net: dsa: allow changing the tag protocol via the "tagging" device attribute

Currently DSA exposes the following sysfs: $ cat /sys/class/net/eno2/dsa/tagging ocelot which is a read-only device attribute, introduced in the kernel as commit 98cdb48071 ("net: dsa: Expose tagging protocol to user-space"), and used by libpcap since its commit 993db3800d7d ("Add support for DSA link-layer types"). It would be nice if we could extend this device attribute by making it writable: $ echo ocelot-8021q > /sys/class/net/eno2/dsa/tagging This is useful with DSA switches that can make use of more than one tagging protocol. It may be useful in dsa_loop in the future too, to perform offline testing of various taggers, or for changing between dsa and edsa on Marvell switches, if that is desirable. In terms of implementation, drivers can support this feature by implementing .change_tag_protocol, which should always leave the switch in a consistent state: either with the new protocol if things went well, or with the old one if something failed. Teardown of the old protocol, if necessary, must be handled by the driver. Some things remain as before: - The .get_tag_protocol is currently only called at probe time, to load the initial tagging protocol driver. Nonetheless, new drivers should report the tagging protocol in current use now. - The driver should manage by itself the initial setup of tagging protocol, no later than the .setup() method, as well as destroying resources used by the last tagger in use, no earlier than the .teardown() method. For multi-switch DSA trees, error handling is a bit more complicated, since e.g. the 5th out of 7 switches may fail to change the tag protocol. When that happens, a revert to the original tag protocol is attempted, but that may fail too, leaving the tree in an inconsistent state despite each individual switch implementing .change_tag_protocol transactionally. Since the intersection between drivers that implement .change_tag_protocol and drivers that support D in DSA is currently the empty set, the possibility for this error to happen is ignored for now. Testing: $ insmod mscc_felix.ko [ 79.549784] mscc_felix 0000:00:00.5: Adding to iommu group 14 [ 79.565712] mscc_felix 0000:00:00.5: Failed to register DSA switch: -517 $ insmod tag_ocelot.ko $ rmmod mscc_felix.ko $ insmod mscc_felix.ko [ 97.261724] libphy: VSC9959 internal MDIO bus: probed [ 97.267363] mscc_felix 0000:00:00.5: Found PCS at internal MDIO address 0 [ 97.274998] mscc_felix 0000:00:00.5: Found PCS at internal MDIO address 1 [ 97.282561] mscc_felix 0000:00:00.5: Found PCS at internal MDIO address 2 [ 97.289700] mscc_felix 0000:00:00.5: Found PCS at internal MDIO address 3 [ 97.599163] mscc_felix 0000:00:00.5 swp0 (uninitialized): PHY [0000:00:00.3:10] driver [Microsemi GE VSC8514 SyncE] (irq=POLL) [ 97.862034] mscc_felix 0000:00:00.5 swp1 (uninitialized): PHY [0000:00:00.3:11] driver [Microsemi GE VSC8514 SyncE] (irq=POLL) [ 97.950731] mscc_felix 0000:00:00.5 swp0: configuring for inband/qsgmii link mode [ 97.964278] 8021q: adding VLAN 0 to HW filter on device swp0 [ 98.146161] mscc_felix 0000:00:00.5 swp2 (uninitialized): PHY [0000:00:00.3:12] driver [Microsemi GE VSC8514 SyncE] (irq=POLL) [ 98.238649] mscc_felix 0000:00:00.5 swp1: configuring for inband/qsgmii link mode [ 98.251845] 8021q: adding VLAN 0 to HW filter on device swp1 [ 98.433916] mscc_felix 0000:00:00.5 swp3 (uninitialized): PHY [0000:00:00.3:13] driver [Microsemi GE VSC8514 SyncE] (irq=POLL) [ 98.485542] mscc_felix 