bonding: add sysfs /slave dir for bond slave devices.

Add sub-directory under /sys/class/net/<interface>/slave with
read-only attributes for slave. Directory only appears when
<interface> is a slave.

$ tree /sys/class/net/eth2/slave/
/sys/class/net/eth2/slave/
├── ad_aggregator_id
├── link_failure_count
├── mii_status
├── perm_hwaddr
├── queue_id
└── state

$ cat /sys/class/net/eth2/slave/*
2
0
up
40:02:10:ef:06:01
0
active

Signed-off-by: Scott Feldman <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/bonding/Makefile

···
 
 obj-$(CONFIG_BONDING) += bonding.o
 
-bonding-objs := bond_main.o bond_3ad.o bond_alb.o bond_sysfs.o bond_debugfs.o bond_netlink.o bond_options.o
+bonding-objs := bond_main.o bond_3ad.o bond_alb.o bond_sysfs.o bond_sysfs_slave.o bond_debugfs.o bond_netlink.o bond_options.o
 
 proc-$(CONFIG_PROC_FS) += bond_procfs.o
 bonding-objs += $(proc-y)

drivers/net/bonding/bond_main.c

···
 	return;
 }
 
+const char *bond_slave_link_status(s8 link)
+{
+	switch (link) {
+	case BOND_LINK_UP:
+		return "up";
+	case BOND_LINK_FAIL:
+		return "going down";
+	case BOND_LINK_DOWN:
+		return "down";
+	case BOND_LINK_BACK:
+		return "going back";
+	default:
+		return "unknown";
+	}
+}
+
 /*
  * if <dev> supports MII link status reporting, check its link status.
  *
···
 		goto err_unregister;
 	}
 
+	res = bond_sysfs_slave_add(new_slave);
+	if (res) {
+		pr_debug("Error %d calling bond_sysfs_slave_add\n", res);
+		goto err_upper_unlink;
+	}
+
 	bond->slave_cnt++;
 	bond_compute_features(bond);
 	bond_set_carrier(bond);
···
 	return 0;
 
 /* Undo stages on error */
+err_upper_unlink:
+	bond_upper_dev_unlink(bond_dev, slave_dev);
+
 err_unregister:
 	netdev_rx_handler_unregister(slave_dev);
 
···
 
 	/* release the slave from its bond */
 	bond->slave_cnt--;
+
+	bond_sysfs_slave_del(slave);
 
 	bond_upper_dev_unlink(bond_dev, slave_dev);
 	/* unregister rx_handler early so bond_handle_frame wouldn't be called

drivers/net/bonding/bond_procfs.c

···
 	}
 }
 
-static const char *bond_slave_link_status(s8 link)
-{
-	static const char * const status[] = {
-		[BOND_LINK_UP] = "up",
-		[BOND_LINK_FAIL] = "going down",
-		[BOND_LINK_DOWN] = "down",
-		[BOND_LINK_BACK] = "going back",
-	};
-
-	return status[link];
-}
-
 static void bond_info_show_slave(struct seq_file *seq,
 				 const struct slave *slave)
 {

