tx.c

linux 内核源代码

	if (!(tx->flags & IEEE80211_TXRXD_FRAGMENTED))
		return TXRX_CONTINUE;

	first = tx->skb;

	hdrlen = ieee80211_get_hdrlen(tx->fc);
	payload_len = first->len - hdrlen;
	per_fragm = frag_threshold - hdrlen - FCS_LEN;
	num_fragm = DIV_ROUND_UP(payload_len, per_fragm);

	frags = kzalloc(num_fragm * sizeof(struct sk_buff *), GFP_ATOMIC);
	if (!frags)
		goto fail;

	hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_MOREFRAGS);
	seq = le16_to_cpu(hdr->seq_ctrl) & IEEE80211_SCTL_SEQ;
	pos = first->data + hdrlen + per_fragm;
	left = payload_len - per_fragm;
	for (i = 0; i < num_fragm - 1; i++) {
		struct ieee80211_hdr *fhdr;
		size_t copylen;

		if (left <= 0)
			goto fail;

		/* reserve enough extra head and tail room for possible
		 * encryption */
		frag = frags[i] =
			dev_alloc_skb(tx->local->tx_headroom +
				      frag_threshold +
				      IEEE80211_ENCRYPT_HEADROOM +
				      IEEE80211_ENCRYPT_TAILROOM);
		if (!frag)
			goto fail;
		/* Make sure that all fragments use the same priority so
		 * that they end up using the same TX queue */
		frag->priority = first->priority;
		skb_reserve(frag, tx->local->tx_headroom +
				  IEEE80211_ENCRYPT_HEADROOM);
		fhdr = (struct ieee80211_hdr *) skb_put(frag, hdrlen);
		memcpy(fhdr, first->data, hdrlen);
		if (i == num_fragm - 2)
			fhdr->frame_control &= cpu_to_le16(~IEEE80211_FCTL_MOREFRAGS);
		fhdr->seq_ctrl = cpu_to_le16(seq | ((i + 1) & IEEE80211_SCTL_FRAG));
		copylen = left > per_fragm ? per_fragm : left;
		memcpy(skb_put(frag, copylen), pos, copylen);

		pos += copylen;
		left -= copylen;
	}
	skb_trim(first, hdrlen + per_fragm);

	tx->u.tx.num_extra_frag = num_fragm - 1;
	tx->u.tx.extra_frag = frags;

	return TXRX_CONTINUE;

 fail:
	printk(KERN_DEBUG "%s: failed to fragment frame\n", tx->dev->name);
	if (frags) {
		for (i = 0; i < num_fragm - 1; i++)
			if (frags[i])
				dev_kfree_skb(frags[i]);
		kfree(frags);
	}
	I802_DEBUG_INC(tx->local->tx_handlers_drop_fragment);
	return TXRX_DROP;
}

static ieee80211_txrx_result
ieee80211_tx_h_encrypt(struct ieee80211_txrx_data *tx)
{
	if (!tx->key)
		return TXRX_CONTINUE;

	switch (tx->key->conf.alg) {
	case ALG_WEP:
		return ieee80211_crypto_wep_encrypt(tx);
	case ALG_TKIP:
		return ieee80211_crypto_tkip_encrypt(tx);
	case ALG_CCMP:
		return ieee80211_crypto_ccmp_encrypt(tx);
	}

	/* not reached */
	WARN_ON(1);
	return TXRX_DROP;
}

static ieee80211_txrx_result
ieee80211_tx_h_rate_ctrl(struct ieee80211_txrx_data *tx)
{
	struct rate_control_extra extra;

	if (likely(!tx->u.tx.rate)) {
		memset(&extra, 0, sizeof(extra));
		extra.mode = tx->u.tx.mode;
		extra.ethertype = tx->ethertype;

		tx->u.tx.rate = rate_control_get_rate(tx->local, tx->dev,
						      tx->skb, &extra);
		if (unlikely(extra.probe != NULL)) {
			tx->u.tx.control->flags |=
				IEEE80211_TXCTL_RATE_CTRL_PROBE;
			tx->flags |= IEEE80211_TXRXD_TXPROBE_LAST_FRAG;
			tx->u.tx.control->alt_retry_rate = tx->u.tx.rate->val;
			tx->u.tx.rate = extra.probe;
		} else
			tx->u.tx.control->alt_retry_rate = -1;

		if (!tx->u.tx.rate)
			return TXRX_DROP;
	} else
		tx->u.tx.control->alt_retry_rate = -1;

