Versions affected: 2.04, 2.06
Reproduced on: UEFI PXE with DHCPv6 Relay Agent
Tested on: QEMU virtual machine (x86_64) with Linux

A DHCPv6 relay agent, which may reside on the client's link, is used to relay messages between the client and the server. It allows a DHCPv6 client to send a message to a DHCPv6 server that is not connected to the same link.

In the PXE scenario, if the client and server are not connected to the same link,  grub2 needs to configure the default gateway after requesting an IP address from the server through a DHCPv6 relay agent, otherwise grub2 does not know which network interface to use to send tftp requests.

I think grub2 needs to send an ICMPv6 (type 133) Router Solicitation (RS) message to inquire about the local IPv6-capable router on the network. In response to the RS, the router immediately sends an ICMPv6 (type 134) Routing Advertisement (RA) message, then grub2 can configure the default gateway through the RA message. And perhaps this process should be done in the function of grub_efi_net_config_real(). Is this feasible?