPACK | client hw addr and 'yiaddr' |
|         |          |       |   | broadcasts |      DHCPNACK       |         0xffffffff          |

In all cases, when 'giaddr' is zero, the server broadcasts any DHCPNAK
messages to 0xffffffff.