Align HTTP Boot behavior with PXE by inserting a delay to wait for IPv6 Duplicate Address Detection (DAD) to complete before issuing DHCPv6 requests. This avoids EFI_NO_MAPPING errors caused by early DHCP attempts before a valid IPv6 address is ready.
Problem:
On some platforms, HTTP boot over IPv6 fails with EFI_NO_MAPPING during initial DHCPv6 attempts. The failure is due to the system trying to send Solicit messages before IPv6 DAD finishes, resulting in no usable IP address at that time.
Solution:
Insert a retry mechanism to poll DAD completion when the initial call to Dhcp6->Start() fails with EFI_NO_MAPPING. This behavior mirrors PXE's handling, where it waits for a valid IPv6 address to be assigned before retrying the DHCPv6 flow.
Signed-off-by: Sam Tsai [Wiwynn] <sam_tsai@wiwynn.com>
11f1d28bcb