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[Xen-devel] [RFC v2 3/4] xen-netback: use a random MAC address

From: "Luis R. Rodriguez" <mcgrof@xxxxxxxx>

The purpose of using a static MAC address of FE:FF:FF:FF:FF:FF
was to prevent our backend interfaces from being used by the
bridge and nominating our interface as a root bridge. This was
possible given that the bridge code will use the lowest MAC
address for a port once a new interface gets added to the bridge.
The bridge code has a generic feature now to allow interfaces
to opt out from root bridge nominations, use that instead.

Cc: Paul Durrant <Paul.Durrant@xxxxxxxxxx>
Cc: Ian Campbell <ian.campbell@xxxxxxxxxx>
Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx
Cc: netdev@xxxxxxxxxxxxxxx
Signed-off-by: Luis R. Rodriguez <mcgrof@xxxxxxxx>
 drivers/net/xen-netback/interface.c | 14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/drivers/net/xen-netback/interface.c 
index fff8cdd..d380e3f 100644
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -42,6 +42,8 @@
+static const u8 xen_oui[3] = { 0x00, 0x16, 0x3e };
 int xenvif_schedulable(struct xenvif *vif)
        return netif_running(vif->dev) && netif_carrier_ok(vif->dev);
@@ -347,15 +349,9 @@ struct xenvif *xenvif_alloc(struct device *parent, domid_t 
        for (i = 0; i < MAX_PENDING_REQS; i++)
                vif->mmap_pages[i] = NULL;
-       /*
-        * Initialise a dummy MAC address. We choose the numerically
-        * largest non-broadcast address to prevent the address getting
-        * stolen by an Ethernet bridge for STP purposes.
-        * (FE:FF:FF:FF:FF:FF)
-        */
-       memset(dev->dev_addr, 0xFF, ETH_ALEN);
-       dev->dev_addr[0] &= ~0x01;
+       eth_hw_addr_random(dev);
+       memcpy(dev->dev_addr, xen_oui, 3);
+       dev->priv_flags |= IFF_BRIDGE_NON_ROOT;
        netif_napi_add(dev, &vif->napi, xenvif_poll, XENVIF_NAPI_WEIGHT);

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