10 files changed, 392 insertions, 8 deletions

diff --git a/include/linux/ieee80211.h b/include/linux/ieee80211.h
index 09301b0768d0..db84e2f6b289 100644
--- a/include/linux/ieee80211.h
+++ b/include/linux/ieee80211.h
@@ -1439,6 +1439,18 @@ enum ieee80211_tdls_actioncode {
 #define WLAN_TDLS_SNAP_RFTYPE   0x2
 
 /**
+ * enum - mesh synchronization method identifier
+ *
+ * @IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET: the default synchronization method
+ * @IEEE80211_SYNC_METHOD_VENDOR: a vendor specific synchronization method
+ * that will be specified in a vendor specific information element
+ */
+enum {
+        IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET = 1,
+        IEEE80211_SYNC_METHOD_VENDOR = 255,
+};
+
+/**
  * enum - mesh path selection protocol identifier
  *
  * @IEEE80211_PATH_PROTOCOL_HWMP: the default path selection protocol
diff --git a/net/mac80211/Kconfig b/net/mac80211/Kconfig
index 96ddb72760b9..8d249d705980 100644
--- a/net/mac80211/Kconfig
+++ b/net/mac80211/Kconfig
@@ -225,6 +225,17 @@ config MAC80211_VERBOSE_MHWMP_DEBUG
 
           Do not select this option.
 
+config MAC80211_VERBOSE_MESH_SYNC_DEBUG
+        bool "Verbose mesh mesh synchronization debugging"
+        depends on MAC80211_DEBUG_MENU
+        depends on MAC80211_MESH
+        ---help---
+          Selecting this option causes mac80211 to print out very verbose mesh
+          synchronization debugging messages (when mac80211 is taking part in a
+          mesh network).
+
+          Do not select this option.
+
 config MAC80211_VERBOSE_TDLS_DEBUG
         bool "Verbose TDLS debugging"
         depends on MAC80211_DEBUG_MENU
diff --git a/net/mac80211/Makefile b/net/mac80211/Makefile
index 1be7a454aa77..3e9d931bba35 100644
--- a/net/mac80211/Makefile
+++ b/net/mac80211/Makefile
@@ -38,7 +38,8 @@ mac80211-$(CONFIG_MAC80211_MESH) += \
         mesh.o \
         mesh_pathtbl.o \
         mesh_plink.o \
-        mesh_hwmp.o
+        mesh_hwmp.o \
+        mesh_sync.o
 
 mac80211-$(CONFIG_PM) += pm.o
 
diff --git a/net/mac80211/debugfs_sta.c b/net/mac80211/debugfs_sta.c
index 6d45804d09bc..ceeefd424103 100644
--- a/net/mac80211/debugfs_sta.c
+++ b/net/mac80211/debugfs_sta.c
@@ -63,7 +63,7 @@ static ssize_t sta_flags_read(struct file *file, char __user *userbuf,
         test_sta_flag(sta, WLAN_STA_##flg) ? #flg "\n" : ""
 
         int res = scnprintf(buf, sizeof(buf),
-                            "%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s",
+                            "%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s",
                             TEST(AUTH), TEST(ASSOC), TEST(PS_STA),
                             TEST(PS_DRIVER), TEST(AUTHORIZED),
                             TEST(SHORT_PREAMBLE),
@@ -71,7 +71,8 @@ static ssize_t sta_flags_read(struct file *file, char __user *userbuf,
                             TEST(MFP), TEST(BLOCK_BA), TEST(PSPOLL),
                             TEST(UAPSD), TEST(SP), TEST(TDLS_PEER),
                             TEST(TDLS_PEER_AUTH), TEST(4ADDR_EVENT),
-                            TEST(INSERTED), TEST(RATE_CONTROL));
+                            TEST(INSERTED), TEST(RATE_CONTROL),
+                            TEST(TOFFSET_KNOWN));
 #undef TEST
         return simple_read_from_buffer(userbuf, count, ppos, buf, res);
 }
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 8e7af7cee013..ea9623cbd969 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -554,6 +554,24 @@ struct ieee80211_if_ibss {
         } state;
 };
 
