mac80211解析二

在实现无线网络设备分配时，

ieee80211_register_hw

关联了

ieee80211_ops

结构体：

ieee80211_ops

结构体是mac80211到设备驱动的回调操作函数集合，定义如下：

/**
* struct ieee80211_ops - callbacks from mac80211 to the driver
*
* This structure contains various callbacks that the driver may
* handle or, in some cases, must handle, for example to configure
* the hardware to a new channel or to transmit a frame.
*/
struct ieee80211_ops {
void (*tx)(struct ieee80211_hw *hw,
struct ieee80211_tx_control *control,
struct sk_buff *skb);
int (*start)(struct ieee80211_hw *hw);
void (*stop)(struct ieee80211_hw *hw);
#ifdef CONFIG_PM
int (*suspend)(struct ieee80211_hw *hw, struct cfg80211_wowlan *wowlan);
int (*resume)(struct ieee80211_hw *hw);
void (*set_wakeup)(struct ieee80211_hw *hw, bool enabled);
#endif
int (*add_interface)(struct ieee80211_hw *hw,
struct ieee80211_vif *vif);
int (*change_interface)(struct ieee80211_hw *hw,
struct ieee80211_vif *vif,
enum nl80211_iftype new_type, bool p2p);
void (*remove_interface)(struct ieee80211_hw *hw,
struct ieee80211_vif *vif);
int (*config)(struct ieee80211_hw *hw, u32 changed);
void (*bss_info_changed)(struct ieee80211_hw *hw,
struct ieee80211_vif *vif,
struct ieee80211_bss_conf *info,
u32 changed);

int (*start_ap)(struct ieee80211_hw *hw, struct ieee80211_vif *vif);
void (*stop_ap)(struct ieee80211_hw *hw, struct ieee80211_vif *vif);

u64 (*prepare_multicast)(struct ieee80211_hw *hw,
struct netdev_hw_addr_list *mc_list);
void (*configure_filter)(struct ieee80211_hw *hw,
unsigned int changed_flags,
unsigned int *total_flags,
u64 multicast);
int (*set_tim)(struct ieee80211_hw *hw, struct ieee80211_sta *sta,
bool set);
int (*set_key)(struct ieee80211_hw *hw, enum set_key_cmd cmd,
struct ieee80211_vif *vif, struct ieee80211_sta *sta,
struct ieee80211_key_conf *key);
void (*update_tkip_key)(struct ieee80211_hw *hw,
struct ieee80211_vif *vif,
struct ieee80211_key_conf *conf,
struct ieee80211_sta *sta,
u32 iv32, u16 *phase1key);
void (*set_rekey_data)(struct ieee80211_hw *hw,
struct ieee80211_vif *vif,
struct cfg80211_gtk_rekey_data *data);
void (*set_default_unicast_key)(struct ieee80211_hw *hw,
struct ieee80211_vif *vif, int idx);
int (*hw_scan)(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
struct cfg80211_scan_request *req);
void (*cancel_hw_scan)(struct ieee80211_hw *hw,
struct ieee80211_vif *vif);
int (*sched_scan_start)(struct ieee80211_hw *hw,
struct ieee80211_vif *vif,
struct cfg80211_sched_scan_request *req,
struct ieee80211_sched_scan_ies *ies);
int (*sched_scan_stop)(struct ieee80211_hw *hw,
struct ieee80211_vif *vif);
void (*sw_scan_start)(struct ieee80211_hw *hw);
void (*sw_scan_complete)(struct ieee80211_hw *hw);
int (*get_stats)(struct ieee80211_hw *hw,
struct ieee80211_low_level_stats *stats);
void (*get_tkip_seq)(struct ieee80211_hw *hw, u8 hw_key_idx,
u32 *iv32, u16 *iv16);
int (*set_frag_threshold)(struct ieee80211_hw *hw, u32 value);
int (*set_rts_threshold)(struct ieee80211_hw *hw, u32 value);
int (*sta_add)(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
struct ieee80211_sta *sta);
int (*sta_remove)(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
struct ieee80211_sta *sta);
#ifdef CPTCFG_MAC80211_DEBUGFS
void (*sta_add_debugfs)(struct ieee80211_hw *hw,
struct ieee80211_vif *vif,
struct ieee80211_sta *sta,
struct dentry *dir);
void (*sta_remove_debugfs)(struct ieee80211_hw *hw,
struct ieee80211_vif *vif,
struct ieee80211_sta *sta,
struct dentry *dir);
#endif
void (*sta_notify)(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
enum sta_notify_cmd, struct ieee80211_sta *sta);
int (*sta_state)(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
struct ieee80211_sta *sta,
enum ieee80211_sta_state old_state,
enum ieee80211_sta_state new_state);
void (*sta_pre_rcu_remove)(struct ieee80211_hw *hw,
struct ieee80211_vif *vif,
struct ieee80211_sta *sta);
void (*sta_rc_update)(struct ieee80211_hw *hw,
struct ieee80211_vif *vif,
struct ieee80211_sta *sta,
u32 changed);
int (*conf_tx)(struct ieee80211_hw *hw,
struct ieee80211_vif *vif, u16 ac,
const struct ieee80211_tx_queue_params *params);
u64 (*get_tsf)(struct ieee80211_hw *hw, struct ieee80211_vif *vif);
void (*set_tsf)(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
u64 tsf);
void (*reset_tsf)(struct ieee80211_hw *hw, struct ieee80211_vif *vif);
int (*tx_last_beacon)(struct ieee80211_hw *hw);
int (*ampdu_action)(struct ieee80211_hw *hw,
struct ieee80211_vif *vif,
enum ieee80211_ampdu_mlme_action action,
struct ieee80211_sta *sta, u16 tid, u16 *ssn,
u8 buf_size);
int (*get_survey)(struct ieee80211_hw *hw, int idx,
struct survey_info *survey);
void (*rfkill_poll)(struct ieee80211_hw *hw);
void (*set_coverage_class)(struct ieee80211_hw *hw, u8 coverage_class);
#ifdef CPTCFG_NL80211_TESTMODE
int (*testmode_cmd)(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
void *data, int len);
int (*testmode_dump)(struct ieee80211_hw *hw, struct sk_buff *skb,
struct netlink_callback *cb,
void *data, int len);
#endif
void (*flush)(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
u32 queues, bool drop);
void (*channel_switch)(struct ieee80211_hw *hw,
struct ieee80211_channel_switch *ch_switch);
int (*set_antenna)(struct ieee80211_hw *hw, u32 tx_ant, u32 rx_ant);
int (*get_antenna)(struct ieee80211_hw *hw, u32 *tx_ant, u32 *rx_ant);