0000:00:00.5: configuring for fixed/internal link mode [ 98.503584] mscc_felix 0000:00:00.5: Link is Up - 2.5Gbps/Full - flow control rx/tx [ 98.527948] device eno2 entered promiscuous mode [ 98.544755] DSA: tree 0 setup $ ping 10.0.0.1 PING 10.0.0.1 (10.0.0.1): 56 data bytes 64 bytes from 10.0.0.1: seq=0 ttl=64 time=2.337 ms 64 bytes from 10.0.0.1: seq=1 ttl=64 time=0.754 ms ^C - 10.0.0.1 ping statistics - 2 packets transmitted, 2 packets received, 0% packet loss round-trip min/avg/max = 0.754/1.545/2.337 ms $ cat /sys/class/net/eno2/dsa/tagging ocelot $ cat ./test_ocelot_8021q.sh #!/bin/bash ip link set swp0 down ip link set swp1 down ip link set swp2 down ip link set swp3 down ip link set swp5 down ip link set eno2 down echo ocelot-8021q > /sys/class/net/eno2/dsa/tagging ip link set eno2 up ip link set swp0 up ip link set swp1 up ip link set swp2 up ip link set swp3 up ip link set swp5 up $ ./test_ocelot_8021q.sh ./test_ocelot_8021q.sh: line 9: echo: write error: Protocol not available $ rmmod tag_ocelot.ko rmmod: can't unload module 'tag_ocelot': Resource temporarily unavailable $ insmod tag_ocelot_8021q.ko $ ./test_ocelot_8021q.sh $ cat /sys/class/net/eno2/dsa/tagging ocelot-8021q $ rmmod tag_ocelot.ko $ rmmod tag_ocelot_8021q.ko rmmod: can't unload module 'tag_ocelot_8021q': Resource temporarily unavailable $ ping 10.0.0.1 PING 10.0.0.1 (10.0.0.1): 56 data bytes 64 bytes from 10.0.0.1: seq=0 ttl=64 time=0.953 ms 64 bytes from 10.0.0.1: seq=1 ttl=64 time=0.787 ms 64 bytes from 10.0.0.1: seq=2 ttl=64 time=0.771 ms $ rmmod mscc_felix.ko [ 645.544426] mscc_felix 0000:00:00.5: Link is Down [ 645.838608] DSA: tree 0 torn down $ rmmod tag_ocelot_8021q.ko Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2021-01-29 03:00:06 +02:00 · 2021-01-29 03:00:06 +02:00 · 53da0ebaad
commit 53da0ebaad
parent 357f203bb3
9 changed files with 235 additions and 18 deletions
--- a/Documentation/ABI/testing/sysfs-class-net-dsa
+++ b/Documentation/ABI/testing/sysfs-class-net-dsa
@ -3,5 +3,12 @@ Date:		August 2018
 KernelVersion:	4.20
 Contact:	netdev@vger.kernel.org
 Description:
-		String indicating the type of tagging protocol used by the
-		DSA slave network device.
+		On read, this file returns a string indicating the type of
+		tagging protocol used by the DSA network devices that are
+		attached to this master interface.
+		On write, this file changes the tagging protocol of the
+		attached DSA switches, if this operation is supported by the
+		driver. Changing the tagging protocol must be done with the DSA
+		interfaces and the master interface all administratively down.
+		See the "name" field of each registered struct dsa_device_ops
+		for a list of valid values.
--- a/include/net/dsa.h
+++ b/include/net/dsa.h
@ -485,9 +485,18 @@ static inline bool dsa_port_is_vlan_filtering(const struct dsa_port *dp)
 typedef int dsa_fdb_dump_cb_t(const unsigned char *addr, u16 vid,
 			      bool is_static, void *data);
 struct dsa_switch_ops {
+	/*
+	 * Tagging protocol helpers called for the CPU ports and DSA links.
+	 * @get_tag_protocol retrieves the initial tagging protocol and is
+	 * mandatory. Switches which can operate using multiple tagging
+	 * protocols should implement @change_tag_protocol and report in
+	 * @get_tag_protocol the tagger in current use.
+	 */
 	enum dsa_tag_protocol (*get_tag_protocol)(struct dsa_switch *ds,
 						  int port,
 						  enum dsa_tag_protocol mprot);
+	int	(*change_tag_protocol)(struct dsa_switch *ds, int port,
+				       enum dsa_tag_protocol proto);

