[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH 1/2] avoid to allcate used macaddr to to new nic
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH 1/2] avoid to allcate used macaddr to to new nic |
Date: |
Mon, 17 Jun 2013 17:00:18 +0300 |
On Mon, Jun 17, 2013 at 09:35:10PM +0800, Amos Kong wrote:
> QEMU allocates macaddr to nic if user doesn't assigne macaddr.
> But we didn't check if the allocated macaddr is used, it might
> cause macaddr repeated.
>
> # qemu -device e1000,netdev=h1,mac=52:54:00:12:34:56
> (qemu) device_add e1000
> (qemu) info network
> e1000.0: index=0,type=nic,model=e1000,macaddr=52:54:00:12:34:56
> \ h1: index=0,type=user,net=10.0.2.0,restrict=off
> e1000.1: index=0,type=nic,model=e1000,macaddr=52:54:00:12:34:56
>
> This patch adds a check in allocating macaddr, reallocate macaddr
> if it's used by other nic.
>
> Signed-off-by: Amos Kong <address@hidden>
I'm not sure this is not exactly what was intended in this case.
Also this ptotects against an unlikely case of mixing
implicit and explicit addresses, but not against
a likely case of multiple qemu on same LAN using same MAC.
In short, implicit mac is a bad idea, don't use it.
I'd ack a patch that marks mac non-optional in
help text and documentation.
> ---
> net/net.c | 28 ++++++++++++++++++++++++++++
> 1 file changed, 28 insertions(+)
>
> diff --git a/net/net.c b/net/net.c
> index 43a74e4..f019da4 100644
> --- a/net/net.c
> +++ b/net/net.c
> @@ -143,15 +143,43 @@ void qemu_macaddr_default_if_unset(MACAddr *macaddr)
> {
> static int index = 0;
> static const MACAddr zero = { .a = { 0,0,0,0,0,0 } };
> + char info_str[256];
> + NetClientState *nc, *peer;
> + NetClientOptionsKind type;
>
> if (memcmp(macaddr, &zero, sizeof(zero)) != 0)
> return;
> +
> +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++;
> +
> + QTAILQ_FOREACH(nc, &net_clients, next) {
> + peer = nc->peer;
> + type = nc->info->type;
> +
> + if (net_hub_id_for_client(nc, NULL) == 0) {
> + continue;
> + }
> +
> + if (!peer || type == NET_CLIENT_OPTIONS_KIND_NIC) {
> + snprintf(info_str, sizeof(info_str),
> + "model=%s,macaddr=%02x:%02x:%02x:%02x:%02x:%02x",
> + nc->model,
> + macaddr->a[0], macaddr->a[1], macaddr->a[2],
> + macaddr->a[3], macaddr->a[4], macaddr->a[5]);
> +
> + /* reallocate macaddr if it's used by other nic */
> + if (!strcmp(nc->info_str, info_str)) {
> + goto realloc_mac;
Please don't code loops like that.
> + }
> + }
> + }
> +
> }
>
> /**
> --
> 1.8.1.4
Re: [Qemu-devel] [PATCH 0/2] fix macaddr allocation, Stefan Hajnoczi, 2013/06/18