int (*remain_on_channel)(struct ieee80211_hw *hw,
struct ieee80211_vif *vif,
struct ieee80211_channel *chan,
int duration,
enum ieee80211_roc_type type);
int (*cancel_remain_on_channel)(struct ieee80211_hw *hw);
int (*set_ringparam)(struct ieee80211_hw *hw, u32 tx, u32 rx);
void (*get_ringparam)(struct ieee80211_hw *hw,
u32 *tx, u32 *tx_max, u32 *rx, u32 *rx_max);
bool (*tx_frames_pending)(struct ieee80211_hw *hw);
int (*set_bitrate_mask)(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
const struct cfg80211_bitrate_mask *mask);
void (*rssi_callback)(struct ieee80211_hw *hw,
struct ieee80211_vif *vif,
enum ieee80211_rssi_event rssi_event);

void (*allow_buffered_frames)(struct ieee80211_hw *hw,
struct ieee80211_sta *sta,
u16 tids, int num_frames,
enum ieee80211_frame_release_type reason,
bool more_data);
void (*release_buffered_frames)(struct ieee80211_hw *hw,
struct ieee80211_sta *sta,
u16 tids, int num_frames,
enum ieee80211_frame_release_type reason,
bool more_data);

int (*get_et_sset_count)(struct ieee80211_hw *hw,
struct ieee80211_vif *vif, int sset);
void    (*get_et_stats)(struct ieee80211_hw *hw,
struct ieee80211_vif *vif,
struct ethtool_stats *stats, u64 *data);
void    (*get_et_strings)(struct ieee80211_hw *hw,
struct ieee80211_vif *vif,
u32 sset, u8 *data);
int (*get_rssi)(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
struct ieee80211_sta *sta, s8 *rssi_dbm);

void    (*mgd_prepare_tx)(struct ieee80211_hw *hw,
struct ieee80211_vif *vif);

int (*add_chanctx)(struct ieee80211_hw *hw,
struct ieee80211_chanctx_conf *ctx);
void (*remove_chanctx)(struct ieee80211_hw *hw,
struct ieee80211_chanctx_conf *ctx);
void (*change_chanctx)(struct ieee80211_hw *hw,
struct ieee80211_chanctx_conf *ctx,
u32 changed);
int (*assign_vif_chanctx)(struct ieee80211_hw *hw,
struct ieee80211_vif *vif,
struct ieee80211_chanctx_conf *ctx);
void (*unassign_vif_chanctx)(struct ieee80211_hw *hw,
struct ieee80211_vif *vif,
struct ieee80211_chanctx_conf *ctx);

void (*restart_complete)(struct ieee80211_hw *hw);

