mac80211: probe unexercised mesh links

The requirement for mesh link metric refreshing, is that from one
mesh point we be able to send some data frames to other mesh points
which are not currently selected as a primary traffic path, but which
are only 1 hop away. The absence of the primary path to the chosen node
makes it necessary to apply some form of marking on a chosen packet
stream so that the packets can be properly steered to the selected node
for testing, and not by the regular mesh path lookup.

Tested-by: Pradeep Kumar Chitrapu <pradeepc@codeaurora.org>
Signed-off-by: Rajkumar Manoharan <rmanohar@codeaurora.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

Author: Rajkumar Manoharan

include/net/mac80211.h

@@ -807,6 +807,7 @@ enum mac80211_tx_info_flags {
  * @IEEE80211_TX_CTRL_RATE_INJECT: This frame is injected with rate information
  * @IEEE80211_TX_CTRL_AMSDU: This frame is an A-MSDU frame
  * @IEEE80211_TX_CTRL_FAST_XMIT: This frame is going through the fast_xmit path
+ * @IEEE80211_TX_CTRL_SKIP_MPATH_LOOKUP: This frame skips mesh path lookup
  *
  * These flags are used in tx_info->control.flags.
  */
@@ -816,6 +817,7 @@ enum mac80211_tx_control_flags {
 	IEEE80211_TX_CTRL_RATE_INJECT		= BIT(2),
 	IEEE80211_TX_CTRL_AMSDU			= BIT(3),
 	IEEE80211_TX_CTRL_FAST_XMIT		= BIT(4),
+	IEEE80211_TX_CTRL_SKIP_MPATH_LOOKUP	= BIT(5),
 };
 
 /*

net/mac80211/cfg.c

@@ -4035,4 +4035,5 @@ const struct cfg80211_ops mac80211_config_ops = {
 	.get_ftm_responder_stats = ieee80211_get_ftm_responder_stats,
 	.start_pmsr = ieee80211_start_pmsr,
 	.abort_pmsr = ieee80211_abort_pmsr,
+	.probe_mesh_link = ieee80211_probe_mesh_link,
 };

net/mac80211/ieee80211_i.h

@@ -1779,6 +1779,8 @@ void ieee80211_clear_fast_xmit(struct sta_info *sta);
 int ieee80211_tx_control_port(struct wiphy *wiphy, struct net_device *dev,
 			      const u8 *buf, size_t len,
 			      const u8 *dest, __be16 proto, bool unencrypted);
+int ieee80211_probe_mesh_link(struct wiphy *wiphy, struct net_device *dev,
+			      const u8 *buf, size_t len);
 
 /* HT */
 void ieee80211_apply_htcap_overrides(struct ieee80211_sub_if_data *sdata,

net/mac80211/mesh_hwmp.c

@@ -1135,6 +1135,10 @@ int mesh_nexthop_resolve(struct ieee80211_sub_if_data *sdata,
 	if (ieee80211_is_qos_nullfunc(hdr->frame_control))
 		return 0;
 
+	/* Allow injected packets to bypass mesh routing */
+	if (info->control.flags & IEEE80211_TX_CTRL_SKIP_MPATH_LOOKUP)
+		return 0;
+
 	if (!mesh_nexthop_lookup(sdata, skb))
 		return 0;
 

net/mac80211/tx.c

@@ -2607,6 +2607,13 @@ static struct sk_buff *ieee80211_build_hdr(struct ieee80211_sub_if_data *sdata,
 			goto free;
 		}
 		band = chanctx_conf->def.chan->band;
+
+		/* For injected frames, fill RA right away as nexthop lookup
+		 * will be skipped.
+		 */
+		if ((ctrl_flags & IEEE80211_TX_CTRL_SKIP_MPATH_LOOKUP) &&
+		    is_zero_ether_addr(hdr.addr1))
+			memcpy(hdr.addr1, skb->data, ETH_ALEN);
 		break;
 #endif
 	case NL80211_IFTYPE_STATION:
@@ -5091,3 +5098,32 @@ int ieee80211_tx_control_port(struct wiphy *wiphy, struct net_device *dev,
 
 	return 0;
 }
+
+int ieee80211_probe_mesh_link(struct wiphy *wiphy, struct net_device *dev,
+			      const u8 *buf, size_t len)
+{
+	struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev);
+	struct ieee80211_local *local = sdata->local;
+	struct sk_buff *skb;
+
+	skb = dev_alloc_skb(local->hw.extra_tx_headroom + len +
+			    30 + /* header size */
+			    18); /* 11s header size */
+	if (!skb)
+		return -ENOMEM;
+
+	skb_reserve(skb, local->hw.extra_tx_headroom);
+	skb_put_data(skb, buf, len);
+
+	skb->dev = dev;
+	skb->protocol = htons(ETH_P_802_3);
+	skb_reset_network_header(skb);
+	skb_reset_mac_header(skb);
+
+	local_bh_disable();
+	__ieee80211_subif_start_xmit(skb, skb->dev, 0,
+				     IEEE80211_TX_CTRL_SKIP_MPATH_LOOKUP);
+	local_bh_enable();
+
+	return 0;
+}