loader_4th.efi "IPv4 PXE" net booting no longer works

Hi,

sorry I cannot gather more parts of the console before this easily; this
is a remote machine booting via IPv4 (just in case you wonder with me).

It's a EDK II firmware, boot options is IPv4 PXE.  Boot file is loader.efi,
which is loader_4th.efi in that setup.

I updated to a kernel/world from the last 48 hours and the boot hangs:

--- 8< 8< 8< -----------------------------------------------------------
    Console: efi (0x1000)
    Load Path:
    BootCurrent: 0004
    BootOrder: 0004[*] 0008 0005 0007 0006 0001 0002 0000 0003
Setting currdev to md0:
MD not present
    BootInfo Path: MAC(ABCDEFABCDEF,0x1)/IPv4(0.0.0.0)
Ignoring Boot0004: Only one DP found
Setting currdev to net0:
--- 8< 8< 8< -----------------------------------------------------------

Then things hang.


I switched back to a loader_4th.efi from early July which still worked:

--- 8< 8< 8< -----------------------------------------------------------
    Console: efi (0x1000)
    Load Path:
    Load Device: MAC(ABCDEFABCDEF,0x1)/IPv4(0.0.0.0)
    BootCurrent: 0004
    BootOrder: 0004[*] 0008 0005 0007 0006 0001 0002 0000 0003
    BootInfo Path: MAC(ABCDEFABCDEF,0x1)/IPv4(0.0.0.0)
Ignoring Boot0004: Only one DP found
Setting currdev to net0:
\
...
<loader.rc derived output>
--- 8< 8< 8< -----------------------------------------------------------

Do I need to start a bisect?


-- 
For there shall arise false Christs, and false prophets, and shall shew
great signs and wonders; insomuch that, if it were possible, they shall
deceive the very elect. Behold, I have told you before. [Mat. 24:24-25]