#if IS_ENABLED(CONFIG_IPV6)
void (*ipv6_addr_change)(struct ieee80211_hw *hw,
struct ieee80211_vif *vif,
struct inet6_dev *idev);
#endif
void (*channel_switch_beacon)(struct ieee80211_hw *hw,
struct ieee80211_vif *vif,
struct cfg80211_chan_def *chandef);

int (*join_ibss)(struct ieee80211_hw *hw, struct ieee80211_vif *vif);
void (*leave_ibss)(struct ieee80211_hw *hw, struct ieee80211_vif *vif);
u32 (*get_expected_throughput)(struct ieee80211_sta *sta);
};

ieee80211_register_hw

中初始化了tasklet的响应中断，如下，

tasklet_init(&local->tasklet,
ieee80211_tasklet_handler,
(unsigned long) local);

其中中断函数

ieee80211_tasklet_handler

实现网络数据的中断接收。

static void ieee80211_tasklet_handler(unsigned long data)
{
struct ieee80211_local *local = (struct ieee80211_local *) data;
struct sk_buff *skb;

while ((skb = skb_dequeue(&local->skb_queue)) ||
(skb = skb_dequeue(&local->skb_queue_unreliable))) {
switch (skb->pkt_type) {
case IEEE80211_RX_MSG:
/* Clear skb->pkt_type in order to not confuse kernel
* netstack. */
skb->pkt_type = 0;
ieee80211_rx(&local->hw, skb);
break;
case IEEE80211_TX_STATUS_MSG:
skb->pkt_type = 0;
ieee80211_tx_status(&local->hw, skb);
break;
default:
WARN(1, "mac80211: Packet is of unknown type %d\n",
skb->pkt_type);
dev_kfree_skb(skb);
break;
}
}
}

经过数据包的类型判断后，调用

ieee80211_rx

函数进行数据接收，

/*
* This is the receive path handler. It is called by a low level driver when an
* 802.11 MPDU is received from the hardware.
*/
void ieee80211_rx(struct ieee80211_hw *hw, struct sk_buff *skb)
{
struct ieee80211_local *local = hw_to_local(hw);
struct ieee80211_rate *rate = NULL;
struct ieee80211_supported_band *sband;
struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);

WARN_ON_ONCE(softirq_count() == 0);

if (WARN_ON(status->band >= IEEE80211_NUM_BANDS))
goto drop;

sband = local->hw.wiphy->bands[status->band];
if (WARN_ON(!sband))
goto drop;

/*
* If we're suspending, it is possible although not too likely
* that we'd be receiving frames after having already partially
* quiesced the stack. We can't process such frames then since
* that might, for example, cause stations to be added or other
* driver callbacks be invoked.
*/
if (unlikely(local->quiescing || local->suspended))
goto drop;

/* We might be during a HW reconfig, prevent Rx for the same reason */
if (unlikely(local->in_reconfig))
goto drop;

/*
* The same happens when we're not even started,
* but that's worth a warning.
*/
if (WARN_ON(!local->started))
goto drop;

if (likely(!(status->flag & RX_FLAG_FAILED_PLCP_CRC))) {
/*
* Validate the rate, unless a PLCP error means that
* we probably can't have a valid rate here anyway.
*/

if (status->flag & RX_FLAG_HT) {
/*
* rate_idx is MCS index, which can be [0-76]
* as documented on:
*
* http://wireless.kernel.org/en/developers/Documentation/ieee80211/802.11n *
* Anything else would be some sort of driver or
* hardware error. The driver should catch hardware
* errors.
*/
if (WARN(status->rate_idx > 76,
"Rate marked as an HT rate but passed "
"status->rate_idx is not "
"an MCS index [0-76]: %d (0x%02x)\n",
status->rate_idx,
status->rate_idx))
goto drop;
} else if (status->flag & RX_FLAG_VHT) {
if (WARN_ONCE(status->rate_idx > 9 ||
!status->vht_nss ||
status->vht_nss > 8,
"Rate marked as a VHT rate but data is invalid: MCS: %d, NSS: %d\n",
status->rate_idx, status->vht_nss))
goto drop;
} else {
if (WARN_ON(status->rate_idx >= sband->n_bitrates))
goto drop;
rate = &sband->bitrates[status->rate_idx];
}
}

status->rx_flags = 0;