+/**
+ * struct ieee80211_mesh_sync_ops - Extensible synchronization framework interface
+ *
+ * these declarations define the interface, which enables
+ * vendor-specific mesh synchronization
+ *
+ */
+struct ieee802_11_elems;
+struct ieee80211_mesh_sync_ops {
+        void (*rx_bcn_presp)(struct ieee80211_sub_if_data *sdata,
+                             u16 stype,
+                             struct ieee80211_mgmt *mgmt,
+                             struct ieee802_11_elems *elems,
+                             struct ieee80211_rx_status *rx_status);
+        void (*adjust_tbtt)(struct ieee80211_sub_if_data *sdata);
+        /* add other framework functions here */
+};
+
 struct ieee80211_if_mesh {
         struct timer_list housekeeping_timer;
         struct timer_list mesh_path_timer;
@@ -602,6 +620,11 @@ struct ieee80211_if_mesh {
                 IEEE80211_MESH_SEC_AUTHED = 0x1,
                 IEEE80211_MESH_SEC_SECURED = 0x2,
         } security;
+        /* Extensible Synchronization Framework */
+        struct ieee80211_mesh_sync_ops *sync_ops;
+        s64 sync_offset_clockdrift_max;
+        spinlock_t sync_offset_lock;
+        bool adjusting_tbtt;
 };
 
 #ifdef CONFIG_MAC80211_MESH
diff --git a/net/mac80211/mesh.c b/net/mac80211/mesh.c
index b05fa9ef866c..386dbca1eab3 100644
--- a/net/mac80211/mesh.c
+++ b/net/mac80211/mesh.c
@@ -13,9 +13,6 @@
 #include "ieee80211_i.h"
 #include "mesh.h"
 
-#define MESHCONF_CAPAB_ACCEPT_PLINKS 0x01
-#define MESHCONF_CAPAB_FORWARDING    0x08
-
 #define TMR_RUNNING_HK  0
 #define TMR_RUNNING_MP  1
 #define TMR_RUNNING_MPR 2
@@ -251,8 +248,10 @@ mesh_add_meshconf_ie(struct sk_buff *skb, struct ieee80211_sub_if_data *sdata)
         /* Mesh capability */
         ifmsh->accepting_plinks = mesh_plink_availables(sdata);
         *pos = MESHCONF_CAPAB_FORWARDING;
-        *pos++ |= ifmsh->accepting_plinks ?
+        *pos |= ifmsh->accepting_plinks ?
             MESHCONF_CAPAB_ACCEPT_PLINKS : 0x00;
+        *pos++ |= ifmsh->adjusting_tbtt ?
+            MESHCONF_CAPAB_TBTT_ADJUSTING : 0x00;
         *pos++ = 0x00;
 
         return 0;
@@ -573,8 +572,11 @@ void ieee80211_start_mesh(struct ieee80211_sub_if_data *sdata)
         ieee80211_configure_filter(local);
 
         ifmsh->mesh_cc_id = 0;  /* Disabled */
-        ifmsh->mesh_sp_id = 0;  /* Neighbor Offset */
         ifmsh->mesh_auth_id = 0;        /* Disabled */
+        /* register sync ops from extensible synchronization framework */
+        ifmsh->sync_ops = ieee80211_mesh_sync_ops_get(ifmsh->mesh_sp_id);
+        ifmsh->adjusting_tbtt = false;
+        ifmsh->sync_offset_clockdrift_max = 0;
         set_bit(MESH_WORK_HOUSEKEEPING, &ifmsh->wrkq_flags);
         ieee80211_mesh_root_setup(ifmsh);
         ieee80211_queue_work(&local->hw, &sdata->work);
@@ -616,6 +618,7 @@ static void ieee80211_mesh_rx_bcn_presp(struct ieee80211_sub_if_data *sdata,
                                         struct ieee80211_rx_status *rx_status)
 {
         struct ieee80211_local *local = sdata->local;
+        struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
         struct ieee802_11_elems elems;
         struct ieee80211_channel *channel;
         u32 supp_rates = 0;
@@ -654,6 +657,10 @@ static void ieee80211_mesh_rx_bcn_presp(struct ieee80211_sub_if_data *sdata,
                 supp_rates = ieee80211_sta_get_rates(local, &elems, band);
                 mesh_neighbour_update(mgmt->sa, supp_rates, sdata, &elems);
         }
+
+        if (ifmsh->sync_ops)
+                ifmsh->sync_ops->rx_bcn_presp(sdata,
+                        stype, mgmt, &elems, rx_status);
 }
 
