Commit e3718a61 authored by Linus Lüssing's avatar Linus Lüssing Committed by Johannes Berg
Browse files

cfg80211/mac80211: add mesh_param "mesh_nolearn" to skip path discovery 



Currently, before being able to forward a packet between two 802.11s
nodes, both a PLINK handshake is performed upon receiving a beacon and
then later a PREQ/PREP exchange for path discovery is performed on
demand upon receiving a data frame to forward.

When running a mesh protocol on top of an 802.11s interface, like
batman-adv, we do not need the multi-hop mesh routing capabilities of
802.11s and usually set mesh_fwding=0. However, even with mesh_fwding=0
the PREQ/PREP path discovery is still performed on demand. Even though
in this scenario the next hop PREQ/PREP will determine is always the
direct 11s neighbor node.

The new mesh_nolearn parameter allows to skip the PREQ/PREP exchange in
this scenario, leading to a reduced delay, reduced packet buffering and
simplifies HWMP in general.

mesh_nolearn is still rather conservative in that if the packet destination
is not a direct 11s neighbor, it will fall back to PREQ/PREP path
discovery.

For normal, multi-hop 802.11s mesh routing it is usually not advisable
to enable mesh_nolearn as a transmission to a direct but distant neighbor
might be worse than reaching that same node via a more robust /
higher throughput etc. multi-hop path.

Cc: Sven Eckelmann <sven@narfation.org>
Cc: Simon Wunderlich <sw@simonwunderlich.de>
Signed-off-by: default avatarLinus Lüssing <ll@simonwunderlich.de>
Link: https://lore.kernel.org/r/20200617073034.26149-1-linus.luessing@c0d3.blue


[fix nl80211 policy to range 0/1 only]
Signed-off-by: default avatarJohannes Berg <johannes.berg@intel.com>
parent 2f1805ea

include/net/cfg80211.h

+6 −0
Original line number Diff line number Diff line
@@ -1870,6 +1870,11 @@ struct bss_parameters { 
 *      connected to a mesh gate in mesh formation info.  If false, the

 *      value in mesh formation is determined by the presence of root paths

 *      in the mesh path table

 * @dot11MeshNolearn: Try to avoid multi-hop path discovery (e.g. PREQ/PREP

 *      for HWMP) if the destination is a direct neighbor. Note that this might

 *      not be the optimal decision as a multi-hop route might be better. So

 *      if using this setting you will likely also want to disable

 *      dot11MeshForwarding and use another mesh routing protocol on top.

 */

struct mesh_config {

	u16 dot11MeshRetryTimeout;
@@ -1901,6 +1906,7 @@ struct mesh_config { 
	enum nl80211_mesh_power_mode power_mode;

	u16 dot11MeshAwakeWindowDuration;

	u32 plink_timeout;

	bool dot11MeshNolearn;

};



/**

include/uapi/linux/nl80211.h

+7 −0
Original line number Diff line number Diff line
@@ -4236,6 +4236,12 @@ enum nl80211_mesh_power_mode { 
 *	field.  If left unset then the mesh formation field will only

 *	advertise such if there is an active root mesh path.

 *

 * @NL80211_MESHCONF_NOLEARN: Try to avoid multi-hop path discovery (e.g.

 *      PREQ/PREP for HWMP) if the destination is a direct neighbor. Note that

 *      this might not be the optimal decision as a multi-hop route might be

 *      better. So if using this setting you will likely also want to disable

 *      dot11MeshForwarding and use another mesh routing protocol on top.

