[systemd-devel] Antw: Re: [systemd‑devel] Antw: [EXT] Re: Q: non‑ASCII in syslog

[Ulrich Windl]

>>> Lennart Poettering <lennart at poettering.net> schrieb am 28.04.2022 um 10:27
in
Nachricht <YmpQCYN0Y/gxlzGU at gardel-login>:
> On Do, 28.04.22 09:32, Ulrich Windl (Ulrich.Windl at rz.uni‑regensburg.de)
wrote:
> 
>> Actually I wasn't quite sure about the default config in SLES12.
>> It seems the flow is journald ‑> local rsyslogd ‑> remote syslogd
>>
>> > rsyslogd already knows if messages are UTF‑8 because the system's $LANG
>> > (well, nl_langinfo) says so. And if rsyslog can't trust that for some
>> > reason (e.g. because a user might have a different locale), then
>> > systemd‑journald won't be able to trust it either, so it won't know
whether
>> > it could add the BOM.
>>
>> How could a remote syslog server know what the locale on the sending
system
>> is?
> 
> Your local rsyslogd could add the BOM when it transforms journal
> messages to syslog datagrams.
> 
>> > RFC 3164 over the network to a remote server? Outside the scope for
>> > systemd, since it doesn't generate the network packets; your local
rsyslogd
>> > forwarder does. (Also, why RFC 3164 and not 5425?)
>>
>> If you look outside the world of systemd, about 99% of systems create the 
> RFC
>> 3164 type of messages.
> 
> That's a wild claim, and simply wrong actually.

Well actually as systemd cannot send syslog messages to remote, which systems
do you know that send RFC 5424 messages?
Actually I know none here.

> 
> I am pretty sure that more than 50% of syslog messages generated on
> this earth probably are synthesized by glibc's syslog() API. And that
> turns out to be neither conformant to RFC 3164 nor to RFC 5425.

No idea. Can you give an example?

> 
> What glibc sends is close to RFC 3164 but omits one key field that
> isn't really optionally according to RFC 3164: the 'HOSTNAME' field.

Maybe the API is not used correctly. The RFC 3164 says:
"A relay will add a TIMESTAMP and SHOULD add a HOSTNAME as follows (...)"
So when sending to any remote syslog a HOSTNAME should be there.
(It's like a MTA adding a Message-ID (and other fields) if none is present)

Most notable the RFC seems to allow a missing hostname initially.

> 
> systemd is focussed on reality: we generate and process the same
> format glibc generates.

I'm wondering which API all those programs use that create correct syslog
entries.
I tried with my own program:
It sends:
connect(1, {sa_family=AF_LOCAL, sun_path="/dev/log"}, 110) = 0
sendto(1, "<31>Apr 28 11:08:32 iotwatch[239"..., 56, MSG_NOSIGNAL, NULL, 0) =
56

What's logged is:
Apr 28 11:08:32 host-name iotwatch[239...

Also from the syntax being sent by the application, one cannot really say
whether the hostname is missing.
Maybe the trick is that /dev/log is specified as source for _local_ syslog
messages (so that there's no reason or sense in supplying the local hostname).
Also I'm not sure whether the messages in /dev/log are covered by the RFC.

Regards,
Ulrich Windl

> 
> Lennart
> 
> ‑‑
> Lennart Poettering, Berlin