Subject: Re: [RFC PATCH v2 net-next 2/7] bridge: Keep track of ports capable of automatic discovery.

From: Vlad Yasevich <[email-masked]>
Date: Wed, 30 Apr 2014 09:47:37 -0400

On 04/30/2014 06:18 AM, Michael S. Tsirkin wrote:
> On Tue, Apr 29, 2014 at 05:20:23PM -0400, Vlad Yasevich wrote:
>> By default, ports on the bridge are capable of automatic
>> discovery of nodes located behind the port.  This is accomplished
>> via flooding of unknown traffic (BR_FLOOD) and learning the
>> mac addresses from these packets (BR_LEARNING).
>> If the above functionality is diabled by turning off these
>> flags, the port requires static configuration in the form
>> of static FDB entries to function properly.
>>
>> This patch adds functionality to keep track of all ports
>> capable of automatic discovery.  This will later be used
>> to control promiscuity settings.
>>
>> Signed-off-by: Vlad Yasevich <[email-masked]>
>> ---
>>  net/bridge/br_if.c       | 27 +++++++++++++++++++++++++++
>>  net/bridge/br_netlink.c  |  3 +++
>>  net/bridge/br_private.h  |  6 ++++++
>>  net/bridge/br_sysfs_if.c |  6 +++++-
>>  4 files changed, 41 insertions(+), 1 deletion(-)
>>
>> diff --git a/net/bridge/br_if.c b/net/bridge/br_if.c
>> index 5262b86..7e60c4c 100644
>> --- a/net/bridge/br_if.c
>> +++ b/net/bridge/br_if.c
>> @@ -85,6 +85,18 @@ void br_port_carrier_check(struct net_bridge_port *p)
>>  	spin_unlock_bh(&br->lock);
>>  }
>>  
>> +static void nbp_update_port_count(struct net_bridge *br)
>> +{
>> +	struct net_bridge_port *p;
>> +	u32 cnt = 0;
>> +
>> +	list_for_each_entry(p, &br->port_list, list) {
>> +		if (br_is_auto_port(p))
>> +			cnt++;
>> +	}
>> +	br->auto_cnt = cnt;
>> +}
>> +
>>  static void release_nbp(struct kobject *kobj)
>>  {
>>  	struct net_bridge_port *p
>> @@ -146,6 +158,8 @@ static void del_nbp(struct net_bridge_port *p)
>>  
>>  	list_del_rcu(&p->list);
>>  
>> +	nbp_update_port_count(br);
>> +
>>  	dev->priv_flags &= ~IFF_BRIDGE_PORT;
>>  
>>  	netdev_rx_handler_unregister(dev);
>> @@ -384,6 +398,8 @@ int br_add_if(struct net_bridge *br, struct net_device *dev)
>>  
>>  	list_add_rcu(&p->list, &br->port_list);
>>  
>> +	nbp_update_port_count(br);
>> +
>>  	netdev_update_features(br->dev);
>>  
>>  	if (br->dev->needed_headroom < dev->needed_headroom)
>> @@ -455,3 +471,14 @@ int br_del_if(struct net_bridge *br, struct net_device *dev)
>>  
>>  	return 0;
>>  }
>> +
>> +void br_port_flags_change(struct net_bridge_port *p, unsigned long old_flags)
>> +{
>> +	struct net_bridge *br = p->br;
>> +	unsigned long mask = old_flags ^ p->flags;
>> +
>> +	if (!(mask & BR_AUTO_MASK))
>> +		return;
>> +
>> +	nbp_update_port_count(br);
>> +}
>> diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
>> index e74b6d53..01382b9 100644
>> --- a/net/bridge/br_netlink.c
>> +++ b/net/bridge/br_netlink.c
>> @@ -328,6 +328,7 @@ static void br_set_port_flag(struct net_bridge_port *p, struct nlattr *tb[],
>>  static int br_setport(struct net_bridge_port *p, struct nlattr *tb[])
>>  {
>>  	int err;
>> +	unsigned long old_flags = p->flags;
>>  
>>  	br_set_port_flag(p, tb, IFLA_BRPORT_MODE, BR_HAIRPIN_MODE);
>>  	br_set_port_flag(p, tb, IFLA_BRPORT_GUARD, BR_BPDU_GUARD);
>> @@ -353,6 +354,8 @@ static int br_setport(struct net_bridge_port *p, struct nlattr *tb[])
>>  		if (err)
>>  			return err;
>>  	}
>> +
>> +	br_port_flags_change(p, old_flags ^ p->flags);
>>  	return 0;
>>  }
>>  
>> diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
>> index 06811d7..db714a1 100644
>> --- a/net/bridge/br_private.h
>> +++ b/net/bridge/br_private.h
>> @@ -174,6 +174,7 @@ struct net_bridge_port
>>  #define BR_ADMIN_COST		0x00000010
>>  #define BR_LEARNING		0x00000020
>>  #define BR_FLOOD		0x00000040
>> +#define BR_AUTO_MASK (BR_FLOOD | BR_LEARNING)
>>  
>>  #ifdef CONFIG_BRIDGE_IGMP_SNOOPING
>>  	struct bridge_mcast_query	ip4_query;
>> @@ -198,6 +199,8 @@ struct net_bridge_port
>>  #endif
>>  };
>>  
>> +#define br_is_auto_port(p) (((p)->flags & BR_AUTO_MASK) == BR_AUTO_MASK)
>> +
> 
> I think you
> really want ((p)->flags & BR_AUTO_MASK) instead without
>  == BR_AUTO_MASK.
> 
> For example if learning is off but flood is on, things work
> (slowly) automatically without configuring static entries.
> 
> OTOH if flood is off but learning is on, a bunch of packets
> might get dropped but eventually you might learn the
> mac and then networking will start working.
> 

