From b478e06a16a8baa00c5ecc87c1d636981f2206d5 Mon Sep 17 00:00:00 2001
From: Johannes Berg <johannes.berg@intel.com>
Date: Tue, 29 Oct 2019 10:25:25 +0100
Subject: [PATCH] mac80211: sta: randomize BA session dialog token allocator

We currently always start the dialog token generator at zero,
so the first dialog token we use is always 1. This would be
OK if we had a perfect guarantee that we always do a proper
deauth/re-auth handshake, but in IBSS mode this doesn't always
happen properly.

To make problems with block ack (aggregation) sessions getting
stuck less likely, randomize the dialog token so if we start a
new session but the peer still has old state for us, it can
better detect this.

This is really just a workaround to make things a bit more
robust than they are now - a better fix would be to do a full
authentication handshake in IBSS mode upon having discovered a
new station, and on the receiver resetting the state (removing
and re-adding the station) on receiving the authentication
packet.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
---
 net/mac80211/sta_info.c | 1 +
 1 file changed, 1 insertion(+)

--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -561,6 +561,11 @@ __sta_info_alloc(struct ieee80211_sub_if
 	INIT_WORK(&sta->drv_deliver_wk, sta_deliver_ps_frames);
 	INIT_WORK(&sta->ampdu_mlme.work, ieee80211_ba_session_work);
 	mutex_init(&sta->ampdu_mlme.mtx);
+#if LINUX_VERSION_IS_LESS(6,2,0)
+	sta->ampdu_mlme.dialog_token_allocator = prandom_u32_max(U8_MAX);
+#else
+	sta->ampdu_mlme.dialog_token_allocator = get_random_u32_below(U8_MAX);
+#endif
 #ifdef CPTCFG_MAC80211_MESH
 	if (ieee80211_vif_is_mesh(&sdata->vif)) {
 		sta->mesh = kzalloc(sizeof(*sta->mesh), gfp);