Xubuntu ping command leading to all of sessions closed

[Yang yanbo]

Hi,my server version is Ubuntu 18.04.3 LTS. When I use ping command, all the sessions will be closed and returned socket error 10053. However,it is normal when I ping the valid address likes: ping -c 4 bugs.launchpad.net. But when I ping other address which would return "Destination Host Unreachable", all the distal session in putty or another shell would be colsed with "Connection closed by foreign host". Other commands like netcat have the same error.

I checked the syslog without no returned error after using ping for this strange phenomenon, through syslog included some related information:

syslog.1:Oct 22 21:15:16 dell systemd-timesyncd[1298]: Synchronized to time server 91.189.89.199:123 (ntp.ubuntu.com).
syslog.1:Oct 22 21:17:35 dell systemd-timesyncd[1298]: Timed out waiting for reply from 91.189.89.199:123 (ntp.ubuntu.com).

or

messages:Oct 22 23:14:53 dell blueman.desktop[3974]: ERROR:dbus.proxies:Introspect error on org.bluez:/: dbus.exceptions.DBusException: org.freedesktop.DBus.Error.TimedOut: Failed to activate service 'org.bluez': timed out (service_start_timeout=25000ms)
messages:Oct 22 23:14:53 dell blueman.desktop[3974]: ERROR:dbus.proxies:Introspect error on org.bluez:/org/bluez: dbus.exceptions.DBusException: org.freedesktop.DBus.Error.TimedOut: Failed to activate service 'org.bluez': timed out (service_start_timeout=25000ms)
messages:Oct 22 23:14:53 dell blueman.desktop[3974]: ERROR:dbus.proxies:Introspect error on org.bluez:/: dbus.exceptions.DBusException: org.freedesktop.DBus.Error.TimedOut: Failed to activate service 'org.bluez': timed out (service_start_timeout=25000ms)

I guess some daemon programs may peform their function via ping or other ways. User sessions always be closed immediately and connection refusion time usually takes no more than 1 min, and it won't kill running jobs in closed session.

Especially, this phenomenon never happens in apt-get and conda or wget command.

I have no idea what lead to this strange phenomenon. Please give me advice.

Thanks!

[Sebastien Bacher (seb128)]

Could you add a journalctl log of a session having the issue?

[Yang yanbo (boiscat)]

Sorry for that I haven't received logs. I have tested the session with ping and the session dropped down,then I used "journalctl _PID=25564" command in root with no related logs return.("lsof -i" was used for checking the session number)

[Sebastien Bacher (seb128)]

Could you just 'journalctl -b 0' and attach that? there could be kernel error or such which aren't to do with the specific pid

[Yang yanbo (boiscat)]

Thanks for your suggestion, I have test ping in 15:32:26 using 'journalctl -b 0' without related return.
I have point this in the file. Do you need complete file?

[Yang yanbo (boiscat)]

In addition, I found that after 15:32:26, the journalctl -b 0 logs won't generate until thesession can be connected again.
Because of my server being attacked all the time, the log used to be continuous.

[Launchpad Janitor (janitor)]

[Expired for iputils (Ubuntu) because there has been no activity for 60 days.]