Question: ath10k and tcpdump antenna noise information missing

Tomi Saarnio Tomi.Saarnio at
Thu Nov 5 05:38:17 PST 2015

Hi All,

After some digging, I found  this piece of code in Linux kernel 4.1 file
net/mac80211/rx.c in function ieee80211_add_rx_radiotap_header:

	if (local->hw.flags & IEEE80211_HW_SIGNAL_DBM &&
	    !(status->flag & RX_FLAG_NO_SIGNAL_VAL)) {
		*pos = status->signal;
		rthdr->it_present |=
			cpu_to_le32(1 << IEEE80211_RADIOTAP_DBM_ANTSIGNAL);

	/* IEEE80211_RADIOTAP_LOCK_QUALITY is missing */

	if (!status->chains) {
		*pos = status->antenna;

	/* IEEE80211_RADIOTAP_DB_ANTNOISE is not used */

	/* ensure 2 byte alignment for the 2 byte field as required */

The comment 	/* IEEE80211_RADIOTAP_DB_ANTNOISE is not used */ tells quite
clearly why the antenna noise information is not be available in the radiotap and tcpdump.

Clearly this is not a driver issue any more, but a network layer issue. I will try to look
a solution elsewhere how to get the antenna noise information into userspace in a proper way.

Best regards,
Tomi Saarnio

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