/*
* key references and virtual interfaces are protected using RCU
* and this requires that we are in a read-side RCU section during
* receive processing
*/
rcu_read_lock();

/*
* Frames with failed FCS/PLCP checksum are not returned,
* all other frames are returned without radiotap header
* if it was previously present.
* Also, frames with less than 16 bytes are dropped.
*/
skb = ieee80211_rx_monitor(local, skb, rate);
if (!skb) {
rcu_read_unlock();
return;
}

ieee80211_tpt_led_trig_rx(local,
((struct ieee80211_hdr *)skb->data)->frame_control,
skb->len);
__ieee80211_rx_handle_packet(hw, skb);

rcu_read_unlock();

return;
drop:
kfree_skb(skb);
}

在

ieee80211_rx()

函数中调用

ieee80211_rx_monitor()

拷贝帧传递给所有监听接口

/*
* This function copies a received frame to all monitor interfaces and
* returns a cleaned-up SKB that no longer includes the FCS nor the
* radiotap header the driver might have added.
*/
static struct sk_buff *
ieee80211_rx_monitor(struct ieee80211_local *local, struct sk_buff *origskb,
struct ieee80211_rate *rate)
{
struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(origskb);
struct ieee80211_sub_if_data *sdata;
int needed_headroom;
struct sk_buff *skb, *skb2;
struct net_device *prev_dev = NULL;
int present_fcs_len = 0;

/*
* First, we may need to make a copy of the skb because
*  (1) we need to modify it for radiotap (if not present), and
*  (2) the other RX handlers will modify the skb we got.
*
* We don't need to, of course, if we aren't going to return
* the SKB because it has a bad FCS/PLCP checksum.
*/

if (local->hw.flags & IEEE80211_HW_RX_INCLUDES_FCS)
present_fcs_len = FCS_LEN;

/* ensure hdr->frame_control is in skb head */
if (!pskb_may_pull(origskb, 2)) {
dev_kfree_skb(origskb);
return NULL;
}

if (!local->monitors) {
if (should_drop_frame(origskb, present_fcs_len)) {
dev_kfree_skb(origskb);
return NULL;
}

return remove_monitor_info(local, origskb);
}

/* room for the radiotap header based on driver features */
needed_headroom = ieee80211_rx_radiotap_space(local, status);

if (should_drop_frame(origskb, present_fcs_len)) {
/* only need to expand headroom if necessary */
skb = origskb;
origskb = NULL;

/*
* This shouldn't trigger often because most devices have an
* RX header they pull before we get here, and that should
* be big enough for our radiotap information. We should
* probably export the length to drivers so that we can have
* them allocate enough headroom to start with.
*/
if (skb_headroom(skb) < needed_headroom &&
pskb_expand_head(skb, needed_headroom, 0, GFP_ATOMIC)) {
dev_kfree_skb(skb);
return NULL;
}
} else {
/*
* Need to make a copy and possibly remove radiotap header
* and FCS from the original.
*/
skb = skb_copy_expand(origskb, needed_headroom, 0, GFP_ATOMIC);

origskb = remove_monitor_info(local, origskb);

if (!skb)
return origskb;
}

/* prepend radiotap information */
ieee80211_add_rx_radiotap_header(local, skb, rate, needed_headroom,
true);

skb_reset_mac_header(skb);
skb->ip_summed = CHECKSUM_UNNECESSARY;
skb->pkt_type = PACKET_OTHERHOST;
skb->protocol = htons(ETH_P_802_2);

list_for_each_entry_rcu(sdata, &local->interfaces, list) {
if (sdata->vif.type != NL80211_IFTYPE_MONITOR)
continue;

if (sdata->u.mntr_flags & MONITOR_FLAG_COOK_FRAMES)
continue;

if (!ieee80211_sdata_running(sdata))
continue;

if (prev_dev) {
skb2 = skb_clone(skb, GFP_ATOMIC);
if (skb2) {
skb2->dev = prev_dev;
netif_receive_skb(skb2);
}
}

prev_dev = sdata->dev;
sdata->dev->stats.rx_packets++;
sdata->dev->stats.rx_bytes += skb->len;
}

if (prev_dev) {
skb->dev = prev_dev;
netif_receive_skb(skb);
} else
dev_kfree_skb(skb);

return origskb;
}

ieee80211_rx

在调用

__ieee80211_rx_handle_packet

进行数据帧操作，

__ieee80211_rx_handle_packet
---->ieee80211_prepare_and_rx_handle
---->ieee80211_invoke_rx_handlers
---->ieee80211_rx_handlers

