PPT hangs on failed connection to Pi OS image server about pi-power-tools

[mtlynch]

I figured out that this only happens over WiFi. There's an issue on my network where the Pi fails to complete TLS handshakes over WiFi, but it works over wired. If I run the same steps over wired LAN, PPT works as expected.

So, this isn't PPT's fault, but it could be handy if it reports the connection error to the user to hint at the problem. Curently, PPT's behavior looks mostly indistinguishable from an app crash.

[Botspot]

Interesting. I'd like more info from you about that, since PPT is supposed to tell you if the network is unreachable.
See the below error dialog:

I'd like an exact terminal output to try to figure out why that dialog does not show up in your use-case.

[mtlynch]

I tried the command-line version, but it got to this line and hung for about 5 mins:

$ /home/pi/Pi-Power-Tools/img-mode
Output: 
Raspberry Pi OS
3829399552
https://downloads.raspberrypi.org/raspios_armhf_latestEOO

[Botspot]

OK, it appears the problem originates from line 70 of img-mode. And with your (weird) network, wget doesn't give up right away, but instead retries for 900 seconds - the default timeout value.
I'd like you to run this command in the terminal: (while connected to your problematic WiFi)

wget -qO- https://downloads.raspberrypi.org/raspios_armhf_latest | dd bs=1M count=1 2>/dev/null | busybox unzip -lq - 2>/dev/null | sed -n 3p | awk '{print $4}'

If I have isolated the right line, that above command should continue running for 900 seconds. (and not exit right away like it should)
If it does indeed continue running, and running, and running, then I'd like you to kill the process and now run this one:

wget --timeout=10 -qO- https://downloads.raspberrypi.org/raspios_armhf_latest | dd bs=1M count=1 2>/dev/null | busybox unzip -lq - 2>/dev/null | sed -n 3p | awk '{print $4}'

That has a timeout of 10 seconds, and it should exit by then. If it does, then I'll update line 70 to fix the problem.

[mtlynch]

I get kind of strange behavior out of wget. It properly times out according to the --timeout flag, but it doesn't respect the --tries flag for some reason. It keeps trying different IPv6 addresses, which all fail. It switches over to an IPv4 address, and the download starts:

$ wget --tries=1 --timeout=1 https://downloads.raspberrypi.org/raspios_armhf_latest
--2020-08-18 00:57:40--  https://downloads.raspberrypi.org/raspios_armhf_latest
Resolving downloads.raspberrypi.org (downloads.raspberrypi.org)... 2a00:1098:82:47::1:1, 2a00:1098:84:1e0::3, 2a00:1098:80:56::2:1, ...
Connecting to downloads.raspberrypi.org (downloads.raspberrypi.org)|2a00:1098:82:47::1:1|:443... failed: Connection timed out.
Connecting to downloads.raspberrypi.org (downloads.raspberrypi.org)|2a00:1098:84:1e0::3|:443... failed: Connection timed out.
Connecting to downloads.raspberrypi.org (downloads.raspberrypi.org)|2a00:1098:80:56::2:1|:443... failed: Connection timed out.
Connecting to downloads.raspberrypi.org (downloads.raspberrypi.org)|2a00:1098:88:26::1:1|:443... failed: Connection timed out.
Connecting to downloads.raspberrypi.org (downloads.raspberrypi.org)|2a00:1098:80:56::1:1|:443... failed: Connection timed out.
Connecting to downloads.raspberrypi.org (downloads.raspberrypi.org)|2a00:1098:82:47::1|:443... failed: Connection timed out.
Connecting to downloads.raspberrypi.org (downloads.raspberrypi.org)|2a00:1098:88:26::2:1|:443... failed: Connection timed out.
Connecting to downloads.raspberrypi.org (downloads.raspberrypi.org)|2a00:1098:84:1e0::2|:443... failed: Connection timed out.
Connecting to downloads.raspberrypi.org (downloads.raspberrypi.org)|2a00:1098:80:56::3:1|:443... failed: Connection timed out.
Connecting to downloads.raspberrypi.org (downloads.raspberrypi.org)|2a00:1098:84:1e0::1|:443... failed: Connection timed out.
Connecting to downloads.raspberrypi.org (downloads.raspberrypi.org)|2a00:1098:88:26::1|:443... failed: Connection timed out.
Connecting to downloads.raspberrypi.org (downloads.raspberrypi.org)|2a00:1098:82:47::2:1|:443... failed: Connection timed out.
Connecting to downloads.raspberrypi.org (downloads.raspberrypi.org)|176.126.240.86|:443... connected.
HTTP request sent, awaiting response... 302 Found
Location: http://downloads.raspberrypi.org/raspios_armhf/images/raspios_armhf-2020-05-28/2020-05-27-raspios-buster-armhf.zip [following]
--2020-08-18 00:57:53--  http://downloads.raspberrypi.org/raspios_armhf/images/raspios_armhf-2020-05-28/2020-05-27-raspios-buster-armhf.zip
Connecting to downloads.raspberrypi.org (downloads.raspberrypi.org)|176.126.240.86|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 1181855929 (1.1G) [application/zip]
Saving to: ‘raspios_armhf_latest.2’

raspios_armhf_lates   3%[                    ]  41.80M  7.41MB/s    eta 2m 43s

An alternative might be to use curl. On my system, it connects immediately, despite my wonky network:

curl --retry-max-time 10 --connect-timeout 10 --silent --show-error --location https://downloads.raspberrypi.org/raspios_armhf_latest

And if I put in a dummy IP to force a connection error, it seems to time out in the proper amount of time:

$ curl --retry-max-time 10 --connect-timeout 10 --show-error --silent --location https://123.3.4.5 > /dev/null
curl: (28) Connection timed out after 10001 milliseconds

[Botspot]

I'm not familiar enough with wget or curl to make comments or to come up with a solution.
What I do know: it took hundreds of tests to maximize the download speed, and if I switched to curl I'd have to redo a bunch of testing. And doing all that to solve a niche problem isn't worth it.

Two things to try, inspired from here:

• Try changing --timeout= to --read-timeout=. See if wget fails sooner like it should.

• If that doesn't work, there's always brute-force methods like:

  wget http://www.somesite.com/file.zip &
  PID=$!
  sleep 10
  if [ ps ax | grep $PID -ne '' ]
  then
  kill $PID
  fi

[mtlynch]

Neither worked for me, unfortunately:

$ wget --tries=1 --read-timeout=1 https://downloads.raspberrypi.org/raspios_armhf_latest

Still hung for ~10 seconds per IP.

pi@pibuilder:~ $ wget --tries=1 --timeout=1 https://downloads.raspberrypi.org/raspios_armhf_latest &
[1] 1200
pi@pibuilder:~ $ PID=$!
pi@pibuilder:~ $ sleep 10

Redirecting output to ‘wget-log.3’.
pi@pibuilder:~ $ if [ ps ax | grep $PID -ne '' ]
> then
>   kill $PID
> fi
bash: [: missing `]'
grep: 1200: No such file or directory
grep: ]: No such file or directory

But this is probably too niche a bug to spend so much time on, so I'll close it out.