	if (tx->u.tx.mode->mode == MODE_IEEE80211G &&
	    (tx->sdata->flags & IEEE80211_SDATA_USE_PROTECTION) &&
	    (tx->flags & IEEE80211_TXRXD_FRAGMENTED) && extra.nonerp) {
		tx->u.tx.last_frag_rate = tx->u.tx.rate;
		if (extra.probe)
			tx->flags &= ~IEEE80211_TXRXD_TXPROBE_LAST_FRAG;
		else
			tx->flags |= IEEE80211_TXRXD_TXPROBE_LAST_FRAG;
		tx->u.tx.rate = extra.nonerp;
		tx->u.tx.control->rate = extra.nonerp;
		tx->u.tx.control->flags &= ~IEEE80211_TXCTL_RATE_CTRL_PROBE;
	} else {
		tx->u.tx.last_frag_rate = tx->u.tx.rate;
		tx->u.tx.control->rate = tx->u.tx.rate;
	}
	tx->u.tx.control->tx_rate = tx->u.tx.rate->val;

	return TXRX_CONTINUE;
}

static ieee80211_txrx_result
ieee80211_tx_h_misc(struct ieee80211_txrx_data *tx)
{
	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) tx->skb->data;
	u16 fc = le16_to_cpu(hdr->frame_control);
	u16 dur;
	struct ieee80211_tx_control *control = tx->u.tx.control;
	struct ieee80211_hw_mode *mode = tx->u.tx.mode;

	if (!control->retry_limit) {
		if (!is_multicast_ether_addr(hdr->addr1)) {
			if (tx->skb->len + FCS_LEN > tx->local->rts_threshold
			    && tx->local->rts_threshold <
					IEEE80211_MAX_RTS_THRESHOLD) {
				control->flags |=
					IEEE80211_TXCTL_USE_RTS_CTS;
				control->flags |=
					IEEE80211_TXCTL_LONG_RETRY_LIMIT;
				control->retry_limit =
					tx->local->long_retry_limit;
			} else {
				control->retry_limit =
					tx->local->short_retry_limit;
			}
		} else {
			control->retry_limit = 1;
		}
	}

	if (tx->flags & IEEE80211_TXRXD_FRAGMENTED) {
		/* Do not use multiple retry rates when sending fragmented
		 * frames.
		 * TODO: The last fragment could still use multiple retry
		 * rates. */
		control->alt_retry_rate = -1;
	}

	/* Use CTS protection for unicast frames sent using extended rates if
	 * there are associated non-ERP stations and RTS/CTS is not configured
	 * for the frame. */
	if (mode->mode == MODE_IEEE80211G &&
	    (tx->u.tx.rate->flags & IEEE80211_RATE_ERP) &&
	    (tx->flags & IEEE80211_TXRXD_TXUNICAST) &&
	    (tx->sdata->flags & IEEE80211_SDATA_USE_PROTECTION) &&
	    !(control->flags & IEEE80211_TXCTL_USE_RTS_CTS))
		control->flags |= IEEE80211_TXCTL_USE_CTS_PROTECT;

	/* Transmit data frames using short preambles if the driver supports
	 * short preambles at the selected rate and short preambles are
	 * available on the network at the current point in time. */
	if (((fc & IEEE80211_FCTL_FTYPE) == IEEE80211_FTYPE_DATA) &&
	    (tx->u.tx.rate->flags & IEEE80211_RATE_PREAMBLE2) &&
	    (tx->sdata->flags & IEEE80211_SDATA_SHORT_PREAMBLE) &&
	    (!tx->sta || (tx->sta->flags & WLAN_STA_SHORT_PREAMBLE))) {
		tx->u.tx.control->tx_rate = tx->u.tx.rate->val2;
	}

	/* Setup duration field for the first fragment of the frame. Duration
	 * for remaining fragments will be updated when they are being sent
	 * to low-level driver in ieee80211_tx(). */
	dur = ieee80211_duration(tx, is_multicast_ether_addr(hdr->addr1),
				 (tx->flags & IEEE80211_TXRXD_FRAGMENTED) ?
				 tx->u.tx.extra_frag[0]->len : 0);
	hdr->duration_id = cpu_to_le16(dur);

	if ((control->flags & IEEE80211_TXCTL_USE_RTS_CTS) ||
	    (control->flags & IEEE80211_TXCTL_USE_CTS_PROTECT)) {
		struct ieee80211_rate *rate;

		/* Do not use multiple retry rates when using RTS/CTS */
		control->alt_retry_rate = -1;

