mac80211: process the CSA frame for mesh accordingly

Process the CSA frame according to the procedures define in IEEE Std
802.11-2012 section 10.9.8.4.3 as follow:
* The mesh channel switch parameters element (MCSP) must be availabe.
* If the MCSP's TTL is 1, drop the frame but still process the CSA.
* If the MCSP's precedence value is less than or equal to the current
  precedence value, drop the frame and do not process the CSA.
* The CSA frame is forwarded after TTL is decremented by 1 and the
  initiator field is set to 0. Transmit restrict field and others
  are maintained as is.
* No beacon or probe response frame are handled here.

Also, introduce the debug message used for mesh CSA purpose.

Signed-off-by: Chun-Yeow Yeoh <yeohchunyeow@cozybit.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

5 files changed, 114 insertions, 3 deletions

diff --git a/net/mac80211/Kconfig b/net/mac80211/Kconfig
index dc31ec3db404..97b5dcad5025 100644
--- a/net/mac80211/Kconfig
+++ b/net/mac80211/Kconfig
@@ -259,6 +259,17 @@ config MAC80211_MESH_SYNC_DEBUG
 
           Do not select this option.
 
+config MAC80211_MESH_CSA_DEBUG
+        bool "Verbose mesh channel switch debugging"
+        depends on MAC80211_DEBUG_MENU
+        depends on MAC80211_MESH
+        ---help---
+          Selecting this option causes mac80211 to print out very verbose mesh
+          channel switch debugging messages (when mac80211 is taking part in a
+          mesh network).
+
+          Do not select this option.
+
 config MAC80211_MESH_PS_DEBUG
         bool "Verbose mesh powersave debugging"
         depends on MAC80211_DEBUG_MENU
diff --git a/net/mac80211/debug.h b/net/mac80211/debug.h
index 4ccc5ed6237d..493d68061f0c 100644
--- a/net/mac80211/debug.h
+++ b/net/mac80211/debug.h
@@ -44,6 +44,12 @@
 #define MAC80211_MESH_SYNC_DEBUG 0
 #endif
 
+#ifdef CONFIG_MAC80211_MESH_CSA_DEBUG
+#define MAC80211_MESH_CSA_DEBUG 1
+#else
+#define MAC80211_MESH_CSA_DEBUG 0
+#endif
+
 #ifdef CONFIG_MAC80211_MESH_PS_DEBUG
 #define MAC80211_MESH_PS_DEBUG 1
 #else
@@ -157,6 +163,10 @@ do {									\
         _sdata_dbg(MAC80211_MESH_SYNC_DEBUG,                            \
                    sdata, fmt, ##__VA_ARGS__)
 
+#define mcsa_dbg(sdata, fmt, ...)                                       \
+        _sdata_dbg(MAC80211_MESH_CSA_DEBUG,                             \
+                   sdata, fmt, ##__VA_ARGS__)
+
 #define mps_dbg(sdata, fmt, ...)                                        \
         _sdata_dbg(MAC80211_MESH_PS_DEBUG,                              \
                    sdata, fmt, ##__VA_ARGS__)
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index cbaea32bccf1..4ebbcc6f67e0 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -603,6 +603,9 @@ struct ieee80211_if_mesh {
         int ps_peers_light_sleep;
         int ps_peers_deep_sleep;
         struct ps_data ps;
+        /* Channel Switching Support */
+        bool chsw_init;
+        u16 pre_value;
 };
 
 #ifdef CONFIG_MAC80211_MESH
@@ -1252,6 +1255,7 @@ struct ieee802_11_elems {
         const struct ieee80211_timeout_interval_ie *timeout_int;
         const u8 *opmode_notif;
         const struct ieee80211_sec_chan_offs_ie *sec_chan_offs;
+        const struct ieee80211_mesh_chansw_params_ie *mesh_chansw_params_ie;
 
         /* length of them, respectively */
         u8 ssid_len;
diff --git a/net/mac80211/mesh.c b/net/mac80211/mesh.c
index 707ac61d63e5..0a3ccaa275f9 100644
--- a/net/mac80211/mesh.c
+++ b/net/mac80211/mesh.c
@@ -920,6 +920,82 @@ static void ieee80211_mesh_rx_bcn_presp(struct ieee80211_sub_if_data *sdata,
                         stype, mgmt, &elems, rx_status);
 }
 
