mac80211: don't initiate path discovery when forwarding frame with unknown DA

We used to initiate a path discovery when receiving a frame for which
there is no forwarding information. To cut down on PREQ spam, just send
a (gated) PERR in response.

Also separate path discovery logic from nexthop querying. This patch
means we no longer queue frames when forwarding, so kill the PERR TX
stuff in discard_frame().

Signed-off-by: Thomas Pedersen <thomas@cozybit.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

5 files changed, 79 insertions, 77 deletions

diff --git a/net/mac80211/mesh.h b/net/mac80211/mesh.h
index 622cc96eb4d..bd14bd26a2b 100644
--- a/net/mac80211/mesh.h
+++ b/net/mac80211/mesh.h
@@ -233,6 +233,8 @@ void ieee80211_mesh_root_setup(struct ieee80211_if_mesh *ifmsh);
 /* Mesh paths */
 int mesh_nexthop_lookup(struct sk_buff *skb,
                 struct ieee80211_sub_if_data *sdata);
+int mesh_nexthop_resolve(struct sk_buff *skb,
+                         struct ieee80211_sub_if_data *sdata);
 void mesh_path_start_discovery(struct ieee80211_sub_if_data *sdata);
 struct mesh_path *mesh_path_lookup(u8 *dst,
                 struct ieee80211_sub_if_data *sdata);
diff --git a/net/mac80211/mesh_hwmp.c b/net/mac80211/mesh_hwmp.c
index fe93386d6aa..73abb7524b2 100644
--- a/net/mac80211/mesh_hwmp.c
+++ b/net/mac80211/mesh_hwmp.c
@@ -982,72 +982,97 @@ enddiscovery:
         kfree(preq_node);
 }
 
-/**
- * mesh_nexthop_lookup - put the appropriate next hop on a mesh frame
+/* mesh_nexthop_resolve - lookup next hop for given skb and start path
+ * discovery if no forwarding information is found.
  *
  * @skb: 802.11 frame to be sent
  * @sdata: network subif the frame will be sent through
  *
- * Returns: 0 if the next hop was found. Nonzero otherwise. If no next hop is
- * found, the function will start a path discovery and queue the frame so it is
- * sent when the path is resolved. This means the caller must not free the skb
- * in this case.
+ * Returns: 0 if the next hop was found and -ENOENT if the frame was queued.
+ * skb is freeed here if no mpath could be allocated.
  */
-int mesh_nexthop_lookup(struct sk_buff *skb,
-                        struct ieee80211_sub_if_data *sdata)
+int mesh_nexthop_resolve(struct sk_buff *skb,
+                         struct ieee80211_sub_if_data *sdata)
 {
-        struct sk_buff *skb_to_free = NULL;
-        struct mesh_path *mpath;
-        struct sta_info *next_hop;
         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
+        struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
+        struct mesh_path *mpath;
+        struct sk_buff *skb_to_free = NULL;
         u8 *target_addr = hdr->addr3;
         int err = 0;
 
         rcu_read_lock();
-        mpath = mesh_path_lookup(target_addr, sdata);
+        err = mesh_nexthop_lookup(skb, sdata);
+        if (!err)
+                goto endlookup;
 
+        /* no nexthop found, start resolving */
+        mpath = mesh_path_lookup(target_addr, sdata);
         if (!mpath) {
                 mesh_path_add(target_addr, sdata);
                 mpath = mesh_path_lookup(target_addr, sdata);
                 if (!mpath) {
-                        sdata->u.mesh.mshstats.dropped_frames_no_route++;
+                        mesh_path_discard_frame(skb, sdata);
                         err = -ENOSPC;
                         goto endlookup;
                 }
         }
 
