cfg80211: fix regression in multi-vif AP start

Commit "cfg80211: provide channel to start_ap function" assumes that the
channel is always passed to the NL80211_CMD_START_AP command, however
in case of multi-BSSID, hostapd only passes the channel for the first vif.
This makes starting beaconing on secondary vifs fail with -EINVAL.

Fix this by storing the channel provided to .start_ap in wdev->preset_chan
and picking the first AP vif's channel for secondary vifs if not provided.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 32 insertions, 2 deletions

diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index 06623d064606..888fadc4d63e 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -2335,6 +2335,33 @@ static int nl80211_parse_beacon(struct genl_info *info,
         return 0;
 }
 
+static bool nl80211_get_ap_channel(struct cfg80211_registered_device *rdev,
+                                   struct cfg80211_ap_settings *params)
+{
+        struct wireless_dev *wdev;
+        bool ret = false;
+
+        mutex_lock(&rdev->devlist_mtx);
+
+        list_for_each_entry(wdev, &rdev->netdev_list, list) {
+                if (wdev->iftype != NL80211_IFTYPE_AP &&
+                    wdev->iftype != NL80211_IFTYPE_P2P_GO)
+                        continue;
+
+                if (!wdev->preset_chan)
+                        continue;
+
+                params->channel = wdev->preset_chan;
+                params->channel_type = wdev->preset_chantype;
+                ret = true;
+                break;
+        }
+
+        mutex_unlock(&rdev->devlist_mtx);
+
+        return ret;
+}
+
 static int nl80211_start_ap(struct sk_buff *skb, struct genl_info *info)
 {
         struct cfg80211_registered_device *rdev = info->user_ptr[0];
@@ -2437,7 +2464,7 @@ static int nl80211_start_ap(struct sk_buff *skb, struct genl_info *info)
         } else if (wdev->preset_chan) {
                 params.channel = wdev->preset_chan;
                 params.channel_type = wdev->preset_chantype;
-        } else
+        } else if (!nl80211_get_ap_channel(rdev, &params))
                 return -EINVAL;
 
         if (!cfg80211_can_beacon_sec_chan(&rdev->wiphy, params.channel,
@@ -2445,8 +2472,11 @@ static int nl80211_start_ap(struct sk_buff *skb, struct genl_info *info)
                 return -EINVAL;
 
         err = rdev->ops->start_ap(&rdev->wiphy, dev, &params);
-        if (!err)
+        if (!err) {
+                wdev->preset_chan = params.channel;
+                wdev->preset_chantype = params.channel_type;
                 wdev->beacon_interval = params.beacon_interval;
+        }
         return err;
 }