rx.c

linux 内核源代码

/*
 * Copyright 2002-2005, Instant802 Networks, Inc.
 * Copyright 2005-2006, Devicescape Software, Inc.
 * Copyright 2006-2007	Jiri Benc <[e-mail]>
 * Copyright 2007	Johannes Berg <[e-mail]>
 *
 * 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 <linux/kernel.h>
#include <linux/skbuff.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/rcupdate.h>
#include <net/mac80211.h>
#include <net/ieee80211_radiotap.h>

#include "ieee80211_i.h"
#include "ieee80211_led.h"
#include "wep.h"
#include "wpa.h"
#include "tkip.h"
#include "wme.h"

/*
 * monitor mode reception
 *
 * This function cleans up the SKB, i.e. it removes all the stuff
 * only useful for monitoring.
 */
static struct sk_buff *remove_monitor_info(struct ieee80211_local *local,
					   struct sk_buff *skb,
					   int rtap_len)
{
	skb_pull(skb, rtap_len);

	if (local->hw.flags & IEEE80211_HW_RX_INCLUDES_FCS) {
		if (likely(skb->len > FCS_LEN))
			skb_trim(skb, skb->len - FCS_LEN);
		else {
			/* driver bug */
			WARN_ON(1);
			dev_kfree_skb(skb);
			skb = NULL;
		}
	}

	return skb;
}

static inline int should_drop_frame(struct ieee80211_rx_status *status,
				    struct sk_buff *skb,
				    int present_fcs_len,
				    int radiotap_len)
{
	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;

	if (status->flag & (RX_FLAG_FAILED_FCS_CRC | RX_FLAG_FAILED_PLCP_CRC))
		return 1;
	if (unlikely(skb->len < 16 + present_fcs_len + radiotap_len))
		return 1;
	if ((hdr->frame_control & cpu_to_le16(IEEE80211_FCTL_FTYPE)) ==
			cpu_to_le16(IEEE80211_FTYPE_CTL))
		return 1;
	return 0;
}

/*
 * 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_rx_status *status)
{
	struct ieee80211_sub_if_data *sdata;
	struct ieee80211_rate *rate;
	int needed_headroom = 0;
	struct ieee80211_rtap_hdr {
		struct ieee80211_radiotap_header hdr;
		u8 flags;
		u8 rate;
		__le16 chan_freq;
		__le16 chan_flags;
		u8 antsignal;
		u8 padding_for_rxflags;
		__le16 rx_flags;
	} __attribute__ ((packed)) *rthdr;
	struct sk_buff *skb, *skb2;
	struct net_device *prev_dev = NULL;
	int present_fcs_len = 0;
	int rtap_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 (status->flag & RX_FLAG_RADIOTAP)
		rtap_len = ieee80211_get_radiotap_len(origskb->data);
	else
		needed_headroom = sizeof(*rthdr);

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

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

		return remove_monitor_info(local, origskb, rtap_len);
	}

	if (should_drop_frame(status, origskb, present_fcs_len, rtap_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, sizeof(*rthdr), 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, rtap_len);

		if (!skb)
			return origskb;
	}

	/* if necessary, prepend radiotap information */
	if (!(status->flag & RX_FLAG_RADIOTAP)) {
		rthdr = (void *) skb_push(skb, sizeof(*rthdr));
		memset(rthdr, 0, sizeof(*rthdr));
		rthdr->hdr.it_len = cpu_to_le16(sizeof(*rthdr));
		rthdr->hdr.it_present =
			cpu_to_le32((1 << IEEE80211_RADIOTAP_FLAGS) |
				    (1 << IEEE80211_RADIOTAP_RATE) |
				    (1 << IEEE80211_RADIOTAP_CHANNEL) |
				    (1 << IEEE80211_RADIOTAP_DB_ANTSIGNAL) |
				    (1 << IEEE80211_RADIOTAP_RX_FLAGS));
		rthdr->flags = local->hw.flags & IEEE80211_HW_RX_INCLUDES_FCS ?
			       IEEE80211_RADIOTAP_F_FCS : 0;

