https://stainless.corp.google.com/search?view=matrix&row=build&col=board&days=14&test=platform_PrinterPpds.all_digests

Failure reason: 
Autotest client was disconnected: Timeout encountered: /usr/bin/ssh -a -x -o ControlPath=/tmp/_autotmp_jF6vJvssh-master/socket -o Protocol=2 -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -o BatchMode=yes -o ConnectTimeout=30 -o ServerAliveInterval=900 -o ServerAliveCountMax=3 -o ConnectionAttempts=4 -l root -p 22 chromeos6-row3-rack3-host17 "export LIBC_FATAL_STDERR_=1; if type \"logger\" > /dev/null 2>&1; then logger -tag \"autotest\" \"server[stack::execute_section|_execute_daemon|run] -> ssh_run(/usr/local/autotest/bin/autotestd_monitor /tmp/autoserv-ssoQ64 0 0)\";fi; /usr/local/autotest/bin/autotestd_monitor /tmp/autoserv-ssoQ64 0 0", Test failed for 10 PPD files:...

Samle logs at https://stainless.corp.google.com/browse/chromeos-autotest-results/255137794-chromeos-test/



The test starts and runs well. It reports valid issues with 10 PPD files: 
hplip-3.18.3-hp-deskjet_d1600_series.ppd.gz, 
hplip-3.18.3-hp-deskjet_ink_advant_k109a-z.ppd.gz, 
hplip-3.18.3-hp-officejet_100_mobile_l411.ppd.gz, 
hplip-3.18.3-hp-officejet_150_mobile_l511.ppd.gz, 
hplip-3.18.3-hp-officejet_pro_8000_a809.ppd.gz, 
hplip-3.18.3-hp-officejet_pro_8500_a909a.ppd.gz, 
hplip-3.18.3-hp-officejet_pro_8500_a909g.ppd.gz, 
hplip-3.18.3-hp-officejet_pro_8500_a909n.ppd.gz, 
hplip-3.18.3-hp-officejet_pro_8500_a910.ppd.gz, 
hplip-3.18.3-hp-postscript-laserjet-pro.ppd.gz


After test reports the failure, a disconnect happens and test finalizing steps timeout:

11/05 01:05:55.224 DEBUG|              test:0386| Starting after_iteration_hooks for platform_PrinterPpds
11/05 01:05:55.225 DEBUG|      base_sysinfo:0124| Loggable saves logs to /usr/local/autotest/results/default/platform_PrinterPpds/sysinfo/iteration.1/interrupts.after
11/05 01:05:55.226 DEBUG|             utils:0219| Running 'mkdir -p /usr/local/autotest/results/default/platform_PrinterPpds/sysinfo/iteration.1/var/spool'
11/05 01:05:55.238 DEBUG|             utils:0219| Running 'rsync --no-perms --chmod=ugo+r -a --safe-links --exclude=/crash/**autoserv* --exclude=/crash/*.core /var/spool/crash /usr/local/autotest/results/default/platform_PrinterPpds/sysinfo/iteration.1/var/spool'
11/05 01:05:55.256 DEBUG|             utils:0219| Running 'rm -rf /var/spool/crash/*'
11/05 01:05:55.269 DEBUG|      base_sysinfo:0124| Loggable saves logs to /usr/local/autotest/results/default/platform_PrinterPpds/sysinfo/iteration.1/meminfo.after
11/05 01:05:55.270 DEBUG|      base_sysinfo:0124| Loggable saves logs to /usr/local/autotest/results/default/platform_PrinterPpds/sysinfo/iteration.1/slabinfo.after
11/05 01:05:55.271 DEBUG|      base_sysinfo:0124| Loggable saves logs to /usr/local/autotest/results/default/platform_PrinterPpds/sysinfo/iteration.1/schedstat.after
11/05 01:05:55.271 DEBUG|             utils:0219| Running 'logger "autotest finished iteration /usr/local/autotest/results/default/platform_PrinterPpds/sysinfo/iteration.1"'
11/05 01:05:55.282 DEBUG|              test:0391| after_iteration_hooks completed
11/05 01:05:55.282 WARNI|              test:0606| The test failed with the following exception
Traceback (most recent call last):
  File "/usr/local/autotest/common_lib/test.py", line 600, in _exec
    _call_test_function(self.execute, *p_args, **p_dargs)
  File "/usr/local/autotest/common_lib/test.py", line 800, in _call_test_function
    return func(*args, **dargs)
  File "/usr/local/autotest/common_lib/test.py", line 464, in execute
    postprocess_profiled_run, args, dargs)
  File "/usr/local/autotest/common_lib/test.py", line 371, in _call_run_once
    self.run_once(*args, **dargs)
  File "/usr/local/autotest/tests/platform_PrinterPpds/platform_PrinterPpds.py", line 266, in run_once
    % (len(failures), ', '.join(failures)) )
TestFail: Test failed for 10 PPD files: hplip-3.18.3-hp-deskjet_d1600_series.ppd.gz, hplip-3.18.3-hp-deskjet_ink_advant_k109a-z.ppd.gz, hplip-3.18.3-hp-officejet_100_mobile_l411.ppd.gz, hplip-3.18.3-hp-officejet_150_mobile_l511.ppd.gz, hplip-3.18.3-hp-officejet_pro_8000_a809.ppd.gz, hplip-3.18.3-hp-officejet_pro_8500_a909a.ppd.gz, hplip-3.18.3-hp-officejet_pro_8500_a909g.ppd.gz, hplip-3.18.3-hp-officejet_pro_8500_a909n.ppd.gz, hplip-3.18.3-hp-officejet_pro_8500_a910.ppd.gz, hplip-3.18.3-hp-postscript-laserjet-pro.ppd.gz
11/05 01:05:55.290 DEBUG|              test:0611| Running cleanup for test.


The test fails same way for different boards - hana and samus(being the only boards in this weekly suite run).

We do not know how or why this ssh timeout is happening. 
How can this timeout be investigated?