On Tue, Mar 03, 2020 at 12:36:42AM +0100, deloptes wrote:
> john doe wrote:
[...]
> The trick was to add following line to the dhcpd.conf
>
> option vendor-encapsulated-options
> 6:1:3:a:4:0:50:58:45:9:14:0:0:11:52:61:73:70:62:65:72:72:79:20:50:69:20:42:6f:6f:74:ff;
>
> This could be added to a class, but I have only one rpi4, so added directly
> to the client config.
>
> The other trick is to set root-path to the tftp boot directory.
>
> If there is more curiosity what happens on the network, use this
>
> tcpdump -Xvv udp port 67 or port 68 or port 69
>
> Amazing!
>
> I would like to know what vendor-encapsulated-options is. The end of it
> translates to Raspberry Pi Boot\0. But the first part ... ???
> In anycase it does the magic
Thanks for making all of us smarter. To throw my two cents in, I did some
legwork, and (as usually) Wikipedia [1] provides some light.
Those options are encoded as
- code: 1 octet
- length (of following data): 1 octet
- data <length> octets.
They are closed off by one "option" 0xff with no length octet.
So taking apart your magic string above (and rewriting a bit to
make more readable):
06 01 03
0a 04 00 50 58 45
09 14 00 00 11 52 61 73 70 62
65 72 72 79 20 50 69 20
42 6f 6f 74
ff
But the codes, alas, are not interpretable according to the
ref given. An exercise for the reader :)
Cheers
[1] https://en.wikipedia.org/wiki/DHCP#Options
-- tomás
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