mac80211: ibss: use beacon_data struct for beacon and probe response

Instead of having an SKB all the time, use a beacon_data struct
with just the information required. This also allows removing a
synchronize_rcu() and using kfree_rcu() instead.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 64 insertions, 67 deletions

diff --git a/net/mac80211/ibss.c b/net/mac80211/ibss.c
index bd02fac188bd..5ab32e2a7b56 100644
--- a/net/mac80211/ibss.c
+++ b/net/mac80211/ibss.c
@@ -44,7 +44,6 @@ static void __ieee80211_sta_join_ibss(struct ieee80211_sub_if_data *sdata,
         struct ieee80211_if_ibss *ifibss = &sdata->u.ibss;
         struct ieee80211_local *local = sdata->local;
         int rates, i;
-        struct sk_buff *skb;
         struct ieee80211_mgmt *mgmt;
         u8 *pos;
         struct ieee80211_supported_band *sband;
@@ -52,6 +51,8 @@ static void __ieee80211_sta_join_ibss(struct ieee80211_sub_if_data *sdata,
         u32 bss_change;
         u8 supp_rates[IEEE80211_MAX_SUPP_RATES];
         struct cfg80211_chan_def chandef;
+        struct beacon_data *presp;
+        int frame_len;
 
         lockdep_assert_held(&ifibss->mtx);
 
@@ -72,13 +73,11 @@ static void __ieee80211_sta_join_ibss(struct ieee80211_sub_if_data *sdata,
                                                  BSS_CHANGED_BEACON_ENABLED);
         }
 
-        skb = ifibss->skb;
-        RCU_INIT_POINTER(ifibss->presp, NULL);
-        synchronize_rcu();
-        skb->data = skb->head;
-        skb->len = 0;
-        skb_reset_tail_pointer(skb);
-        skb_reserve(skb, sdata->local->hw.extra_tx_headroom);
+        presp = rcu_dereference_protected(ifibss->presp,
+                                          lockdep_is_held(&ifibss->mtx));
+        rcu_assign_pointer(ifibss->presp, NULL);
+        if (presp)
+                kfree_rcu(presp, rcu_head);
 
         sdata->drop_unencrypted = capability & WLAN_CAPABILITY_PRIVACY ? 1 : 0;
 
@@ -101,19 +100,24 @@ static void __ieee80211_sta_join_ibss(struct ieee80211_sub_if_data *sdata,
 
         sband = local->hw.wiphy->bands[chan->band];
 
-        /* build supported rates array */
-        pos = supp_rates;
-        for (i = 0; i < sband->n_bitrates; i++) {
-                int rate = sband->bitrates[i].bitrate;
-                u8 basic = 0;
-                if (basic_rates & BIT(i))
-                        basic = 0x80;
-                *pos++ = basic | (u8) (rate / 5);
-        }
-
         /* Build IBSS probe response */
-        mgmt = (void *) skb_put(skb, 24 + sizeof(mgmt->u.beacon));
-        memset(mgmt, 0, 24 + sizeof(mgmt->u.beacon));
+        frame_len = sizeof(struct ieee80211_hdr_3addr) +
+                    12 /* struct ieee80211_mgmt.u.beacon */ +
+                    2 + IEEE80211_MAX_SSID_LEN /* max SSID */ +
+                    2 + 8 /* max Supported Rates */ +
+                    3 /* max DS params */ +
+                    4 /* IBSS params */ +
+                    2 + (IEEE80211_MAX_SUPP_RATES - 8) +
+                    2 + sizeof(struct ieee80211_ht_cap) +
+                    2 + sizeof(struct ieee80211_ht_operation) +
+                    ifibss->ie_len;
+        presp = kzalloc(sizeof(*presp) + frame_len, GFP_KERNEL);
+        if (!presp)
+                return;
+
+        presp->head = (void *)(presp + 1);
+
+        mgmt = (void *) presp->head;
         mgmt->frame_control = cpu_to_le16(IEEE80211_FTYPE_MGMT |
                                           IEEE80211_STYPE_PROBE_RESP);
         eth_broadcast_addr(mgmt->da);
@@ -123,27 +127,30 @@ static void __ieee80211_sta_join_ibss(struct ieee80211_sub_if_data *sdata,
         mgmt->u.beacon.timestamp = cpu_to_le64(tsf);
         mgmt->u.beacon.capab_info = cpu_to_le16(capability);
 
-        pos = skb_put(skb, 2 + ifibss->ssid_len);
+        pos = (u8 *)mgmt + offsetof(struct ieee80211_mgmt, u.beacon.variable);
+
         *pos++ = WLAN_EID_SSID;
         *pos++ = ifibss->ssid_len;
         memcpy(pos, ifibss->ssid, ifibss->ssid_len);
+        pos += ifibss->ssid_len;
 
