nl80211/cfg80211: add channel switch command

To allow channel switch announcements within beacons, add
the channel switch command to nl80211/cfg80211. This is
implementation is intended for AP and (later) IBSS mode.

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>

5 files changed, 229 insertions, 1 deletions

diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
index aeaf6dff6e05..b7495c72061c 100644
--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h
@@ -666,6 +666,30 @@ struct cfg80211_ap_settings {
 };
 
 /**
+ * struct cfg80211_csa_settings - channel switch settings
+ *
+ * Used for channel switch
+ *
+ * @chandef: defines the channel to use after the switch
+ * @beacon_csa: beacon data while performing the switch
+ * @counter_offset_beacon: offset for the counter within the beacon (tail)
+ * @counter_offset_presp: offset for the counter within the probe response
+ * @beacon_after: beacon data to be used on the new channel
+ * @radar_required: whether radar detection is required on the new channel
+ * @block_tx: whether transmissions should be blocked while changing
+ * @count: number of beacons until switch
+ */
+struct cfg80211_csa_settings {
+        struct cfg80211_chan_def chandef;
+        struct cfg80211_beacon_data beacon_csa;
+        u16 counter_offset_beacon, counter_offset_presp;
+        struct cfg80211_beacon_data beacon_after;
+        bool radar_required;
+        bool block_tx;
+        u8 count;
+};
+
+/**
  * enum station_parameters_apply_mask - station parameter values to apply
  * @STATION_PARAM_APPLY_UAPSD: apply new uAPSD parameters (uapsd_queues, max_sp)
  * @STATION_PARAM_APPLY_CAPABILITY: apply new capability
@@ -2139,6 +2163,8 @@ struct cfg80211_update_ft_ies_params {
  * @crit_proto_stop: Indicates critical protocol no longer needs increased link
  *      reliability. This operation can not fail.
  * @set_coalesce: Set coalesce parameters.
+ *
+ * @channel_switch: initiate channel-switch procedure (with CSA)
  */
 struct cfg80211_ops {
         int     (*suspend)(struct wiphy *wiphy, struct cfg80211_wowlan *wow);
@@ -2376,6 +2402,10 @@ struct cfg80211_ops {
                                    struct wireless_dev *wdev);
         int     (*set_coalesce)(struct wiphy *wiphy,
                                 struct cfg80211_coalesce *coalesce);
+
+        int     (*channel_switch)(struct wiphy *wiphy,
+                                  struct net_device *dev,
+                                  struct cfg80211_csa_settings *params);
 };
 
 /*
@@ -2441,6 +2471,8 @@ struct cfg80211_ops {
  * @WIPHY_FLAG_OFFCHAN_TX: Device supports direct off-channel TX.
  * @WIPHY_FLAG_HAS_REMAIN_ON_CHANNEL: Device supports remain-on-channel call.
  * @WIPHY_FLAG_SUPPORTS_5_10_MHZ: Device supports 5 MHz and 10 MHz channels.
+ * @WIPHY_FLAG_HAS_CHANNEL_SWITCH: Device supports channel switch in
+ *      beaconing mode (AP, IBSS, Mesh, ...).
  */
 enum wiphy_flags {
         WIPHY_FLAG_CUSTOM_REGULATORY            = BIT(0),
@@ -2465,6 +2497,7 @@ enum wiphy_flags {
         WIPHY_FLAG_OFFCHAN_TX                   = BIT(20),
         WIPHY_FLAG_HAS_REMAIN_ON_CHANNEL        = BIT(21),
         WIPHY_FLAG_SUPPORTS_5_10_MHZ            = BIT(22),
+        WIPHY_FLAG_HAS_CHANNEL_SWITCH           = BIT(23),
 };
 