 static void ieee80211_mesh_rx_mgmt_action(struct ieee80211_sub_if_data *sdata,
@@ -721,6 +728,9 @@ void ieee80211_mesh_work(struct ieee80211_sub_if_data *sdata)
 
         if (test_and_clear_bit(MESH_WORK_ROOT, &ifmsh->wrkq_flags))
                 ieee80211_mesh_rootpath(sdata);
+
+        if (test_and_clear_bit(MESH_WORK_DRIFT_ADJUST, &ifmsh->wrkq_flags))
+                mesh_sync_adjust_tbtt(sdata);
 }
 
 void ieee80211_mesh_notify_scan_completed(struct ieee80211_local *local)
@@ -761,4 +771,5 @@ void ieee80211_mesh_init_sdata(struct ieee80211_sub_if_data *sdata)
                     (unsigned long) sdata);
         INIT_LIST_HEAD(&ifmsh->preq_queue.list);
         spin_lock_init(&ifmsh->mesh_preq_queue_lock);
+        spin_lock_init(&ifmsh->sync_offset_lock);
 }
diff --git a/net/mac80211/mesh.h b/net/mac80211/mesh.h
index 3e52439ed112..fa7d9704c175 100644
--- a/net/mac80211/mesh.h
+++ b/net/mac80211/mesh.h
@@ -19,6 +19,20 @@
 /* Data structures */
 
 /**
+ * enum mesh_config_capab_flags - mesh config IE capability flags
+ *
+ * @MESHCONF_CAPAB_ACCEPT_PLINKS: STA is willing to establish
+ * additional mesh peerings with other mesh STAs
+ * @MESHCONF_CAPAB_FORWARDING: the STA forwards MSDUs
+ * @MESHCONF_CAPAB_TBTT_ADJUSTING: TBTT adjustment procedure is ongoing
+ */
+enum mesh_config_capab_flags {
+        MESHCONF_CAPAB_ACCEPT_PLINKS = BIT(0),
+        MESHCONF_CAPAB_FORWARDING = BIT(3),
+        MESHCONF_CAPAB_TBTT_ADJUSTING = BIT(5),
+};
+
+/**
  * enum mesh_path_flags - mac80211 mesh path flags
  *
  *
@@ -56,12 +70,15 @@ enum mesh_path_flags {
  * @MESH_WORK_GROW_MPP_TABLE: the mesh portals table is full and needs to
  * grow
  * @MESH_WORK_ROOT: the mesh root station needs to send a frame
+ * @MESH_WORK_DRIFT_ADJUST: time to compensate for clock drift relative to other
+ * mesh nodes
  */
 enum mesh_deferred_task_flags {
         MESH_WORK_HOUSEKEEPING,
         MESH_WORK_GROW_MPATH_TABLE,
         MESH_WORK_GROW_MPP_TABLE,
         MESH_WORK_ROOT,
+        MESH_WORK_DRIFT_ADJUST,
 };
 
