The standard kernel API to add new virtual interfaces and attach other interfaces to it is rtnl-link. batman-adv supports it since v3.10. This functionality should be used instead of the legacy batman-adv-only sysfs interface.

Signed-off-by: Sven Eckelmann sven@narfation.org --- v4: - rebase on top of current master v3: - rebased on top of current master to fix conflicts with newest patches v2: - rebased on top of current master to fix conflicts with newest patches --- Documentation/networking/batman-adv.txt | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/Documentation/networking/batman-adv.txt b/Documentation/networking/batman-adv.txt index 1b5e7a7..8a8d3d9 100644 --- a/Documentation/networking/batman-adv.txt +++ b/Documentation/networking/batman-adv.txt @@ -43,10 +43,15 @@ new interfaces to verify the compatibility. There is no need to reload the module if you plug your USB wifi adapter into your ma- chine after batman advanced was initially loaded.

-To activate a given interface simply write "bat0" into its -"mesh_iface" file inside the batman_adv subfolder: +The batman-adv soft-interface can be created using the iproute2 +tool "ip"

-# echo bat0 > /sys/class/net/eth0/batman_adv/mesh_iface +# ip link add name bat0 type batadv + +To activate a given interface simply attach it to the "bat0" +interface + +# ip link set dev eth0 master bat0

Repeat this step for all interfaces you wish to add. Now batman starts using/broadcasting on this/these interface(s). @@ -56,10 +61,10 @@ By reading the "iface_status" file you can check its status: # cat /sys/class/net/eth0/batman_adv/iface_status # active

-To deactivate an interface you have to write "none" into its -"mesh_iface" file: +To deactivate an interface you have to detach it from the +"bat0" interface:

-# echo none > /sys/class/net/eth0/batman_adv/mesh_iface +# ip link set dev eth0 nomaster

All mesh wide settings can be found in batman's own interface

The legacy sysfs interface to modify interfaces belonging to batman-adv is run inside a region holding s_lock. And to add a net_device, it has to also get the rtnl_lock. This is exactly the other way around than in other virtual net_devices and conflicts with netdevice notifier which executes inside rtnl_lock.

The inverted lock situation is currently solved by executing the removal of netdevices via workqueue. The workqueue isn't executed inside rtnl_lock and thus can independently get the s_lock and the rtnl_lock.

But this workaround fails when the netdevice notifier creates events in quick succession and the earlier triggered removal of a net_device isn't processed in the workqueue before the adding of the new netdevice (with same name) event is issued.

Instead the legacy sysfs interface store events have to be enqueued in a workqueue to loose the s_lock. The worker is then free to get the required locks and the deadlock is avoided.

Signed-off-by: Sven Eckelmann sven@narfation.org --- v4: - rebase on top of current master v3: - rebased on top of current master to fix conflicts with newest patches v2: - rebased on top of current master to fix conflicts with newest patches --- net/batman-adv/sysfs.c | 107 +++++++++++++++++++++++++++++++++++++------------ net/batman-adv/types.h | 13 ++++++ 2 files changed, 94 insertions(+), 26 deletions(-)

diff --git a/net/batman-adv/sysfs.c b/net/batman-adv/sysfs.c index fe9ca94..8528959 100644 --- a/net/batman-adv/sysfs.c +++ b/net/batman-adv/sysfs.c @@ -37,6 +37,7 @@ #include <linux/stddef.h> #include <linux/string.h> #include <linux/stringify.h> +#include <linux/workqueue.h>

#include "bridge_loop_avoidance.h" #include "distributed-arp-table.h" @@ -828,31 +829,31 @@ static ssize_t batadv_show_mesh_iface(struct kobject *kobj, return length; }

