network: 0.758
graphic: 0.640
kernel: 0.626
device: 0.597
semantic: 0.569
peripherals: 0.475
performance: 0.445
ppc: 0.417
PID: 0.413
vnc: 0.403
architecture: 0.365
register: 0.353
user-level: 0.348
socket: 0.340
VMM: 0.292
boot: 0.262
arm: 0.254
debug: 0.228
files: 0.214
TCG: 0.212
virtual: 0.206
permissions: 0.190
x86: 0.185
hypervisor: 0.145
i386: 0.145
KVM: 0.136
mistranslation: 0.136
risc-v: 0.133
assembly: 0.084

qemu network adapter initialization fails when using macaddr=<multicast MAC-address>

Not sure if ultra-strange, nondocumented feature in qemu (or linux kernel) or really bug: Network card initialization fails if first byte of mac address  is not 00. The problem occurs at least with model=pcnet/rtl8139, in both cases the network adapter is not usable.

How to reproduce:

* Take standard  initrd/kernel (tested with hardy)

* Start qemu (cmd see below) and enter "modprobe pcnet32" at prompt:
qemu -name SetupTest -no-acpi -m 128 -drive file=/dev/null,if=ide,index=0 -net nic,macaddr=00:22:33:44:55:66,model=pcnet -net user -kernel vmlinuz-2.6.24-26-generic -initrd initrd.img-2.6.24-26-generic -append break=premount

You will see "pcnet32 ... at 0x..., 00:22:33:44:55:66

* Do same with mac address 11:22:33:44:55:66
qemu -name SetupTest -no-acpi -m 128 -drive file=/dev/null,if=ide,index=0 -net nic,macaddr=11:22:33:44:55:66,model=pcnet -net user -kernel vmlinuz-2.6.24-26-generic -initrd initrd.img-2.6.24-26-generic -append break=premount

You will see "pcnet32 ... at 0x..., 00:00:00:00:00:00

The network adapter is non-functional, "ip link set eth0 up" does not report error, but does not work (indicates at least some linux kernel influence)

With the rtl8139 adapter, mac-address in guest is correct, but adapter does not work either (indicates qemu influence)

Tested other mac addrs, seems that the first byte has to be even. Would it make sense to issue a warning if a user requests a mac address with an odd first byte? What is the special meaning of the bit 0?

That bit indicates whether the address is a multicast or unicast address.  A network card cannot have a multicast address.

It would make sense to do sanity checking for this.

A check for multicast MAC addresses has been introduced by this commit here:
http://git.qemu.org/?p=qemu.git;a=commitdiff;h=d60b20cf2ae6644b051
So I think we can close this ticket now.