 	int	(*setup)(struct dsa_switch *ds);
 	void	(*teardown)(struct dsa_switch *ds);
--- a/net/dsa/dsa.c
+++ b/net/dsa/dsa.c
@ -84,6 +84,32 @@ const char *dsa_tag_protocol_to_str(const struct dsa_device_ops *ops)
 	return ops->name;
 };

+/* Function takes a reference on the module owning the tagger,
+ * so dsa_tag_driver_put must be called afterwards.
+ */
+const struct dsa_device_ops *dsa_find_tagger_by_name(const char *buf)
+{
+	const struct dsa_device_ops *ops = ERR_PTR(-ENOPROTOOPT);
+	struct dsa_tag_driver *dsa_tag_driver;
+
+	mutex_lock(&dsa_tag_drivers_lock);
+	list_for_each_entry(dsa_tag_driver, &dsa_tag_drivers_list, list) {
+		const struct dsa_device_ops *tmp = dsa_tag_driver->ops;
+
+		if (!sysfs_streq(buf, tmp->name))
+			continue;
+
+		if (!try_module_get(dsa_tag_driver->owner))
+			break;
+
+		ops = tmp;
+		break;
+	}
+	mutex_unlock(&dsa_tag_drivers_lock);
+
+	return ops;
+}
+
 const struct dsa_device_ops *dsa_tag_driver_get(int tag_protocol)
 {
 	struct dsa_tag_driver *dsa_tag_driver;
--- a/net/dsa/dsa2.c
+++ b/net/dsa/dsa2.c
@ -942,6 +942,57 @@ static void dsa_tree_teardown(struct dsa_switch_tree *dst)
 	dst->setup = false;
 }

+/* Since the dsa/tagging sysfs device attribute is per master, the assumption
+ * is that all DSA switches within a tree share the same tagger, otherwise
+ * they would have formed disjoint trees (different "dsa,member" values).
+ */
+int dsa_tree_change_tag_proto(struct dsa_switch_tree *dst,
+			      struct net_device *master,
+			      const struct dsa_device_ops *tag_ops,
+			      const struct dsa_device_ops *old_tag_ops)
+{
+	struct dsa_notifier_tag_proto_info info;
+	struct dsa_port *dp;
+	int err = -EBUSY;
+
+	if (!rtnl_trylock())
+		return restart_syscall();
+
+	/* At the moment we don't allow changing the tag protocol under
+	 * traffic. The rtnl_mutex also happens to serialize concurrent
+	 * attempts to change the tagging protocol. If we ever lift the IFF_UP
+	 * restriction, there needs to be another mutex which serializes this.
+	 */
+	if (master->flags & IFF_UP)
+		goto out_unlock;
+
+	list_for_each_entry(dp, &dst->ports, list) {
+		if (!dsa_is_user_port(dp->ds, dp->index))
+			continue;
+
+		if (dp->slave->flags & IFF_UP)
+			goto out_unlock;
+	}
+
+	info.tag_ops = tag_ops;
+	err = dsa_tree_notify(dst, DSA_NOTIFIER_TAG_PROTO, &info);
+	if (err)
+		goto out_unwind_tagger;
+
+	dst->tag_ops = tag_ops;
+
+	rtnl_unlock();
+
+	return 0;
+
+out_unwind_tagger:
+	info.tag_ops = old_tag_ops;
+	dsa_tree_notify(dst, DSA_NOTIFIER_TAG_PROTO, &info);
+out_unlock:
+	rtnl_unlock();
+	return err;
+}
+
 static struct dsa_port *dsa_port_touch(struct dsa_switch *ds, int index)
 {
 	struct dsa_switch_tree *dst = ds->dst;
@ -1038,9 +1089,7 @@ static int dsa_port_parse_cpu(struct dsa_port *dp, struct net_device *master)

