On 8/5/23 08:25, Greg Troxel wrote:
Jim Klimov via Nut-upsuser <nut-upsuser@alioth-lists.debian.net> writes:
I've recently found that at least on my test box the `LISTEN *` line had
only set up an IPv4 `0.0.0.0` listener but not an IPv6 `::0` listener for
`upsd`.
Interesting. On one system I checked, I have 4 explicit directives for
127.0.0.1, ::1, and the LAN on v4/v6. On another, I have an empty
upsd.conf and it is listening:
nut upsd 1047 4* internet stream tcp 127.0.0.1:3493
nut upsd 1047 5* internet6 stream tcp [::1]:3493
In fact, at least on a "dual-stack" system, it seems impossible to
bind to both - so depending on binding order I either lose IPv6 or lose
IPv4 directly (but have it practically as IPv4-over-IPv6).
That is not intrinsic to a system that does v4 and v6. It is about a
misfeature which if turned on, when one binds to v6 also sets up a
listener on v4 which connects as a mapped address. These days, I view
it as a bug for a system to be configuret hat way. On NetBSD, from
ip6(4):
IPV6_V6ONLY int *
Get or set whether only IPv6 connections can be made to this
socket. For wildcard sockets, this can restrict connections to
IPv6 only.
which is 1 on my system.
Given that `LISTEN *` support is in fact not documented explicitly (I
think), I am inclined to define it as listening to "any" on whatever
address families are available and supported by the NUT build, and somehow
ensuring that to the best of our capability (technical puzzles exist - see
GitHub issue).
It seems really obvious that * means anything, so agreed.
I think it's important that the default, if there are no LISTEN
directives, be "listen on all localhost addresses of all address
familes". And probably there should be a way to say that explicitly,
like "LISTEN localhost".
Practically, LISTEN localhost should:
#ifdef v6 at compile time
open a socket and bind to [::1]:3493
error log that v6 bind failed
#endif
open a socket and bind to 127.0.0.1:3493
if error:
if there is a v6 socket:
debug log that v4 bind failed, maybe, or maybe it's a real
error? need to figure out if v6only=0 systems some try to map
this. The point being not to fight os/sysadmin choice even if
misguided :-)
else:
error log that v4 bind failed
and LISTEN * should
#ifdef v6 at compile time
open a socket and bind to INADDR6_ANY:3493
error log that v6 bind failed
#endif
open a socket and bind to INADDR_ANY:3493
if error:
if there is a v6 socket:
debug log that v4 bind failed
else:
error log that v4 bind failed
As outlined here, that does resemble a good universal approach. However
for me, who is likely 100 miles from the nearest working ipv6 address,
the current situation seems to suffice.
The only problems I've had with bookworm are related to shifting all the
system logging into journald, So it been very difficult to troubleshoot
the new access problems with my raid10 based /home partition. And that
has nothing to do with nut that I've observed..
My reliance on nut is nearly moot since a ups only has to survive 5
seconds until my 20kw Kohler gets started.
Detailed musing and logs are posted in
https://github.com/networkupstools/nut/issues/2012
Pro/Con ideas are welcome :)
Cheers, Gene Heskett.
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
Genes Web page <http://geneslinuxbox.net:6309/>
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