Add support for Option 59 (RFC 5970)

[FelixJacobi]

This adds support for Option 59 as descriped in #16. A new bootfile section is introduced in configuration, which looks like this:

[bootfile_eth1_ipxe]
bootfile_url = tftp://[fdbd:66a9:ca20:7afd:0000:0aff:fe46:fb00]/efi32/default.ipxe
client_architecture = 0009
user_class = iPXE

• The parameter bootfile_url is the URL embedded in option 59 and is sent to the client.
• The parameters user_class and client_architecture can be used to restrict this boot file to several user classes (like iPXE which uses the boot file parameter to fetch the initial script after bootstrapping) or client architectures. The client_architecture parameter can either contain the plain numeric architecture identifier (like 0009 for EFI on AMD64 systems) or the well-known names listed in https://tools.ietf.org/html/rfc4578#section-2.1:
  • Intel x86PC
  • NEC/PC98
  • EFI Itanium
  • DEC Alpha
  • Arc x86
  • Intel Lean Client
  • EFI IA32
  • EFI BC
  • EFI Xscale
  • EFI x86-64

The bootfile sections can be referenced from classes:

[class_eth1]
addresses = eth1
bootfiles = eth1_ipxe eth1_efi64 eth1_efi32 eth1_efibc
[...]

The first entry which have a matching user_class and client_architecture value is chosen.

TODO:

• Check impact on database-based backends.
• The filtering by user class may also could be added to the classes itself.
• Check if general adjustments are required.
• Add explicit preference logic which does not depend on order in bootfiles value?
• Validate values of bootfile sections.

[HenriWahl]

May I merge or do you plan to add more? Like documentation in manpages?

[FelixJacobi]

I think before this is merged, I will add some documentation to the manpages.

[FelixJacobi]

I think before this is merged, I will add some documentation to the manpages.

Will take a few days, as I am on vacation next week, I will report back, when I have finished and remove the WIP from the PR's title.

[HenriWahl]

Hi - did you make any progress so I could pull?

[FelixJacobi]

Hi,

Unfortunaly not, as I was involved in other important projects. I will work again on it starting this weekend and I am hoping to finish it within the four next weeks.

[FelixJacobi]

I think I will finish this evening.

[FelixJacobi]

Added manpage documentation and basic config validation.

Should be done, in my opinion. Feel free to merge, if there are no issues with the changes.

[HenriWahl]

Thanks!