[U-Boot] Unable to receive DHCP packets (qemu-system-arm)

[pietrushnic]

Hi all,
I'm unable to receive DHCP packets using qemu-system-arm 1.4.91 with 
u-boot (commit: 2988eac). Problem occurs on Ubuntu 12.04 (I tried also 
Debian wheezy and there was no issue). I accidentally discover that 
adding '-net dump,file=/tmp/dump.pcap' cause that problem disapear, but 
want to dig it and find out what the root cause is.

I tried to debug issue from u-boot source code perspective and added 
verbose logging, but can't see anything strange enough:
- log with fail - qemu w/o additional dump command - 
https://gist.github.com/pietrushnic/5561859
- log with pass - qemu w/ addional dump param - 
https://gist.github.com/pietrushnic/5561866
Difference:
- smc_rcv status is always 0 , NetLoop timeouts for failed case
- on failed case u-boot receive some packets but not DHCP offer (I 
positively verified w/ tcpdump that server sent this packet)

I'm trying to narrow down this problem from both (qemu and u-boot) side. 
Is there anything else what I can do to confirm that this is not u-boot 
issue ?
Maybe someone heard about this kind of problem ?

My network configuration based on: http://toast.djw.org.uk/qemu.html
I'm using versatilepb_config compiled with arm-unknown-linux-gnueabi 
(created using crosstool-NG).

If provided information are insufficient, just let me know.

Regards,
pietrushnic