My laptop batery discharged while I slept and look like my file system was broken. Or maybe I run an update and forgot. Anyway, after reboot I still had a problem: no any website was opening with some weird error that DNS can't be resolved.
And yes, the ping doesn't worked for any domain. Dig was failed too. It turned out that systemd-resolvd DNS daemon didn't started. I checked logs with
journalctl -u systemd-resolved
In logs I found that the resolved fails with an error "cannot allocate memory".and after that the servive crashed.