 	dp->master = master;
 	dp->type = DSA_PORT_TYPE_CPU;
-	dp->filter = dst->tag_ops->filter;
-	dp->rcv = dst->tag_ops->rcv;
-	dp->tag_ops = dst->tag_ops;
+	dsa_port_set_tag_protocol(dp, dst->tag_ops);
 	dp->dst = dst;

 	return 0;
--- a/net/dsa/dsa_priv.h
+++ b/net/dsa/dsa_priv.h
@ -28,6 +28,7 @@ enum {
 	DSA_NOTIFIER_VLAN_ADD,
 	DSA_NOTIFIER_VLAN_DEL,
 	DSA_NOTIFIER_MTU,
+	DSA_NOTIFIER_TAG_PROTO,
 };

 /* DSA_NOTIFIER_AGEING_TIME */
@ -82,6 +83,11 @@ struct dsa_notifier_mtu_info {
 	int mtu;
 };

+/* DSA_NOTIFIER_TAG_PROTO_* */
+struct dsa_notifier_tag_proto_info {
+	const struct dsa_device_ops *tag_ops;
+};
+
 struct dsa_switchdev_event_work {
 	struct dsa_switch *ds;
 	int port;
@ -115,6 +121,7 @@ struct dsa_slave_priv {
 /* dsa.c */
 const struct dsa_device_ops *dsa_tag_driver_get(int tag_protocol);
 void dsa_tag_driver_put(const struct dsa_device_ops *ops);
+const struct dsa_device_ops *dsa_find_tagger_by_name(const char *buf);

 bool dsa_schedule_work(struct work_struct *work);
 const char *dsa_tag_protocol_to_str(const struct dsa_device_ops *ops);
@ -139,6 +146,8 @@ static inline struct net_device *dsa_master_find_slave(struct net_device *dev,
 }

 /* port.c */
+void dsa_port_set_tag_protocol(struct dsa_port *cpu_dp,
+			       const struct dsa_device_ops *tag_ops);
 int dsa_port_set_state(struct dsa_port *dp, u8 state);
 int dsa_port_enable_rt(struct dsa_port *dp, struct phy_device *phy);
 int dsa_port_enable(struct dsa_port *dp, struct phy_device *phy);
@ -201,6 +210,8 @@ int dsa_slave_suspend(struct net_device *slave_dev);
 int dsa_slave_resume(struct net_device *slave_dev);
 int dsa_slave_register_notifier(void);
 void dsa_slave_unregister_notifier(void);
+void dsa_slave_setup_tagger(struct net_device *slave);
+int dsa_slave_change_mtu(struct net_device *dev, int new_mtu);

 static inline struct dsa_port *dsa_slave_to_port(const struct net_device *dev)
 {
@ -285,6 +296,10 @@ void dsa_lag_map(struct dsa_switch_tree *dst, struct net_device *lag);
 void dsa_lag_unmap(struct dsa_switch_tree *dst, struct net_device *lag);
 int dsa_tree_notify(struct dsa_switch_tree *dst, unsigned long e, void *v);
 int dsa_broadcast(unsigned long e, void *v);
+int dsa_tree_change_tag_proto(struct dsa_switch_tree *dst,
+			      struct net_device *master,
+			      const struct dsa_device_ops *tag_ops,
+			      const struct dsa_device_ops *old_tag_ops);

 extern struct list_head dsa_tree_list;

