mac80211: send a CSA action frame when changing channel

IBSS members may not immediately be able to send out their beacon when
performing CSA, therefore also send a CSA action frame.

Signed-off-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
Signed-off-by: Mathias Kretschmer <mathias.kretschmer@fokus.fraunhofer.de>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 60 insertions, 0 deletions

diff --git a/net/mac80211/ibss.c b/net/mac80211/ibss.c
index c0042136f1d8..5ea9b3ae303e 100644
--- a/net/mac80211/ibss.c
+++ b/net/mac80211/ibss.c
@@ -428,6 +428,60 @@ static void ieee80211_sta_join_ibss(struct ieee80211_sub_if_data *sdata,
                                   tsf, false);
 }
 
+static int ieee80211_send_action_csa(struct ieee80211_sub_if_data *sdata,
+                                     struct cfg80211_csa_settings *csa_settings)
+{
+        struct sk_buff *skb;
+        struct ieee80211_mgmt *mgmt;
+        struct ieee80211_if_ibss *ifibss = &sdata->u.ibss;
+        struct ieee80211_local *local = sdata->local;
+        int freq;
+        int hdr_len = offsetof(struct ieee80211_mgmt, u.action.u.chan_switch) +
+                      sizeof(mgmt->u.action.u.chan_switch);
+        u8 *pos;
+
+        skb = dev_alloc_skb(local->tx_headroom + hdr_len +
+                            5 + /* channel switch announcement element */
+                            3); /* secondary channel offset element */
+        if (!skb)
+                return -1;
+
+        skb_reserve(skb, local->tx_headroom);
+        mgmt = (struct ieee80211_mgmt *)skb_put(skb, hdr_len);
+        memset(mgmt, 0, hdr_len);
+        mgmt->frame_control = cpu_to_le16(IEEE80211_FTYPE_MGMT |
+                                          IEEE80211_STYPE_ACTION);
+
+        eth_broadcast_addr(mgmt->da);
+        memcpy(mgmt->sa, sdata->vif.addr, ETH_ALEN);
+        memcpy(mgmt->bssid, ifibss->bssid, ETH_ALEN);
+        mgmt->u.action.category = WLAN_CATEGORY_SPECTRUM_MGMT;
+        mgmt->u.action.u.chan_switch.action_code = WLAN_ACTION_SPCT_CHL_SWITCH;
+        pos = skb_put(skb, 5);
+        *pos++ = WLAN_EID_CHANNEL_SWITCH;                       /* EID */
+        *pos++ = 3;                                             /* IE length */
+        *pos++ = csa_settings->block_tx ? 1 : 0;                /* CSA mode */
+        freq = csa_settings->chandef.chan->center_freq;
+        *pos++ = ieee80211_frequency_to_channel(freq);          /* channel */
+        *pos++ = csa_settings->count;                           /* count */
+
+        if (csa_settings->chandef.width == NL80211_CHAN_WIDTH_40) {
+                enum nl80211_channel_type ch_type;
+
+                skb_put(skb, 3);
+                *pos++ = WLAN_EID_SECONDARY_CHANNEL_OFFSET;     /* EID */
+                *pos++ = 1;                                     /* IE length */
+                ch_type = cfg80211_get_chandef_type(&csa_settings->chandef);
+                if (ch_type == NL80211_CHAN_HT40PLUS)
+                        *pos++ = IEEE80211_HT_PARAM_CHA_SEC_ABOVE;
+                else
+                        *pos++ = IEEE80211_HT_PARAM_CHA_SEC_BELOW;
+        }
+
+        ieee80211_tx_skb(sdata, skb);
+        return 0;
+}
+
 int ieee80211_ibss_csa_beacon(struct ieee80211_sub_if_data *sdata,
                               struct cfg80211_csa_settings *csa_settings)
 {
@@ -480,6 +534,12 @@ int ieee80211_ibss_csa_beacon(struct ieee80211_sub_if_data *sdata,
         if (old_presp)
                 kfree_rcu(old_presp, rcu_head);
 
+        /* it might not send the beacon for a while. send an action frame
+         * immediately to announce the channel switch.
+         */
+        if (csa_settings)
+                ieee80211_send_action_csa(sdata, csa_settings);
+
         ieee80211_bss_info_change_notify(sdata, BSS_CHANGED_BEACON);
  out:
         return ret;