 /**
diff --git a/include/uapi/linux/nl80211.h b/include/uapi/linux/nl80211.h
index eb68735b3318..1f42bc3dcb9c 100644
--- a/include/uapi/linux/nl80211.h
+++ b/include/uapi/linux/nl80211.h
@@ -676,6 +676,16 @@
  * @NL80211_CMD_GET_COALESCE: Get currently supported coalesce rules.
  * @NL80211_CMD_SET_COALESCE: Configure coalesce rules or clear existing rules.
  *
+ * @NL80211_CMD_CHANNEL_SWITCH: Perform a channel switch by announcing the
+ *      the new channel information (Channel Switch Announcement - CSA)
+ *      in the beacon for some time (as defined in the
+ *      %NL80211_ATTR_CH_SWITCH_COUNT parameter) and then change to the
+ *      new channel. Userspace provides the new channel information (using
+ *      %NL80211_ATTR_WIPHY_FREQ and the attributes determining channel
+ *      width). %NL80211_ATTR_CH_SWITCH_BLOCK_TX may be supplied to inform
+ *      other station that transmission must be blocked until the channel
+ *      switch is complete.
+ *
  * @NL80211_CMD_MAX: highest used command number
  * @__NL80211_CMD_AFTER_LAST: internal use
  */
@@ -841,6 +851,8 @@ enum nl80211_commands {
         NL80211_CMD_GET_COALESCE,
         NL80211_CMD_SET_COALESCE,
 
+        NL80211_CMD_CHANNEL_SWITCH,
+
         /* add new commands above here */
 
         /* used to define NL80211_CMD_MAX below */
@@ -1469,6 +1481,18 @@ enum nl80211_commands {
  *
  * @NL80211_ATTR_COALESCE_RULE: Coalesce rule information.
  *
+ * @NL80211_ATTR_CH_SWITCH_COUNT: u32 attribute specifying the number of TBTT's
+ *      until the channel switch event.
+ * @NL80211_ATTR_CH_SWITCH_BLOCK_TX: flag attribute specifying that transmission
+ *      must be blocked on the current channel (before the channel switch
+ *      operation).
+ * @NL80211_ATTR_CSA_IES: Nested set of attributes containing the IE information
+ *      for the time while performing a channel switch.
+ * @NL80211_ATTR_CSA_C_OFF_BEACON: Offset of the channel switch counter
+ *      field in the beacons tail (%NL80211_ATTR_BEACON_TAIL).
+ * @NL80211_ATTR_CSA_C_OFF_PRESP: Offset of the channel switch counter
+ *      field in the probe response (%NL80211_ATTR_PROBE_RESP).
+ *
  * @NL80211_ATTR_MAX: highest attribute number currently defined
  * @__NL80211_ATTR_AFTER_LAST: internal use
  */
@@ -1771,6 +1795,12 @@ enum nl80211_attrs {
 
         NL80211_ATTR_COALESCE_RULE,
 
+        NL80211_ATTR_CH_SWITCH_COUNT,
+        NL80211_ATTR_CH_SWITCH_BLOCK_TX,
+        NL80211_ATTR_CSA_IES,
+        NL80211_ATTR_CSA_C_OFF_BEACON,
+        NL80211_ATTR_CSA_C_OFF_PRESP,
+
         /* add attributes here, update the policy in nl80211.c */
 
         __NL80211_ATTR_AFTER_LAST,
diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index 03d4ef95292e..f7cb12178bd2 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -349,6 +349,11 @@ static const struct nla_policy nl80211_policy[NL80211_ATTR_MAX+1] = {
         [NL80211_ATTR_IE_RIC] = { .type = NLA_BINARY,
                                   .len = IEEE80211_MAX_DATA_LEN },
         [NL80211_ATTR_PEER_AID] = { .type = NLA_U16 },
+        [NL80211_ATTR_CH_SWITCH_COUNT] = { .type = NLA_U32 },
+        [NL80211_ATTR_CH_SWITCH_BLOCK_TX] = { .type = NLA_FLAG },
+        [NL80211_ATTR_CSA_IES] = { .type = NLA_NESTED },
+        [NL80211_ATTR_CSA_C_OFF_BEACON] = { .type = NLA_U16 },
+        [NL80211_ATTR_CSA_C_OFF_PRESP] = { .type = NLA_U16 },
 };
 
 /* policy for the key attributes */
@@ -1422,6 +1427,8 @@ static int nl80211_send_wiphy(struct cfg80211_registered_device *dev,
                 if (state->split) {
                         CMD(crit_proto_start, CRIT_PROTOCOL_START);
                         CMD(crit_proto_stop, CRIT_PROTOCOL_STOP);
+                        if (dev->wiphy.flags & WIPHY_FLAG_HAS_CHANNEL_SWITCH)
+                                CMD(channel_switch, CHANNEL_SWITCH);
                 }
 
