From:   Bob Copeland <me@bobcopeland.com>
To:     Johannes Berg <johannes@sipsolutions.net>
Cc:     linux-wireless@vger.kernel.org, kernel-team@fb.com,
        Bob Copeland <me@bobcopeland.com>,
        Bob Copeland <bobcopeland@fb.com>
Subject: [PATCH] mac80211: fix miscounting of ttl-dropped frames
Date:   Thu, 17 Jan 2019 16:32:42 -0500
Message-Id: <20190117213242.31588-1-me@bobcopeland.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: linux-wireless-owner@vger.kernel.org
Precedence: bulk

In ieee80211_rx_h_mesh_fwding, we increment the 'dropped_frames_ttl'
counter when we decrement the ttl to zero.  For unicast frames
destined for other hosts, we stop processing the frame at that point.

For multicast frames, we do not rebroadcast it in this case, but we
do pass the frame up the stack to process it on this STA.  That
doesn't match the usual definition of "dropped," so don't count
those as such.

With this change, something like `ping6 -i0.2 ff02::1%mesh0` from a
peer in a ttl=1 network no longer increments the counter rapidly.

Signed-off-by: Bob Copeland <bobcopeland@fb.com>
---
 net/mac80211/rx.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index dddd498e1338..ffd312b8c432 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -2531,7 +2531,9 @@ ieee80211_rx_h_mesh_fwding(struct ieee80211_rx_data *rx)
 	skb_set_queue_mapping(skb, q);
 
 	if (!--mesh_hdr->ttl) {
-		IEEE80211_IFSTA_MESH_CTR_INC(ifmsh, dropped_frames_ttl);
+		if (!is_multicast_ether_addr(hdr->addr1))
+			IEEE80211_IFSTA_MESH_CTR_INC(ifmsh,
+						     dropped_frames_ttl);
 		goto out;
 	}
 
-- 
2.20.1