Yes, you are completely correct.  I flipped the meaning of the
macro, but forgot to account correctly for it.

static == not flooding && not learning.
auto != static.

The reason I count "auto" ports is so I only have to keep 1 counter
around.  If I counted static, I'd also have to count all ports as well.
Not much of a difference, but it's one less counter.

Fill fix.
Thanks
-vlad

> 
>>  #define br_port_exists(dev) (dev->priv_flags & IFF_BRIDGE_PORT)
>>  
>>  static inline struct net_bridge_port *br_port_get_rcu(const struct net_device *dev)
>> @@ -290,6 +293,7 @@ struct net_bridge
>>  	struct timer_list		topology_change_timer;
>>  	struct timer_list		gc_timer;
>>  	struct kobject			*ifobj;
>> +	u32				auto_cnt;
>>  #ifdef CONFIG_BRIDGE_VLAN_FILTERING
>>  	u8				vlan_enabled;
>>  	struct net_port_vlans __rcu	*vlan_info;
>> @@ -415,6 +419,8 @@ int br_del_if(struct net_bridge *br, struct net_device *dev);
>>  int br_min_mtu(const struct net_bridge *br);
>>  netdev_features_t br_features_recompute(struct net_bridge *br,
>>  					netdev_features_t features);
>> +void br_port_flags_change(struct net_bridge_port *port,
>> +			  unsigned long old_flags);
>>  
>>  /* br_input.c */
>>  int br_handle_frame_finish(struct sk_buff *skb);
>> diff --git a/net/bridge/br_sysfs_if.c b/net/bridge/br_sysfs_if.c
>> index 112a25e..58c26e3 100644
>> --- a/net/bridge/br_sysfs_if.c
>> +++ b/net/bridge/br_sysfs_if.c
>> @@ -49,7 +49,10 @@ static BRPORT_ATTR(_name, S_IRUGO | S_IWUSR,			\
>>  static int store_flag(struct net_bridge_port *p, unsigned long v,
>>  		     unsigned long mask)
>>  {
>> -	unsigned long flags = p->flags;
>> +	unsigned long flags;
>> +	unsigned long old_flags;
>> +
>> +	old_flags = flags = p->flags;
>>  
>>  	if (v)
>>  		flags |= mask;
>> @@ -58,6 +61,7 @@ static int store_flag(struct net_bridge_port *p, unsigned long v,
>>  
>>  	if (flags != p->flags) {
>>  		p->flags = flags;
>> +		br_port_flags_change(p, old_flags ^ flags);
>>  		br_ifinfo_notify(RTM_NEWLINK, p);
>>  	}
>>  	return 0;
>> -- 
>> 1.9.0
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