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 <ga58taw@xxxxxxxx>
Signed-off-by: Charlie Groh <ga58taw@xxxxxxxx>
Signed-off-by: Julius Niedworok <julius.n@xxxxxxx>
---
net/mac80211/debugfs.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++
net/mac80211/ieee80211_i.h | 1 +
net/mac80211/tx.c | 10 +++++++++
3 files changed, 64 insertions(+)
diff --git a/net/mac80211/debugfs.c b/net/mac80211/debugfs.c
index 2d43bc1..da8f27c 100644
--- a/net/mac80211/debugfs.c
+++ b/net/mac80211/debugfs.c
@@ -150,6 +150,58 @@ static const struct file_operations aqm_ops = {
.llseek = default_llseek,
};
+static ssize_t force_tx_status_read(struct file *file,
+ char __user *user_buf,
+ size_t count,
+ loff_t *ppos)
+{
+ struct ieee80211_local *local = file->private_data;
+ char buf[3];
+ int len = 0;
+
+ len = scnprintf(buf, sizeof(buf), "%d\n", (int)local->force_tx_status);
+
+ return simple_read_from_buffer(user_buf, count, ppos,
+ buf, len);
+}
+
+static ssize_t force_tx_status_write(struct file *file,
+ const char __user *user_buf,
+ size_t count,
+ loff_t *ppos)
+{
+ struct ieee80211_local *local = file->private_data;
+ char buf[3];
+ size_t len;
+
+ if (count > sizeof(buf))
+ return -EINVAL;
+
+ if (copy_from_user(buf, user_buf, count))
+ return -EFAULT;
+
+ buf[sizeof(buf) - 1] = '\0';
+ len = strlen(buf);
+ if (len > 0 && buf[len - 1] == '\n')
+ buf[len - 1] = 0;
+
+ if (buf[0] == '0' && buf[1] == '\0')
+ local->force_tx_status = 0;
+ else if (buf[0] == '1' && buf[1] == '\0')
+ local->force_tx_status = 1;
+ else
+ return -EINVAL;
+
+ return count;
+}
+
+static const struct file_operations force_tx_status_ops = {
+ .write = force_tx_status_write,
+ .read = force_tx_status_read,
+ .open = simple_open,
+ .llseek = default_llseek,
+};
+
#ifdef CONFIG_PM
static ssize_t reset_write(struct file *file, const char __user *user_buf,
size_t count, loff_t *ppos)
@@ -382,6 +434,7 @@ void debugfs_hw_add(struct ieee80211_local *local)
DEBUGFS_ADD(hwflags);
DEBUGFS_ADD(user_power);
DEBUGFS_ADD(power);
+ DEBUGFS_ADD_MODE(force_tx_status, 0600);
if (local->ops->wake_tx_queue)
DEBUGFS_ADD_MODE(aqm, 0600);
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index e170f98..28ac87c 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -1384,6 +1384,7 @@ struct ieee80211_local {
struct dentry *rcdir;
struct dentry *keys;
} debugfs;
+ bool force_tx_status;
#endif
/*
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 8a49a74..a39ce49 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -2470,6 +2470,11 @@ 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];
@@ -3475,6 +3480,11 @@ 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
+
if (hdr->frame_control & cpu_to_le16(IEEE80211_STYPE_QOS_DATA)) {
tid = skb->priority & IEEE80211_QOS_CTL_TAG1D_MASK;
*ieee80211_get_qos_ctl(hdr) = tid;
--
2.10.1 (Apple Git-78)