		/* Use min(data rate, max base rate) as CTS/RTS rate */
		rate = tx->u.tx.rate;
		while (rate > mode->rates &&
		       !(rate->flags & IEEE80211_RATE_BASIC))
			rate--;

		control->rts_cts_rate = rate->val;
		control->rts_rate = rate;
	}

	if (tx->sta) {
		tx->sta->tx_packets++;
		tx->sta->tx_fragments++;
		tx->sta->tx_bytes += tx->skb->len;
		if (tx->u.tx.extra_frag) {
			int i;
			tx->sta->tx_fragments += tx->u.tx.num_extra_frag;
			for (i = 0; i < tx->u.tx.num_extra_frag; i++) {
				tx->sta->tx_bytes +=
					tx->u.tx.extra_frag[i]->len;
			}
		}
	}

	/*
	 * Tell hardware to not encrypt when we had sw crypto.
	 * Because we use the same flag to internally indicate that
	 * no (software) encryption should be done, we have to set it
	 * after all crypto handlers.
	 */
	if (tx->key && !(tx->key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE))
		tx->u.tx.control->flags |= IEEE80211_TXCTL_DO_NOT_ENCRYPT;

	return TXRX_CONTINUE;
}

static ieee80211_txrx_result
ieee80211_tx_h_load_stats(struct ieee80211_txrx_data *tx)
{
	struct ieee80211_local *local = tx->local;
	struct ieee80211_hw_mode *mode = tx->u.tx.mode;
	struct sk_buff *skb = tx->skb;
	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
	u32 load = 0, hdrtime;

	/* TODO: this could be part of tx_status handling, so that the number
	 * of retries would be known; TX rate should in that case be stored
	 * somewhere with the packet */

	/* Estimate total channel use caused by this frame */

	/* 1 bit at 1 Mbit/s takes 1 usec; in channel_use values,
	 * 1 usec = 1/8 * (1080 / 10) = 13.5 */

	if (mode->mode == MODE_IEEE80211A ||
	    (mode->mode == MODE_IEEE80211G &&
	     tx->u.tx.rate->flags & IEEE80211_RATE_ERP))
		hdrtime = CHAN_UTIL_HDR_SHORT;
	else
		hdrtime = CHAN_UTIL_HDR_LONG;

	load = hdrtime;
	if (!is_multicast_ether_addr(hdr->addr1))
		load += hdrtime;

	if (tx->u.tx.control->flags & IEEE80211_TXCTL_USE_RTS_CTS)
		load += 2 * hdrtime;
	else if (tx->u.tx.control->flags & IEEE80211_TXCTL_USE_CTS_PROTECT)
		load += hdrtime;

	load += skb->len * tx->u.tx.rate->rate_inv;

	if (tx->u.tx.extra_frag) {
		int i;
		for (i = 0; i < tx->u.tx.num_extra_frag; i++) {
			load += 2 * hdrtime;
			load += tx->u.tx.extra_frag[i]->len *
				tx->u.tx.rate->rate;
		}
	}

	/* Divide channel_use by 8 to avoid wrapping around the counter */
	load >>= CHAN_UTIL_SHIFT;
	local->channel_use_raw += load;
	if (tx->sta)
		tx->sta->channel_use_raw += load;
	tx->sdata->channel_use_raw += load;

	return TXRX_CONTINUE;
}

/* TODO: implement register/unregister functions for adding TX/RX handlers
 * into ordered list */

ieee80211_tx_handler ieee80211_tx_handlers[] =
{
	ieee80211_tx_h_check_assoc,
	ieee80211_tx_h_sequence,
	ieee80211_tx_h_ps_buf,
	ieee80211_tx_h_select_key,
	ieee80211_tx_h_michael_mic_add,
	ieee80211_tx_h_fragment,
	ieee80211_tx_h_encrypt,
	ieee80211_tx_h_rate_ctrl,
	ieee80211_tx_h_misc,
	ieee80211_tx_h_load_stats,
	NULL
};

/* actual transmit path */

/*
 * deal with packet injection down monitor interface
 * with Radiotap Header -- only called for monitor mode interface
 */
static ieee80211_txrx_result
__ieee80211_parse_tx_radiotap(struct ieee80211_txrx_data *tx,
			      struct sk_buff *skb)
{
	/*
	 * this is the moment to interpret and discard the radiotap header that
	 * must be at the start of the packet injected in Monitor mode
	 *
	 * Need to take some care with endian-ness since radiotap
	 * args are little-endian
	 */

	struct ieee80211_radiotap_iterator iterator;
	struct ieee80211_radiotap_header *rthdr =
		(struct ieee80211_radiotap_header *) skb->data;
	struct ieee80211_hw_mode *mode = tx->local->hw.conf.mode;
	int ret = ieee80211_radiotap_iterator_init(&iterator, rthdr, skb->len);
	struct ieee80211_tx_control *control = tx->u.tx.control;

	control->flags |= IEEE80211_TXCTL_DO_NOT_ENCRYPT;
	tx->flags |= IEEE80211_TXRXD_TX_INJECTED;
	tx->flags &= ~IEEE80211_TXRXD_FRAGMENTED;