经过一些列数据帧的判别，最后在

ieee80211_rx_handlers

中实现接收处理。

在

ieee80211_register_hw

注册函数中，使用了

ieee80211_if_add

函数创建了网络接口，并提供了网络接口操作函数

net_device_ops

，定义如下：

static const struct net_device_ops ieee80211_dataif_ops = {
.ndo_open       = ieee80211_open,
.ndo_stop       = ieee80211_stop,
.ndo_uninit     = ieee80211_uninit,
.ndo_start_xmit     = ieee80211_subif_start_xmit,
.ndo_set_rx_mode    = ieee80211_set_multicast_list,
.ndo_change_mtu     = ieee80211_change_mtu,
.ndo_set_mac_address    = ieee80211_change_mac,
.ndo_select_queue   = ieee80211_netdev_select_queue,
};

其中

ieee80211_subif_start_xmit

实现了数据的发送，

/**
* ieee80211_subif_start_xmit - netif start_xmit function for Ethernet-type
* subinterfaces (wlan#, WDS, and VLAN interfaces)
* This function takes in an Ethernet header and encapsulates it with suitable
* IEEE 802.11 header based on which interface the packet is coming in. The
* encapsulated packet will then be passed to master interface, wlan#.11, for
* transmission (through low-level driver).
*/
netdev_tx_t ieee80211_subif_start_xmit(struct sk_buff *skb,
struct net_device *dev)
{
struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev);
struct ieee80211_local *local = sdata->local;
struct ieee80211_tx_info *info;
int head_need;
u16 ethertype, hdrlen,  meshhdrlen = 0;
__le16 fc;
struct ieee80211_hdr hdr;
struct ieee80211s_hdr mesh_hdr __maybe_unused;
struct mesh_path __maybe_unused *mppath = NULL, *mpath = NULL;
const u8 *encaps_data;
int encaps_len, skip_header_bytes;
int nh_pos, h_pos;
struct sta_info *sta = NULL;
bool wme_sta = false, authorized = false, tdls_auth = false;
bool tdls_direct = false;
bool multicast;
u32 info_flags = 0;
u16 info_id = 0;
struct ieee80211_chanctx_conf *chanctx_conf;
struct ieee80211_sub_if_data *ap_sdata;
enum ieee80211_band band;

if (unlikely(skb->len < ETH_HLEN))
goto fail;

/* convert Ethernet header to proper 802.11 header (based on
* operation mode) */
ethertype = (skb->data[12] << 8) | skb->data[13];
fc = cpu_to_le16(IEEE80211_FTYPE_DATA | IEEE80211_STYPE_DATA);

rcu_read_lock();

/* Measure frame arrival for Tx latency statistics calculation */
ieee80211_tx_latency_start_msrmnt(local, skb);

switch (sdata->vif.type) {
case NL80211_IFTYPE_AP_VLAN:
sta = rcu_dereference(sdata->u.vlan.sta);
if (sta) {
fc |= cpu_to_le16(IEEE80211_FCTL_FROMDS | IEEE80211_FCTL_TODS);
/* RA TA DA SA */
memcpy(hdr.addr1, sta->sta.addr, ETH_ALEN);
memcpy(hdr.addr2, sdata->vif.addr, ETH_ALEN);
memcpy(hdr.addr3, skb->data, ETH_ALEN);
memcpy(hdr.addr4, skb->data + ETH_ALEN, ETH_ALEN);
hdrlen = 30;
authorized = test_sta_flag(sta, WLAN_STA_AUTHORIZED);
wme_sta = test_sta_flag(sta, WLAN_STA_WME);
}
ap_sdata = container_of(sdata->bss, struct ieee80211_sub_if_data,
u.ap);
chanctx_conf = rcu_dereference(ap_sdata->vif.chanctx_conf);
if (!chanctx_conf)
goto fail_rcu;
band = chanctx_conf->def.chan->band;
if (sta)
break;
/* fall through */
case NL80211_IFTYPE_AP:
if (sdata->vif.type == NL80211_IFTYPE_AP)
chanctx_conf = rcu_dereference(sdata->vif.chanctx_conf);
if (!chanctx_conf)
goto fail_rcu;
fc |= cpu_to_le16(IEEE80211_FCTL_FROMDS);
/* DA BSSID SA */
memcpy(hdr.addr1, skb->data, ETH_ALEN);
memcpy(hdr.addr2, sdata->vif.addr, ETH_ALEN);
memcpy(hdr.addr3, skb->data + ETH_ALEN, ETH_ALEN);
hdrlen = 24;
band = chanctx_conf->def.chan->band;
break;
case NL80211_IFTYPE_WDS:
fc |= cpu_to_le16(IEEE80211_FCTL_FROMDS | IEEE80211_FCTL_TODS);
/* RA TA DA SA */
memcpy(hdr.addr1, sdata->u.wds.remote_addr, ETH_ALEN);
memcpy(hdr.addr2, sdata->vif.addr, ETH_ALEN);
memcpy(hdr.addr3, skb->data, ETH_ALEN);
memcpy(hdr.addr4, skb->data + ETH_ALEN, ETH_ALEN);
hdrlen = 30;
/*
* This is the exception! WDS style interfaces are prohibited
* when channel contexts are in used so this must be valid
*/
band = local->hw.conf.chandef.chan->band;
break;
#ifdef CPTCFG_MAC80211_MESH
case NL80211_IFTYPE_MESH_POINT:
if (!is_multicast_ether_addr(skb->data)) {
struct sta_info *next_hop;
bool mpp_lookup = true;

