[ipxe-devel] uuid mangling patch

Michael Brown mbrown at fensystems.co.uk
Wed Mar 20 01:22:26 UTC 2013

On Wednesday 20 Mar 2013 00:30:13 Michael Brown wrote:
> UUIDs are still treated by iPXE as being in network byte order.  At the
> point of trying to read a UUID from SMBIOS (identified using a heuristic;
> it won't catch all cases but should catch most), we check the SMBIOS
> version number and, if it's 2.6 or newer, byte-swap the relevant fields to
> pretend that the data was stored in network byte order to begin with.
> The upshot is that using ${uuid} should perform magical byte-swapping as
> needed, while the raw bytes can still be extracted using e.g. ${uuid:hex}.

I've pushed a further patch:


which unconditionally mangles the UUID byte order at the point of constructing 
a DHCP request.  This seems to conform to the PXE spec and RFC4578, and does 
at least cause the UUID as reported by Wireshark to match the UUID as reported 
by iPXE.

To anyone who has already built infrastructure which relies on the previous 
(probably incorrect) byte ordering in DHCP packets: sorry.


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