[PATCH v3 0/3] Improve wireless netdev detection

[PATCH v3 0/3] Improve wireless netdev detection

[Denis Kenzior]

The current mechanism to detect hot-plug / unplug of wireless devices is
somewhat arcane.  One has to listen to NEW_WIPHY/DEL_WIPHY events over
nl80211 as well as RTM_NEWLINK / RTM_DELLINK events over rtnl, then
somehow find a correlation between these events.  This involves userspace
sending GET_INTERFACE or GET_WIPHY commands to the kernel, which incurs
additional roundtrips.

This patch series proposes that NEW_INTERFACE and DEL_INTERFACE events are
always emitted, regardless of whether a netdev was added/removed by the
driver or explicitly via NEW_INTERFACE/DEL_INTERFACE commands.

v2: Squished patches 2+3, 4+5.  DEL_INTERFACE event notification is now
sent inside cfg80211_unregister_wdev instead of nl80211_del_interface.

v3: No changes, non-RFC version.

Denis Kenzior (3):
  nl80211: Add nl80211_notify_iface
  core: Always notify of new wireless netdevs
  core: Always notify when wireless netdev is removed

 net/wireless/core.c    |  6 +++++
 net/wireless/nl80211.c | 69 +++++++++++++++++++++++++++-----------------------
 net/wireless/nl80211.h |  3 +++
 3 files changed, 47 insertions(+), 31 deletions(-)

-- 
2.7.3

[PATCH v3 1/3] nl80211: Add nl80211_notify_iface

[Denis Kenzior]

This function emits NL80211_CMD_NEW_INTERFACE or
NL80211_CMD_DEL_INTERFACE events.  This is meant to be used by the core
to notify userspace applications such as wpa_supplicant when a netdev
related to a wireless device has been added or removed.

Signed-off-by: Denis Kenzior <denkenz@gmail.com>
---
 net/wireless/nl80211.c | 28 ++++++++++++++++++++++++++++
 net/wireless/nl80211.h |  3 +++
 2 files changed, 31 insertions(+)

diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index ac19eb8..c174770 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -11855,6 +11855,34 @@ void nl80211_notify_wiphy(struct cfg80211_registered_device *rdev,
 				NL80211_MCGRP_CONFIG, GFP_KERNEL);
 }
 
+void nl80211_notify_iface(struct cfg80211_registered_device *rdev,
+				struct wireless_dev *wdev,
+				enum nl80211_commands cmd)
+{
+	struct sk_buff *msg;
+	bool removal;
+
+	WARN_ON(cmd != NL80211_CMD_NEW_INTERFACE &&
+		cmd != NL80211_CMD_DEL_INTERFACE);
+
+	if (cmd == NL80211_CMD_DEL_INTERFACE)
+		removal = true;
+	else
+		removal = false;
+
+	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	if (!msg)
+		return;
+
+	if (nl80211_send_iface(msg, 0, 0, 0, rdev, wdev, removal) < 0) {
+		nlmsg_free(msg);
+		return;
+	}
+
+	genlmsg_multicast_netns(&nl80211_fam, wiphy_net(&rdev->wiphy), msg, 0,
+				NL80211_MCGRP_CONFIG, GFP_KERNEL);
+}
+
 static int nl80211_add_scan_req(struct sk_buff *msg,
 				struct cfg80211_registered_device *rdev)
 {
diff --git a/net/wireless/nl80211.h b/net/wireless/nl80211.h
index a63f402..6f6b73c 100644
--- a/net/wireless/nl80211.h
+++ b/net/wireless/nl80211.h
@@ -7,6 +7,9 @@ int nl80211_init(void);
 void nl80211_exit(void);
 void nl80211_notify_wiphy(struct cfg80211_registered_device *rdev,
 			  enum nl80211_commands cmd);
+void nl80211_notify_iface(struct cfg80211_registered_device *rdev,
+				struct wireless_dev *wdev,
+				enum nl80211_commands cmd);
 void nl80211_send_scan_start(struct cfg80211_registered_device *rdev,
 			     struct wireless_dev *wdev);
 struct sk_buff *nl80211_build_scan_msg(struct cfg80211_registered_device *rdev,
-- 
2.7.3

[PATCH v3 2/3] core: Always notify of new wireless netdevs

[Denis Kenzior]

This change alters the semantics of NL80211_CMD_NEW_INTERFACE events
by always sending this event whenever a new net_device object
associated with a wdev is registered.  Prior to this change, this event
was only sent as a result of NL80211_CMD_NEW_INTERFACE command sent
from userspace.  This allows userspace to reliably detect new wireless
interfaces (e.g. due to hardware hot-plug events, etc).