--- a/net/dsa/master.c
+++ b/net/dsa/master.c
@ -280,7 +280,44 @@ static ssize_t tagging_show(struct device *d, struct device_attribute *attr,
 	return sprintf(buf, "%s\n",
 		       dsa_tag_protocol_to_str(cpu_dp->tag_ops));
 }
-static DEVICE_ATTR_RO(tagging);
+
+static ssize_t tagging_store(struct device *d, struct device_attribute *attr,
+			     const char *buf, size_t count)
+{
+	const struct dsa_device_ops *new_tag_ops, *old_tag_ops;
+	struct net_device *dev = to_net_dev(d);
+	struct dsa_port *cpu_dp = dev->dsa_ptr;
+	int err;
+
+	old_tag_ops = cpu_dp->tag_ops;
+	new_tag_ops = dsa_find_tagger_by_name(buf);
+	/* Bad tagger name, or module is not loaded? */
+	if (IS_ERR(new_tag_ops))
+		return PTR_ERR(new_tag_ops);
+
+	if (new_tag_ops == old_tag_ops)
+		/* Drop the temporarily held duplicate reference, since
+		 * the DSA switch tree uses this tagger.
+		 */
+		goto out;
+
+	err = dsa_tree_change_tag_proto(cpu_dp->ds->dst, dev, new_tag_ops,
+					old_tag_ops);
+	if (err) {
+		/* On failure the old tagger is restored, so we don't need the
+		 * driver for the new one.
+		 */
+		dsa_tag_driver_put(new_tag_ops);
+		return err;
+	}
+
+	/* On success we no longer need the module for the old tagging protocol
+	 */
+out:
+	dsa_tag_driver_put(old_tag_ops);
+	return count;
+}
+static DEVICE_ATTR_RW(tagging);

 static struct attribute *dsa_slave_attrs[] = {
 	&dev_attr_tagging.attr,
--- a/net/dsa/port.c
+++ b/net/dsa/port.c
@ -526,6 +526,14 @@ int dsa_port_vlan_del(struct dsa_port *dp,
 	return dsa_port_notify(dp, DSA_NOTIFIER_VLAN_DEL, &info);
 }

+void dsa_port_set_tag_protocol(struct dsa_port *cpu_dp,
+			       const struct dsa_device_ops *tag_ops)
+{
+	cpu_dp->filter = tag_ops->filter;
+	cpu_dp->rcv = tag_ops->rcv;
+	cpu_dp->tag_ops = tag_ops;
+}
+
 static struct phy_device *dsa_port_get_phy_device(struct dsa_port *dp)
 {
 	struct device_node *phy_dn;
--- a/net/dsa/slave.c
+++ b/net/dsa/slave.c
@ -1430,7 +1430,7 @@ out:
 	dsa_hw_port_list_free(&hw_port_list);
 }

-static int dsa_slave_change_mtu(struct net_device *dev, int new_mtu)
+int dsa_slave_change_mtu(struct net_device *dev, int new_mtu)
 {
 	struct net_device *master = dsa_slave_to_master(dev);
 	struct dsa_port *dp = dsa_slave_to_port(dev);
@ -1708,6 +1708,27 @@ static int dsa_slave_phy_setup(struct net_device *slave_dev)
 	return ret;
 }

+void dsa_slave_setup_tagger(struct net_device *slave)
+{
+	struct dsa_port *dp = dsa_slave_to_port(slave);
+	struct dsa_slave_priv *p = netdev_priv(slave);
+	const struct dsa_port *cpu_dp = dp->cpu_dp;
+	struct net_device *master = cpu_dp->master;
+
+	if (cpu_dp->tag_ops->tail_tag)
+		slave->needed_tailroom = cpu_dp->tag_ops->overhead;
+	else
+		slave->needed_headroom = cpu_dp->tag_ops->overhead;
+	/* Try to save one extra realloc later in the TX path (in the master)
+	 * by also inheriting the master's needed headroom and tailroom.
+	 * The 8021q driver also does this.
+	 */
+	slave->needed_headroom += master->needed_headroom;
+	slave->needed_tailroom += master->needed_tailroom;
+
+	p->xmit = cpu_dp->tag_ops->xmit;
+}
+
 static struct lock_class_key dsa_slave_netdev_xmit_lock_key;
 static void dsa_slave_set_lockdep_class_one(struct net_device *dev,
 					    struct netdev_queue *txq,
@ -1782,16 +1803,6 @@ int dsa_slave_create(struct dsa_port *port)
 	slave_dev->netdev_ops = &dsa_slave_netdev_ops;
 	if (ds->ops->port_max_mtu)
 		slave_dev->max_mtu = ds->ops->port_max_mtu(ds, port->index);
-	if (cpu_dp->tag_ops->tail_tag)
-		slave_dev->needed_tailroom = cpu_dp->tag_ops->overhead;
-	else
-		slave_dev->needed_headroom = cpu_dp->tag_ops->overhead;
-	/* Try to save one extra realloc later in the TX path (in the master)
-	 * by also inheriting the master's needed headroom and tailroom.
-	 * The 8021q driver also does this.
-	 */
-	slave_dev->needed_headroom += master->needed_headroom;
-	slave_dev->needed_tailroom += master->needed_tailroom;
 	SET_NETDEV_DEVTYPE(slave_dev, &dsa_type);