mpath = mesh_path_lookup(sdata, skb->data);
if (mpath) {
mpp_lookup = false;
next_hop = rcu_dereference(mpath->next_hop);
if (!next_hop ||
!(mpath->flags & (MESH_PATH_ACTIVE |
MESH_PATH_RESOLVING)))
mpp_lookup = true;
}

if (mpp_lookup)
mppath = mpp_path_lookup(sdata, skb->data);

if (mppath && mpath)
mesh_path_del(mpath->sdata, mpath->dst);
}

/*
* Use address extension if it is a packet from
* another interface or if we know the destination
* is being proxied by a portal (i.e. portal address
* differs from proxied address)
*/
if (ether_addr_equal(sdata->vif.addr, skb->data + ETH_ALEN) &&
!(mppath && !ether_addr_equal(mppath->mpp, skb->data))) {
hdrlen = ieee80211_fill_mesh_addresses(&hdr, &fc,
skb->data, skb->data + ETH_ALEN);
meshhdrlen = ieee80211_new_mesh_header(sdata, &mesh_hdr,
NULL, NULL);
} else {
/* DS -> MBSS (802.11-2012 13.11.3.3).
* For unicast with unknown forwarding information,
* destination might be in the MBSS or if that fails
* forwarded to another mesh gate. In either case
* resolution will be handled in ieee80211_xmit(), so
* leave the original DA. This also works for mcast */
const u8 *mesh_da = skb->data;

if (mppath)
mesh_da = mppath->mpp;
else if (mpath)
mesh_da = mpath->dst;

hdrlen = ieee80211_fill_mesh_addresses(&hdr, &fc,
mesh_da, sdata->vif.addr);
if (is_multicast_ether_addr(mesh_da))
/* DA TA mSA AE:SA */
meshhdrlen = ieee80211_new_mesh_header(
sdata, &mesh_hdr,
skb->data + ETH_ALEN, NULL);
else
/* RA TA mDA mSA AE:DA SA */
meshhdrlen = ieee80211_new_mesh_header(
sdata, &mesh_hdr, skb->data,
skb->data + ETH_ALEN);

}
chanctx_conf = rcu_dereference(sdata->vif.chanctx_conf);
if (!chanctx_conf)
goto fail_rcu;
band = chanctx_conf->def.chan->band;
break;
#endif
case NL80211_IFTYPE_STATION:
if (sdata->wdev.wiphy->flags & WIPHY_FLAG_SUPPORTS_TDLS) {
bool tdls_peer = false;

sta = sta_info_get(sdata, skb->data);
if (sta) {
authorized = test_sta_flag(sta,
WLAN_STA_AUTHORIZED);
wme_sta = test_sta_flag(sta, WLAN_STA_WME);
tdls_peer = test_sta_flag(sta,
WLAN_STA_TDLS_PEER);
tdls_auth = test_sta_flag(sta,
WLAN_STA_TDLS_PEER_AUTH);
}

/*
* If the TDLS link is enabled, send everything
* directly. Otherwise, allow TDLS setup frames
* to be transmitted indirectly.
*/
tdls_direct = tdls_peer && (tdls_auth ||
!(ethertype == ETH_P_TDLS && skb->len > 14 &&
skb->data[14] == WLAN_TDLS_SNAP_RFTYPE));
}

if (tdls_direct) {
/* link during setup - throw out frames to peer */
if (!tdls_auth)
goto fail_rcu;