 *

 * @__NL80211_MESHCONF_ATTR_AFTER_LAST: internal use

 */

enum nl80211_meshconf_params {
@@ -4269,6 +4275,7 @@ enum nl80211_meshconf_params { 
	NL80211_MESHCONF_AWAKE_WINDOW,

	NL80211_MESHCONF_PLINK_TIMEOUT,

	NL80211_MESHCONF_CONNECTED_TO_GATE,

	NL80211_MESHCONF_NOLEARN,



	/* keep last */

	__NL80211_MESHCONF_ATTR_AFTER_LAST,

net/mac80211/cfg.c

+2 −0
Original line number Diff line number Diff line
@@ -2126,6 +2126,8 @@ static int ieee80211_update_mesh_config(struct wiphy *wiphy, 
	if (_chg_mesh_attr(NL80211_MESHCONF_CONNECTED_TO_GATE, mask))

		conf->dot11MeshConnectedToMeshGate =

			nconf->dot11MeshConnectedToMeshGate;

	if (_chg_mesh_attr(NL80211_MESHCONF_NOLEARN, mask))

		conf->dot11MeshNolearn = nconf->dot11MeshNolearn;

	ieee80211_mbss_info_change_notify(sdata, BSS_CHANGED_BEACON);

	return 0;

}

net/mac80211/debugfs_netdev.c

+2 −0
Original line number Diff line number Diff line
@@ -638,6 +638,7 @@ IEEE80211_IF_FILE(dot11MeshAwakeWindowDuration, 
		  u.mesh.mshcfg.dot11MeshAwakeWindowDuration, DEC);

IEEE80211_IF_FILE(dot11MeshConnectedToMeshGate,

		  u.mesh.mshcfg.dot11MeshConnectedToMeshGate, DEC);

IEEE80211_IF_FILE(dot11MeshNolearn, u.mesh.mshcfg.dot11MeshNolearn, DEC);

#endif



#define DEBUGFS_ADD_MODE(name, mode) \
@@ -762,6 +763,7 @@ static void add_mesh_config(struct ieee80211_sub_if_data *sdata) 
	MESHPARAMS_ADD(power_mode);

	MESHPARAMS_ADD(dot11MeshAwakeWindowDuration);

	MESHPARAMS_ADD(dot11MeshConnectedToMeshGate);

	MESHPARAMS_ADD(dot11MeshNolearn);

#undef MESHPARAMS_ADD

}

#endif

net/mac80211/mesh_hwmp.c

+39 −0
Original line number Diff line number Diff line
@@ -1172,6 +1172,40 @@ int mesh_nexthop_resolve(struct ieee80211_sub_if_data *sdata, 
	return -ENOENT;

}



/**

 * mesh_nexthop_lookup_nolearn - try to set next hop without path discovery

 * @skb: 802.11 frame to be sent

 * @sdata: network subif the frame will be sent through

 *

 * Check if the meshDA (addr3) of a unicast frame is a direct neighbor.

 * And if so, set the RA (addr1) to it to transmit to this node directly,

 * avoiding PREQ/PREP path discovery.

 *

 * Returns: 0 if the next hop was found and -ENOENT otherwise.

 */

static int mesh_nexthop_lookup_nolearn(struct ieee80211_sub_if_data *sdata,

				       struct sk_buff *skb)

{

	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;

	struct sta_info *sta;



	if (is_multicast_ether_addr(hdr->addr1))

		return -ENOENT;



	rcu_read_lock();

	sta = sta_info_get(sdata, hdr->addr3);



	if (!sta || sta->mesh->plink_state != NL80211_PLINK_ESTAB) {

		rcu_read_unlock();

		return -ENOENT;

	}

	rcu_read_unlock();



	memcpy(hdr->addr1, hdr->addr3, ETH_ALEN);

	memcpy(hdr->addr2, sdata->vif.addr, ETH_ALEN);

	return 0;

}



/**

 * 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
@@ -1185,11 +1219,16 @@ int mesh_nexthop_resolve(struct ieee80211_sub_if_data *sdata, 
int mesh_nexthop_lookup(struct ieee80211_sub_if_data *sdata,

			struct sk_buff *skb)

{

	struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;

	struct mesh_path *mpath;

	struct sta_info *next_hop;

	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;

	u8 *target_addr = hdr->addr3;



	if (ifmsh->mshcfg.dot11MeshNolearn &&

	    !mesh_nexthop_lookup_nolearn(sdata, skb))

		return 0;



	mpath = mesh_path_lookup(sdata, target_addr);

	if (!mpath || !(mpath->flags & MESH_PATH_ACTIVE))

		return -ENOENT;