On Samstag, 4. Februar 2017 20:16:20 CET dh@synoia.com wrote:
Stefan Thanks for the reply I suspect it is the offer response to the DHCP u-boot command.
Options 66/67 are important in the netboot scenario.
Regards Duncan Hare
Dear Duncan,
it would be good if you were more specific in your messages. Scenario, DHCP server, what do you want to achieve. You should also tell what you are referring to - messages on the wire, u-boot environment variables, ... Please be terse in your questions, but also give *all* necessary information. If in doubt, there is seldom to much information.
Of course bootserver and image url are typically [2] required for netboot scenarios. Although Option 66/67 is one possibility to specify this information, the "traditional"/non-PXE method of specifying these values is using the siaddr/sname/file fields. U-Boot currently evaluates siaddr and the file field. The sname field is ignored, as it would eventually require DNS resolution.
It is the obligation of the DHCP server to set these fields. The DHCP client *must not* use the sname/file fields in its DISCOVER/REQUEST (but for option overloading).
Specifically which information the DHCP *should* give to the client is specified in the DHCP Parameter Request List option (55). As u-boot uses siaddr/file for the bootstrapping, it omits the options 66/67. *If* a DHCP server sends out option 67 (bootfile name) although not requested, u-boot prefers its value over the file field.
Kind regards,
Stefan
[2] both values can be pre-set in the u-boot environment