Re: git: e9ae9fa93745 - main - syslog(3): unbreak log generation using fabricated PID

On 9 Aug 2022, at 10:30, Eugene Grosbein wrote:
> The branch main has been updated by eugen:
>
> URL: https://cgit.FreeBSD.org/src/commit/?id=e9ae9fa93745669b7dd0341d333257ad6cfe8e37
>
> commit e9ae9fa93745669b7dd0341d333257ad6cfe8e37
> Author:     Eugene Grosbein <eugen@FreeBSD.org>
> AuthorDate: 2022-08-08 22:21:02 +0000
> Commit:     Eugene Grosbein <eugen@FreeBSD.org>
> CommitDate: 2022-08-08 22:21:02 +0000
>
>     syslog(3): unbreak log generation using fabricated PID
>
>     Recover application ability to supply fabricated PID
>     embedded into ident that was lost when libc switched
>     to generation of RFC 5424 log messages, for example:
>
>     logger -t "ident[$$]" -p user.notice "test"
>
>     It is essential for long running scripts.
>     Also, this change unbreaks matching resulted entries
>     by ident in syslog.conf:
>
>     !ident
>     *.* /var/log/ident.log
>
>     Without the fix, the log (and matching) was broken:
>
>     Aug  1 07:36:58 hostname ident[123][86483]: test
>
>     Now it works as expected and worked before breakage:
>
>     Aug  1 07:39:40 hostname ident[123]: test
>
>     Differential:   https://reviews.freebsd.org/D36005
>     MFC after:      2 weeks
> ---
>  lib/libc/gen/syslog.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++---
>  1 file changed, 51 insertions(+), 3 deletions(-)
>
<snip>

> -	(void)fprintf(fp, "%d ", getpid());
> +	if (LogPid == -1)
> +		LogPid = getpid();

I believe this introduced unexpected behaviour for syslog(). If we log something prior to fork()ing we’ll keep logging with the old pid. That’s a fairly common pattern for daemonising code, and it’s something openvpn ran into: https://github.com/OpenVPN/openvpn/issues/198

Best regards,
Kristof