Re: [Qemu-devel] [PATCH 2/2] extend the macaddr space to 0xffffffff

[Michael S. Tsirkin]

On Mon, Jun 17, 2013 at 09:35:11PM +0800, Amos Kong wrote:
> Currently we only support to allocate 0xff mac-addresses,
> if we start guest by pci-bridge/multiple-func, the macaddr
> are not enough.
> 
> This patch extends the mac-address space to 0xffffffff
> 
> 52:54:00:00:00:00 ~ 52:54:ff:ff:ff:ff
> 
> Signed-off-by: Amos Kong <address@hidden>


And then there's even more chance a user error
(forgot to specify mac) will lead to broken
LANs because of collisions.

Why is it that whoever wants >256 NICs can't just
specify the addresses explicitly?

> ---
>  net/net.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/net/net.c b/net/net.c
> index f019da4..78bb080 100644
> --- a/net/net.c
> +++ b/net/net.c
> @@ -153,10 +153,12 @@ void qemu_macaddr_default_if_unset(MACAddr *macaddr)
>  realloc_mac:
>      macaddr->a[0] = 0x52;
>      macaddr->a[1] = 0x54;
> -    macaddr->a[2] = 0x00;
> -    macaddr->a[3] = 0x12;
> -    macaddr->a[4] = 0x34;
> -    macaddr->a[5] = 0x56 + index++;
> +    macaddr->a[2] = 0x00 + ((0x120000 + 0x3400 + 0x56 + index) >> 24 & 0xff);
> +    macaddr->a[3] = 0x12 + ((0x3400 + 0x56 + index) >> 16 & 0xff);
> +    macaddr->a[4] = 0x34 + ((0x56 + index) >> 8 & 0xff);
> +    macaddr->a[5] = 0x56 + (index & 0xff);
> +
> +    index++;
>  
>      QTAILQ_FOREACH(nc, &net_clients, next) {
>          peer = nc->peer;
> -- 
> 1.8.1.4