		/* FIXME: when radiotap gets a 'bad PLCP' flag use it here */
		rthdr->rx_flags = 0;
		if (status->flag &
		    (RX_FLAG_FAILED_FCS_CRC | RX_FLAG_FAILED_PLCP_CRC))
			rthdr->rx_flags |=
				cpu_to_le16(IEEE80211_RADIOTAP_F_RX_BADFCS);

		rate = ieee80211_get_rate(local, status->phymode,
					  status->rate);
		if (rate)
			rthdr->rate = rate->rate / 5;

		rthdr->chan_freq = cpu_to_le16(status->freq);

		if (status->phymode == MODE_IEEE80211A)
			rthdr->chan_flags =
				cpu_to_le16(IEEE80211_CHAN_OFDM |
					    IEEE80211_CHAN_5GHZ);
		else
			rthdr->chan_flags =
				cpu_to_le16(IEEE80211_CHAN_DYN |
					    IEEE80211_CHAN_2GHZ);

		rthdr->antsignal = status->ssi;
	}

	skb_set_mac_header(skb, 0);
	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 (!netif_running(sdata->dev))
			continue;

		if (sdata->type != IEEE80211_IF_TYPE_MNTR)
			continue;

		if (prev_dev) {
			skb2 = skb_clone(skb, GFP_ATOMIC);
			if (skb2) {
				skb2->dev = prev_dev;
				netif_rx(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_rx(skb);
	} else
		dev_kfree_skb(skb);

	return origskb;
}


/* pre-rx handlers
 *
 * these don't have dev/sdata fields in the rx data
 * The sta value should also not be used because it may
 * be NULL even though a STA (in IBSS mode) will be added.
 */

static ieee80211_txrx_result
ieee80211_rx_h_parse_qos(struct ieee80211_txrx_data *rx)
{
	u8 *data = rx->skb->data;
	int tid;

	/* does the frame have a qos control field? */
	if (WLAN_FC_IS_QOS_DATA(rx->fc)) {
		u8 *qc = data + ieee80211_get_hdrlen(rx->fc) - QOS_CONTROL_LEN;
		/* frame has qos control */
		tid = qc[0] & QOS_CONTROL_TID_MASK;
	} else {
		if (unlikely((rx->fc & IEEE80211_FCTL_FTYPE) == IEEE80211_FTYPE_MGMT)) {
			/* Separate TID for management frames */
			tid = NUM_RX_DATA_QUEUES - 1;
		} else {
			/* no qos control present */
			tid = 0; /* 802.1d - Best Effort */
		}
	}

	I802_DEBUG_INC(rx->local->wme_rx_queue[tid]);
	/* only a debug counter, sta might not be assigned properly yet */
	if (rx->sta)
		I802_DEBUG_INC(rx->sta->wme_rx_queue[tid]);

	rx->u.rx.queue = tid;
	/* Set skb->priority to 1d tag if highest order bit of TID is not set.
	 * For now, set skb->priority to 0 for other cases. */
	rx->skb->priority = (tid > 7) ? 0 : tid;

	return TXRX_CONTINUE;
}

static ieee80211_txrx_result
ieee80211_rx_h_load_stats(struct ieee80211_txrx_data *rx)
{
	struct ieee80211_local *local = rx->local;
	struct sk_buff *skb = rx->skb;
	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
	u32 load = 0, hdrtime;
	struct ieee80211_rate *rate;
	struct ieee80211_hw_mode *mode = local->hw.conf.mode;
	int i;

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

	if (unlikely(mode->num_rates < 0))
		return TXRX_CONTINUE;

	rate = &mode->rates[0];
	for (i = 0; i < mode->num_rates; i++) {
		if (mode->rates[i].val == rx->u.rx.status->rate) {
			rate = &mode->rates[i];
			break;
		}
	}

	/* 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 &&
	     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;

	load += skb->len * rate->rate_inv;

	/* Divide channel_use by 8 to avoid wrapping around the counter */
	load >>= CHAN_UTIL_SHIFT;
	local->channel_use_raw += load;
	rx->u.rx.load = load;

	return TXRX_CONTINUE;
}

ieee80211_rx_handler ieee80211_rx_pre_handlers[] =
{
	ieee80211_rx_h_parse_qos,
	ieee80211_rx_h_load_stats,
	NULL
};

