Commit e0509d3b authored by Christian Lamparter's avatar Christian Lamparter Committed by John W. Linville
Browse files

carl9170: fix spurious transmissions in sniffer mode

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: default avatarJohannes Berg <johannes@sipsolutions.net>
Reported-by: default avatarMarco Fonseca <marco@tampabay.rr.com>
Reported-by: default avatarJanusz Dziedzic <janusz.dziedzic@gmail.com>
Signed-off-by: default avatarChristian Lamparter <chunkeey@googlemail.com>
Signed-off-by: default avatarJohn W. Linville <linville@tuxdriver.com>
parent e298c79e
......@@ -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;
}
......
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