On Thu, Dec 31, 2020 at 04:13:56PM +0000, Björn Gohla wrote: > > Stefan Sperling writes: > > > On Thu, Dec 31, 2020 at 02:28:35PM +0000, Björn Gohla wrote: > >> Hi all, > [...] > >> So how do I get the it? Am I looking in the wrong place, or does the > >> driver just not expose this information? > > > > Rate/MCS + channel width + some other parameters map to a Tx bitrate: > > https://en.wikipedia.org/wiki/IEEE_802.11n-2009#Data_rates > > > > This Tx bitrate will vary on a per-frame basis, though. And actual user data > > throughput is always below this, due to protocol overhead, re-transmissions, > > interference, other traffic on the same channel, and so on. > > Right, so by using the values in that table one could extract a nominal > Tx rate, but not the actual one (much less the Rx); correct?
Rx rates can only be observed with tcpdump -v -y IEEE802_11_RADIO -i urtwn0 > > In 11g mode the per-frame Tx rate is displayed by ifconfig in Mbit/s. > > However, some realtek devices (like the 8192CU) perform Tx rate-adjustment > > in firmware and do not even expose the chosen Tx data rate to the driver. > > In that case ifconfig always displays 54M which is usually incorrect. > > ifconfig says this: > urtwn0: flags=808843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST,AUTOCONF4> mtu > 1500 > lladdr 54:2a:a2:4c:0e:b5 > index 8 priority 4 llprio 3 > groups: wlan egress > media: IEEE802.11 autoselect (OFDM54 mode 11g) > status: active > ieee80211: join "451UnavailableForLegalReasons " chan 11 bssid > b0:bb:e5:13:7b:d4 -72dBm wpakey wpaprotos wpa2 wpaakms psk wpaciphers ccmp > wpagroupcipher tkip > inet 192.168.1.182 netmask 0xffffff00 broadcast 192.168.1.255 > > I suppose the "media" line is what you're referring to here, right? Yes. > dmesg says: > urtwn0 at uhub0 port 2 configuration 1 interface 0 "Realtek Wireless N Nano > USB Adapter" rev 2.10/2.00 addr 2 > urtwn0: MAC/BB RTL8192EU, RF 6052 2T2R, address 54:2a:a2:4c:0e:b5 > > the device looks similar to the one you mentioned, so maybe that's > what's going on here. On 8192EU devices the driver will adjust the Tx rate. If you send a lot of traffic the displayed Tx rate should change while you change the physical distance to your AP, for example. > > What problem are you trying to solve? > > I just want to show the network activity in my desktop status line. Understood, fair enough. The chosen Tx rate is not a very reliable indicator of actual throughput but it can serve as a wifi link quality indicator to some extent.