 /**
@@ -234,6 +251,7 @@ void ieee80211_mesh_init_sdata(struct ieee80211_sub_if_data *sdata);
 void ieee80211_start_mesh(struct ieee80211_sub_if_data *sdata);
 void ieee80211_stop_mesh(struct ieee80211_sub_if_data *sdata);
 void ieee80211_mesh_root_setup(struct ieee80211_if_mesh *ifmsh);
+struct ieee80211_mesh_sync_ops *ieee80211_mesh_sync_ops_get(u8 method);
 
 /* Mesh paths */
 int mesh_nexthop_lookup(struct sk_buff *skb,
@@ -327,6 +345,7 @@ void ieee80211_mesh_quiesce(struct ieee80211_sub_if_data *sdata);
 void ieee80211_mesh_restart(struct ieee80211_sub_if_data *sdata);
 void mesh_plink_quiesce(struct sta_info *sta);
 void mesh_plink_restart(struct sta_info *sta);
+void mesh_sync_adjust_tbtt(struct ieee80211_sub_if_data *sdata);
 #else
 #define mesh_allocated  0
 static inline void
diff --git a/net/mac80211/mesh_sync.c b/net/mac80211/mesh_sync.c
new file mode 100644
index 000000000000..f78b0139856f
--- /dev/null
+++ b/net/mac80211/mesh_sync.c
@@ -0,0 +1,296 @@
+/*
+ * Copyright 2011-2012, Pavel Zubarev <pavel.zubarev@gmail.com>
+ * Copyright 2011-2012, Marco Porsch <marco.porsch@s2005.tu-chemnitz.de>
+ * Copyright 2011-2012, cozybit Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include "ieee80211_i.h"
+#include "mesh.h"
+#include "driver-ops.h"
+
+#ifdef CONFIG_MAC80211_VERBOSE_MESH_SYNC_DEBUG
+#define msync_dbg(fmt, args...) \
+        printk(KERN_DEBUG "Mesh sync (%s): " fmt "\n", sdata->name, ##args)
+#else
+#define msync_dbg(fmt, args...)   do { (void)(0); } while (0)
+#endif
+
+/* This is not in the standard.  It represents a tolerable tbtt drift below
+ * which we do no TSF adjustment.
+ */
+#define TBTT_MINIMUM_ADJUSTMENT 10
+
+struct sync_method {
+        u8 method;
+        struct ieee80211_mesh_sync_ops ops;
+};
+
+/**
+ * mesh_peer_tbtt_adjusting - check if an mp is currently adjusting its TBTT
+ *
+ * @ie: information elements of a management frame from the mesh peer
+ */
+static bool mesh_peer_tbtt_adjusting(struct ieee802_11_elems *ie)
+{
+        return (ie->mesh_config->meshconf_cap &
+            MESHCONF_CAPAB_TBTT_ADJUSTING) != 0;
+}
+
+void mesh_sync_adjust_tbtt(struct ieee80211_sub_if_data *sdata)
+{
+        struct ieee80211_local *local = sdata->local;
+        struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
+        /* sdata->vif.bss_conf.beacon_int in 1024us units, 0.04% */
+        u64 beacon_int_fraction = sdata->vif.bss_conf.beacon_int * 1024 / 2500;
+        u64 tsf;
+        u64 tsfdelta;
+
+        spin_lock_bh(&ifmsh->sync_offset_lock);
+
+        if (ifmsh->sync_offset_clockdrift_max < beacon_int_fraction) {
+                msync_dbg("TBTT : max clockdrift=%lld; adjusting",
+                        (long long) ifmsh->sync_offset_clockdrift_max);
+                tsfdelta = -ifmsh->sync_offset_clockdrift_max;
+                ifmsh->sync_offset_clockdrift_max = 0;
+        } else {
+                msync_dbg("TBTT : max clockdrift=%lld; adjusting by %llu",
+                        (long long) ifmsh->sync_offset_clockdrift_max,
+                        (unsigned long long) beacon_int_fraction);
+                tsfdelta = -beacon_int_fraction;
+                ifmsh->sync_offset_clockdrift_max -= beacon_int_fraction;
+        }
+
+        tsf = drv_get_tsf(local, sdata);
+        if (tsf != -1ULL)
+                drv_set_tsf(local, sdata, tsf + tsfdelta);
+        spin_unlock_bh(&ifmsh->sync_offset_lock);
+}
+
+static void mesh_sync_offset_rx_bcn_presp(struct ieee80211_sub_if_data *sdata,
+                                   u16 stype,
+                                   struct ieee80211_mgmt *mgmt,
+                                   struct ieee802_11_elems *elems,
+                                   struct ieee80211_rx_status *rx_status)
+{
+        struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
+        struct ieee80211_local *local = sdata->local;
+        struct sta_info *sta;
+        u64 t_t, t_r;
+
+        WARN_ON(ifmsh->mesh_sp_id != IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET);
+
+        /* standard mentions only beacons */
+        if (stype != IEEE80211_STYPE_BEACON)
+                return;
+
+        /* The current tsf is a first approximation for the timestamp
+         * for the received beacon.  Further down we try to get a
+         * better value from the rx_status->mactime field if
+         * available. Also we have to call drv_get_tsf() before
