[MAC80211]: improve radiotap injection

This improves radiotap injection by removing the shortcut over TX handlers
that led to BUGS when injecting frames without setting a rate and also
resulted in various other quirks. Now, TX handlers are run but some
information that was present in the radiotap header is used instead of
automatic settings.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Cc: Andy Green <andy@warmcat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

3 files changed, 131 insertions, 97 deletions

diff --git a/Documentation/networking/mac80211-injection.txt b/Documentation/networking/mac80211-injection.txt
index 53ef7a06f49c..84906ef3ed6e 100644
--- a/Documentation/networking/mac80211-injection.txt
+++ b/Documentation/networking/mac80211-injection.txt
@@ -13,15 +13,35 @@ The radiotap format is discussed in
 ./Documentation/networking/radiotap-headers.txt.
 
 Despite 13 radiotap argument types are currently defined, most only make sense
-to appear on received packets.  Currently three kinds of argument are used by
-the injection code, although it knows to skip any other arguments that are
-present (facilitating replay of captured radiotap headers directly):
+to appear on received packets.  The following information is parsed from the
+radiotap headers and used to control injection:
 
- - IEEE80211_RADIOTAP_RATE - u8 arg in 500kbps units (0x02 --> 1Mbps)
+ * IEEE80211_RADIOTAP_RATE
 
- - IEEE80211_RADIOTAP_ANTENNA - u8 arg, 0x00 = ant1, 0x01 = ant2
+   rate in 500kbps units, automatic if invalid or not present
 
- - IEEE80211_RADIOTAP_DBM_TX_POWER - u8 arg, dBm
+
+ * IEEE80211_RADIOTAP_ANTENNA
+
+   antenna to use, automatic if not present
+
+
+ * IEEE80211_RADIOTAP_DBM_TX_POWER
+
+   transmit power in dBm, automatic if not present
+
+
+ * IEEE80211_RADIOTAP_FLAGS
+
+   IEEE80211_RADIOTAP_F_FCS: FCS will be removed and recalculated
+   IEEE80211_RADIOTAP_F_WEP: frame will be encrypted if key available
+   IEEE80211_RADIOTAP_F_FRAG: frame will be fragmented if longer than the
+                              current fragmentation threshold. Note that
+                              this flag is only reliable when software
+                              fragmentation is enabled)
+
+The injection code can also skip all other currently defined radiotap fields
+facilitating replay of captured radiotap headers directly.
 
 Here is an example valid radiotap header defining these three parameters
 
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index d24b0574c436..0fe077747082 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -122,6 +122,7 @@ typedef enum {
 #define IEEE80211_TXRXD_RXIN_SCAN               BIT(4)
 /* frame is destined to interface currently processed (incl. multicast frames) */
 #define IEEE80211_TXRXD_RXRA_MATCH              BIT(5)
+#define IEEE80211_TXRXD_TX_INJECTED             BIT(6)
 struct ieee80211_txrx_data {
         struct sk_buff *skb;
         struct net_device *dev;
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 47416b0645db..1a531543bccb 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -222,6 +222,9 @@ ieee80211_tx_h_check_assoc(struct ieee80211_txrx_data *tx)
 #endif /* CONFIG_MAC80211_VERBOSE_DEBUG */
         u32 sta_flags;
 
+        if (unlikely(tx->flags & IEEE80211_TXRXD_TX_INJECTED))
+                return TXRX_CONTINUE;
+
         if (unlikely(tx->local->sta_scanning != 0) &&
             ((tx->fc & IEEE80211_FCTL_FTYPE) != IEEE80211_FTYPE_MGMT ||
              (tx->fc & IEEE80211_FCTL_STYPE) != IEEE80211_STYPE_PROBE_REQ))
@@ -566,22 +569,27 @@ ieee80211_tx_h_rate_ctrl(struct ieee80211_txrx_data *tx)
 {
         struct rate_control_extra extra;
 
-        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 {
+        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.rate)
-                return TXRX_DROP;
+
         if (tx->u.tx.mode->mode == MODE_IEEE80211G &&
             (tx->sdata->flags & IEEE80211_SDATA_USE_PROTECTION) &&
             (tx->flags & IEEE80211_TXRXD_FRAGMENTED) && extra.nonerp) {
@@ -611,19 +619,24 @@ ieee80211_tx_h_misc(struct ieee80211_txrx_data *tx)
         struct ieee80211_tx_control *control = tx->u.tx.control;
         struct ieee80211_hw_mode *mode = tx->u.tx.mode;
 
