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ath9k: improve reliability of MIC error detection 

For unicast the hardware sometimes reports MIC errors even though the
frame that it received actually contains a valid MIC - on some chips this
can happen frequently enough to trigger TKIP countermeasures.
Fix this issue by not reporting MIC errors for unicast frames with a
valid key, letting mac80211 validate the MIC instead.

Additionally, strip the MIC for all frames that the hardware considers
valid to avoid wasting CPU cycles re-validating it.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
This commit is contained in:
Felix Fietkau 2011-07-13 23:35:05 +08:00 committed by John W. Linville
parent 933d594313
commit 66760eac00
1 changed files with 32 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

53
drivers/net/wireless/ath/ath9k/recv.c
View File

@ -814,16 +814,19 @@ static bool ath9k_rx_accept(struct ath_common *common,
struct ath_rx_status *rx_stats,
bool *decrypt_error)
{
#define is_mc_or_valid_tkip_keyix ((is_mc || \
(rx_stats->rs_keyix != ATH9K_RXKEYIX_INVALID && \
test_bit(rx_stats->rs_keyix, common->tkip_keymap))))
bool is_mc, is_valid_tkip, strip_mic, mic_error;
struct ath_hw *ah = common->ah;
__le16 fc;
u8 rx_status_len = ah->caps.rx_status_len;
fc = hdr->frame_control;
is_mc = !!is_multicast_ether_addr(hdr->addr1);
is_valid_tkip = rx_stats->rs_keyix != ATH9K_RXKEYIX_INVALID &&
test_bit(rx_stats->rs_keyix, common->tkip_keymap);
strip_mic = is_valid_tkip && !(rx_stats->rs_status &
(ATH9K_RXERR_DECRYPT | ATH9K_RXERR_CRC | ATH9K_RXERR_MIC));
if (!rx_stats->rs_datalen)
return false;
/*
@ -838,6 +841,11 @@ static bool ath9k_rx_accept(struct ath_common *common,
if (rx_stats->rs_more)
return true;
mic_error = is_valid_tkip && !ieee80211_is_ctl(fc) &&
!ieee80211_has_morefrags(fc) &&
!(le16_to_cpu(hdr->seq_ctrl) & IEEE80211_SCTL_FRAG) &&
(rx_stats->rs_status & ATH9K_RXERR_MIC);
/*
* The rx_stats->rs_status will not be set until the end of the
* chained descriptors so it can be ignored if rs_more is set. The
@ -845,30 +853,18 @@ static bool ath9k_rx_accept(struct ath_common *common,
* descriptors.
*/
if (rx_stats->rs_status != 0) {
if (rx_stats->rs_status & ATH9K_RXERR_CRC)
if (rx_stats->rs_status & ATH9K_RXERR_CRC) {
rxs->flag |= RX_FLAG_FAILED_FCS_CRC;
mic_error = false;
}
if (rx_stats->rs_status & ATH9K_RXERR_PHY)
return false;
if (rx_stats->rs_status & ATH9K_RXERR_DECRYPT) {
*decrypt_error = true;
} else if (rx_stats->rs_status & ATH9K_RXERR_MIC) {
bool is_mc;
/*
* The MIC error bit is only valid if the frame
* is not a control frame or fragment, and it was
* decrypted using a valid TKIP key.
*/
is_mc = !!is_multicast_ether_addr(hdr->addr1);
if (!ieee80211_is_ctl(fc) &&
!ieee80211_has_morefrags(fc) &&
!(le16_to_cpu(hdr->seq_ctrl) & IEEE80211_SCTL_FRAG) &&
is_mc_or_valid_tkip_keyix)
rxs->flag |= RX_FLAG_MMIC_ERROR;
else
rx_stats->rs_status &= ~ATH9K_RXERR_MIC;
mic_error = false;
}
/*
* Reject error frames with the exception of
* decryption and MIC failures. For monitor mode,
@ -886,6 +882,18 @@ static bool ath9k_rx_accept(struct ath_common *common,
}
}
}
/*
* For unicast frames the MIC error bit can have false positives,
* so all MIC error reports need to be validated in software.
* False negatives are not common, so skip software verification
* if the hardware considers the MIC valid.
*/
if (strip_mic)
rxs->flag |= RX_FLAG_MMIC_STRIPPED;
else if (is_mc && mic_error)
rxs->flag |= RX_FLAG_MMIC_ERROR;
return true;
}
@ -1938,6 +1946,9 @@ int ath_rx_tasklet(struct ath_softc *sc, int flush, bool hp)
sc->rx.rxotherant = 0;
}
if (rxs->flag & RX_FLAG_MMIC_STRIPPED)
skb_trim(skb, skb->len - 8);
spin_lock_irqsave(&sc->sc_pm_lock, flags);
if ((sc->ps_flags & (PS_WAIT_FOR_BEACON |