+         * entering the rcu-read section.*/
+        t_r = drv_get_tsf(local, sdata);
+
+        rcu_read_lock();
+        sta = sta_info_get(sdata, mgmt->sa);
+        if (!sta)
+                goto no_sync;
+
+        /* check offset sync conditions (13.13.2.2.1)
+         *
+         * TODO also sync to
+         * dot11MeshNbrOffsetMaxNeighbor non-peer non-MBSS neighbors
+         */
+
+        if (elems->mesh_config && mesh_peer_tbtt_adjusting(elems)) {
+                clear_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
+                msync_dbg("STA %pM : is adjusting TBTT", sta->sta.addr);
+                goto no_sync;
+        }
+
+        if (rx_status->flag & RX_FLAG_MACTIME_MPDU && rx_status->mactime) {
+                /*
+                 * The mactime is defined as the time the first data symbol
+                 * of the frame hits the PHY, and the timestamp of the beacon
+                 * is defined as "the time that the data symbol containing the
+                 * first bit of the timestamp is transmitted to the PHY plus
+                 * the transmitting STA's delays through its local PHY from the
+                 * MAC-PHY interface to its interface with the WM" (802.11
+                 * 11.1.2)
+                 *
+                 * T_r, in 13.13.2.2.2, is just defined as "the frame reception
+                 * time" but we unless we interpret that time to be the same
+                 * time of the beacon timestamp, the offset calculation will be
+                 * off.  Below we adjust t_r to be "the time at which the first
+                 * symbol of the timestamp element in the beacon is received".
+                 * This correction depends on the rate.
+                 *
+                 * Based on similar code in ibss.c
+                 */
+                int rate;
+
+                if (rx_status->flag & RX_FLAG_HT) {
+                        /* TODO:
+                         * In principle there could be HT-beacons (Dual Beacon
+                         * HT Operation options), but for now ignore them and
+                         * just use the primary (i.e. non-HT) beacons for
+                         * synchronization.
+                         * */
+                        goto no_sync;
+                } else
+                        rate = local->hw.wiphy->bands[rx_status->band]->
+                                bitrates[rx_status->rate_idx].bitrate;
+
+                /* 24 bytes of header * 8 bits/byte *
+                 * 10*(100 Kbps)/Mbps / rate (100 Kbps)*/
+                t_r = rx_status->mactime + (24 * 8 * 10 / rate);
+        }
+
+        /* Timing offset calculation (see 13.13.2.2.2) */
+        t_t = le64_to_cpu(mgmt->u.beacon.timestamp);
+        sta->t_offset = t_t - t_r;
+
+        if (test_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN)) {
+                s64 t_clockdrift = sta->t_offset_setpoint
+                                   - sta->t_offset;
+
+                msync_dbg("STA %pM : sta->t_offset=%lld,"
+                          " sta->t_offset_setpoint=%lld,"
+                          " t_clockdrift=%lld",
+                          sta->sta.addr,
+                          (long long) sta->t_offset,
+                          (long long)
+                          sta->t_offset_setpoint,
+                          (long long) t_clockdrift);
+                rcu_read_unlock();
+
+                spin_lock_bh(&ifmsh->sync_offset_lock);
+                if (t_clockdrift >
+                    ifmsh->sync_offset_clockdrift_max)
+                        ifmsh->sync_offset_clockdrift_max
+                                = t_clockdrift;
+                spin_unlock_bh(&ifmsh->sync_offset_lock);
+
+        } else {
+                sta->t_offset_setpoint = sta->t_offset;
+                set_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
+                msync_dbg("STA %pM : offset was invalid, "
+                          " sta->t_offset=%lld",
+                          sta->sta.addr,
+                          (long long) sta->t_offset);
+                rcu_read_unlock();
+        }
+        return;
+
+no_sync:
+        rcu_read_unlock();
+}
+
+static void mesh_sync_offset_adjust_tbtt(struct ieee80211_sub_if_data *sdata)
+{
+        struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
+