-static ssize_t batadv_store_mesh_iface(struct kobject *kobj, - struct attribute *attr, char *buff, - size_t count) +/** + * batadv_store_mesh_iface_finish - store new hardif mesh_iface state + * @net_dev: netdevice to add/remove to/from batman-adv soft-interface + * @ifname: name of soft-interface to modify + * + * Changes the parts of the hard+soft interface which can not be modified under + * sysfs lock (to prevent deadlock situations). + * + * Return: 0 on success, 0 < on failure + */ +static int batadv_store_mesh_iface_finish(struct net_device *net_dev, + char ifname[IFNAMSIZ]) { - struct net_device *net_dev = batadv_kobj_to_netdev(kobj); struct net *net = dev_net(net_dev); struct batadv_hard_iface *hard_iface; - int status_tmp = -1; - int ret = count; + int status_tmp; + int ret = 0; + + ASSERT_RTNL();

hard_iface = batadv_hardif_get_by_netdev(net_dev); if (!hard_iface) - return count; - - if (buff[count - 1] == '\n') - buff[count - 1] = '\0'; - - if (strlen(buff) >= IFNAMSIZ) { - pr_err("Invalid parameter for 'mesh_iface' setting received: interface name too long '%s'\n", - buff); - batadv_hardif_put(hard_iface); - return -EINVAL; - } + return 0;

- if (strncmp(buff, "none", 4) == 0) + if (strncmp(ifname, "none", 4) == 0) status_tmp = BATADV_IF_NOT_IN_USE; else status_tmp = BATADV_IF_I_WANT_YOU; @@ -861,15 +862,13 @@ static ssize_t batadv_store_mesh_iface(struct kobject *kobj, goto out;

if ((hard_iface->soft_iface) && - (strncmp(hard_iface->soft_iface->name, buff, IFNAMSIZ) == 0)) + (strncmp(hard_iface->soft_iface->name, ifname, IFNAMSIZ) == 0)) goto out;

- rtnl_lock(); - if (status_tmp == BATADV_IF_NOT_IN_USE) { batadv_hardif_disable_interface(hard_iface, BATADV_IF_CLEANUP_AUTO); - goto unlock; + goto out; }

/* if the interface already is in use */ @@ -877,15 +876,71 @@ static ssize_t batadv_store_mesh_iface(struct kobject *kobj, batadv_hardif_disable_interface(hard_iface, BATADV_IF_CLEANUP_AUTO);

- ret = batadv_hardif_enable_interface(hard_iface, net, buff); - -unlock: - rtnl_unlock(); + ret = batadv_hardif_enable_interface(hard_iface, net, ifname); out: batadv_hardif_put(hard_iface); return ret; }

+/** + * batadv_store_mesh_iface_work - store new hardif mesh_iface state + * @work: work queue item + * + * Changes the parts of the hard+soft interface which can not be modified under + * sysfs lock (to prevent deadlock situations). + */ +static void batadv_store_mesh_iface_work(struct work_struct *work) +{ + struct batadv_store_mesh_work *store_work; + int ret; + + store_work = container_of(work, struct batadv_store_mesh_work, work); + + rtnl_lock(); + ret = batadv_store_mesh_iface_finish(store_work->net_dev, + store_work->soft_iface_name); + rtnl_unlock(); + + if (ret < 0) + pr_err("Failed to store new mesh_iface state %s for %s: %d\n", + store_work->soft_iface_name, store_work->net_dev->name, + ret); + + dev_put(store_work->net_dev); + kfree(store_work); +} + +static ssize_t batadv_store_mesh_iface(struct kobject *kobj, + struct attribute *attr, char *buff, + size_t count) +{ + struct net_device *net_dev = batadv_kobj_to_netdev(kobj); + struct batadv_store_mesh_work *store_work; + + if (buff[count - 1] == '\n') + buff[count - 1] = '\0'; + + if (strlen(buff) >= IFNAMSIZ) { + pr_err("Invalid parameter for 'mesh_iface' setting received: interface name too long '%s'\n", + buff); + return -EINVAL; + } + + store_work = kmalloc(sizeof(*store_work), GFP_KERNEL); + if (!store_work) + return -ENOMEM; + + dev_hold(net_dev); + INIT_WORK(&store_work->work, batadv_store_mesh_iface_work); + store_work->net_dev = net_dev; + strlcpy(store_work->soft_iface_name, buff, + sizeof(store_work->soft_iface_name)); + + queue_work(batadv_event_workqueue, &store_work->work); + + return count; +} + static ssize_t batadv_show_iface_status(struct kobject *kobj, struct attribute *attr, char *buff) { diff --git a/net/batman-adv/types.h b/net/batman-adv/types.h index 43db7b6..d966c31 100644 --- a/net/batman-adv/types.h +++ b/net/batman-adv/types.h @@ -1560,4 +1560,17 @@ enum batadv_tvlv_handler_flags { BATADV_TVLV_HANDLER_OGM_CALLED = BIT(2), };