-        rates = sband->n_bitrates;
-        if (rates > 8)
-                rates = 8;
-        pos = skb_put(skb, 2 + rates);
+        rates = min_t(int, 8, sband->n_bitrates);
         *pos++ = WLAN_EID_SUPP_RATES;
         *pos++ = rates;
-        memcpy(pos, supp_rates, rates);
+        for (i = 0; i < rates; i++) {
+                int rate = sband->bitrates[i].bitrate;
+                u8 basic = 0;
+                if (basic_rates & BIT(i))
+                        basic = 0x80;
+                *pos++ = basic | (u8) (rate / 5);
+        }
 
         if (sband->band == IEEE80211_BAND_2GHZ) {
-                pos = skb_put(skb, 2 + 1);
                 *pos++ = WLAN_EID_DS_PARAMS;
                 *pos++ = 1;
                 *pos++ = ieee80211_frequency_to_channel(chan->center_freq);
         }
 
-        pos = skb_put(skb, 2 + 2);
         *pos++ = WLAN_EID_IBSS_PARAMS;
         *pos++ = 2;
         /* FIX: set ATIM window based on scan results */
@@ -151,23 +158,25 @@ static void __ieee80211_sta_join_ibss(struct ieee80211_sub_if_data *sdata,
         *pos++ = 0;
 
         if (sband->n_bitrates > 8) {
-                rates = sband->n_bitrates - 8;
-                pos = skb_put(skb, 2 + rates);
                 *pos++ = WLAN_EID_EXT_SUPP_RATES;
-                *pos++ = rates;
-                memcpy(pos, &supp_rates[8], rates);
+                *pos++ = sband->n_bitrates - 8;
+                for (i = 8; i < sband->n_bitrates; i++) {
+                        int rate = sband->bitrates[i].bitrate;
+                        u8 basic = 0;
+                        if (basic_rates & BIT(i))
+                                basic = 0x80;
+                        *pos++ = basic | (u8) (rate / 5);
+                }
         }
 
-        if (ifibss->ie_len)
-                memcpy(skb_put(skb, ifibss->ie_len),
-                       ifibss->ie, ifibss->ie_len);
+        if (ifibss->ie_len) {
+                memcpy(pos, ifibss->ie, ifibss->ie_len);
+                pos += ifibss->ie_len;
+        }
 
         /* add HT capability and information IEs */
         if (chandef.width != NL80211_CHAN_WIDTH_20_NOHT &&
             sband->ht_cap.ht_supported) {
-                pos = skb_put(skb, 4 +
-                                   sizeof(struct ieee80211_ht_cap) +
-                                   sizeof(struct ieee80211_ht_operation));
                 pos = ieee80211_ie_build_ht_cap(pos, &sband->ht_cap,
                                                 sband->ht_cap.cap);
                 /*
@@ -180,7 +189,6 @@ static void __ieee80211_sta_join_ibss(struct ieee80211_sub_if_data *sdata,
         }
 
         if (local->hw.queues >= IEEE80211_NUM_ACS) {
-                pos = skb_put(skb, 9);
                 *pos++ = WLAN_EID_VENDOR_SPECIFIC;
                 *pos++ = 7; /* len */
                 *pos++ = 0x00; /* Microsoft OUI 00:50:F2 */
@@ -192,7 +200,11 @@ static void __ieee80211_sta_join_ibss(struct ieee80211_sub_if_data *sdata,
                 *pos++ = 0; /* U-APSD no in use */
         }
 
-        rcu_assign_pointer(ifibss->presp, skb);
+        presp->head_len = pos - presp->head;
+        if (WARN_ON(presp->head_len > frame_len))
+                return;
+
+        rcu_assign_pointer(ifibss->presp, presp);
 
         sdata->vif.bss_conf.enable_beacon = true;
         sdata->vif.bss_conf.beacon_int = beacon_int;
@@ -230,7 +242,7 @@ static void __ieee80211_sta_join_ibss(struct ieee80211_sub_if_data *sdata,
                   round_jiffies(jiffies + IEEE80211_IBSS_MERGE_INTERVAL));
 
         bss = cfg80211_inform_bss_frame(local->hw.wiphy, chan,
-                                        mgmt, skb->len, 0, GFP_KERNEL);
+                                        mgmt, presp->head_len, 0, GFP_KERNEL);
         cfg80211_put_bss(local->hw.wiphy, bss);
         netif_carrier_on(sdata->dev);
         cfg80211_ibss_joined(sdata->dev, ifibss->bssid, GFP_KERNEL);
@@ -825,8 +837,7 @@ static void ieee80211_rx_mgmt_probe_req(struct ieee80211_sub_if_data *sdata,
         struct ieee80211_local *local = sdata->local;
         int tx_last_beacon, len = req->len;
         struct sk_buff *skb;
-        struct ieee80211_mgmt *resp;
-        struct sk_buff *presp;
+        struct beacon_data *presp;
         u8 *pos, *end;
 
         lockdep_assert_held(&ifibss->mtx);
@@ -867,13 +878,15 @@ static void ieee80211_rx_mgmt_probe_req(struct ieee80211_sub_if_data *sdata,
         }
 