/* rx handlers */

static ieee80211_txrx_result
ieee80211_rx_h_if_stats(struct ieee80211_txrx_data *rx)
{
	if (rx->sta)
		rx->sta->channel_use_raw += rx->u.rx.load;
	rx->sdata->channel_use_raw += rx->u.rx.load;
	return TXRX_CONTINUE;
}

static ieee80211_txrx_result
ieee80211_rx_h_passive_scan(struct ieee80211_txrx_data *rx)
{
	struct ieee80211_local *local = rx->local;
	struct sk_buff *skb = rx->skb;

	if (unlikely(local->sta_scanning != 0)) {
		ieee80211_sta_rx_scan(rx->dev, skb, rx->u.rx.status);
		return TXRX_QUEUED;
	}

	if (unlikely(rx->flags & IEEE80211_TXRXD_RXIN_SCAN)) {
		/* scanning finished during invoking of handlers */
		I802_DEBUG_INC(local->rx_handlers_drop_passive_scan);
		return TXRX_DROP;
	}

	return TXRX_CONTINUE;
}

static ieee80211_txrx_result
ieee80211_rx_h_check(struct ieee80211_txrx_data *rx)
{
	struct ieee80211_hdr *hdr;
	hdr = (struct ieee80211_hdr *) rx->skb->data;

	/* Drop duplicate 802.11 retransmissions (IEEE 802.11 Chap. 9.2.9) */
	if (rx->sta && !is_multicast_ether_addr(hdr->addr1)) {
		if (unlikely(rx->fc & IEEE80211_FCTL_RETRY &&
			     rx->sta->last_seq_ctrl[rx->u.rx.queue] ==
			     hdr->seq_ctrl)) {
			if (rx->flags & IEEE80211_TXRXD_RXRA_MATCH) {
				rx->local->dot11FrameDuplicateCount++;
				rx->sta->num_duplicates++;
			}
			return TXRX_DROP;
		} else
			rx->sta->last_seq_ctrl[rx->u.rx.queue] = hdr->seq_ctrl;
	}

	if (unlikely(rx->skb->len < 16)) {
		I802_DEBUG_INC(rx->local->rx_handlers_drop_short);
		return TXRX_DROP;
	}

	if (!(rx->flags & IEEE80211_TXRXD_RXRA_MATCH))
		rx->skb->pkt_type = PACKET_OTHERHOST;
	else if (compare_ether_addr(rx->dev->dev_addr, hdr->addr1) == 0)
		rx->skb->pkt_type = PACKET_HOST;
	else if (is_multicast_ether_addr(hdr->addr1)) {
		if (is_broadcast_ether_addr(hdr->addr1))
			rx->skb->pkt_type = PACKET_BROADCAST;
		else
			rx->skb->pkt_type = PACKET_MULTICAST;
	} else
		rx->skb->pkt_type = PACKET_OTHERHOST;

	/* Drop disallowed frame classes based on STA auth/assoc state;
	 * IEEE 802.11, Chap 5.5.
	 *
	 * 80211.o does filtering only based on association state, i.e., it
	 * drops Class 3 frames from not associated stations. hostapd sends
	 * deauth/disassoc frames when needed. In addition, hostapd is
	 * responsible for filtering on both auth and assoc states.
	 */
	if (unlikely(((rx->fc & IEEE80211_FCTL_FTYPE) == IEEE80211_FTYPE_DATA ||
		      ((rx->fc & IEEE80211_FCTL_FTYPE) == IEEE80211_FTYPE_CTL &&
		       (rx->fc & IEEE80211_FCTL_STYPE) == IEEE80211_STYPE_PSPOLL)) &&
		     rx->sdata->type != IEEE80211_IF_TYPE_IBSS &&
		     (!rx->sta || !(rx->sta->flags & WLAN_STA_ASSOC)))) {
		if ((!(rx->fc & IEEE80211_FCTL_FROMDS) &&
		     !(rx->fc & IEEE80211_FCTL_TODS) &&
		     (rx->fc & IEEE80211_FCTL_FTYPE) == IEEE80211_FTYPE_DATA)
		    || !(rx->flags & IEEE80211_TXRXD_RXRA_MATCH)) {
			/* Drop IBSS frames and frames for other hosts
			 * silently. */
			return TXRX_DROP;
		}

		return TXRX_DROP;
	}

	return TXRX_CONTINUE;
}


static ieee80211_txrx_result
ieee80211_rx_h_decrypt(struct ieee80211_txrx_data *rx)
{
	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) rx->skb->data;
	int keyidx;
	int hdrlen;
	ieee80211_txrx_result result = TXRX_DROP;
	struct ieee80211_key *stakey = NULL;

