Re: [PATCH RFC v2] mac80211: debugfs option to force TX status frames
From: Kalle Valo <hidden>
Date: 2019-03-07 15:42:15
Also in:
linux-wireless, lkml
Julius Niedworok [off-list ref] writes:
At Technical University of Munich we use MAC 802.11 TX status frames to
perform several measurements in MAC 802.11 setups.
With ath based drivers this was possible until commit d94a461d7a7df6
("ath9k: use ieee80211_tx_status_noskb where possible") as the driver
ignored the IEEE80211_TX_CTL_REQ_TX_STATUS flag and always delivered
tx_status frames. Since that commit, this behavior was changed and the
driver now adheres to IEEE80211_TX_CTL_REQ_TX_STATUS.
Due to performance reasons, IEEE80211_TX_CTL_REQ_TX_STATUS is not set for
data frames from interfaces in managed mode. Hence, frames that are sent
from a managed mode interface do never deliver tx_status frames. This
remains true even if a monitor mode interface (the measurement interface)
is added to the same ieee80211 physical device. Thus, there is no
possibility for receiving tx_status frames for frames sent on an interface
in managed mode, if the driver adheres to IEEE80211_TX_CTL_REQ_TX_STATUS.
In order to force delivery of tx_status frames for research and debugging
purposes, implement a debugfs option force_tx_status for ieee80211 physical
devices. When this option is set for a physical device,
IEEE80211_TX_CTL_REQ_TX_STATUS is enabled in all packets sent from that
device. This option can be set via
/sys/kernel/debug/ieee80211/<dev>/force_tx_status. The default is disabled.
Co-developed-by: Charlie Groh <redacted>
Signed-off-by: Charlie Groh <redacted>
Signed-off-by: Julius Niedworok <redacted>[...]
+ len = scnprintf(buf, sizeof(buf), "%d\n", (int)local->force_tx_status);
I wonder about the cast, is it guaranteed that a bool is always of the same size as an int?
quoted hunk
--- a/net/mac80211/ieee80211_i.h +++ b/net/mac80211/ieee80211_i.h@@ -1367,6 +1367,7 @@ struct ieee80211_local { struct dentry *rcdir; struct dentry *keys; } debugfs; + bool force_tx_status;
[...]
quoted hunk
#endif /*diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c index 928f13a..717fa71 100644 --- a/net/mac80211/tx.c +++ b/net/mac80211/tx.c@@ -2463,6 +2463,11 @@ static struct sk_buff *ieee80211_build_hdr(struct ieee80211_sub_if_data *sdata, if (IS_ERR(sta)) sta = NULL; +#ifdef CONFIG_MAC80211_DEBUGFS + if (local->force_tx_status) + info_flags |= IEEE80211_TX_CTL_REQ_TX_STATUS; +#endif + /* convert Ethernet header to proper 802.11 header (based on * operation mode) */ ethertype = (skb->data[12] << 8) | skb->data[13];@@ -3468,6 +3473,11 @@ static bool ieee80211_xmit_fast(struct ieee80211_sub_if_data *sdata, (tid_tx ? IEEE80211_TX_CTL_AMPDU : 0); info->control.flags = IEEE80211_TX_CTRL_FAST_XMIT; +#ifdef CONFIG_MAC80211_DEBUGFS + if (local->force_tx_status) + info->flags |= IEEE80211_TX_CTL_REQ_TX_STATUS; +#endif
IMHO the ifdefs look pointless just to save four bytes. I would move force_tx_status outside of ifdef in the struct so that the actual code doesn't have ugly ifdefs. -- Kalle Valo