+        WARN_ON(ifmsh->mesh_sp_id
+                != IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET);
+        BUG_ON(!rcu_read_lock_held());
+
+        spin_lock_bh(&ifmsh->sync_offset_lock);
+
+        if (ifmsh->sync_offset_clockdrift_max >
+                TBTT_MINIMUM_ADJUSTMENT) {
+                /* Since ajusting the tsf here would
+                 * require a possibly blocking call
+                 * to the driver tsf setter, we punt
+                 * the tsf adjustment to the mesh tasklet
+                 */
+                msync_dbg("TBTT : kicking off TBTT "
+                          "adjustment with "
+                          "clockdrift_max=%lld",
+                  ifmsh->sync_offset_clockdrift_max);
+                set_bit(MESH_WORK_DRIFT_ADJUST,
+                        &ifmsh->wrkq_flags);
+        } else {
+                msync_dbg("TBTT : max clockdrift=%lld; "
+                          "too small to adjust",
+                          (long long)
+                       ifmsh->sync_offset_clockdrift_max);
+                ifmsh->sync_offset_clockdrift_max = 0;
+        }
+        spin_unlock_bh(&ifmsh->sync_offset_lock);
+}
+
+static const u8 *mesh_get_vendor_oui(struct ieee80211_sub_if_data *sdata)
+{
+        struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
+        u8 offset;
+
+        if (!ifmsh->ie || !ifmsh->ie_len)
+                return NULL;
+
+        offset = ieee80211_ie_split_vendor(ifmsh->ie,
+                                        ifmsh->ie_len, 0);
+
+        if (!offset)
+                return NULL;
+
+        return ifmsh->ie + offset + 2;
+}
+
+static void mesh_sync_vendor_rx_bcn_presp(struct ieee80211_sub_if_data *sdata,
+                                   u16 stype,
+                                   struct ieee80211_mgmt *mgmt,
+                                   struct ieee802_11_elems *elems,
+                                   struct ieee80211_rx_status *rx_status)
+{
+        const u8 *oui;
+
+        WARN_ON(sdata->u.mesh.mesh_sp_id != IEEE80211_SYNC_METHOD_VENDOR);
+        msync_dbg("called mesh_sync_vendor_rx_bcn_presp");
+        oui = mesh_get_vendor_oui(sdata);
+        /*  here you would implement the vendor offset tracking for this oui */
+}
+
+static void mesh_sync_vendor_adjust_tbtt(struct ieee80211_sub_if_data *sdata)
+{
+        const u8 *oui;
+
+        WARN_ON(sdata->u.mesh.mesh_sp_id != IEEE80211_SYNC_METHOD_VENDOR);
+        msync_dbg("called mesh_sync_vendor_adjust_tbtt");
+        oui = mesh_get_vendor_oui(sdata);
+        /*  here you would implement the vendor tsf adjustment for this oui */
+}
+
+/* global variable */
+static struct sync_method sync_methods[] = {
+        {
+                .method = IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET,
+                .ops = {
+                        .rx_bcn_presp = &mesh_sync_offset_rx_bcn_presp,
+                        .adjust_tbtt = &mesh_sync_offset_adjust_tbtt,
+                }
+        },
+        {
+                .method = IEEE80211_SYNC_METHOD_VENDOR,
+                .ops = {
+                        .rx_bcn_presp = &mesh_sync_vendor_rx_bcn_presp,
+                        .adjust_tbtt = &mesh_sync_vendor_adjust_tbtt,
+                }
+        },
+};
+
+struct ieee80211_mesh_sync_ops *ieee80211_mesh_sync_ops_get(u8 method)
+{
+        struct ieee80211_mesh_sync_ops *ops = NULL;
+        u8 i;
+
+        for (i = 0 ; i < ARRAY_SIZE(sync_methods); ++i) {
+                if (sync_methods[i].method == method) {
+                        ops = &sync_methods[i].ops;
+                        break;
+                }
+        }
+        return ops;
+}
diff --git a/net/mac80211/sta_info.h b/net/mac80211/sta_info.h
index b1b4b1413c74..f75f5d9ac06d 100644
--- a/net/mac80211/sta_info.h
+++ b/net/mac80211/sta_info.h
@@ -55,6 +55,7 @@
  * @WLAN_STA_4ADDR_EVENT: 4-addr event was already sent for this frame.
  * @WLAN_STA_INSERTED: This station is inserted into the hash table.
  * @WLAN_STA_RATE_CONTROL: rate control was initialized for this station.
+ * @WLAN_STA_TOFFSET_KNOWN: toffset calculated for this station is valid.
  */
 enum ieee80211_sta_info_flags {
         WLAN_STA_AUTH,
@@ -76,6 +77,7 @@ enum ieee80211_sta_info_flags {
         WLAN_STA_4ADDR_EVENT,
         WLAN_STA_INSERTED,
         WLAN_STA_RATE_CONTROL,
+        WLAN_STA_TOFFSET_KNOWN,
 };
 
