openresolv-discuss

On 05/02/2021 14:44, Petr Menšík wrote:
> Thanks for quick reply.
>
> Unfortunately such test would not work on Fedora, because resolvconf is
> always present. It is linked to systemd by default. >
> lrwxrwxrwx. 1 root root 17 Dec 16 12:26 /usr/sbin/resolvconf ->
> ../bin/resolvectl

/sbin/resolvconf is always present on NetBSD and FreeBSD as well.

> Because systemd-resolved does not have its own package, but is part of
> systemd package, uninstallation is far from simple. It is usually just
> disabled by command "systemctl disable systemd-resolved".
>
> I used alternatives system as a workaround, resulting in:
> $ ls -l /usr/sbin/resolvconf /etc/alternatives/resolvconf
> lrwxrwxrwx. 1 root root 31 Feb  1 17:39 /etc/alternatives/resolvconf ->
> /usr/sbin/resolvconf.openresolv
> lrwxrwxrwx. 1 root root 28 Feb  1 17:39 /usr/sbin/resolvconf ->
> /etc/alternatives/resolvconf
>
> But that would mean, some resolvconf is always there. But not always
> would be active.

Shame that the implementation is poor.
Disabled just means it writes directly to resolv.conf for you.
Actually that's not entirely true.
You can set resolvconf=NO in /etc/etc/resolvconf.conf.
This just stops the subscribers from running, including libc - so 
/etc/resolv.conf is never updated.
Howver, the input is still accepted so that if the user turns the flag 
resolvconf back on they can then run `resolvconf -u` and it will apply the 
latest configuration.
So maybe semi disabled?

Anyway, the original design was so the calling application didn't have to think 
too hard, keeping it simple.

What I would do is have /sbin/resolvconf as a shell application

#/sbin/sh
# Has user installed openresolv?
# YES - pipe stdin to openresolv and pass args
# NO  - pipe stdin to systemd resovlconf and pass args
# return result

You could then make this flexable and just this like so

if [ -x /sbin/resolvconf ] && [ -e /etc/resolvconf.enabled ]; then
	echo "$resolv" | resolvconf -a interface.foo
else
	echo "$resolv" > /etc/resolv.conf
fi

You could then make the enabled test whatever you like if that's what you need.

Saying that, this patch also adds the Debian option if you prefer

diff --git a/resolvconf.in b/resolvconf.in
index 198096b..f70b27f 100644
--- a/resolvconf.in
+++ b/resolvconf.in
@@ -708,6 +708,15 @@ make_vars()
        echo "DOMAINS='$newdomains'"
 }

+# getopts doesn't support long options and some application expect
+# to check this Debian resolvconf option.
+if [ "$1" = "--updates-are-enabled" ]; then
+       case "${resolvconf:-YES}" in
+       [Yy][Ee][Ss]|[Tt][Rr][Uu][Ee]|[Oo][Nn]|1) exit 0;;
+       *) exit 1;;
+       esac
+fi
+
 force=false
 VFLAG=
 while getopts a:C:c:Dd:fhIilm:pRruvVx OPT; do

Roy