This regression was introduced in #14913.
The current_file variable can be NULL, as, for example, with the
following commands:
* journalctl --list-boots
* journalctl -b -1 --no-pager
Since current_file is only checked for pointer equality with f, removing
the assertion is safe here.
When having a service which intentionally outputs multiple equal lines,
all these messages might be inserted with the same timestamp.
journalctl has a mechanism to avoid duplicate lines, which might be in
different journal files.
This patch allows duplicate lines, if they are from the same file.
The RFC states that lifetime (AdvDefaultLifetime) must be at least
MaxRtrAdvInterval (which more or less corresponds to SD_RADV_DEFAULT_MAX_TIMEOUT_USEC
in systemd).
To fulfill this limit, virtually lower MaxRtrAdvInterval and MinRtrAdvInterval
accordingly.
Also check that min is not lower than 3s and max is not lower than 4s.