Subject: Re: [RFC PATCH bridge 5/5] bridge: Add sysfs interface to display VLANS

From: "Michael S. Tsirkin" <[email-masked]>
Date: Thu, 30 Aug 2012 15:27:24 +0300

On Thu, Aug 23, 2012 at 03:29:55PM -0400, Vlad Yasevich wrote:
> Add a binary sysfs file that will dump out vlans currently configured on the
> port.
> 
> Signed-off-by: Vlad Yasevich <[email-masked]>

So what's the format here? I could not tell.
List of vlans? Why binary? Why not make it text in that case?
This would also allow reporting "all" if filtering
is disabled and "untagged" for untagged packets.

> ---
>  include/linux/if_bridge.h |    1 +
>  net/bridge/br_if.c        |   34 ++++++++++++++++++++++++++++++++++
>  net/bridge/br_private.h   |    2 ++
>  net/bridge/br_sysfs_if.c  |   28 ++++++++++++++++++++++++++++
>  4 files changed, 65 insertions(+), 0 deletions(-)
> 
> diff --git a/include/linux/if_bridge.h b/include/linux/if_bridge.h
> index ab750dd..d0f869b 100644
> --- a/include/linux/if_bridge.h
> +++ b/include/linux/if_bridge.h
> @@ -20,6 +20,7 @@
>  #define SYSFS_BRIDGE_PORT_SUBDIR "brif"
>  #define SYSFS_BRIDGE_PORT_ATTR	"brport"
>  #define SYSFS_BRIDGE_PORT_LINK	"bridge"
> +#define SYSFS_BRIDGE_PORT_VLANS "vlans"
>  
>  #define BRCTL_VERSION 1
>  
> diff --git a/net/bridge/br_if.c b/net/bridge/br_if.c
> index 90c1038..3963748 100644
> --- a/net/bridge/br_if.c
> +++ b/net/bridge/br_if.c
> @@ -510,6 +510,40 @@ int br_del_port_vlan(struct net_bridge_port *p, unsigned long vlan)
>  	return 0;
>  }
>  
> +size_t br_port_fill_vlans(struct net_bridge_port *p, char* buf,
> +			unsigned long max, unsigned long skip)
> +{
> +	unsigned long *map;
> +	unsigned short *vid = (unsigned short *)buf;
> +	unsigned short i;
> +	int num = 0;
> +
> +	if (skip > (VLAN_N_VID+1))
> +		return -EINVAL;
> +
> +	memset(buf, 0, max * sizeof(unsigned short));

Isn't max is in bytes? why is this safe?

> +
> +	rcu_read_lock();
> +	map = rcu_dereference(p->vlan_map);
> +	if (!map)
> +		goto out;
> +
> +	for (i = skip + 1; i < VLAN_N_VID + 1; i++) {

Isn't skip in bytes too? Why do you compare it to i which is
in dwords?

> +		if (test_bit(i, map)) {
> +			if (num > max)
> +				goto out;
> +
> +			*vid = i-1;
> +			vid++;
> +			num++;
> +		}
> +	}
> +out:
> +	rcu_read_unlock();
> +
> +	return num*sizeof(unsigned short);
> +}
> +
>  void __net_exit br_net_exit(struct net *net)
>  {
>  	struct net_device *dev;
> diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
> index 5639c1c..cf95cd7 100644
> --- a/net/bridge/br_private.h
> +++ b/net/bridge/br_private.h
> @@ -404,6 +404,8 @@ extern netdev_features_t br_features_recompute(struct net_bridge *br,
>  	netdev_features_t features);
>  extern int br_set_port_vlan(struct net_bridge_port *p, unsigned long vid);
>  extern int br_del_port_vlan(struct net_bridge_port *p, unsigned long vid);
> +extern size_t br_port_fill_vlans(struct net_bridge_port *p, char *buf,
> +				unsigned long max, unsigned long skip);
>  
>  /* br_input.c */
>  extern 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 13b36bd..a81e2ef 100644
> --- a/net/bridge/br_sysfs_if.c
> +++ b/net/bridge/br_sysfs_if.c
> @@ -234,6 +234,29 @@ const struct sysfs_ops brport_sysfs_ops = {
>  };
>  
>  /*
> + * Export the vlan table for a given port as a binary file.
> + * The records are unsgined shorts.
> + *
> + * Returns the number of bytes read.
> + */
> +static ssize_t brport_vlans_read(struct file *filp, struct kobject *kobj,
> +				struct bin_attribute *bin_attr,
> +				char *buf, loff_t off, size_t count)
> +{
> +	struct net_bridge_port *p = to_brport(kobj);
> +
> +	return br_port_fill_vlans(p, buf,
> +				count/sizeof(unsigned short),
> +				off/sizeof(unsigned short));
> +}
> +
> +static struct bin_attribute port_vlans = {
> +	.attr = { .name = SYSFS_BRIDGE_PORT_VLANS,
> +		  .mode = S_IRUGO, },
> +	.read = brport_vlans_read,
> +};
> +
> +/*
>   * Add sysfs entries to ethernet device added to a bridge.
>   * Creates a brport subdirectory with bridge attributes.
>   * Puts symlink in bridge's brif subdirectory
> @@ -255,6 +278,11 @@ int br_sysfs_addif(struct net_bridge_port *p)
>  			return err;
>  	}
>  
> +	err = sysfs_create_bin_file(&p->kobj, &port_vlans);
> +	if (err) {
> +		return err;
> +	}
> +
>  	strlcpy(p->sysfs_name, p->dev->name, IFNAMSIZ);
>  	return sysfs_create_link(br->ifobj, &p->kobj, p->sysfs_name);
>  }
> -- 
> 1.7.7.6
> 
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