Re: [PATCH net-next] net: Add phys_port identifier to struct net_device and export it to sysfs

[Jiri Pirko <jiri@resnulli.us>]

Mon, Jun 17, 2013 at 08:10:32PM CEST, Narendra_K@Dell.com wrote:
>It is useful to know if network interfaces from NIC partitions
>'map to/use the' same physical port. For example,  when creating
>bonding in fault tolerance mode, if  two network interfaces map to/use
>the same physical port, it might not have the desired result. This
>information is not available today in a standard format or it is not
>present.  If this information can be made available in a generic  way
>to user space, tools such as NetworkManager or Libteam or Wicked can
>make smarter bonding decisions (such as warn users when setting up
>configurations which will not have desired effect).
>
>The requirement is to have a generic interface using which
>kernel/drivers can provide information/hints to user space about the
>physical port number used by a network interface.
>
>The following options were explored -
>
>1. 'dev_id' sysfs attribute:
>
>In addition to being used to differentiate between devices that share
>the same link layer address, it is being used to indicate the physical
>port number used by a network interface.
>
>As dev_id exists to differentiate between devices sharing the same
>link layer address, dev_id option is not selected.
>
>2. Re-using 'if_port' field in 'struct net_device':
>
>if_port field exists to indicate the media type(please refer to
>netdevice.h). It seemed like it was also used to indicate the physical
>port number.
>
>As re-using 'if_port' might possibly break user space, this option is
>not selected.
>
>3. Add a new field 'phys_port' to 'struct net_device' and export it
>to sysfs:
>
>The 'phys_port' will be a universally unique identifier, which
>would be a MAC-48 or EUI-64 or a 128 bit UUID value, but not
>restricted to these spaces. It will uniquely identify the physical
>port used by a network interface. The 'length' of the identifier will
>be zero if the field is not set for a network interface.
>
>This patch implements option 3. It creates a new sysfs attribute
>'phys_port' -


I think that correct way is to (Ben mentioned already part of it):
1) introduce ndo_phys_port_id() which would be used by core to get the
struct port_identifier filled by the driver (struct port_identifier is
not really a good name (namespace prefix should be there))

2) add netdev nofitier event type which would allow driver to propagate
changes of phys to to rtnetlink code and drivers which might be
interested (like bond/bridge/whatever) as well.

3) export phys port id through rtnetlink api to userspace.

I can cook up a patch like this after I return from my weekend trip if
you are interested :)

Jiri

>
>/sys/class/net/<interface name>/phys_port
>
>References: http://marc.info/?l=linux-netdev&m=136920998009209&w=2
>References: http://marc.info/?l=linux-netdev&m=136992041432498&w=2
>
>Signed-off-by: Narendra K <narendra_k@dell.com>
>---
>Changes from RFC version:
>
>Suggestions from Ben Hutchings -
>1. 'struct port_identifier' is changed to be generic instead of
>restricting it to MAC-48 or EUI-64 or 128 bit UUID.
>2. Commit message updated to indicate point 1.
>3. 'show_phys_port' function modified to handle zero length
>instead of returning -EINVAL
>4. 'show_phys_port' function made generic to handle all
>lengths instead 6, 8 or 16 bytes.
>
>Hi Ben, I have retained the commit message to indicate that 'dev_id'
>is being used to indicate the physical port number also.
>
>Thank you.
>
> include/linux/netdevice.h | 13 +++++++++++++
> net/core/net-sysfs.c      | 17 +++++++++++++++++
> 2 files changed, 30 insertions(+)
>
>diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
>index 09b4188..ddb14ef 100644
>--- a/include/linux/netdevice.h
>+++ b/include/linux/netdevice.h
>@@ -1062,6 +1062,14 @@ struct net_device_ops {
> 						      bool new_carrier);
> };
> 
>+/* This structure holds a universally unique identifier to
>+ * identify the physical port used by a netdevice
>+ */
>+struct port_identifier {
>+	unsigned char port_id[MAX_ADDR_LEN];
>+	unsigned port_id_len;
>+};
>+
> /*
>  *	The DEVICE structure.
>  *	Actually, this whole structure is a big mistake.  It mixes I/O
>@@ -1181,6 +1189,11 @@ struct net_device {
> 						 * that share the same link
> 						 * layer address
> 						 */
>+	struct port_identifier	phys_port;	/* Universally unique physical
>+						 * port identifier, MAC-48 or
>+						 * EUI-64 or 128 bit UUID,
>+						 * length is zero if not set
>+						 */
> 	spinlock_t		addr_list_lock;
> 	struct netdev_hw_addr_list	uc;	/* Unicast mac addresses */
> 	struct netdev_hw_addr_list	mc;	/* Multicast mac addresses */
>diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
>index 981fed3..3245e90 100644
>--- a/net/core/net-sysfs.c
>+++ b/net/core/net-sysfs.c
>@@ -334,6 +334,22 @@ static ssize_t store_group(struct device *dev, struct device_attribute *attr,
> 	return netdev_store(dev, attr, buf, len, change_group);
> }
> 
>+static ssize_t show_phys_port(struct device *dev,
>+			      struct device_attribute *attr, char *buf)
>+{
>+	struct net_device *net = to_net_dev(dev);
>+	unsigned char len;
>+
>+	if (!dev_isalive(net))
>+		return -EINVAL;
>+
>+	len = net->phys_port.port_id_len;
>+	if (!len)
>+		return 0;
>+
>+	return sysfs_format_mac(buf, net->phys_port.port_id, len);
>+}
>+
> static struct device_attribute net_class_attributes[] = {
> 	__ATTR(addr_assign_type, S_IRUGO, show_addr_assign_type, NULL),
> 	__ATTR(addr_len, S_IRUGO, show_addr_len, NULL),
>@@ -355,6 +371,7 @@ static struct device_attribute net_class_attributes[] = {
> 	__ATTR(tx_queue_len, S_IRUGO | S_IWUSR, show_tx_queue_len,
> 	       store_tx_queue_len),
> 	__ATTR(netdev_group, S_IRUGO | S_IWUSR, show_group, store_group),
>+	__ATTR(phys_port, S_IRUGO, show_phys_port, NULL),
> 	{}
> };
> 
>-- 
>1.8.0.1
>
>-- 
>With regards,
>Narendra K
>Linux Engineering
>Dell Inc.
>--
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