tx.c

linux 内核源代码

		encaps_len = sizeof(rfc1042_header);
		skip_header_bytes -= 2;
	} else {
		encaps_data = NULL;
		encaps_len = 0;
	}

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

	/* TODO: implement support for fragments so that there is no need to
	 * reallocate and copy payload; it might be enough to support one
	 * extra fragment that would be copied in the beginning of the frame
	 * data.. anyway, it would be nice to include this into skb structure
	 * somehow
	 *
	 * There are few options for this:
	 * use skb->cb as an extra space for 802.11 header
	 * allocate new buffer if not enough headroom
	 * make sure that there is enough headroom in every skb by increasing
	 * build in headroom in __dev_alloc_skb() (linux/skbuff.h) and
	 * alloc_skb() (net/core/skbuff.c)
	 */
	head_need = hdrlen + encaps_len + local->tx_headroom;
	head_need -= skb_headroom(skb);

	/* We are going to modify skb data, so make a copy of it if happens to
	 * be cloned. This could happen, e.g., with Linux bridge code passing
	 * us broadcast frames. */

	if (head_need > 0 || skb_cloned(skb)) {
#if 0
		printk(KERN_DEBUG "%s: need to reallocate buffer for %d bytes "
		       "of headroom\n", dev->name, head_need);
#endif

		if (skb_cloned(skb))
			I802_DEBUG_INC(local->tx_expand_skb_head_cloned);
		else
			I802_DEBUG_INC(local->tx_expand_skb_head);
		/* Since we have to reallocate the buffer, make sure that there
		 * is enough room for possible WEP IV/ICV and TKIP (8 bytes
		 * before payload and 12 after). */
		if (pskb_expand_head(skb, (head_need > 0 ? head_need + 8 : 8),
				     12, GFP_ATOMIC)) {
			printk(KERN_DEBUG "%s: failed to reallocate TX buffer"
			       "\n", dev->name);
			goto fail;
		}
	}

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

	if (fc & IEEE80211_STYPE_QOS_DATA) {
		__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;

	pkt_data = (struct ieee80211_tx_packet_data *)skb->cb;
	memset(pkt_data, 0, sizeof(struct ieee80211_tx_packet_data));
	pkt_data->ifindex = dev->ifindex;

	skb->dev = local->mdev;
	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);

	dev->trans_start = jiffies;
	dev_queue_xmit(skb);

	return 0;

 fail:
	if (!ret)
		dev_kfree_skb(skb);

	return ret;
}

/*
 * This is the transmit routine for the 802.11 type interfaces
 * called by upper layers of the linux networking
 * stack when it has a frame to transmit
 */
int ieee80211_mgmt_start_xmit(struct sk_buff *skb, struct net_device *dev)
{
	struct ieee80211_sub_if_data *sdata;
	struct ieee80211_tx_packet_data *pkt_data;
	struct ieee80211_hdr *hdr;
	u16 fc;

	sdata = IEEE80211_DEV_TO_SUB_IF(dev);

	if (skb->len < 10) {
		dev_kfree_skb(skb);
		return 0;
	}

	if (skb_headroom(skb) < sdata->local->tx_headroom) {
		if (pskb_expand_head(skb, sdata->local->tx_headroom,
				     0, GFP_ATOMIC)) {
			dev_kfree_skb(skb);
			return 0;
		}
	}

	hdr = (struct ieee80211_hdr *) skb->data;
	fc = le16_to_cpu(hdr->frame_control);

	pkt_data = (struct ieee80211_tx_packet_data *) skb->cb;
	memset(pkt_data, 0, sizeof(struct ieee80211_tx_packet_data));
	pkt_data->ifindex = sdata->dev->ifindex;

	skb->priority = 20; /* use hardcoded priority for mgmt TX queue */
	skb->dev = sdata->local->mdev;

	/*
	 * We're using the protocol field of the the frame control header
	 * to request TX callback for hostapd. BIT(1) is checked.
	 */
	if ((fc & BIT(1)) == BIT(1)) {
		pkt_data->flags |= IEEE80211_TXPD_REQ_TX_STATUS;
		fc &= ~BIT(1);
		hdr->frame_control = cpu_to_le16(fc);
	}

	if (!(fc & IEEE80211_FCTL_PROTECTED))
		pkt_data->flags |= IEEE80211_TXPD_DO_NOT_ENCRYPT;