 #define STA_TID_NUM 16
@@ -268,6 +270,7 @@ struct sta_ampdu_mlme {
  * @plink_timeout: timeout of peer link
  * @plink_timer: peer link watch timer
  * @plink_timer_was_running: used by suspend/resume to restore timers
+ * @t_offset: timing offset relative to this host
  * @debugfs: debug filesystem info
  * @dead: set to true when sta is unlinked
  * @uploaded: set to true when sta is uploaded to the driver
@@ -357,6 +360,8 @@ struct sta_info {
         enum nl80211_plink_state plink_state;
         u32 plink_timeout;
         struct timer_list plink_timer;
+        s64 t_offset;
+        s64 t_offset_setpoint;
 #endif
 
 #ifdef CONFIG_MAC80211_DEBUGFS
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index e0b89780b472..daab5adeb93c 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -2373,6 +2373,7 @@ struct sk_buff *ieee80211_beacon_get_tim(struct ieee80211_hw *hw,
                                                  IEEE80211_STYPE_BEACON);
         } else if (ieee80211_vif_is_mesh(&sdata->vif)) {
                 struct ieee80211_mgmt *mgmt;
+                struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
                 u8 *pos;
                 int hdr_len = offsetof(struct ieee80211_mgmt, u.beacon) +
                               sizeof(mgmt->u.beacon);
@@ -2382,6 +2383,10 @@ struct sk_buff *ieee80211_beacon_get_tim(struct ieee80211_hw *hw,
                         goto out;
 #endif
 
+                if (ifmsh->sync_ops)
+                        ifmsh->sync_ops->adjust_tbtt(
+                                                sdata);
+
                 skb = dev_alloc_skb(local->tx_headroom +
                                     hdr_len +
                                     2 + /* NULL SSID */