	/*
	 * Key selection 101
	 *
	 * There are three types of keys:
	 *  - GTK (group keys)
	 *  - PTK (pairwise keys)
	 *  - STK (station-to-station pairwise keys)
	 *
	 * When selecting a key, we have to distinguish between multicast
	 * (including broadcast) and unicast frames, the latter can only
	 * use PTKs and STKs while the former always use GTKs. Unless, of
	 * course, actual WEP keys ("pre-RSNA") are used, then unicast
	 * frames can also use key indizes like GTKs. Hence, if we don't
	 * have a PTK/STK we check the key index for a WEP key.
	 *
	 * Note that in a regular BSS, multicast frames are sent by the
	 * AP only, associated stations unicast the frame to the AP first
	 * which then multicasts it on their behalf.
	 *
	 * There is also a slight problem in IBSS mode: GTKs are negotiated
	 * with each station, that is something we don't currently handle.
	 * The spec seems to expect that one negotiates the same key with
	 * every station but there's no such requirement; VLANs could be
	 * possible.
	 */

	if (!(rx->fc & IEEE80211_FCTL_PROTECTED))
		return TXRX_CONTINUE;

	/*
	 * No point in finding a key and decrypting if the frame is neither
	 * addressed to us nor a multicast frame.
	 */
	if (!(rx->flags & IEEE80211_TXRXD_RXRA_MATCH))
		return TXRX_CONTINUE;

	if (rx->sta)
		stakey = rcu_dereference(rx->sta->key);

	if (!is_multicast_ether_addr(hdr->addr1) && stakey) {
		rx->key = stakey;
	} else {
		/*
		 * The device doesn't give us the IV so we won't be
		 * able to look up the key. That's ok though, we
		 * don't need to decrypt the frame, we just won't
		 * be able to keep statistics accurate.
		 * Except for key threshold notifications, should
		 * we somehow allow the driver to tell us which key
		 * the hardware used if this flag is set?
		 */
		if ((rx->u.rx.status->flag & RX_FLAG_DECRYPTED) &&
		    (rx->u.rx.status->flag & RX_FLAG_IV_STRIPPED))
			return TXRX_CONTINUE;

		hdrlen = ieee80211_get_hdrlen(rx->fc);

		if (rx->skb->len < 8 + hdrlen)
			return TXRX_DROP; /* TODO: count this? */

		/*
		 * no need to call ieee80211_wep_get_keyidx,
		 * it verifies a bunch of things we've done already
		 */
		keyidx = rx->skb->data[hdrlen + 3] >> 6;

		rx->key = rcu_dereference(rx->sdata->keys[keyidx]);

		/*
		 * RSNA-protected unicast frames should always be sent with
		 * pairwise or station-to-station keys, but for WEP we allow
		 * using a key index as well.
		 */
		if (rx->key && rx->key->conf.alg != ALG_WEP &&
		    !is_multicast_ether_addr(hdr->addr1))
			rx->key = NULL;
	}

	if (rx->key) {
		rx->key->tx_rx_count++;
		/* TODO: add threshold stuff again */
	} else {
#ifdef CONFIG_MAC80211_DEBUG
		if (net_ratelimit())
			printk(KERN_DEBUG "%s: RX protected frame,"
			       " but have no key\n", rx->dev->name);
#endif /* CONFIG_MAC80211_DEBUG */
		return TXRX_DROP;
	}

	/* Check for weak IVs if possible */
	if (rx->sta && rx->key->conf.alg == ALG_WEP &&
	    ((rx->fc & IEEE80211_FCTL_FTYPE) == IEEE80211_FTYPE_DATA) &&
	    (!(rx->u.rx.status->flag & RX_FLAG_IV_STRIPPED) ||
	     !(rx->u.rx.status->flag & RX_FLAG_DECRYPTED)) &&
	    ieee80211_wep_is_weak_iv(rx->skb, rx->key))
		rx->sta->wep_weak_iv_count++;

	switch (rx->key->conf.alg) {
	case ALG_WEP:
		result = ieee80211_crypto_wep_decrypt(rx);
		break;