[U-Boot] DHCP Command Does Not Populate all DHCP Options supplied by DHCP Server

[Stefan Bruens]

On Samstag, 4. Februar 2017 18:38:38 CET dh at synoia.com wrote:
> The u-boot DHCP Command appears to populate some DHCP options, for example:
> rootpath and gateway, netamsk and ipaddress. It does not appear to populate
> Bootfile Name (Option 67) and Boot Server Host Name (Option 66)
> 
> Can populating all option returned from DHCP. BOOTP etc be added?
> 
> I can (possibly) write the code, but an not that skilled, nor do I have much
> understanding of the u-boot code review and approval process. Duncan Hare

Unfortunately you are not stating which messages you are referring to, I 
assume you refer to DHCPDISCOVER and DHCPREQUEST.

DHCP is an extension to BOOTP, but there are some points where DHCP deviates 
from BOOTP behaviour. One such point are the sname and file fields. While in 
BOOTP these are used to select a specific server/image to boot, in DHCP these 
are no longer used as such in the DHCPDISCOVER/REQUEST messages. The server/
file are selected by the DHCP server based on e.g. MAC address, client 
identifier or any other option.

RFC2131, page 37 [1] states for both sname/file, DISCOVER/REQUEST:

"options, if indicated in 'sname/file' option; otherwise unused"

Option 67 and 66 are only relevant in OFFER/ACK messages.

Kind regards,

Stefan


[1] https://tools.ietf.org/html/rfc2131#page-37


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