[Xen-devel] [PATCH][qemu-xen] Change tap device mac address to prevent change of bridge's mac

[Miroslav Rezanina <mrezanin@xxxxxxxxxx>]

Qemu tap device is created with random mac address and then add to bridge. Due 
to linux kernel handlig, bridge change its mac address to tap mac in case tap 
mac is lower than bridge one. This can lead to short network breakage for dom0 
and guests. 

This patch set tap device mac adress to FE:FF:FF:FF:FF:FF to ensure tap device 
mac is always higher then bridge one.

Signed-off-by: Miroslav Rezanina <mrezanin@xxxxxxxxxx>

Patch:
--
diff --git a/i386-dm/qemu-ifup-Linux b/i386-dm/qemu-ifup-Linux
index bcbee92..c706a10 100644
--- a/i386-dm/qemu-ifup-Linux
+++ b/i386-dm/qemu-ifup-Linux
@@ -33,5 +33,8 @@ then
    fi
 fi
 
+# We have to change mac address of tap device to not change bridge mac
+ip link set $1 addr fe:ff:ff:ff:ff:ff
+
 ifconfig $1 0.0.0.0 up
 brctl addif $bridge $1 || true
-- 
Miroslav Rezanina
Software Engineer - Virtualization Team - XEN kernel


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