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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

drivers/net/wireless/ath/carl9170/mac.c

+18 −3
Original line number Diff line number Diff line
@@ -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;

	}