 	netdev_for_each_tx_queue(slave_dev, dsa_slave_set_lockdep_class_one,
@ -1814,8 +1825,8 @@ int dsa_slave_create(struct dsa_port *port)

 	p->dp = port;
 	INIT_LIST_HEAD(&p->mall_tc_list);
-	p->xmit = cpu_dp->tag_ops->xmit;
 	port->slave = slave_dev;
+	dsa_slave_setup_tagger(slave_dev);

 	rtnl_lock();
 	ret = dsa_slave_change_mtu(slave_dev, ETH_DATA_LEN);
--- a/net/dsa/switch.c
+++ b/net/dsa/switch.c
@ -297,6 +297,58 @@ static int dsa_switch_vlan_del(struct dsa_switch *ds,
 	return 0;
 }

+static bool dsa_switch_tag_proto_match(struct dsa_switch *ds, int port,
+				       struct dsa_notifier_tag_proto_info *info)
+{
+	if (dsa_is_cpu_port(ds, port) || dsa_is_dsa_port(ds, port))
+		return true;
+
+	return false;
+}
+
+static int dsa_switch_change_tag_proto(struct dsa_switch *ds,
+				       struct dsa_notifier_tag_proto_info *info)
+{
+	const struct dsa_device_ops *tag_ops = info->tag_ops;
+	int port, err;
+
+	if (!ds->ops->change_tag_protocol)
+		return -EOPNOTSUPP;
+
+	ASSERT_RTNL();
+
+	for (port = 0; port < ds->num_ports; port++) {
+		if (dsa_switch_tag_proto_match(ds, port, info)) {
+			err = ds->ops->change_tag_protocol(ds, port,
+							   tag_ops->proto);
+			if (err)
+				return err;
+
+			if (dsa_is_cpu_port(ds, port))
+				dsa_port_set_tag_protocol(dsa_to_port(ds, port),
+							  tag_ops);
+		}
+	}
+
+	/* Now that changing the tag protocol can no longer fail, let's update
+	 * the remaining bits which are "duplicated for faster access", and the
+	 * bits that depend on the tagger, such as the MTU.
+	 */
+	for (port = 0; port < ds->num_ports; port++) {
+		if (dsa_is_user_port(ds, port)) {
+			struct net_device *slave;
+
+			slave = dsa_to_port(ds, port)->slave;
+			dsa_slave_setup_tagger(slave);
+
+			/* rtnl_mutex is held in dsa_tree_change_tag_proto */
+			dsa_slave_change_mtu(slave, slave->mtu);
+		}
+	}
+
+	return 0;
+}
+
 static int dsa_switch_event(struct notifier_block *nb,
 			    unsigned long event, void *info)
 {
@ -343,6 +395,9 @@ static int dsa_switch_event(struct notifier_block *nb,
 	case DSA_NOTIFIER_MTU:
 		err = dsa_switch_mtu(ds, info);
 		break;
+	case DSA_NOTIFIER_TAG_PROTO:
+		err = dsa_switch_change_tag_proto(ds, info);
+		break;
 	default:
 		err = -EOPNOTSUPP;
 		break;