Re^2: net::OpenSSH several commands, stdout are mixed up

I tried something. I added a tee to the remote command to log its output in a file (on the host, a different file for each call).
It appears that it is traceroute that is mixing up its outputs on the host; Net::OpenSSH is working fine.

For info, what the recorded file through tee is returning (second line is wrong and belongs to another traceroute call, but the hop number is wrong as well as in the other call, it is hop #1, this ip is never hop #5).

root@HERMES:/tmp/mnt/sda1$ cat test_77.95.71.196.tee 
traceroute to 77.95.64.123 (77.95.64.123), 6 hops max, 38 byte packets
 5  10.2.0.211  8.592 ms  2.467 ms  2.718 ms  2.530 ms  2.561 ms  2.56
+1 ms  2.687 ms  2.749 ms  2.405 ms  2.561 ms  2.562 ms  2.562 ms
 6  77.95.70.196  18.432 ms  18.244 ms  18.431 ms  18.119 ms  18.463 m
+s  18.213 ms  18.619 ms  18.151 ms  18.369 ms  18.119 ms  18.556 ms  
+18.682 ms
[download]

What the traceroute should return:

root@HERMES:/tmp/mnt/sda1$ traceroute -w 1 -f 5 -m 6 -q 12 -n 77.95.64
+.123
traceroute to 77.95.64.123 (77.95.64.123), 6 hops max, 38 byte packets
 5  77.95.71.196  18.806 ms  18.244 ms  18.619 ms  17.995 ms  18.807 m
+s  18.463 ms  18.495 ms  18.307 ms  18.744 ms  18.276 ms  18.588 ms  
+18.307 ms
 6  77.95.70.196  18.588 ms  18.276 ms  18.432 ms  18.089 ms  18.588 m
+s  18.088 ms  18.463 ms  18.119 ms  18.432 ms  18.151 ms  18.588 ms  
+18.181 ms
[download]

So this traceroute does not work properly when called multiple times at the same time.
Net::OpenSSH output is similar to the one on the tee file, so behaves as expected.

Comment on Re^2: net::OpenSSH several commands, stdout are mixed up Select or Download Code

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Re^3: net::OpenSSH several commands, stdout are mixed up by salva (Canon) on Sep 17, 2020 at 20:50 UTC
Well, maybe the ICMP packets coming back with the expired message notices are being captured by the wrong process. Try running a different command on the remote host instead of traceroute.	[reply]
Re^4: net::OpenSSH several commands, stdout are mixed up by Bolemo (Acolyte) on Sep 17, 2020 at 23:24 UTC
Yes, I am sure that you put exactly your finger on the issue. Since the output is the same on the remote host than on the SSH slave sessions, the problem is not Net::OpenSSH or even Perl related. It is really about this busybox traceroute implementation on the host and therefore outside the scope of this very helpful place ;) I was able to solve (avoid) the problem by having the Smokeping using only one instance at a time for that custom probe, so no multiplexed ICMP return packets can be mixed up by traceroute on the host. By the way, this Net::OpenSSH module is great (thanks Salva for it) and use very little CPU on the local device and the remote host. I started by simply changing the TraceroutePing probe to use ‘ssh user@host traceroute etc...’ instead of ‘traceroute etc...’. It worked but the toll on local and remote CPUs was very bad.	[reply]


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