From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=sender:from:to:cc:subject:date:message-id:in-reply-to:references; bh=gDQ1Y9wndA7UI4344gXUV7tagrzkJlQf6jFlCaesT48=; b=SEkSNW0svTw3fc+Whd3tHaVlxhnhlr4J1CSJsDlmvTYkwenJcdoyB7Tg8dtMOwD+P0 9CNCXvPWjKS/MCzE9aBFYrtSj105w8jbeeVRCzcFsR1tFQlq9MgvosuRuzPimWyorQvu FJCYkHwgeTlg6ZWW0q/vQ3Dj+bf5fY7qBpRmgZWzhbqBNNK0sPjpHDhE7qygo9hO0Pap ky79dpDkplU6H80wyogRQqha8B7SULle37fuiYKj2XEu+wXbE3ZOly75hHM4kW5Og2IB MQ9JcdTYy4JKKqz3j77rvFDdpq+2eEe0Y8e+szUXbwybypFX8Roka7AC6pThCRuzS4UU U8Cw== Sender: "Luis R. Rodriguez" From: "Luis R. Rodriguez" Date: Mon, 3 Mar 2014 14:47:04 -0800 Message-Id: <1393886825-24323-6-git-send-email-mcgrof@do-not-panic.com> In-Reply-To: <1393886825-24323-1-git-send-email-mcgrof@do-not-panic.com> References: <1393886825-24323-1-git-send-email-mcgrof@do-not-panic.com> Subject: [Bridge] [RFC v3 5/6] xen-netback: use a random MAC address and force bridge root block List-Id: Linux Ethernet Bridging List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: netdev@vger.kernel.org Cc: kvm@vger.kernel.org, mcgrof@suse.com, bridge@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Stephen Hemminger , xen-devel@lists.xenproject.org From: "Luis R. Rodriguez" 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 port on the 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. Sticking to a static MAC address is undesirable for a few reasons: a) using a static MAC address by default on all interfaces can lead to possible conflicts with IPv6 SLAAC and DAD b) The bridge code has a generic bridge port 'root block' feature to allow interfaces to opt out from root bridge port nominations. We want to help stop spreading the use of a high MAC address as a hack to do root port block, and instead get folks to use the proper APIs for this. This modifies xen-netback to use a random MAC address with the xen OUI prefix and enables the bridge root block feature since initialization. Although toggling the root block feature requires the iproute2 bridge tool [0] or sysfs [1] xen-netback users would only need to toggle this off in the case that the net_device is required to be a candidate for root port nomination on the bridge. This is an acceptable compromise in order to avoid the possible conflicts with IPv6 SLAAC and DAD. [0] bridge link set dev vif2.0 root_block off [1] echo 1 > /sys/devices/vif-2-0/net/vif2.0/brport/root_block Cc: Stephen Hemminger Cc: bridge@lists.linux-foundation.org Cc: netdev@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: xen-devel@lists.xenproject.org Cc: kvm@vger.kernel.org Signed-off-by: Luis R. Rodriguez --- drivers/net/xen-netback/interface.c | 14 +++++--------- 1 file changed, 5 insertions(+), 9 deletions(-) diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c index 7669d49..79d71ec 100644 --- a/drivers/net/xen-netback/interface.c +++ b/drivers/net/xen-netback/interface.c @@ -42,6 +42,8 @@ #define XENVIF_QUEUE_LENGTH 32 #define XENVIF_NAPI_WEIGHT 64 +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); @@ -346,15 +348,9 @@ struct xenvif *xenvif_alloc(struct device *parent, domid_t domid, 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_ROOT_BLOCK; netif_napi_add(dev, &vif->napi, xenvif_poll, XENVIF_NAPI_WEIGHT); netif_carrier_off(dev); -- 1.9.0