-        if (mpath->flags & MESH_PATH_ACTIVE) {
-                if (time_after(jiffies,
-                               mpath->exp_time -
-                               msecs_to_jiffies(sdata->u.mesh.mshcfg.path_refresh_time)) &&
-                    !memcmp(sdata->vif.addr, hdr->addr4, ETH_ALEN) &&
-                    !(mpath->flags & MESH_PATH_RESOLVING) &&
-                    !(mpath->flags & MESH_PATH_FIXED)) {
-                        mesh_queue_preq(mpath,
-                                        PREQ_Q_F_START | PREQ_Q_F_REFRESH);
-                }
-                next_hop = rcu_dereference(mpath->next_hop);
-                if (next_hop) {
-                        memcpy(hdr->addr1, next_hop->sta.addr, ETH_ALEN);
-                        memcpy(hdr->addr2, sdata->vif.addr, ETH_ALEN);
-                } else
-                        err = -ENOENT;
-        } else {
-                struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
-                if (!(mpath->flags & MESH_PATH_RESOLVING)) {
-                        /* Start discovery only if it is not running yet */
-                        mesh_queue_preq(mpath, PREQ_Q_F_START);
-                }
+        if (!(mpath->flags & MESH_PATH_RESOLVING))
+                mesh_queue_preq(mpath, PREQ_Q_F_START);
+
+        if (skb_queue_len(&mpath->frame_queue) >= MESH_FRAME_QUEUE_LEN)
+                skb_to_free = skb_dequeue(&mpath->frame_queue);
+
+        info->flags |= IEEE80211_TX_INTFL_NEED_TXPROCESSING;
+        ieee80211_set_qos_hdr(sdata, skb);
+        skb_queue_tail(&mpath->frame_queue, skb);
+        err = -ENOENT;
+        if (skb_to_free)
+                mesh_path_discard_frame(skb_to_free, sdata);
+
+endlookup:
+        rcu_read_unlock();
+        return err;
+}
+/**
+ * mesh_nexthop_lookup - put the appropriate next hop on a mesh frame. Calling
+ * this function is considered "using" the associated mpath, so preempt a path
+ * refresh if this mpath expires soon.
+ *
+ * @skb: 802.11 frame to be sent
+ * @sdata: network subif the frame will be sent through
+ *
+ * Returns: 0 if the next hop was found. Nonzero otherwise.
+ */
+int mesh_nexthop_lookup(struct sk_buff *skb,
+                        struct ieee80211_sub_if_data *sdata)
+{
+        struct mesh_path *mpath;
+        struct sta_info *next_hop;
+        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
+        u8 *target_addr = hdr->addr3;
+        int err = -ENOENT;
 
-                if (skb_queue_len(&mpath->frame_queue) >= MESH_FRAME_QUEUE_LEN)
-                        skb_to_free = skb_dequeue(&mpath->frame_queue);
+        rcu_read_lock();
+        mpath = mesh_path_lookup(target_addr, sdata);
+
+        if (!mpath || !(mpath->flags & MESH_PATH_ACTIVE))
+                goto endlookup;
+
+        if (time_after(jiffies,
+                       mpath->exp_time -
+                       msecs_to_jiffies(sdata->u.mesh.mshcfg.path_refresh_time)) &&
+            !memcmp(sdata->vif.addr, hdr->addr4, ETH_ALEN) &&
+            !(mpath->flags & MESH_PATH_RESOLVING) &&
+            !(mpath->flags & MESH_PATH_FIXED))
+                mesh_queue_preq(mpath, PREQ_Q_F_START | PREQ_Q_F_REFRESH);
 
-                info->flags |= IEEE80211_TX_INTFL_NEED_TXPROCESSING;
-                ieee80211_set_qos_hdr(sdata, skb);
-                skb_queue_tail(&mpath->frame_queue, skb);
-                if (skb_to_free)
-                        mesh_path_discard_frame(skb_to_free, sdata);
-                err = -ENOENT;
+        next_hop = rcu_dereference(mpath->next_hop);
+        if (next_hop) {
+                memcpy(hdr->addr1, next_hop->sta.addr, ETH_ALEN);
+                memcpy(hdr->addr2, sdata->vif.addr, ETH_ALEN);
+                err = 0;
         }
 