drivers/net/bonding/bond_sysfs_slave.c

···
+/*	Sysfs attributes of bond slaves
+ *
+ *      Copyright (c) 2014 Scott Feldman <[e-mail]>
+ *
+ *	This program is free software; you can redistribute it and/or
+ *	modify it under the terms of the GNU General Public License
+ *	as published by the Free Software Foundation; either version
+ *	2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/capability.h>
+#include <linux/kernel.h>
+#include <linux/netdevice.h>
+
+#include "bonding.h"
+
+struct slave_attribute {
+	struct attribute attr;
+	ssize_t (*show)(struct slave *, char *);
+};
+
+#define SLAVE_ATTR(_name, _mode, _show)				\
+const struct slave_attribute slave_attr_##_name = {		\
+	.attr = {.name = __stringify(_name),			\
+		 .mode = _mode },				\
+	.show	= _show,					\
+};
+#define SLAVE_ATTR_RO(_name) \
+	SLAVE_ATTR(_name, S_IRUGO, _name##_show)
+
+static ssize_t state_show(struct slave *slave, char *buf)
+{
+	switch (bond_slave_state(slave)) {
+	case BOND_STATE_ACTIVE:
+		return sprintf(buf, "active\n");
+	case BOND_STATE_BACKUP:
+		return sprintf(buf, "backup\n");
+	default:
+		return sprintf(buf, "UNKONWN\n");
+	}
+}
+static SLAVE_ATTR_RO(state);
+
+static ssize_t mii_status_show(struct slave *slave, char *buf)
+{
+	return sprintf(buf, "%s\n", bond_slave_link_status(slave->link));
+}
+static SLAVE_ATTR_RO(mii_status);
+
+static ssize_t link_failure_count_show(struct slave *slave, char *buf)
+{
+	return sprintf(buf, "%d\n", slave->link_failure_count);
+}
+static SLAVE_ATTR_RO(link_failure_count);
+
+static ssize_t perm_hwaddr_show(struct slave *slave, char *buf)
+{
+	return sprintf(buf, "%pM\n", slave->perm_hwaddr);
+}
+static SLAVE_ATTR_RO(perm_hwaddr);
+
+static ssize_t queue_id_show(struct slave *slave, char *buf)
+{
+	return sprintf(buf, "%d\n", slave->queue_id);
+}
+static SLAVE_ATTR_RO(queue_id);
+
+static ssize_t ad_aggregator_id_show(struct slave *slave, char *buf)
+{
+	const struct aggregator *agg;
+
+	if (slave->bond->params.mode == BOND_MODE_8023AD) {
+		agg = SLAVE_AD_INFO(slave).port.aggregator;
+		if (agg)
+			return sprintf(buf, "%d\n",
+				       agg->aggregator_identifier);
+	}
+
+	return sprintf(buf, "N/A\n");
+}
+static SLAVE_ATTR_RO(ad_aggregator_id);
+
+static const struct slave_attribute *slave_attrs[] = {
+	&slave_attr_state,
+	&slave_attr_mii_status,
+	&slave_attr_link_failure_count,
+	&slave_attr_perm_hwaddr,
+	&slave_attr_queue_id,
+	&slave_attr_ad_aggregator_id,
+	NULL
+};
+
+#define to_slave_attr(_at) container_of(_at, struct slave_attribute, attr)
+#define to_slave(obj)	container_of(obj, struct slave, kobj)
+
+static ssize_t slave_show(struct kobject *kobj,
+			  struct attribute *attr, char *buf)
+{
+	struct slave_attribute *slave_attr = to_slave_attr(attr);
+	struct slave *slave = to_slave(kobj);
+
+	return slave_attr->show(slave, buf);
+}
+
+const struct sysfs_ops slave_sysfs_ops = {
+	.show = slave_show,
+};
+
+static struct kobj_type slave_ktype = {
+#ifdef CONFIG_SYSFS
+	.sysfs_ops = &slave_sysfs_ops,
+#endif
+};
+
+int bond_sysfs_slave_add(struct slave *slave)
+{
+	const struct slave_attribute **a;
+	int err;
+
+	err = kobject_init_and_add(&slave->kobj, &slave_ktype,
+				   &(slave->dev->dev.kobj), "slave");
+	if (err)
+		return err;
+
+	for (a = slave_attrs; *a; ++a) {
+		err = sysfs_create_file(&slave->kobj, &((*a)->attr));
+		if (err) {
+			kobject_del(&slave->kobj);
+			return err;
+		}
+	}
+
+	return 0;
+}
+
+void bond_sysfs_slave_del(struct slave *slave)
+{
+	const struct slave_attribute **a;
+
+	for (a = slave_attrs; *a; ++a)
+		sysfs_remove_file(&slave->kobj, &((*a)->attr));
+
+	kobject_del(&slave->kobj);
+}

drivers/net/bonding/bonding.h

···
 #ifdef CONFIG_NET_POLL_CONTROLLER
 	struct netpoll *np;
 #endif
+	struct kobject kobj;
 };
 
 /*
···
 int bond_create_sysfs(struct bond_net *net);
 void bond_destroy_sysfs(struct bond_net *net);
 void bond_prepare_sysfs_group(struct bonding *bond);
+int bond_sysfs_slave_add(struct slave *slave);
+void bond_sysfs_slave_del(struct slave *slave);
 int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev);
 int bond_release(struct net_device *bond_dev, struct net_device *slave_dev);
 int bond_xmit_hash(struct bonding *bond, struct sk_buff *skb, int count);
···
 int bond_option_ad_select_set(struct bonding *bond, int ad_select);
 struct net_device *bond_option_active_slave_get_rcu(struct bonding *bond);
 struct net_device *bond_option_active_slave_get(struct bonding *bond);
+const char *bond_slave_link_status(s8 link);
 
 struct bond_net {
 	struct net *		net;	/* Associated network namespace */