 #ifdef CONFIG_NL80211_TESTMODE
@@ -5613,6 +5620,111 @@ static int nl80211_start_radar_detection(struct sk_buff *skb,
         return err;
 }
 
+static int nl80211_channel_switch(struct sk_buff *skb, struct genl_info *info)
+{
+        struct cfg80211_registered_device *rdev = info->user_ptr[0];
+        struct net_device *dev = info->user_ptr[1];
+        struct wireless_dev *wdev = dev->ieee80211_ptr;
+        struct cfg80211_csa_settings params;
+        /* csa_attrs is defined static to avoid waste of stack size - this
+         * function is called under RTNL lock, so this should not be a problem.
+         */
+        static struct nlattr *csa_attrs[NL80211_ATTR_MAX+1];
+        u8 radar_detect_width = 0;
+        int err;
+
+        if (!rdev->ops->channel_switch ||
+            !(rdev->wiphy.flags & WIPHY_FLAG_HAS_CHANNEL_SWITCH))
+                return -EOPNOTSUPP;
+
+        /* may add IBSS support later */
+        if (dev->ieee80211_ptr->iftype != NL80211_IFTYPE_AP &&
+            dev->ieee80211_ptr->iftype != NL80211_IFTYPE_P2P_GO)
+                return -EOPNOTSUPP;
+
+        memset(&params, 0, sizeof(params));
+
+        if (!info->attrs[NL80211_ATTR_WIPHY_FREQ] ||
+            !info->attrs[NL80211_ATTR_CH_SWITCH_COUNT])
+                return -EINVAL;
+
+        /* only important for AP, IBSS and mesh create IEs internally */
+        if (!info->attrs[NL80211_ATTR_CSA_IES])
+                return -EINVAL;
+
+        /* useless if AP is not running */
+        if (!wdev->beacon_interval)
+                return -EINVAL;
+
+        params.count = nla_get_u32(info->attrs[NL80211_ATTR_CH_SWITCH_COUNT]);
+
+        err = nl80211_parse_beacon(info->attrs, &params.beacon_after);
+        if (err)
+                return err;
+
+        err = nla_parse_nested(csa_attrs, NL80211_ATTR_MAX,
+                               info->attrs[NL80211_ATTR_CSA_IES],
+                               nl80211_policy);
+        if (err)
+                return err;
+
+        err = nl80211_parse_beacon(csa_attrs, &params.beacon_csa);
+        if (err)
+                return err;
+
+        if (!csa_attrs[NL80211_ATTR_CSA_C_OFF_BEACON])
+                return -EINVAL;
+
+        params.counter_offset_beacon =
+                nla_get_u16(csa_attrs[NL80211_ATTR_CSA_C_OFF_BEACON]);
+        if (params.counter_offset_beacon >= params.beacon_csa.tail_len)
+                return -EINVAL;
+
+        /* sanity check - counters should be the same */
+        if (params.beacon_csa.tail[params.counter_offset_beacon] !=
+            params.count)
+                return -EINVAL;
+
+        if (csa_attrs[NL80211_ATTR_CSA_C_OFF_PRESP]) {
+                params.counter_offset_presp =
+                        nla_get_u16(csa_attrs[NL80211_ATTR_CSA_C_OFF_PRESP]);
+                if (params.counter_offset_presp >=
+                    params.beacon_csa.probe_resp_len)
+                        return -EINVAL;
+
+                if (params.beacon_csa.probe_resp[params.counter_offset_presp] !=
+                    params.count)
+                        return -EINVAL;
+        }
+
+        err = nl80211_parse_chandef(rdev, info, &params.chandef);
+        if (err)
+                return err;
+
+        if (!cfg80211_reg_can_beacon(&rdev->wiphy, &params.chandef))
+                return -EINVAL;
+
+        err = cfg80211_chandef_dfs_required(wdev->wiphy, &params.chandef);
+        if (err < 0) {
+                return err;
+        } else if (err) {
+                radar_detect_width = BIT(params.chandef.width);
+                params.radar_required = true;
+        }
+
+        err = cfg80211_can_use_iftype_chan(rdev, wdev, wdev->iftype,
+                                           params.chandef.chan,
+                                           CHAN_MODE_SHARED,
+                                           radar_detect_width);
+        if (err)
+                return err;
+
+        if (info->attrs[NL80211_ATTR_CH_SWITCH_BLOCK_TX])
+                params.block_tx = true;
+
+        return rdev_channel_switch(rdev, dev, &params);
+}
+
 static int nl80211_send_bss(struct sk_buff *msg, struct netlink_callback *cb,
                             u32 seq, int flags,
                             struct cfg80211_registered_device *rdev,
@@ -9361,7 +9473,15 @@ static struct genl_ops nl80211_ops[] = {
                 .flags = GENL_ADMIN_PERM,
                 .internal_flags = NL80211_FLAG_NEED_WIPHY |
                                   NL80211_FLAG_NEED_RTNL,
-        }
+        },
+        {
+                .cmd = NL80211_CMD_CHANNEL_SWITCH,
+                .doit = nl80211_channel_switch,
+                .policy = nl80211_policy,
+                .flags = GENL_ADMIN_PERM,
+                .internal_flags = NL80211_FLAG_NEED_NETDEV_UP |
+                                  NL80211_FLAG_NEED_RTNL,
+        },
 };
 
