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

From: Vlad Yasevich <[email-masked]>
Date: Thu, 30 Aug 2012 11:52:31 -0400

On 08/30/2012 11:47 AM, Michael S. Tsirkin wrote:
> On Thu, Aug 30, 2012 at 11:07:24AM -0400, Vlad Yasevich wrote:
>> On 08/30/2012 11:03 AM, Michael S. Tsirkin wrote:
>>> On Thu, Aug 30, 2012 at 10:51:35AM -0400, Vlad Yasevich wrote:
>>>> On 08/30/2012 10:44 AM, Michael S. Tsirkin wrote:
>>>>> On Thu, Aug 30, 2012 at 10:36:34AM -0400, Vlad Yasevich wrote:
>>>>>> On 08/30/2012 10:26 AM, Michael S. Tsirkin wrote:
>>>>>>> On Thu, Aug 30, 2012 at 10:05:16AM -0400, Vlad Yasevich wrote:
>>>>>>>> On 08/30/2012 08:27 AM, Michael S. Tsirkin wrote:
>>>>>>>>> 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.
>>>>>>
>>>>>> I initially though of creating a sysfs object per vlan.  That would
>>>>>> have made it easy to see which vlans are configured without any
>>>>>> tools.
>>>>>> But that could result in a lot of objects being created, so I abandoned it.
>>>>>>
>>>>>> I did think about a text interface, but due to a page of output
>>>>>> limitation, I didn't go that route.  The reason is that if someone
>>>>>> cats the file, they may not see all the vlans configured.  So I
>>>>>> decided on the binary interface, since a binary interface with a
>>>>>> tool to read it could avoid the single page limitation.
>>>>>>
>>>>>> -vlad
>>>>>
>>>>> Maybe it's not needed in sysfs then - expose it to
>>>>> brctl or whatever.
>>>>>
>>>>
>>>> brctl uses sysfs for almost everything any more :)
>>>>
>>>> -vlad
>>>
>>> How about a long string of 0 and 1's?
>>> And a separate one for untagged vlans.
>>
>> that would work too.  You really don't like the binary interface, huh?
>>
>> -vlad
>
> Not in sysfs.
> Another possibility: you are adding netlink command
> to add/del a specific vid, add one to test a specific vid.
> This means you will need to scan 4K possibilities if you
> want to list them all, but in real life it's
> probably just debugging tools that need to do this.

Not really.  A show command to see what has been configured is necessary 
not of only for debugging.  It is no different then the show command to 
list fdb entries on the bridge.  There needs to be an easy way to see 
which vlans are configured on which ports.

-vlad
>
>>>
>>>>>>>
>>>>>>>
>>>>>>>>>
>>>>>>>>>> ---
>>>>>>>>>>   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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