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carl9170: fix spurious transmissions in sniffer mode

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Several people have complained about an unusual
and undocumented feature of the AR9170 hardware:

In siffer mode, the hardware generates spurious
ACK frames for every received frame... even
broadcasts.

The reason for this malfunction is unknown:
<http://marc.info/?l=linux-wireless&m=134517238506033>
But there's a workaround: Instead of the special
sniffer mode, the hardware will be put into
station mode and all rx filters are disabled.

Reported-by: Johannes Berg <johannes@sipsolutions.net>
Reported-by: Marco Fonseca <marco@tampabay.rr.com>
Reported-by: Janusz Dziedzic <janusz.dziedzic@gmail.com>
Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
This commit is contained in:
Christian Lamparter 2012-09-11 23:18:34 +02:00 committed by John W. Linville
parent e298c79efc
commit e0509d3bdd
1 changed files with 18 additions and 3 deletions
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21
drivers/net/wireless/ath/carl9170/mac.c
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@ -343,7 +343,24 @@ int carl9170_set_operating_mode(struct ar9170 *ar)
break;
}
} else {
mac_addr = NULL;
/*
* Enable monitor mode
*
* rx_ctrl |= AR9170_MAC_RX_CTRL_ACK_IN_SNIFFER;
* sniffer |= AR9170_MAC_SNIFFER_ENABLE_PROMISC;
*
* When the hardware is in SNIFFER_PROMISC mode,
* it generates spurious ACKs for every incoming
* frame. This confuses every peer in the
* vicinity and the network throughput will suffer
* badly.
*
* Hence, the hardware will be put into station
* mode and just the rx filters are disabled.
*/
cam_mode |= AR9170_MAC_CAM_STA;
rx_ctrl |= AR9170_MAC_RX_CTRL_PASS_TO_HOST;
mac_addr = common->macaddr;
bssid = NULL;
}
rcu_read_unlock();
@ -355,8 +372,6 @@ int carl9170_set_operating_mode(struct ar9170 *ar)
enc_mode |= AR9170_MAC_ENCRYPTION_RX_SOFTWARE;
if (ar->sniffer_enabled) {
rx_ctrl |= AR9170_MAC_RX_CTRL_ACK_IN_SNIFFER;
sniffer |= AR9170_MAC_SNIFFER_ENABLE_PROMISC;
enc_mode |= AR9170_MAC_ENCRYPTION_RX_SOFTWARE;
}