 static struct genl_multicast_group nl80211_mlme_mcgrp = {
diff --git a/net/wireless/rdev-ops.h b/net/wireless/rdev-ops.h
index 9f15f0ac824d..de870d4d0bcc 100644
--- a/net/wireless/rdev-ops.h
+++ b/net/wireless/rdev-ops.h
@@ -923,4 +923,16 @@ static inline void rdev_crit_proto_stop(struct cfg80211_registered_device *rdev,
         trace_rdev_return_void(&rdev->wiphy);
 }
 
+static inline int rdev_channel_switch(struct cfg80211_registered_device *rdev,
+                                      struct net_device *dev,
+                                      struct cfg80211_csa_settings *params)
+{
+        int ret;
+
+        trace_rdev_channel_switch(&rdev->wiphy, dev, params);
+        ret = rdev->ops->channel_switch(&rdev->wiphy, dev, params);
+        trace_rdev_return_int(&rdev->wiphy, ret);
+        return ret;
+}
+
 #endif /* __CFG80211_RDEV_OPS */
diff --git a/net/wireless/trace.h b/net/wireless/trace.h
index 09af6eb426a8..f0ebdcd394ef 100644
--- a/net/wireless/trace.h
+++ b/net/wireless/trace.h
@@ -1841,6 +1841,39 @@ TRACE_EVENT(rdev_crit_proto_stop,
                   WIPHY_PR_ARG, WDEV_PR_ARG)
 );
 
+TRACE_EVENT(rdev_channel_switch,
+        TP_PROTO(struct wiphy *wiphy, struct net_device *netdev,
+                 struct cfg80211_csa_settings *params),
+        TP_ARGS(wiphy, netdev, params),
+        TP_STRUCT__entry(
+                WIPHY_ENTRY
+                NETDEV_ENTRY
+                CHAN_DEF_ENTRY
+                __field(u16, counter_offset_beacon)
+                __field(u16, counter_offset_presp)
+                __field(bool, radar_required)
+                __field(bool, block_tx)
+                __field(u8, count)
+        ),
+        TP_fast_assign(
+                WIPHY_ASSIGN;
+                NETDEV_ASSIGN;
+                CHAN_DEF_ASSIGN(&params->chandef);
+                __entry->counter_offset_beacon = params->counter_offset_beacon;
+                __entry->counter_offset_presp = params->counter_offset_presp;
+                __entry->radar_required = params->radar_required;
+                __entry->block_tx = params->block_tx;
+                __entry->count = params->count;
+        ),
+        TP_printk(WIPHY_PR_FMT ", " NETDEV_PR_FMT ", " CHAN_DEF_PR_FMT
+                  ", block_tx: %d, count: %u, radar_required: %d"
+                  ", counter offsets (beacon/presp): %u/%u",
+                  WIPHY_PR_ARG, NETDEV_PR_ARG, CHAN_DEF_PR_ARG,
+                  __entry->block_tx, __entry->count, __entry->radar_required,
+                  __entry->counter_offset_beacon,
+                  __entry->counter_offset_presp)
+);
+
 /*************************************************************
  *           cfg80211 exported functions traces              *
  *************************************************************/