Unable to fetch TFTP image: Invalid Parameter

When you use dnsmasq in proxy mode and you need PXE Boot in UEFI mode on machine with Secure Boot enabled, then PXE will work, TFTP will work,

shim will work, but next step apparently failed. Check your logs:

Jul 28 18:27:16 dnsmasq-tftp[28673]: sent /srv/tftpboot/efi64/bootx64.efi to 192.168.0.161
Jul 28 18:27:16 dnsmasq-tftp[28673]: file /srv/tftpboot/efi64/grubx64.efi not found

(where bootx64.efi is jusr a renamed shimx64.efi)

Also grubnetx64.efi might not work

Grub 2.06 cannot work with DHCP proxy. It will try to use master DHCP server.

It's a known bug https://bugzilla.redhat.com/show_bug.cgi?id=1809246

As Dan Berkowitz says here https://github.com/rhboot/shim/issues/111#issuecomment-438790478 and here https://serverfault.com/questions/907298/dnsmasq-proxydhcp-pxe-and-efi-start-image-returned-invalid-parameter it is possible to fix with additional setting on master DHCP server.

They have tried to fix it in Grub in Fedora https://github.com/rhboot/grub2/pull/82