-        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;
+        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 =
-                                tx->local->short_retry_limit;
+                        control->retry_limit = 1;
                 }
-        } else {
-                control->retry_limit = 1;
         }
 
         if (tx->flags & IEEE80211_TXRXD_FRAGMENTED) {
@@ -785,9 +798,8 @@ ieee80211_tx_handler ieee80211_tx_handlers[] =
  * 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, struct ieee80211_tx_control *control)
+__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
@@ -802,18 +814,11 @@ __ieee80211_parse_tx_radiotap(
                 (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;
 
-        /*
-         * default control situation for all injected packets
-         * FIXME: this does not suit all usage cases, expand to allow control
-         */
-
-        control->retry_limit = 1; /* no retry */
-        control->flags &= ~(IEEE80211_TXCTL_USE_RTS_CTS |
-                            IEEE80211_TXCTL_USE_CTS_PROTECT);
-        control->flags |= IEEE80211_TXCTL_DO_NOT_ENCRYPT |
-                          IEEE80211_TXCTL_NO_ACK;
-        control->antenna_sel_tx = 0; /* default to default antenna */
+        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
@@ -846,19 +851,10 @@ __ieee80211_parse_tx_radiotap(
                         for (i = 0; i < mode->num_rates; i++) {
                                 struct ieee80211_rate *r = &mode->rates[i];
 
-                                if (r->rate > target_rate)
-                                        continue;
-
-                                control->rate = r;
-
-                                if (r->flags & IEEE80211_RATE_PREAMBLE2)
-                                        control->tx_rate = r->val2;
-                                else
-                                        control->tx_rate = r->val;
-
-                                /* end on exact match */
-                                if (r->rate == target_rate)
-                                        i = mode->num_rates;
+                                if (r->rate == target_rate) {
+                                        tx->u.tx.rate = r;
+                                        break;
+                                }
                         }
                         break;
 
@@ -888,8 +884,19 @@ __ieee80211_parse_tx_radiotap(
 
                                 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;
                 }
@@ -908,14 +915,17 @@ __ieee80211_parse_tx_radiotap(
         return TXRX_CONTINUE;
 }
 
-static ieee80211_txrx_result inline
+/*
+ * 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_hdr *) skb->data;
+        struct ieee80211_hdr *hdr;
         struct ieee80211_sub_if_data *sdata;
         ieee80211_txrx_result res = TXRX_CONTINUE;
 
@@ -926,33 +936,31 @@ __ieee80211_tx_prepare(struct ieee80211_txrx_data *tx,
         tx->dev = dev; /* use original interface */
         tx->local = local;
         tx->sdata = IEEE80211_DEV_TO_SUB_IF(dev);
-
+        tx->u.tx.control = control;
         /*
-         * set defaults for things that can be set by
-         * injected radiotap headers
+         * Set this flag (used below to indicate "automatic fragmentation"),
+         * it will be cleared/left by radiotap as desired.
          */
-        control->power_level = local->hw.conf.power_level;
-        control->antenna_sel_tx = local->hw.conf.antenna_sel_tx;
+        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, control) ==
-                                                                TXRX_DROP) {
+                if (__ieee80211_parse_tx_radiotap(tx, skb) == TXRX_DROP)
                         return TXRX_DROP;
-                }
+
                 /*
-                 * we removed the radiotap header after this point,
-                 * we filled control with what we could use
-                 * set to the actual ieee header now
+                 * __ieee80211_parse_tx_radiotap has now removed
+                 * the radiotap header that was present and pre-filled
+                 * 'tx' with tx control information.
                  */
-                hdr = (struct ieee80211_hdr *) skb->data;
-                res = TXRX_QUEUED; /* indication it was monitor packet */
         }
 