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

	dev_queue_xmit(skb);

	return 0;
}

/* helper functions for pending packets for when queues are stopped */

void ieee80211_clear_tx_pending(struct ieee80211_local *local)
{
	int i, j;
	struct ieee80211_tx_stored_packet *store;

	for (i = 0; i < local->hw.queues; i++) {
		if (!__ieee80211_queue_pending(local, i))
			continue;
		store = &local->pending_packet[i];
		kfree_skb(store->skb);
		for (j = 0; j < store->num_extra_frag; j++)
			kfree_skb(store->extra_frag[j]);
		kfree(store->extra_frag);
		clear_bit(IEEE80211_LINK_STATE_PENDING, &local->state[i]);
	}
}

void ieee80211_tx_pending(unsigned long data)
{
	struct ieee80211_local *local = (struct ieee80211_local *)data;
	struct net_device *dev = local->mdev;
	struct ieee80211_tx_stored_packet *store;
	struct ieee80211_txrx_data tx;
	int i, ret, reschedule = 0;

	netif_tx_lock_bh(dev);
	for (i = 0; i < local->hw.queues; i++) {
		if (__ieee80211_queue_stopped(local, i))
			continue;
		if (!__ieee80211_queue_pending(local, i)) {
			reschedule = 1;
			continue;
		}
		store = &local->pending_packet[i];
		tx.u.tx.control = &store->control;
		tx.u.tx.extra_frag = store->extra_frag;
		tx.u.tx.num_extra_frag = store->num_extra_frag;
		tx.u.tx.last_frag_hwrate = store->last_frag_hwrate;
		tx.u.tx.last_frag_rate = store->last_frag_rate;
		tx.flags = 0;
		if (store->last_frag_rate_ctrl_probe)
			tx.flags |= IEEE80211_TXRXD_TXPROBE_LAST_FRAG;
		ret = __ieee80211_tx(local, store->skb, &tx);
		if (ret) {
			if (ret == IEEE80211_TX_FRAG_AGAIN)
				store->skb = NULL;
		} else {
			clear_bit(IEEE80211_LINK_STATE_PENDING,
				  &local->state[i]);
			reschedule = 1;
		}
	}
	netif_tx_unlock_bh(dev);
	if (reschedule) {
		if (!ieee80211_qdisc_installed(dev)) {
			if (!__ieee80211_queue_stopped(local, 0))
				netif_wake_queue(dev);
		} else
			netif_schedule(dev);
	}
}

/* functions for drivers to get certain frames */

static void ieee80211_beacon_add_tim(struct ieee80211_local *local,
				     struct ieee80211_if_ap *bss,
				     struct sk_buff *skb)
{
	u8 *pos, *tim;
	int aid0 = 0;
	int i, have_bits = 0, n1, n2;

	/* Generate bitmap for TIM only if there are any STAs in power save
	 * mode. */
	read_lock_bh(&local->sta_lock);
	if (atomic_read(&bss->num_sta_ps) > 0)
		/* in the hope that this is faster than
		 * checking byte-for-byte */
		have_bits = !bitmap_empty((unsigned long*)bss->tim,
					  IEEE80211_MAX_AID+1);

	if (bss->dtim_count == 0)
		bss->dtim_count = bss->dtim_period - 1;
	else
		bss->dtim_count--;

	tim = pos = (u8 *) skb_put(skb, 6);
	*pos++ = WLAN_EID_TIM;
	*pos++ = 4;
	*pos++ = bss->dtim_count;
	*pos++ = bss->dtim_period;

	if (bss->dtim_count == 0 && !skb_queue_empty(&bss->ps_bc_buf))
		aid0 = 1;

	if (have_bits) {
		/* Find largest even number N1 so that bits numbered 1 through
		 * (N1 x 8) - 1 in the bitmap are 0 and number N2 so that bits
		 * (N2 + 1) x 8 through 2007 are 0. */
		n1 = 0;
		for (i = 0; i < IEEE80211_MAX_TIM_LEN; i++) {
			if (bss->tim[i]) {
				n1 = i & 0xfe;
				break;
			}
		}
		n2 = n1;
		for (i = IEEE80211_MAX_TIM_LEN - 1; i >= n1; i--) {
			if (bss->tim[i]) {
				n2 = i;
				break;
			}
		}