 endlookup:
diff --git a/net/mac80211/mesh_pathtbl.c b/net/mac80211/mesh_pathtbl.c
index 4c50d8ade04..edf167e3b8f 100644
--- a/net/mac80211/mesh_pathtbl.c
+++ b/net/mac80211/mesh_pathtbl.c
@@ -973,38 +973,11 @@ int mesh_path_send_to_gates(struct mesh_path *mpath)
  * @skb: frame to discard
  * @sdata: network subif the frame was to be sent through
  *
- * If the frame was being forwarded from another MP, a PERR frame will be sent
- * to the precursor.  The precursor's address (i.e. the previous hop) was saved
- * in addr1 of the frame-to-be-forwarded, and would only be overwritten once
- * the destination is successfully resolved.
- *
  * Locking: the function must me called within a rcu_read_lock region
  */
 void mesh_path_discard_frame(struct sk_buff *skb,
                              struct ieee80211_sub_if_data *sdata)
 {
-        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
-        struct mesh_path *mpath;
-        u32 sn = 0;
-        __le16 reason = cpu_to_le16(WLAN_REASON_MESH_PATH_NOFORWARD);
-
-        if (memcmp(hdr->addr4, sdata->vif.addr, ETH_ALEN) != 0) {
-                u8 *ra, *da;
-
-                da = hdr->addr3;
-                ra = hdr->addr2;
-                rcu_read_lock();
-                mpath = mesh_path_lookup(da, sdata);
-                if (mpath) {
-                        spin_lock_bh(&mpath->state_lock);
-                        sn = ++mpath->sn;
-                        spin_unlock_bh(&mpath->state_lock);
-                }
-                rcu_read_unlock();
-                mesh_path_error_tx(sdata->u.mesh.mshcfg.element_ttl, da,
-                                   cpu_to_le32(sn), reason, ra, sdata);
-        }
-
         kfree_skb(skb);
         sdata->u.mesh.mshstats.dropped_frames_no_route++;
 }
diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index 92fa9574176..f842f901d17 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -1899,6 +1899,7 @@ ieee80211_rx_h_mesh_fwding(struct ieee80211_rx_data *rx)
         struct ieee80211_local *local = rx->local;
         struct ieee80211_sub_if_data *sdata = rx->sdata;
         struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
+        __le16 reason = cpu_to_le16(WLAN_REASON_MESH_PATH_NOFORWARD);
         u16 q;
 
         hdr = (struct ieee80211_hdr *) skb->data;
@@ -1985,13 +1986,14 @@ ieee80211_rx_h_mesh_fwding(struct ieee80211_rx_data *rx)
                                                                 fwded_mcast);
                                 memcpy(fwd_hdr->addr2, sdata->vif.addr, ETH_ALEN);
                         } else {
-                                int err;
-                                err = mesh_nexthop_lookup(fwd_skb, sdata);
-                                /* Failed to immediately resolve next hop:
-                                 * fwded frame was dropped or will be added
-                                 * later to the pending skb queue.  */
-                                if (err)
+                                if (mesh_nexthop_lookup(fwd_skb, sdata)) {
+                                /* can't resolve next hop, send a PERR */
+                                        mesh_path_error_tx(sdata->u.mesh.mshcfg.element_ttl,
+                                                           fwd_hdr->addr3, 0, reason,
+                                                           fwd_hdr->addr2, sdata);
+                                        sdata->u.mesh.mshstats.dropped_frames_no_route++;
                                         return RX_DROP_MONITOR;
+                                }
 
                                 IEEE80211_IFSTA_MESH_CTR_INC(&sdata->u.mesh,
                                                                 fwded_unicast);
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 655e3a97f92..c4cb4a536e2 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -1464,7 +1464,7 @@ void ieee80211_xmit(struct ieee80211_sub_if_data *sdata, struct sk_buff *skb)
         if (ieee80211_vif_is_mesh(&sdata->vif) &&
             ieee80211_is_data(hdr->frame_control) &&
                 !is_multicast_ether_addr(hdr->addr1))
-                        if (mesh_nexthop_lookup(skb, sdata)) {
+                        if (mesh_nexthop_resolve(skb, sdata)) {
                                 /* skb queued: don't free */
                                 rcu_read_unlock();
                                 return;