+        hdr = (struct ieee80211_hdr *) skb->data;
+
         tx->sta = sta_info_get(local, hdr->addr1);
         tx->fc = le16_to_cpu(hdr->frame_control);
-        tx->u.tx.control = control;
+
         if (is_multicast_ether_addr(hdr->addr1)) {
                 tx->flags &= ~IEEE80211_TXRXD_TXUNICAST;
                 control->flags |= IEEE80211_TXCTL_NO_ACK;
@@ -960,19 +968,23 @@ __ieee80211_tx_prepare(struct ieee80211_txrx_data *tx,
                 tx->flags |= IEEE80211_TXRXD_TXUNICAST;
                 control->flags &= ~IEEE80211_TXCTL_NO_ACK;
         }
-        if (local->fragmentation_threshold < IEEE80211_MAX_FRAG_THRESHOLD &&
-            (tx->flags & IEEE80211_TXRXD_TXUNICAST) &&
-            skb->len + FCS_LEN > local->fragmentation_threshold &&
-            !local->ops->set_frag_threshold)
-                tx->flags |= IEEE80211_TXRXD_FRAGMENTED;
-        else
-                tx->flags &= ~IEEE80211_TXRXD_FRAGMENTED;
+
+        if (tx->flags & IEEE80211_TXRXD_FRAGMENTED) {
+                if ((tx->flags & IEEE80211_TXRXD_TXUNICAST) &&
+                    skb->len + FCS_LEN > local->fragmentation_threshold &&
+                    !local->ops->set_frag_threshold)
+                        tx->flags |= IEEE80211_TXRXD_FRAGMENTED;
+                else
+                        tx->flags &= ~IEEE80211_TXRXD_FRAGMENTED;
+        }
+
         if (!tx->sta)
                 control->flags |= IEEE80211_TXCTL_CLEAR_DST_MASK;
         else if (tx->sta->clear_dst_mask) {
                 control->flags |= IEEE80211_TXCTL_CLEAR_DST_MASK;
                 tx->sta->clear_dst_mask = 0;
         }
+
         hdrlen = ieee80211_get_hdrlen(tx->fc);
         if (skb->len > hdrlen + sizeof(rfc1042_header) + 2) {
                 u8 *pos = &skb->data[hdrlen + sizeof(rfc1042_header)];
@@ -984,11 +996,14 @@ __ieee80211_tx_prepare(struct ieee80211_txrx_data *tx,
 }
 
 /* Device in tx->dev has a reference added; use dev_put(tx->dev) when
- * finished with it. */
-static int inline ieee80211_tx_prepare(struct ieee80211_txrx_data *tx,
-                                       struct sk_buff *skb,
-                                       struct net_device *mdev,
-                                       struct ieee80211_tx_control *control)
+ * finished with it.
+ *
+ * NB: @tx is uninitialised when passed in here
+ */
+static int ieee80211_tx_prepare(struct ieee80211_txrx_data *tx,
+                                struct sk_buff *skb,
+                                struct net_device *mdev,
+                                struct ieee80211_tx_control *control)
 {
         struct ieee80211_tx_packet_data *pkt_data;
         struct net_device *dev;
@@ -1001,6 +1016,7 @@ static int inline ieee80211_tx_prepare(struct ieee80211_txrx_data *tx,
         }
         if (unlikely(!dev))
                 return -ENODEV;
+        /* initialises tx with control */
         __ieee80211_tx_prepare(tx, skb, dev, control);
         return 0;
 }
@@ -1081,6 +1097,7 @@ static int ieee80211_tx(struct net_device *dev, struct sk_buff *skb,
                 return 0;
         }
 
+        /* initialises tx */
         res_prepare = __ieee80211_tx_prepare(&tx, skb, dev, control);
 
         if (res_prepare == TXRX_DROP) {
@@ -1097,15 +1114,11 @@ static int ieee80211_tx(struct net_device *dev, struct sk_buff *skb,
         sta = tx.sta;
         tx.u.tx.mode = local->hw.conf.mode;
 
-        if (res_prepare == TXRX_QUEUED) { /* if it was an injected packet */
-                res = TXRX_CONTINUE;
-        } else {
-                for (handler = local->tx_handlers; *handler != NULL;
-                     handler++) {
-                        res = (*handler)(&tx);
-                        if (res != TXRX_CONTINUE)
-                                break;
-                }
+        for (handler = local->tx_handlers; *handler != NULL;
+             handler++) {
+                res = (*handler)(&tx);
+                if (res != TXRX_CONTINUE)
+                        break;
         }
 
         skb = tx.skb; /* handlers are allowed to change skb */
@@ -1857,7 +1870,7 @@ ieee80211_get_buffered_bc(struct ieee80211_hw *hw, int if_id,
                                 cpu_to_le16(IEEE80211_FCTL_MOREDATA);
                 }
 
-                if (ieee80211_tx_prepare(&tx, skb, local->mdev, control) == 0)
+                if (!ieee80211_tx_prepare(&tx, skb, local->mdev, control))
                         break;
                 dev_kfree_skb_any(skb);
         }