		/* Bitmap control */
		*pos++ = n1 | aid0;
		/* Part Virt Bitmap */
		memcpy(pos, bss->tim + n1, n2 - n1 + 1);

		tim[1] = n2 - n1 + 4;
		skb_put(skb, n2 - n1);
	} else {
		*pos++ = aid0; /* Bitmap control */
		*pos++ = 0; /* Part Virt Bitmap */
	}
	read_unlock_bh(&local->sta_lock);
}

struct sk_buff *ieee80211_beacon_get(struct ieee80211_hw *hw, int if_id,
				     struct ieee80211_tx_control *control)
{
	struct ieee80211_local *local = hw_to_local(hw);
	struct sk_buff *skb;
	struct net_device *bdev;
	struct ieee80211_sub_if_data *sdata = NULL;
	struct ieee80211_if_ap *ap = NULL;
	struct ieee80211_rate *rate;
	struct rate_control_extra extra;
	u8 *b_head, *b_tail;
	int bh_len, bt_len;

	bdev = dev_get_by_index(&init_net, if_id);
	if (bdev) {
		sdata = IEEE80211_DEV_TO_SUB_IF(bdev);
		ap = &sdata->u.ap;
		dev_put(bdev);
	}

	if (!ap || sdata->type != IEEE80211_IF_TYPE_AP ||
	    !ap->beacon_head) {
#ifdef CONFIG_MAC80211_VERBOSE_DEBUG
		if (net_ratelimit())
			printk(KERN_DEBUG "no beacon data avail for idx=%d "
			       "(%s)\n", if_id, bdev ? bdev->name : "N/A");
#endif /* CONFIG_MAC80211_VERBOSE_DEBUG */
		return NULL;
	}

	/* Assume we are generating the normal beacon locally */
	b_head = ap->beacon_head;
	b_tail = ap->beacon_tail;
	bh_len = ap->beacon_head_len;
	bt_len = ap->beacon_tail_len;

	skb = dev_alloc_skb(local->tx_headroom +
		bh_len + bt_len + 256 /* maximum TIM len */);
	if (!skb)
		return NULL;

	skb_reserve(skb, local->tx_headroom);
	memcpy(skb_put(skb, bh_len), b_head, bh_len);

	ieee80211_include_sequence(sdata, (struct ieee80211_hdr *)skb->data);

	ieee80211_beacon_add_tim(local, ap, skb);

	if (b_tail) {
		memcpy(skb_put(skb, bt_len), b_tail, bt_len);
	}

	if (control) {
		memset(&extra, 0, sizeof(extra));
		extra.mode = local->oper_hw_mode;

		rate = rate_control_get_rate(local, local->mdev, skb, &extra);
		if (!rate) {
			if (net_ratelimit()) {
				printk(KERN_DEBUG "%s: ieee80211_beacon_get: no rate "
				       "found\n", wiphy_name(local->hw.wiphy));
			}
			dev_kfree_skb(skb);
			return NULL;
		}

		control->tx_rate =
			((sdata->flags & IEEE80211_SDATA_SHORT_PREAMBLE) &&
			(rate->flags & IEEE80211_RATE_PREAMBLE2)) ?
			rate->val2 : rate->val;
		control->antenna_sel_tx = local->hw.conf.antenna_sel_tx;
		control->power_level = local->hw.conf.power_level;
		control->flags |= IEEE80211_TXCTL_NO_ACK;
		control->retry_limit = 1;
		control->flags |= IEEE80211_TXCTL_CLEAR_DST_MASK;
	}

	ap->num_beacons++;
	return skb;
}
EXPORT_SYMBOL(ieee80211_beacon_get);

