iwlwifi: mvm: fix deduplication start logic

If the first frame on a given TID is received with seqno 0 and needed
to be retransmitted, we erroneously drop it because the deduplication
data is initialized to zero, and then comparing

        if (unlikely(ieee80211_has_retry(hdr->frame_control) &&
                     dup_data->last_seq[tid] == hdr->seq_ctrl &&
                     dup_data->last_sub_frame[tid] >= sub_frame_idx))
                return true;

will return in iwl_mvm_is_dup() since last_sub_frame is also set to
zero, and sub_frame_idx is usually zero since this only covers the
relatively rare case of A-MSDU.

Fix this by initializing the last_seq array to 0xffff, which is an
impossible value for hdr->seq_ctrl to have here because the lower
four bits are the fragment number, and fragments aren't handled in
this code but go to mac80211 instead.

Fixes: a571f5f635ef ("iwlwifi: mvm: add duplicate packet detection per rx queue")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>

diff --git a/drivers/net/wireless/intel/iwlwifi/mvm/sta.c b/drivers/net/wireless/intel/iwlwifi/mvm/sta.c
index ee7c978fe5abdb1f9bf3921bcae0a6d81eba54f0..4df5f13fcdae7949804d2c8aa4d5fd6a556cb452 100644 (file)
--- a/drivers/net/wireless/intel/iwlwifi/mvm/sta.c
+++ b/drivers/net/wireless/intel/iwlwifi/mvm/sta.c
@@ -1402,11 +1402,24 @@ int iwl_mvm_add_sta(struct iwl_mvm *mvm,
 
        if (iwl_mvm_has_new_rx_api(mvm) &&
            !test_bit(IWL_MVM_STATUS_IN_HW_RESTART, &mvm->status)) {
+               int q;
+
                dup_data = kcalloc(mvm->trans->num_rx_queues,
-                                  sizeof(*dup_data),
-                                  GFP_KERNEL);
+                                  sizeof(*dup_data), GFP_KERNEL);
                if (!dup_data)
                        return -ENOMEM;
+               /*
+                * Initialize all the last_seq values to 0xffff which can never
+                * compare equal to the frame's seq_ctrl in the check in
+                * iwl_mvm_is_dup() since the lower 4 bits are the fragment
+                * number and fragmented packets don't reach that function.
+                *
+                * This thus allows receiving a packet with seqno 0 and the
+                * retry bit set as the very first packet on a new TID.
+                */
+               for (q = 0; q < mvm->trans->num_rx_queues; q++)
+                       memset(dup_data[q].last_seq, 0xff,
+                              sizeof(dup_data[q].last_seq));
                mvm_sta->dup_data = dup_data;
        }