memdisk: bootstrap too large to load (from subfolder)

[sjwk]

Afternoon all,
Not entirely sure if this is a memdisk issue or an iPXE issue but here goes.

I have an ISO that boots into the Windows PE environment, ISO is around 340Mb.

I'm booting it from a simple script (actually from a menu, but this simple script demonstrates the issue):

Code:

#!ipxe
dhcp
initrd http://${net0.dhcp/next-server}:8001/iso/DaRT70.iso
chain /memdisk iso raw

and the script is loaded via TFTP from the boot server, and /tftpboot served via HTTP. (I'm using the value of next-server rather than hard coded as DHCP servers are a load balanced HA pair, and the tftpboot folder is synchronized between nodes. I load the ISO via HTTP for speed.

If the script is in the root of /tftpboot, along with the memdisk loader, and the ISO in an iso subfolder, it works perfectly.
If the script is moved into a scripts subfolder and loaded from that folder, it loads the ISO fine, but when memdisk is run, it fails with 'memdisk: bootstrap too large to load'. I'm loading /memdisk rather than just memdisk so that it works wherever the script is. Given that I'm using absolute paths for memdisk and the ISO, I can't see any reason why it fails to load when the iPXE script to load it is in a subfolder?

The DHCP/TFTP server is running Ubuntu 16.04 and I'm using the packaged versions of iPXE and memdisk (from pxelinux) so versions are
iPXE: 1.0.0+git-20150424.a25a16d-1ubuntu1
pxelinux: 6.03+dfsg-11ubuntu1