         /* Reply with ProbeResp */
-        skb = skb_copy(presp, GFP_KERNEL);
+        skb = dev_alloc_skb(local->tx_headroom + presp->head_len);
         if (!skb)
                 return;
 
-        resp = (struct ieee80211_mgmt *) skb->data;
-        memcpy(resp->da, mgmt->sa, ETH_ALEN);
-        ibss_dbg(sdata, "Sending ProbeResp to %pM\n", resp->da);
+        skb_reserve(skb, local->tx_headroom);
+        memcpy(skb_put(skb, presp->head_len), presp->head, presp->head_len);
+
+        memcpy(((struct ieee80211_mgmt *) skb->data)->da, mgmt->sa, ETH_ALEN);
+        ibss_dbg(sdata, "Sending ProbeResp to %pM\n", mgmt->sa);
         IEEE80211_SKB_CB(skb)->flags |= IEEE80211_TX_INTFL_DONT_ENCRYPT;
         ieee80211_tx_skb(sdata, skb);
 }
@@ -1023,23 +1036,8 @@ void ieee80211_ibss_notify_scan_completed(struct ieee80211_local *local)
 int ieee80211_ibss_join(struct ieee80211_sub_if_data *sdata,
                         struct cfg80211_ibss_params *params)
 {
-        struct sk_buff *skb;
         u32 changed = 0;
 
-        skb = dev_alloc_skb(sdata->local->hw.extra_tx_headroom +
-                            sizeof(struct ieee80211_hdr_3addr) +
-                            12 /* struct ieee80211_mgmt.u.beacon */ +
-                            2 + IEEE80211_MAX_SSID_LEN /* max SSID */ +
-                            2 + 8 /* max Supported Rates */ +
-                            3 /* max DS params */ +
-                            4 /* IBSS params */ +
-                            2 + (IEEE80211_MAX_SUPP_RATES - 8) +
-                            2 + sizeof(struct ieee80211_ht_cap) +
-                            2 + sizeof(struct ieee80211_ht_operation) +
-                            params->ie_len);
-        if (!skb)
-                return -ENOMEM;
-
         mutex_lock(&sdata->u.ibss.mtx);
 
         if (params->bssid) {
@@ -1068,7 +1066,6 @@ int ieee80211_ibss_join(struct ieee80211_sub_if_data *sdata,
                         sdata->u.ibss.ie_len = params->ie_len;
         }
 
-        sdata->u.ibss.skb = skb;
         sdata->u.ibss.state = IEEE80211_IBSS_MLME_SEARCH;
         sdata->u.ibss.ibss_join_req = jiffies;
 
@@ -1104,13 +1101,13 @@ int ieee80211_ibss_join(struct ieee80211_sub_if_data *sdata,
 
 int ieee80211_ibss_leave(struct ieee80211_sub_if_data *sdata)
 {
-        struct sk_buff *skb;
         struct ieee80211_if_ibss *ifibss = &sdata->u.ibss;
         struct ieee80211_local *local = sdata->local;
         struct cfg80211_bss *cbss;
         u16 capability;
         int active_ibss;
         struct sta_info *sta;
+        struct beacon_data *presp;
 
         mutex_lock(&sdata->u.ibss.mtx);
 
@@ -1156,8 +1153,8 @@ int ieee80211_ibss_leave(struct ieee80211_sub_if_data *sdata)
 
         /* remove beacon */
         kfree(sdata->u.ibss.ie);
-        skb = rcu_dereference_protected(sdata->u.ibss.presp,
-                                        lockdep_is_held(&sdata->u.ibss.mtx));
+        presp = rcu_dereference_protected(ifibss->presp,
+                                          lockdep_is_held(&sdata->u.ibss.mtx));
         RCU_INIT_POINTER(sdata->u.ibss.presp, NULL);
         sdata->vif.bss_conf.ibss_joined = false;
         sdata->vif.bss_conf.ibss_creator = false;
@@ -1166,7 +1163,7 @@ int ieee80211_ibss_leave(struct ieee80211_sub_if_data *sdata)
         ieee80211_bss_info_change_notify(sdata, BSS_CHANGED_BEACON_ENABLED |
                                                 BSS_CHANGED_IBSS);
         synchronize_rcu();
-        kfree_skb(skb);
+        kfree(presp);
 
         skb_queue_purge(&sdata->skb_queue);