+static int mesh_fwd_csa_frame(struct ieee80211_sub_if_data *sdata,
+                               struct ieee80211_mgmt *mgmt, size_t len)
+{
+        struct ieee80211_mgmt *mgmt_fwd;
+        struct sk_buff *skb;
+        struct ieee80211_local *local = sdata->local;
+        u8 *pos = mgmt->u.action.u.chan_switch.variable;
+        size_t offset_ttl;
+
+        skb = dev_alloc_skb(local->tx_headroom + len);
+        if (!skb)
+                return -ENOMEM;
+        skb_reserve(skb, local->tx_headroom);
+        mgmt_fwd = (struct ieee80211_mgmt *) skb_put(skb, len);
+
+        /* offset_ttl is based on whether the secondary channel
+         * offset is available or not. Substract 1 from the mesh TTL
+         * and disable the initiator flag before forwarding.
+         */
+        offset_ttl = (len < 42) ? 7 : 10;
+        *(pos + offset_ttl) -= 1;
+        *(pos + offset_ttl + 1) &= ~WLAN_EID_CHAN_SWITCH_PARAM_INITIATOR;
+
+        memcpy(mgmt_fwd, mgmt, len);
+        eth_broadcast_addr(mgmt_fwd->da);
+        memcpy(mgmt_fwd->sa, sdata->vif.addr, ETH_ALEN);
+        memcpy(mgmt_fwd->bssid, sdata->vif.addr, ETH_ALEN);
+
+        ieee80211_tx_skb(sdata, skb);
+        return 0;
+}
+
+static void mesh_rx_csa_frame(struct ieee80211_sub_if_data *sdata,
+                              struct ieee80211_mgmt *mgmt, size_t len)
+{
+        struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
+        struct ieee802_11_elems elems;
+        u16 pre_value;
+        bool block_tx, fwd_csa = true;
+        size_t baselen;
+        u8 *pos, ttl;
+
+        if (mgmt->u.action.u.measurement.action_code !=
+            WLAN_ACTION_SPCT_CHL_SWITCH)
+                return;
+
+        pos = mgmt->u.action.u.chan_switch.variable;
+        baselen = offsetof(struct ieee80211_mgmt,
+                           u.action.u.chan_switch.variable);
+        ieee802_11_parse_elems(pos, len - baselen, false, &elems);
+
+        ttl = elems.mesh_chansw_params_ie->mesh_ttl;
+        if (!--ttl)
+                fwd_csa = false;
+
+        pre_value = le16_to_cpu(elems.mesh_chansw_params_ie->mesh_pre_value);
+        if (ifmsh->pre_value >= pre_value)
+                return;
+
+        ifmsh->pre_value = pre_value;
+
+        /* forward or re-broadcast the CSA frame */
+        if (fwd_csa) {
+                if (mesh_fwd_csa_frame(sdata, mgmt, len) < 0)
+                        mcsa_dbg(sdata, "Failed to forward the CSA frame");
+        }
+
+        /* block the Tx only after forwarding the CSA frame if required */
+        block_tx = elems.mesh_chansw_params_ie->mesh_flags &
+                   WLAN_EID_CHAN_SWITCH_PARAM_TX_RESTRICT;
+        if (block_tx)
+                ieee80211_stop_queues_by_reason(&sdata->local->hw,
+                                IEEE80211_MAX_QUEUE_MAP,
+                                IEEE80211_QUEUE_STOP_REASON_CSA);
+}
+
 static void ieee80211_mesh_rx_mgmt_action(struct ieee80211_sub_if_data *sdata,
                                           struct ieee80211_mgmt *mgmt,
                                           size_t len,
@@ -939,6 +1015,9 @@ static void ieee80211_mesh_rx_mgmt_action(struct ieee80211_sub_if_data *sdata,
                 if (mesh_action_is_path_sel(mgmt))
                         mesh_rx_path_sel_frame(sdata, mgmt, len);
                 break;
+        case WLAN_CATEGORY_SPECTRUM_MGMT:
+                mesh_rx_csa_frame(sdata, mgmt, len);
+                break;
         }
 }
 
@@ -1056,13 +1135,11 @@ void ieee80211_mesh_init_sdata(struct ieee80211_sub_if_data *sdata)
                     (unsigned long) sdata);
 
         ifmsh->accepting_plinks = true;
-        ifmsh->preq_id = 0;
-        ifmsh->sn = 0;
-        ifmsh->num_gates = 0;
         atomic_set(&ifmsh->mpaths, 0);
         mesh_rmc_init(sdata);
         ifmsh->last_preq = jiffies;
         ifmsh->next_perr = jiffies;
+        ifmsh->chsw_init = false;
         /* Allocate all mesh structures when creating the first mesh interface. */
         if (!mesh_allocated)
                 ieee80211s_init();
diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index 65ebe0c5e835..523783cedf6e 100644
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -740,6 +740,7 @@ u32 ieee802_11_parse_elems_crc(const u8 *start, size_t len, bool action,
                 case WLAN_EID_TIMEOUT_INTERVAL:
                 case WLAN_EID_SECONDARY_CHANNEL_OFFSET:
                 case WLAN_EID_WIDE_BW_CHANNEL_SWITCH:
+                case WLAN_EID_CHAN_SWITCH_PARAM:
                 /*
                  * not listing WLAN_EID_CHANNEL_SWITCH_WRAPPER -- it seems possible
                  * that if the content gets bigger it might be needed more than once
@@ -905,6 +906,14 @@ u32 ieee802_11_parse_elems_crc(const u8 *start, size_t len, bool action,
                         }
                         elems->sec_chan_offs = (void *)pos;
                         break;
+                case WLAN_EID_CHAN_SWITCH_PARAM:
+                        if (elen !=
+                            sizeof(*elems->mesh_chansw_params_ie)) {
+                                elem_parse_failed = true;
+                                break;
+                        }
+                        elems->mesh_chansw_params_ie = (void *)pos;
+                        break;
                 case WLAN_EID_WIDE_BW_CHANNEL_SWITCH:
                         if (!action ||
                             elen != sizeof(*elems->wide_bw_chansw_ie)) {