netdev - Re: [PATCH net] bridge: notify user space after fdb update

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Message-ID: <5385F089.9080608@cogentembedded.com>
Date:	Wed, 28 May 2014 18:19:53 +0400
From:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:	Jon Maxwell <jmaxwell37@...il.com>, stephen@...workplumber.org
CC:	davem@...emloft.net, makita.toshiaki@....ntt.co.jp,
	vyasevic@...hat.com, bridge@...ts.linux-foundation.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	jpirko@...hat.com, jmaxwell@...hat.com
Subject: Re: [PATCH net] bridge: notify user space after fdb update

Hello.

On 05/28/2014 02:45 AM, Jon Maxwell wrote:

> There has been a number incidents recently where customers running KVM have
> reported that VM hosts on different Hypervisors are unreachable. Based on
> pcap traces we found that the bridge was broadcasting the ARP request out
> onto the network. However some NICs have an inbuilt switch which on occasions
> were broadcasting the VMs ARP request back through the physical NIC on the
> Hypervisor. This resulted in the bridge changing ports and incorrectly learning
> that the VMs mac address was external. As a result the ARP reply was directed
> back onto the external network and VM never updated it's ARP cache. This patch
> will notify the bridge command, after a fdb has been updated to identify such
> port toggling.

> Signed-off-by: Jon Maxwell <jmaxwell37@...il.com>
> ---
>   net/bridge/br_fdb.c | 8 +++++++-
>   1 file changed, 7 insertions(+), 1 deletion(-)

> diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
> index 9203d5a..f3ee2da 100644
> --- a/net/bridge/br_fdb.c
> +++ b/net/bridge/br_fdb.c
> @@ -487,6 +487,7 @@ void br_fdb_update(struct net_bridge *br, struct net_bridge_port *source,
>   {
>   	struct hlist_head *head = &br->hash[br_mac_hash(addr, vid)];
>   	struct net_bridge_fdb_entry *fdb;
> +	bool fdb_modified = 0;

    s/0/false/.

>
>   	/* some users want to always flood. */
>   	if (hold_time(br) == 0)
> @@ -507,10 +508,15 @@ void br_fdb_update(struct net_bridge *br, struct net_bridge_port *source,
>   					source->dev->name);
>   		} else {
>   			/* fastpath: update of existing entry */
> -			fdb->dst = source;
> +			if (unlikely(source != fdb->dst)) {
> +					fdb->dst = source;
> +					fdb_modified = 1;

   s/1/true/.

> +				}
>   			fdb->updated = jiffies;
>   			if (unlikely(added_by_user))
>   				fdb->added_by_user = 1;
> +			if (unlikely(fdb_modified))
> +				fdb_notify(br, fdb, RTM_NEWNEIGH);
>   		}
>   	} else {
>   		spin_lock(&br->hash_lock);

WBR, Sergei


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