For wdevs created without an associated net_device object (e.g.
NL80211_IFTYPE_P2P_DEVICE), the NL80211_CMD_NEW_INTERFACE event is
still generated inside the relevant nl80211 command handler.

Signed-off-by: Denis Kenzior <denkenz@gmail.com>
---
 net/wireless/core.c    |  2 ++
 net/wireless/nl80211.c | 23 +++++++++--------------
 2 files changed, 11 insertions(+), 14 deletions(-)

diff --git a/net/wireless/core.c b/net/wireless/core.c
index 7645e97..7758c0f 100644
--- a/net/wireless/core.c
+++ b/net/wireless/core.c
@@ -1079,6 +1079,8 @@ static int cfg80211_netdev_notifier_call(struct notifier_block *nb,
 		     wdev->iftype == NL80211_IFTYPE_P2P_CLIENT ||
 		     wdev->iftype == NL80211_IFTYPE_ADHOC) && !wdev->use_4addr)
 			dev->priv_flags |= IFF_DONT_BRIDGE;
+
+		nl80211_notify_iface(rdev, wdev, NL80211_CMD_NEW_INTERFACE);
 		break;
 	case NETDEV_GOING_DOWN:
 		cfg80211_leave(rdev, wdev);
diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index c174770..591c3ab 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -2787,7 +2787,7 @@ static int nl80211_new_interface(struct sk_buff *skb, struct genl_info *info)
 	struct cfg80211_registered_device *rdev = info->user_ptr[0];
 	struct vif_params params;
 	struct wireless_dev *wdev;
-	struct sk_buff *msg, *event;
+	struct sk_buff *msg;
 	int err;
 	enum nl80211_iftype type = NL80211_IFTYPE_UNSPECIFIED;
 	u32 flags;
@@ -2891,20 +2891,15 @@ static int nl80211_new_interface(struct sk_buff *skb, struct genl_info *info)
 		return -ENOBUFS;
 	}
 
-	event = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
-	if (event) {
-		if (nl80211_send_iface(event, 0, 0, 0,
-				       rdev, wdev, false) < 0) {
-			nlmsg_free(event);
-			goto out;
-		}
-
-		genlmsg_multicast_netns(&nl80211_fam, wiphy_net(&rdev->wiphy),
-					event, 0, NL80211_MCGRP_CONFIG,
-					GFP_KERNEL);
-	}
+	/*
+	 * For wdevs which have no associated netdev object (e.g. of type
+	 * NL80211_IFTYPE_P2P_DEVICE), emit the NEW_INTERFACE event here.
+	 * For all other types, the event will be generated from the
+	 * netdev notifier
+	 */
+	if (!wdev->netdev)
+		nl80211_notify_iface(rdev, wdev, NL80211_CMD_NEW_INTERFACE);
 
-out:
 	return genlmsg_reply(msg, info);
 }
 
-- 
2.7.3

[PATCH v3 3/3] core: Always notify when wireless netdev is removed

[Denis Kenzior]

This change alters the semantics of NL80211_CMD_DEL_INTERFACE events
by always sending this event whenever a net_device object associated
with a wdev is destroyed.  Prior to this change, this event was only
emitted as a result of NL80211_CMD_DEL_INTERFACE command sent from
userspace.  This allows userspace to reliably detect when wireless
interfaces have been removed, e.g. due to USB removal events, etc.

For wireless device objects without an associated net_device (e.g.
NL80211_IFTYPE_P2P_DEVICE), the NL80211_CMD_DEL_INTERFACE event is
now generated inside cfg80211_unregister_wdev.