	/*
	 * for every radiotap entry that is present
	 * (ieee80211_radiotap_iterator_next returns -ENOENT when no more
	 * entries present, or -EINVAL on error)
	 */

	while (!ret) {
		int i, target_rate;

		ret = ieee80211_radiotap_iterator_next(&iterator);

		if (ret)
			continue;

		/* see if this argument is something we can use */
		switch (iterator.this_arg_index) {
		/*
		 * You must take care when dereferencing iterator.this_arg
		 * for multibyte types... the pointer is not aligned.  Use
		 * get_unaligned((type *)iterator.this_arg) to dereference
		 * iterator.this_arg for type "type" safely on all arches.
		*/
		case IEEE80211_RADIOTAP_RATE:
			/*
			 * radiotap rate u8 is in 500kbps units eg, 0x02=1Mbps
			 * ieee80211 rate int is in 100kbps units eg, 0x0a=1Mbps
			 */
			target_rate = (*iterator.this_arg) * 5;
			for (i = 0; i < mode->num_rates; i++) {
				struct ieee80211_rate *r = &mode->rates[i];

				if (r->rate == target_rate) {
					tx->u.tx.rate = r;
					break;
				}
			}
			break;

		case IEEE80211_RADIOTAP_ANTENNA:
			/*
			 * radiotap uses 0 for 1st ant, mac80211 is 1 for
			 * 1st ant
			 */
			control->antenna_sel_tx = (*iterator.this_arg) + 1;
			break;

		case IEEE80211_RADIOTAP_DBM_TX_POWER:
			control->power_level = *iterator.this_arg;
			break;

		case IEEE80211_RADIOTAP_FLAGS:
			if (*iterator.this_arg & IEEE80211_RADIOTAP_F_FCS) {
				/*
				 * this indicates that the skb we have been
				 * handed has the 32-bit FCS CRC at the end...
				 * we should react to that by snipping it off
				 * because it will be recomputed and added
				 * on transmission
				 */
				if (skb->len < (iterator.max_length + FCS_LEN))
					return TXRX_DROP;

				skb_trim(skb, skb->len - FCS_LEN);
			}
			if (*iterator.this_arg & IEEE80211_RADIOTAP_F_WEP)
				control->flags &=
					~IEEE80211_TXCTL_DO_NOT_ENCRYPT;
			if (*iterator.this_arg & IEEE80211_RADIOTAP_F_FRAG)
				tx->flags |= IEEE80211_TXRXD_FRAGMENTED;
			break;

		/*
		 * Please update the file
		 * Documentation/networking/mac80211-injection.txt
		 * when parsing new fields here.
		 */

		default:
			break;
		}
	}

	if (ret != -ENOENT) /* ie, if we didn't simply run out of fields */
		return TXRX_DROP;

	/*
	 * remove the radiotap header
	 * iterator->max_length was sanity-checked against
	 * skb->len by iterator init
	 */
	skb_pull(skb, iterator.max_length);

	return TXRX_CONTINUE;
}

/*
 * initialises @tx
 */
static ieee80211_txrx_result
__ieee80211_tx_prepare(struct ieee80211_txrx_data *tx,
		       struct sk_buff *skb,
		       struct net_device *dev,
		       struct ieee80211_tx_control *control)
{
	struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
	struct ieee80211_hdr *hdr;
	struct ieee80211_sub_if_data *sdata;
	ieee80211_txrx_result res = TXRX_CONTINUE;

	int hdrlen;

	memset(tx, 0, sizeof(*tx));
	tx->skb = skb;
	tx->dev = dev; /* use original interface */
	tx->local = local;
	tx->sdata = IEEE80211_DEV_TO_SUB_IF(dev);
	tx->u.tx.control = control;
	/*
	 * Set this flag (used below to indicate "automatic fragmentation"),
	 * it will be cleared/left by radiotap as desired.
	 */
	tx->flags |= IEEE80211_TXRXD_FRAGMENTED;

	/* process and remove the injection radiotap header */
	sdata = IEEE80211_DEV_TO_SUB_IF(dev);
	if (unlikely(sdata->type == IEEE80211_IF_TYPE_MNTR)) {
		if (__ieee80211_parse_tx_radiotap(tx, skb) == TXRX_DROP)
			return TXRX_DROP;

		/*