HTTP ISO boot fails when iSCSI target sanhooked, works otherwise

[jrgruher]

Hello-

If I do this I get the failure shown at the end:
iPXE> ifconf
Configuring (net0 c4:54:44:23:e7:99)...... ok
iPXE> sanhook --drive 0x80 --no-describe http://10.0.0.1/ubuntu-14.04-server-amd64.iso
Registered SAN device 0x80
iPXE> sanhook --drive 0x81 iscsi:10.0.0.3:::1:rbd_base
Registered SAN device 0x81
iPXE> sanboot
Booting from SAN device 0x80
Boot from SAN device 0x80 failed: Exec format error (http://ipxe.org/2e852001)

However, if I only hoot the first target (the ISO) and never hook the second target (iSCSI target) I can boot the ISO just fine. I can even get the failure shown above, then just unhook the second target, and it boots just fine from the ISO:
iPXE> sanunhook --drive 0x81
Unregistered SAN device 0x81
iPXE> sanboot

Is this expected? Is there some restriction on having different types of targets mapped at the same time?

Ideally what I want to do is connect the Ubuntu ISO and an iSCSI target a the same time, then boot, to see if the Ubuntu installer will pick up the iSCSI target through iBFT. Thanks!