The patch is on 9p.io:

/n/sources/patch/dhcpd-rpi-pxeboot


On Wed, Jun 3, 2020 at 12:43 PM Skip Tavakkolian <skip.tavakkolian@gmail.com>
wrote:

> Note that RPi 4 DHCP requests include a parameter request for TFTP Server
> Name (66).  There is a link in the doc to the diffs for
> /sys/src/cmd/ip/dhcpd/dhcpd.c. I'll submit a patch to 9p.io soon.
>
> On Wed, Jun 3, 2020 at 11:26 AM Skip Tavakkolian <
> skip.tavakkolian@gmail.com> wrote:
>
>>
>> FYI, I've updated the HOWTO to include RPi4's. It's here:
>>
>>
>> https://docs.google.com/document/d/1hgcsAgk_FJRYW5r7LVeY23sTZN_giUit-8ra-dlW9ng
>>
>>
>>