+/** + * struct batadv_store_mesh_work - Work queue item to detach add/del interface + * from sysfs locks + * @net_dev: netdevice to add/remove to/from batman-adv soft-interface + * @soft_iface_name: name of soft-interface to modify + * @work: work queue item + */ +struct batadv_store_mesh_work { + struct net_device *net_dev; + char soft_iface_name[IFNAMSIZ]; + struct work_struct work; +}; + #endif /* _NET_BATMAN_ADV_TYPES_H_ */

The kobject_put is only removing the sysfs entry and corresponding entries when its reference counter becomes zero. This tends to lead to collisions when a device is moved between two different network namespaces because some of the sysfs files have to be removed first and then added again to the already moved sysfs entry.

WARNING: CPU: 0 PID: 290 at lib/kobject.c:240 kobject_add_internal+0x5ec/0x8a0 kobject_add_internal failed for batman_adv with -EEXIST, don't try to register things with the same name in the same directory.

But the caller of kobject_put can already remove the sysfs entry before it does the kobject_put. This removal is done even when the reference counter is not yet zero and thus avoids the problem.

Signed-off-by: Sven Eckelmann sven@narfation.org --- v4: - rebase on top of current master - avoid deletes of vlan->kobj when it is a pointer to bat_priv->mesh_obj (happens for untagged vlan and can cause some kernfs warnings) v3: - rebased on top of current master to fix conflicts with newest patches v2: - rebased on top of current master to fix conflicts with newest patches --- net/batman-adv/sysfs.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+)

diff --git a/net/batman-adv/sysfs.c b/net/batman-adv/sysfs.c index 8528959..4e06cb7 100644 --- a/net/batman-adv/sysfs.c +++ b/net/batman-adv/sysfs.c @@ -713,6 +713,8 @@ rem_attr: for (bat_attr = batadv_mesh_attrs; *bat_attr; ++bat_attr) sysfs_remove_file(bat_priv->mesh_obj, &((*bat_attr)->attr));

+ kobject_uevent(bat_priv->mesh_obj, KOBJ_REMOVE); + kobject_del(bat_priv->mesh_obj); kobject_put(bat_priv->mesh_obj); bat_priv->mesh_obj = NULL; out: @@ -727,6 +729,8 @@ void batadv_sysfs_del_meshif(struct net_device *dev) for (bat_attr = batadv_mesh_attrs; *bat_attr; ++bat_attr) sysfs_remove_file(bat_priv->mesh_obj, &((*bat_attr)->attr));

+ kobject_uevent(bat_priv->mesh_obj, KOBJ_REMOVE); + kobject_del(bat_priv->mesh_obj); kobject_put(bat_priv->mesh_obj); bat_priv->mesh_obj = NULL; } @@ -782,6 +786,10 @@ rem_attr: for (bat_attr = batadv_vlan_attrs; *bat_attr; ++bat_attr) sysfs_remove_file(vlan->kobj, &((*bat_attr)->attr));

+ if (vlan->kobj != bat_priv->mesh_obj) { + kobject_uevent(vlan->kobj, KOBJ_REMOVE); + kobject_del(vlan->kobj); + } kobject_put(vlan->kobj); vlan->kobj = NULL; out: @@ -801,6 +809,10 @@ void batadv_sysfs_del_vlan(struct batadv_priv *bat_priv, for (bat_attr = batadv_vlan_attrs; *bat_attr; ++bat_attr) sysfs_remove_file(vlan->kobj, &((*bat_attr)->attr));

+ if (vlan->kobj != bat_priv->mesh_obj) { + kobject_uevent(vlan->kobj, KOBJ_REMOVE); + kobject_del(vlan->kobj); + } kobject_put(vlan->kobj); vlan->kobj = NULL; } @@ -1103,6 +1115,8 @@ out:

void batadv_sysfs_del_hardif(struct kobject **hardif_obj) { + kobject_uevent(*hardif_obj, KOBJ_REMOVE); + kobject_del(*hardif_obj); kobject_put(*hardif_obj); *hardif_obj = NULL; }