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 ---
Changelog v2/v3: * unchanged
mesh.c | 2 ++ nl80211.h | 7 +++++++ 2 files changed, 9 insertions(+)
diff --git a/mesh.c b/mesh.c index 0650d0c..48bbc3f 100644 --- a/mesh.c +++ b/mesh.c @@ -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) diff --git a/nl80211.h b/nl80211.h index c14666b..4c55e89 100644 --- a/nl80211.h +++ b/nl80211.h @@ -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,