/* DA SA BSSID */
memcpy(hdr.addr1, skb->data, ETH_ALEN);
memcpy(hdr.addr2, skb->data + ETH_ALEN, ETH_ALEN);
memcpy(hdr.addr3, sdata->u.mgd.bssid, ETH_ALEN);
hdrlen = 24;
}  else if (sdata->u.mgd.use_4addr &&
cpu_to_be16(ethertype) != sdata->control_port_protocol) {
fc |= cpu_to_le16(IEEE80211_FCTL_FROMDS |
IEEE80211_FCTL_TODS);
/* RA TA DA SA */
memcpy(hdr.addr1, sdata->u.mgd.bssid, ETH_ALEN);
memcpy(hdr.addr2, sdata->vif.addr, ETH_ALEN);
memcpy(hdr.addr3, skb->data, ETH_ALEN);
memcpy(hdr.addr4, skb->data + ETH_ALEN, ETH_ALEN);
hdrlen = 30;
} else {
fc |= cpu_to_le16(IEEE80211_FCTL_TODS);
/* BSSID SA DA */
memcpy(hdr.addr1, sdata->u.mgd.bssid, ETH_ALEN);
memcpy(hdr.addr2, skb->data + ETH_ALEN, ETH_ALEN);
memcpy(hdr.addr3, skb->data, ETH_ALEN);
hdrlen = 24;
}
chanctx_conf = rcu_dereference(sdata->vif.chanctx_conf);
if (!chanctx_conf)
goto fail_rcu;
band = chanctx_conf->def.chan->band;
break;
case NL80211_IFTYPE_ADHOC:
/* DA SA BSSID */
memcpy(hdr.addr1, skb->data, ETH_ALEN);
memcpy(hdr.addr2, skb->data + ETH_ALEN, ETH_ALEN);
memcpy(hdr.addr3, sdata->u.ibss.bssid, ETH_ALEN);
hdrlen = 24;
chanctx_conf = rcu_dereference(sdata->vif.chanctx_conf);
if (!chanctx_conf)
goto fail_rcu;
band = chanctx_conf->def.chan->band;
break;
default:
goto fail_rcu;
}

/*
* There's no need to try to look up the destination
* if it is a multicast address (which can only happen
* in AP mode)
*/
multicast = is_multicast_ether_addr(hdr.addr1);
if (!multicast) {
sta = sta_info_get(sdata, hdr.addr1);
if (sta) {
authorized = test_sta_flag(sta, WLAN_STA_AUTHORIZED);
wme_sta = test_sta_flag(sta, WLAN_STA_WME);
}
}

/* For mesh, the use of the QoS header is mandatory */
if (ieee80211_vif_is_mesh(&sdata->vif))
wme_sta = true;

/* receiver and we are QoS enabled, use a QoS type frame */
if (wme_sta && local->hw.queues >= IEEE80211_NUM_ACS) {
fc |= cpu_to_le16(IEEE80211_STYPE_QOS_DATA);
hdrlen += 2;
}

/*
* Drop unicast frames to unauthorised stations unless they are
* EAPOL frames from the local station.
*/
if (unlikely(!ieee80211_vif_is_mesh(&sdata->vif) &&
!multicast && !authorized &&
(cpu_to_be16(ethertype) != sdata->control_port_protocol ||
!ether_addr_equal(sdata->vif.addr, skb->data + ETH_ALEN)))) {
#ifdef CPTCFG_MAC80211_VERBOSE_DEBUG
net_info_ratelimited("%s: dropped frame to %pM (unauthorized port)\n",
dev->name, hdr.addr1);
#endif

I802_DEBUG_INC(local->tx_handlers_drop_unauth_port);

goto fail_rcu;
}

#if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,3,0))
if (unlikely(!multicast && skb->sk &&
skb_shinfo(skb)->tx_flags & SKBTX_WIFI_STATUS)) {
struct sk_buff *orig_skb = skb;

skb = skb_clone(skb, GFP_ATOMIC);
if (skb) {
unsigned long flags;
int id;

spin_lock_irqsave(&local->ack_status_lock, flags);
id = idr_alloc(&local->ack_status_frames, orig_skb,
1, 0x10000, GFP_ATOMIC);
spin_unlock_irqrestore(&local->ack_status_lock, flags);

if (id >= 0) {
info_id = id;
info_flags |= IEEE80211_TX_CTL_REQ_TX_STATUS;
} else if (skb_shared(skb)) {
kfree_skb(orig_skb);
} else {
kfree_skb(skb);
skb = orig_skb;
}
} else {
/* couldn't clone -- lose tx status ... */
skb = orig_skb;
}
}
#endif

