iw: mesh: add mesh_param "mesh_nolearn" to skip path discovery
Commit Message
From: Linus Lüssing <ll@simonwunderlich.de>
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: Linus Lüssing <ll@simonwunderlich.de>
---
mesh.c | 2 ++
nl80211.h | 7 +++++++
2 files changed, 9 insertions(+)
@@ -264,6 +264,8 @@ static const struct mesh_param_descr _mesh_param_descrs[] =
_my_nla_put_u16, _parse_u16, _print_u16_in_TUs},
{"mesh_plink_timeout", NL80211_MESHCONF_PLINK_TIMEOUT,
_my_nla_put_u32, _parse_u32, _print_u32_in_seconds},
+ {"mesh_nolearn", NL80211_MESHCONF_NOLEARN,
+ _my_nla_put_u8, _parse_u8_as_bool, _print_u8},
};
static void print_all_mesh_param_descr(void)
@@ -4228,6 +4228,12 @@ 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 {
@@ -4261,6 +4267,7 @@ 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,