From: Alvin Šipraga <[email protected]>
Userspace processes such as network daemons may wish to be informed when
any AP interface is brought up on the system, for example to initiate a
(re)configuration of IP settings or to start a DHCP server.
Currently nl80211 does not broadcast any such event on its multicast
groups, leaving userspace only two options:
1. the process must be the one that actually issued the
NL80211_CMD_START_AP request, so that it can react on the response to
that request;
2. the process must react to RTM_NEWLINK events indicating a change in
carrier state, and may query for further information about the AP and
react accordingly.
Option (1) is robust, but it does not cover all scenarios. It is easy to
imagine a situation where this is not the case (e.g. hostapd +
systemd-networkd).
Option (2) is not robust, because RTM_NEWLINK events may be silently
discarded by the linkwatch logic (cf. linkwatch_fire_event()).
Concretely, consider a scenario in which the carrier state flip-flops in
the following way:
^ carrier state (high/low = carrier/no carrier)
|
| _______ _______ ...
| | | |
| ______| "foo" |____| "bar" (SSID in "quotes")
|
+-------A-------B----C---------> time
If the time interval between (A) and (C) is less than 1 second, then
linkwatch may emit only a single RTM_NEWLINK event indicating carrier
gain.
This is problematic because it is possible that the network
configuration that should be applied is a function of the AP's
properties such as SSID (cf. SSID= in systemd.network(5)). As
illustrated in the above diagram, it may be that the AP with SSID "bar"
ends up being configured as though it had SSID "foo".
Address the above issue by having nl80211 emit an NL80211_CMD_START_AP
message on the MLME nl80211 multicast group. This allows for arbitrary
processes to be reliably informed.
Signed-off-by: Alvin Šipraga <[email protected]>
---
v1 -> v2: add MLO link ID to the event per Johannes' comments
---
net/wireless/nl80211.c | 38 ++++++++++++++++++++++++++++++++++++++
1 file changed, 38 insertions(+)
diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index 64cf6110ce9d..7370ddf84fd3 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -5770,6 +5770,42 @@ static bool nl80211_valid_auth_type(struct cfg80211_registered_device *rdev,
}
}
+static void nl80211_send_ap_started(struct wireless_dev *wdev,
+ unsigned int link_id)
+{
+ struct wiphy *wiphy = wdev->wiphy;
+ struct cfg80211_registered_device *rdev = wiphy_to_rdev(wiphy);
+ struct sk_buff *msg;
+ void *hdr;
+
+ msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+ if (!msg)
+ return;
+
+ hdr = nl80211hdr_put(msg, 0, 0, 0, NL80211_CMD_START_AP);
+ if (!hdr)
+ goto out;
+
+ if (nla_put_u32(msg, NL80211_ATTR_WIPHY, rdev->wiphy_idx) ||
+ nla_put_u32(msg, NL80211_ATTR_IFINDEX, wdev->netdev->ifindex) ||
+ nla_put_u64_64bit(msg, NL80211_ATTR_WDEV, wdev_id(wdev),
+ NL80211_ATTR_PAD) ||
+ (wdev->u.ap.ssid_len &&
+ nla_put(msg, NL80211_ATTR_SSID, wdev->u.ap.ssid_len,
+ wdev->u.ap.ssid)) ||
+ (wdev->valid_links &&
+ nla_put_u8(msg, NL80211_ATTR_MLO_LINK_ID, link_id)))
+ goto out;
+
+ genlmsg_end(msg, hdr);
+
+ genlmsg_multicast_netns(&nl80211_fam, wiphy_net(wiphy), msg, 0,
+ NL80211_MCGRP_MLME, GFP_KERNEL);
+ return;
+out:
+ nlmsg_free(msg);
+}
+
static int nl80211_start_ap(struct sk_buff *skb, struct genl_info *info)
{
struct cfg80211_registered_device *rdev = info->user_ptr[0];
@@ -6050,6 +6086,8 @@ static int nl80211_start_ap(struct sk_buff *skb, struct genl_info *info)
if (info->attrs[NL80211_ATTR_SOCKET_OWNER])
wdev->conn_owner_nlportid = info->snd_portid;
+
+ nl80211_send_ap_started(wdev, link_id);
}
out_unlock:
wdev_unlock(wdev);
--
2.39.0
From: Alvin Šipraga <[email protected]>
nl80211_send_ap_stopped() can be called multiple times on the same
netdev for each link when using Multi-Link Operation. Add the
MLO_LINK_ID attribute to the event to allow userspace to distinguish
which link the event is for.
Signed-off-by: Alvin Šipraga <[email protected]>
---
v1 -> v2: new patch
---
net/wireless/ap.c | 2 +-
net/wireless/nl80211.c | 6 ++++--
net/wireless/nl80211.h | 2 +-
3 files changed, 6 insertions(+), 4 deletions(-)
diff --git a/net/wireless/ap.c b/net/wireless/ap.c
index e68923200018..0962770303b2 100644
--- a/net/wireless/ap.c
+++ b/net/wireless/ap.c
@@ -39,7 +39,7 @@ static int ___cfg80211_stop_ap(struct cfg80211_registered_device *rdev,
wdev->u.ap.ssid_len = 0;
rdev_set_qos_map(rdev, dev, NULL);
if (notify)
- nl80211_send_ap_stopped(wdev);
+ nl80211_send_ap_stopped(wdev, link_id);
/* Should we apply the grace period during beaconing interface
* shutdown also?
diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index 7370ddf84fd3..fd231e37ea9d 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -19701,7 +19701,7 @@ void cfg80211_crit_proto_stopped(struct wireless_dev *wdev, gfp_t gfp)
}
EXPORT_SYMBOL(cfg80211_crit_proto_stopped);
-void nl80211_send_ap_stopped(struct wireless_dev *wdev)
+void nl80211_send_ap_stopped(struct wireless_dev *wdev, unsigned int link_id)
{
struct wiphy *wiphy = wdev->wiphy;
struct cfg80211_registered_device *rdev = wiphy_to_rdev(wiphy);
@@ -19719,7 +19719,9 @@ void nl80211_send_ap_stopped(struct wireless_dev *wdev)
if (nla_put_u32(msg, NL80211_ATTR_WIPHY, rdev->wiphy_idx) ||
nla_put_u32(msg, NL80211_ATTR_IFINDEX, wdev->netdev->ifindex) ||
nla_put_u64_64bit(msg, NL80211_ATTR_WDEV, wdev_id(wdev),
- NL80211_ATTR_PAD))
+ NL80211_ATTR_PAD) ||
+ (wdev->valid_links &&
+ nla_put_u8(msg, NL80211_ATTR_MLO_LINK_ID, link_id)))
goto out;
genlmsg_end(msg, hdr);
diff --git a/net/wireless/nl80211.h b/net/wireless/nl80211.h
index ba9457e94c43..0278d817bb02 100644
--- a/net/wireless/nl80211.h
+++ b/net/wireless/nl80211.h
@@ -114,7 +114,7 @@ nl80211_radar_notify(struct cfg80211_registered_device *rdev,
enum nl80211_radar_event event,
struct net_device *netdev, gfp_t gfp);
-void nl80211_send_ap_stopped(struct wireless_dev *wdev);
+void nl80211_send_ap_stopped(struct wireless_dev *wdev, unsigned int link_id);
void cfg80211_rdev_free_coalesce(struct cfg80211_registered_device *rdev);
--
2.39.0