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 18:03:52 +0300

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.

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