Signed-off-by: Denis Kenzior <denkenz@gmail.com>
---
 net/wireless/core.c    |  4 ++++
 net/wireless/nl80211.c | 18 +-----------------
 2 files changed, 5 insertions(+), 17 deletions(-)

diff --git a/net/wireless/core.c b/net/wireless/core.c
index 7758c0f..fccead7 100644
--- a/net/wireless/core.c
+++ b/net/wireless/core.c
@@ -906,6 +906,8 @@ void cfg80211_unregister_wdev(struct wireless_dev *wdev)
 	if (WARN_ON(wdev->netdev))
 		return;
 
+	nl80211_notify_iface(rdev, wdev, NL80211_CMD_DEL_INTERFACE);
+
 	list_del_rcu(&wdev->list);
 	rdev->devlist_generation++;
 
@@ -1159,6 +1161,8 @@ static int cfg80211_netdev_notifier_call(struct notifier_block *nb,
 		 * remove and clean it up.
 		 */
 		if (!list_empty(&wdev->list)) {
+			nl80211_notify_iface(rdev, wdev,
+						NL80211_CMD_DEL_INTERFACE);
 			sysfs_remove_link(&dev->dev.kobj, "phy80211");
 			list_del_rcu(&wdev->list);
 			rdev->devlist_generation++;
diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index 591c3ab..4fa7175 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -2907,18 +2907,10 @@ static int nl80211_del_interface(struct sk_buff *skb, struct genl_info *info)
 {
 	struct cfg80211_registered_device *rdev = info->user_ptr[0];
 	struct wireless_dev *wdev = info->user_ptr[1];
-	struct sk_buff *msg;
-	int status;
 
 	if (!rdev->ops->del_virtual_intf)
 		return -EOPNOTSUPP;
 
-	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
-	if (msg && nl80211_send_iface(msg, 0, 0, 0, rdev, wdev, true) < 0) {
-		nlmsg_free(msg);
-		msg = NULL;
-	}
-
 	/*
 	 * If we remove a wireless device without a netdev then clear
 	 * user_ptr[1] so that nl80211_post_doit won't dereference it
@@ -2929,15 +2921,7 @@ static int nl80211_del_interface(struct sk_buff *skb, struct genl_info *info)
 	if (!wdev->netdev)
 		info->user_ptr[1] = NULL;
 
-	status = rdev_del_virtual_intf(rdev, wdev);
-	if (status >= 0 && msg)
-		genlmsg_multicast_netns(&nl80211_fam, wiphy_net(&rdev->wiphy),
-					msg, 0, NL80211_MCGRP_CONFIG,
-					GFP_KERNEL);
-	else
-		nlmsg_free(msg);
-
-	return status;
+	return rdev_del_virtual_intf(rdev, wdev);
 }
 
 static int nl80211_set_noack_map(struct sk_buff *skb, struct genl_info *info)
-- 
2.7.3

Re: [PATCH v3 0/3] Improve wireless netdev detection

[Johannes Berg]

On Wed, 2016-08-03 at 16:58 -0500, Denis Kenzior wrote:
> The current mechanism to detect hot-plug / unplug of wireless devices
> is
> somewhat arcane.  One has to listen to NEW_WIPHY/DEL_WIPHY events
> over
> nl80211 as well as RTM_NEWLINK / RTM_DELLINK events over rtnl, then
> somehow find a correlation between these events.  This involves
> userspace
> sending GET_INTERFACE or GET_WIPHY commands to the kernel, which
> incurs
> additional roundtrips.
> 

Applied. I squashed 1/2 since it's kinda pointless to have a patch
introducing infrastructure that's not used.

I also made some minor cleanups - please check (both that it's right,
and for next time)

johannes

Re: [PATCH v3 0/3] Improve wireless netdev detection

[Denis Kenzior]

Hi Johannes,

 >
> Applied. I squashed 1/2 since it's kinda pointless to have a patch
> introducing infrastructure that's not used.
>
> I also made some minor cleanups - please check (both that it's right,
> and for next time)
>

Your changes look fine to me.  Thanks for taking these.

Regards,
-Denis