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Date:      Tue, 03 Jan 2023 17:29:08 +1300
From:      Kristof Provost <kp@FreeBSD.org>
To:        Eugene Grosbein <eugen@FreeBSD.org>
Cc:        src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org
Subject:   Re: git: e9ae9fa93745 - main - syslog(3): unbreak log generation using fabricated PID
Message-ID:  <CB6BABC4-5E53-448E-A4BB-2B21CB77B018@FreeBSD.org>
In-Reply-To: <202208082230.278MUYZd078396@gitrepo.freebsd.org>
References:  <202208082230.278MUYZd078396@gitrepo.freebsd.org>

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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=3De9ae9fa93745669b7dd0341d=
333257ad6cfe8e37
>
> 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 =3D=3D -1)
> +		LogPid =3D getpid();

I believe this introduced unexpected behaviour for syslog(). If we log so=
mething prior to fork()ing we=E2=80=99ll keep logging with the old pid. T=
hat=E2=80=99s a fairly common pattern for daemonising code, and it=E2=80=99=
s something openvpn ran into: https://github.com/OpenVPN/openvpn/issues/1=
98

Best regards,
Kristof



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