/*
* If the skb is shared we need to obtain our own copy.
*/
if (skb_shared(skb)) {
struct sk_buff *tmp_skb = skb;

/* can't happen -- skb is a clone if info_id != 0 */
WARN_ON(info_id);

skb = skb_clone(skb, GFP_ATOMIC);
kfree_skb(tmp_skb);

if (!skb)
goto fail_rcu;
}

hdr.frame_control = fc;
hdr.duration_id = 0;
hdr.seq_ctrl = 0;

skip_header_bytes = ETH_HLEN;
if (ethertype == ETH_P_AARP || ethertype == ETH_P_IPX) {
encaps_data = bridge_tunnel_header;
encaps_len = sizeof(bridge_tunnel_header);
skip_header_bytes -= 2;
} else if (ethertype >= ETH_P_802_3_MIN) {
encaps_data = rfc1042_header;
encaps_len = sizeof(rfc1042_header);
skip_header_bytes -= 2;
} else {
encaps_data = NULL;
encaps_len = 0;
}

nh_pos = skb_network_header(skb) - skb->data;
h_pos = skb_transport_header(skb) - skb->data;

skb_pull(skb, skip_header_bytes);
nh_pos -= skip_header_bytes;
h_pos -= skip_header_bytes;

head_need = hdrlen + encaps_len + meshhdrlen - skb_headroom(skb);

/*
* So we need to modify the skb header and hence need a copy of
* that. The head_need variable above doesn't, so far, include
* the needed header space that we don't need right away. If we
* can, then we don't reallocate right now but only after the
* frame arrives at the master device (if it does...)
*
* If we cannot, however, then we will reallocate to include all
* the ever needed space. Also, if we need to reallocate it anyway,
* make it big enough for everything we may ever need.
*/

if (head_need > 0 || skb_cloned(skb)) {
head_need += sdata->encrypt_headroom;
head_need += local->tx_headroom;
head_need = max_t(int, 0, head_need);
if (ieee80211_skb_resize(sdata, skb, head_need, true)) {
ieee80211_free_txskb(&local->hw, skb);
skb = NULL;
goto fail_rcu;
}
}

if (encaps_data) {
memcpy(skb_push(skb, encaps_len), encaps_data, encaps_len);
nh_pos += encaps_len;
h_pos += encaps_len;
}

#ifdef CPTCFG_MAC80211_MESH
if (meshhdrlen > 0) {
memcpy(skb_push(skb, meshhdrlen), &mesh_hdr, meshhdrlen);
nh_pos += meshhdrlen;
h_pos += meshhdrlen;
}
#endif

if (ieee80211_is_data_qos(fc)) {
__le16 *qos_control;

qos_control = (__le16 *) skb_push(skb, 2);
memcpy(skb_push(skb, hdrlen - 2), &hdr, hdrlen - 2);
/*
* Maybe we could actually set some fields here, for now just
* initialise to zero to indicate no special operation.
*/
*qos_control = 0;
} else
memcpy(skb_push(skb, hdrlen), &hdr, hdrlen);

nh_pos += hdrlen;
h_pos += hdrlen;

dev->stats.tx_packets++;
dev->stats.tx_bytes += skb->len;

/* Update skb pointers to various headers since this modified frame
* is going to go through Linux networking code that may potentially
* need things like pointer to IP header. */
skb_set_mac_header(skb, 0);
skb_set_network_header(skb, nh_pos);
skb_set_transport_header(skb, h_pos);

info = IEEE80211_SKB_CB(skb);
memset(info, 0, sizeof(*info));

dev->trans_start = jiffies;

info->flags = info_flags;
info->ack_frame_id = info_id;

ieee80211_xmit(sdata, skb, band);
rcu_read_unlock();

return NETDEV_TX_OK;

fail_rcu:
rcu_read_unlock();
fail:
dev_kfree_skb(skb);
return NETDEV_TX_OK;
}

调用

ieee80211_tx

进行传输数据处理，

ieee80211_tx
----->invoke_tx_handlers
----->__ieee80211_tx
----->ieee80211_tx_frags
----->drv_tx

最后调用

drv_tx()

，把帧传递给底层驱动：

static inline void drv_tx(struct ieee80211_local *local,
struct ieee80211_tx_control *control,
struct sk_buff *skb)
{
local->ops->tx(&local->hw, control, skb);
}

可以看到，调用了

ieee80211_ops

中的

tx()

实现数据的发送。