Subject: network in grub broke between 2:2.12.r226 and 2:2.12.r260

Hello! I'd like to report a bug I encountered on NUC14MNK set top box computer with realtek RTL1815 Gigabit ethernet controller (rev 0c).

I am creating a grub standalone image from Arch Linux using command: grub-mkstandalone -O x86_64-efi -o www/grubx64.efi --modules="tftp net efinet configfile linux normal echo http search" "boot/grub/grub.cfg=$t/grub.cfg

On grub grub-2:2.12.r260.gaae2ea61-1-x86_64.pkg.tar.zst, grub created this way works, but on grub-2:2.12.r283.ga4da71da-1-x86_64.pkg.tar.zst it can't send network packets, and therefore can't complete network boot.

When trying command net_dhcp from grub commandline with grub from grub-2:2.12.r260.gaae2ea61-1-x86_64.pkg.tar.zst, I am greeted with:

grub> net_dhcp
error: couldn't send network packet.
error: couldn't autoconfigure efinet0.
grub> _

On grub-2:2.12.r226.g56ccc5ed-1-x86_64.pkg.tar.zst net_dhcp works and I can even correctly load the kernel from http.

On latest grub 2:2.14rc1-2 the error still persists, this time errors are more descriptive:

grub> net_dhcp
error: net/drivers/efi/efinet.c:send_card_buffer:67:couldn't send network packet.
error: net/bootp.c:grub_cmd_bootp:911:couldn't autoconfigure efinet0.
grub>

Any ideas how to fix this?