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 18:58:36 +0300

On Thu, Aug 30, 2012 at 11:52:31AM -0400, Vlad Yasevich wrote:
> 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

Yes. And

for (vid = 0; vid < 2096; ++vid)
	ioctl(port,vid)

is easier than parsing a binary blob.
Just less efficient but that is I think OK
for the show command.

> >
> >>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>>
> >>>>>>>>>>---
> >>>>>>>>>>  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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