void ieee80211_rts_get(struct ieee80211_hw *hw, int if_id,
		       const void *frame, size_t frame_len,
		       const struct ieee80211_tx_control *frame_txctl,
		       struct ieee80211_rts *rts)
{
	const struct ieee80211_hdr *hdr = frame;
	u16 fctl;

	fctl = IEEE80211_FTYPE_CTL | IEEE80211_STYPE_RTS;
	rts->frame_control = cpu_to_le16(fctl);
	rts->duration = ieee80211_rts_duration(hw, if_id, frame_len, frame_txctl);
	memcpy(rts->ra, hdr->addr1, sizeof(rts->ra));
	memcpy(rts->ta, hdr->addr2, sizeof(rts->ta));
}
EXPORT_SYMBOL(ieee80211_rts_get);

void ieee80211_ctstoself_get(struct ieee80211_hw *hw, int if_id,
			     const void *frame, size_t frame_len,
			     const struct ieee80211_tx_control *frame_txctl,
			     struct ieee80211_cts *cts)
{
	const struct ieee80211_hdr *hdr = frame;
	u16 fctl;

	fctl = IEEE80211_FTYPE_CTL | IEEE80211_STYPE_CTS;
	cts->frame_control = cpu_to_le16(fctl);
	cts->duration = ieee80211_ctstoself_duration(hw, if_id, frame_len, frame_txctl);
	memcpy(cts->ra, hdr->addr1, sizeof(cts->ra));
}
EXPORT_SYMBOL(ieee80211_ctstoself_get);

struct sk_buff *
ieee80211_get_buffered_bc(struct ieee80211_hw *hw, int if_id,
			  struct ieee80211_tx_control *control)
{
	struct ieee80211_local *local = hw_to_local(hw);
	struct sk_buff *skb;
	struct sta_info *sta;
	ieee80211_tx_handler *handler;
	struct ieee80211_txrx_data tx;
	ieee80211_txrx_result res = TXRX_DROP;
	struct net_device *bdev;
	struct ieee80211_sub_if_data *sdata;
	struct ieee80211_if_ap *bss = NULL;

	bdev = dev_get_by_index(&init_net, if_id);
	if (bdev) {
		sdata = IEEE80211_DEV_TO_SUB_IF(bdev);
		bss = &sdata->u.ap;
		dev_put(bdev);
	}
	if (!bss || sdata->type != IEEE80211_IF_TYPE_AP || !bss->beacon_head)
		return NULL;

	if (bss->dtim_count != 0)
		return NULL; /* send buffered bc/mc only after DTIM beacon */
	memset(control, 0, sizeof(*control));
	while (1) {
		skb = skb_dequeue(&bss->ps_bc_buf);
		if (!skb)
			return NULL;
		local->total_ps_buffered--;

		if (!skb_queue_empty(&bss->ps_bc_buf) && skb->len >= 2) {
			struct ieee80211_hdr *hdr =
				(struct ieee80211_hdr *) skb->data;
			/* more buffered multicast/broadcast frames ==> set
			 * MoreData flag in IEEE 802.11 header to inform PS
			 * STAs */
			hdr->frame_control |=
				cpu_to_le16(IEEE80211_FCTL_MOREDATA);
		}

		if (!ieee80211_tx_prepare(&tx, skb, local->mdev, control))
			break;
		dev_kfree_skb_any(skb);
	}
	sta = tx.sta;
	tx.flags |= IEEE80211_TXRXD_TXPS_BUFFERED;
	tx.u.tx.mode = local->hw.conf.mode;

	for (handler = local->tx_handlers; *handler != NULL; handler++) {
		res = (*handler)(&tx);
		if (res == TXRX_DROP || res == TXRX_QUEUED)
			break;
	}
	dev_put(tx.dev);
	skb = tx.skb; /* handlers are allowed to change skb */

	if (res == TXRX_DROP) {
		I802_DEBUG_INC(local->tx_handlers_drop);
		dev_kfree_skb(skb);
		skb = NULL;
	} else if (res == TXRX_QUEUED) {
		I802_DEBUG_INC(local->tx_handlers_queued);
		skb = NULL;
	}

	if (sta)
		sta_info_put(sta);

	return skb;
}
EXPORT_SYMBOL(ieee80211_get_buffered_bc);