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 v3: * fixing typo in mesh_nexthop_lookup_nolearn() kerneldoc ("PREP/PREP" -> "PREQ/PREP") * fixing FILL_IN_MESH_PARAM_IF_SET() invocation

Changelog v2: * moved nolearn lookup closer into the actual nexthop_lookup function, so that the nolearn feature is not confusingly avoided on forwarded frames

include/net/cfg80211.h | 6 ++++++ include/uapi/linux/nl80211.h | 7 +++++++ net/mac80211/cfg.c | 2 ++ net/mac80211/debugfs_netdev.c | 2 ++ net/mac80211/mesh_hwmp.c | 39 +++++++++++++++++++++++++++++++++++ net/wireless/mesh.c | 1 + net/wireless/nl80211.c | 7 ++++++- net/wireless/trace.h | 4 +++- 8 files changed, 66 insertions(+), 2 deletions(-)

diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h index fc7e8807838d..5ffb35592a23 100644 --- a/include/net/cfg80211.h +++ b/include/net/cfg80211.h @@ -1853,6 +1853,11 @@ 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; @@ -1884,6 +1889,7 @@ struct mesh_config { enum nl80211_mesh_power_mode power_mode; u16 dot11MeshAwakeWindowDuration; u32 plink_timeout; + bool dot11MeshNolearn; };

/** diff --git a/include/uapi/linux/nl80211.h b/include/uapi/linux/nl80211.h index 4e6339ab1fce..f6560bb9644c 100644 --- a/include/uapi/linux/nl80211.h +++ b/include/uapi/linux/nl80211.h @@ -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, diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c index 9b360544ad6f..f48e095e912a 100644 --- a/net/mac80211/cfg.c +++ b/net/mac80211/cfg.c @@ -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; } diff --git a/net/mac80211/debugfs_netdev.c b/net/mac80211/debugfs_netdev.c index d7e955127d5c..09eab2c3f380 100644 --- a/net/mac80211/debugfs_netdev.c +++ b/net/mac80211/debugfs_netdev.c @@ -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 diff --git a/net/mac80211/mesh_hwmp.c b/net/mac80211/mesh_hwmp.c index aa5150929996..76745b206658 100644 --- a/net/mac80211/mesh_hwmp.c +++ b/net/mac80211/mesh_hwmp.c @@ -1175,6 +1175,40 @@ 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 @@ -1188,11 +1222,16 @@ 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; diff --git a/net/wireless/mesh.c b/net/wireless/mesh.c index eac5aa1419fc..e4e363138279 100644 --- a/net/wireless/mesh.c +++ b/net/wireless/mesh.c @@ -78,6 +78,7 @@ const struct mesh_config default_mesh_config = { .power_mode = NL80211_MESH_POWER_ACTIVE, .dot11MeshAwakeWindowDuration = MESH_DEFAULT_AWAKE_WINDOW, .plink_timeout = MESH_DEFAULT_PLINK_TIMEOUT, + .dot11MeshNolearn = false, };

const struct mesh_setup default_mesh_setup = { diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c index 263ae395ad44..43b28bab2e64 100644 --- a/net/wireless/nl80211.c +++ b/net/wireless/nl80211.c @@ -6884,7 +6884,9 @@ static int nl80211_get_mesh_config(struct sk_buff *skb, nla_put_u32(msg, NL80211_MESHCONF_PLINK_TIMEOUT, cur_params.plink_timeout) || nla_put_u8(msg, NL80211_MESHCONF_CONNECTED_TO_GATE, - cur_params.dot11MeshConnectedToMeshGate)) + cur_params.dot11MeshConnectedToMeshGate) || + nla_put_u8(msg, NL80211_MESHCONF_NOLEARN, + cur_params.dot11MeshNolearn)) goto nla_put_failure; nla_nest_end(msg, pinfoattr); genlmsg_end(msg, hdr); @@ -6942,6 +6944,7 @@ nl80211_meshconf_params_policy[NL80211_MESHCONF_ATTR_MAX+1] = { [NL80211_MESHCONF_AWAKE_WINDOW] = { .type = NLA_U16 }, [NL80211_MESHCONF_PLINK_TIMEOUT] = { .type = NLA_U32 }, [NL80211_MESHCONF_CONNECTED_TO_GATE] = NLA_POLICY_RANGE(NLA_U8, 0, 1), + [NL80211_MESHCONF_NOLEARN] = { .type = NLA_U8 }, };

static const struct nla_policy @@ -7093,6 +7096,8 @@ do { \ NL80211_MESHCONF_AWAKE_WINDOW, nla_get_u16); FILL_IN_MESH_PARAM_IF_SET(tb, cfg, plink_timeout, mask, NL80211_MESHCONF_PLINK_TIMEOUT, nla_get_u32); + FILL_IN_MESH_PARAM_IF_SET(tb, cfg, dot11MeshNolearn, mask, + NL80211_MESHCONF_NOLEARN, nla_get_u8); if (mask_out) *mask_out = mask;

diff --git a/net/wireless/trace.h b/net/wireless/trace.h index b23cab016521..6e218a0acd4e 100644 --- a/net/wireless/trace.h +++ b/net/wireless/trace.h @@ -68,7 +68,8 @@ __field(u16, ht_opmode) \ __field(u32, dot11MeshHWMPactivePathToRootTimeout) \ __field(u16, dot11MeshHWMProotInterval) \ - __field(u16, dot11MeshHWMPconfirmationInterval) + __field(u16, dot11MeshHWMPconfirmationInterval) \ + __field(bool, dot11MeshNolearn) #define MESH_CFG_ASSIGN \ do { \ __entry->dot11MeshRetryTimeout = conf->dot11MeshRetryTimeout; \ @@ -109,6 +110,7 @@ conf->dot11MeshHWMProotInterval; \ __entry->dot11MeshHWMPconfirmationInterval = \ conf->dot11MeshHWMPconfirmationInterval; \ + __entry->dot11MeshNolearn = conf->dot11MeshNolearn; \ } while (0)

#define CHAN_ENTRY __field(enum nl80211_band, band) \