mac80211: fix virtual interfaces vs. injection

Currently, virtual interface pointers passed to drivers might be
from monitor interfaces and as such completely uninitialised
because we do not tell the driver about monitor interfaces when
those are created. Instead of passing them, we should therefore
indicate to the driver that there is no information; do that by
passing a NULL value and adjust drivers to cope with it.

As a result, some mac80211 API functions also need to cope with
a NULL vif pointer so drivers can still call them unconditionally.

Also, when injecting frames we really don't want to pass NULL all
the time, if we know we are the source address of a frame and have
a local interface for that address, we can to use that interface.
This also helps with processing the frame correctly for that
interface which will help the 802.11w implementation. It's not
entirely correct for VLANs or WDS interfaces because there the MAC
address isn't unique, but it's already a lot better than what we
do now.

Finally, when injecting without a matching local interface, don't
assign sequence numbers at all.

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

1 files changed, 60 insertions, 4 deletions

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 698c8233e6b..c12f361d718 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -624,7 +624,14 @@ ieee80211_tx_h_sequence(struct ieee80211_tx_data *tx)
 	u8 *qc;
 	int tid;
 
-	/* only for injected frames */
+	/*
+	 * Packet injection may want to control the sequence
+	 * number, if we have no matching interface then we
+	 * neither assign one ourselves nor ask the driver to.
+	 */
+	if (unlikely(!info->control.vif))
+		return TX_CONTINUE;
+
 	if (unlikely(ieee80211_is_ctl(hdr->frame_control)))
 		return TX_CONTINUE;
 
@@ -849,7 +856,6 @@ __ieee80211_parse_tx_radiotap(struct ieee80211_tx_data *tx,
 	sband = tx->local->hw.wiphy->bands[tx->channel->band];
 
 	skb->do_not_encrypt = 1;
-	info->flags |= IEEE80211_TX_CTL_INJECTED;
 	tx->flags &= ~IEEE80211_TX_FRAGMENTED;
 
 	/*
@@ -981,7 +987,7 @@ __ieee80211_tx_prepare(struct ieee80211_tx_data *tx,
 
 	/* process and remove the injection radiotap header */
 	sdata = IEEE80211_DEV_TO_SUB_IF(dev);
-	if (unlikely(sdata->vif.type == NL80211_IFTYPE_MONITOR)) {
+	if (unlikely(info->flags & IEEE80211_TX_CTL_INJECTED)) {
 		if (__ieee80211_parse_tx_radiotap(tx, skb) == TX_DROP)
 			return TX_DROP;
 
@@ -1300,6 +1306,11 @@ int ieee80211_master_start_xmit(struct sk_buff *skb,
 	struct ieee80211_sub_if_data *osdata;
 	int headroom;
 	bool may_encrypt;
+	enum {
+		NOT_MONITOR,
+		FOUND_SDATA,
+		UNKNOWN_ADDRESS,
+	} monitor_iface = NOT_MONITOR;
 	int ret;
 
 	if (skb->iif)
@@ -1335,6 +1346,50 @@ int ieee80211_master_start_xmit(struct sk_buff *skb,
 				IEEE80211_IFSTA_MESH_CTR_INC(&osdata->u.mesh,
 							     fwded_frames);
 		}
+	} else if (unlikely(osdata->vif.type == NL80211_IFTYPE_MONITOR)) {
+		struct ieee80211_sub_if_data *sdata;
+		struct ieee80211_local *local = osdata->local;
+		struct ieee80211_hdr *hdr;
+		int hdrlen;
+		u16 len_rthdr;
+
+		info->flags |= IEEE80211_TX_CTL_INJECTED;
+		monitor_iface = UNKNOWN_ADDRESS;
+
+		len_rthdr = ieee80211_get_radiotap_len(skb->data);
+		hdr = (struct ieee80211_hdr *)skb->data + len_rthdr;
+		hdrlen = ieee80211_hdrlen(hdr->frame_control);
+
+		/* check the header is complete in the frame */
+		if (likely(skb->len >= len_rthdr + hdrlen)) {
+			/*
+			 * We process outgoing injected frames that have a
+			 * local address we handle as though they are our
+			 * own frames.
+			 * This code here isn't entirely correct, the local
+			 * MAC address is not necessarily enough to find
+			 * the interface to use; for that proper VLAN/WDS
+			 * support we will need a different mechanism.
+			 */
+
+			rcu_read_lock();
+			list_for_each_entry_rcu(sdata, &local->interfaces,
+						list) {
+				if (!netif_running(sdata->dev))
+					continue;
+				if (compare_ether_addr(sdata->dev->dev_addr,
+						       hdr->addr2)) {
+					dev_hold(sdata->dev);
+					dev_put(odev);
+					osdata = sdata;
+					odev = osdata->dev;
+					skb->iif = sdata->dev->ifindex;
+					monitor_iface = FOUND_SDATA;
+					break;
+				}
+			}
+			rcu_read_unlock();
+		}
 	}
 
 	may_encrypt = !skb->do_not_encrypt;
@@ -1355,7 +1410,8 @@ int ieee80211_master_start_xmit(struct sk_buff *skb,
 		osdata = container_of(osdata->bss,
 				      struct ieee80211_sub_if_data,
 				      u.ap);
-	info->control.vif = &osdata->vif;
+	if (likely(monitor_iface != UNKNOWN_ADDRESS))
+		info->control.vif = &osdata->vif;
 	ret = ieee80211_tx(odev, skb);
 	dev_put(odev);