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Package: cups
Version: 2.2.4-7
Severity: normal
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Hash: SHA256
- From cups.d(5):
ServerName hostname
Specifies the fully-qualified hostname of the server. The default is the value reported by the hostname(1) command.
This is plain wrong in itself, because hostname(1) does not return the
FQDN (except when run with -f). Consequently, CUPS does not listen to
requests to its FQDN by default.
- -- System Information:
Debian Release: buster/sid
APT prefers unstable-debug
APT policy: (500, 'unstable-debug'), (500, 'unstable'), (1, 'experimental-debug')
Architecture: amd64 (x86_64)
Foreign Architectures: i386
Kernel: Linux 4.12.0-2-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8), LANGUAGE=en (charmap=UTF-8)
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
Versions of packages cups depends on:
ii cups-client 2.2.4-7
ii cups-common 2.2.4-7
ii cups-core-drivers 2.2.4-7
ii cups-daemon 2.2.4-7
ii cups-filters 1.16.4-1+b2
ii cups-ppdc 2.2.4-7
ii cups-server-common 2.2.4-7
ii debconf 1.5.63
ii ghostscript 9.21~dfsg-1
ii libavahi-client3 0.7-3
ii libavahi-common3 0.7-3
ii libc-bin 2.24-17
ii libc6 2.24-17
ii libcups2 2.2.4-7
ii libcupscgi1 2.2.4-7
ii libcupsimage2 2.2.4-7
ii libcupsmime1 2.2.4-7
ii libcupsppdc1 2.2.4-7
ii libgcc1 1:7.2.0-7
ii libstdc++6 7.2.0-7
ii libusb-1.0-0 2:1.0.21-2
ii poppler-utils 0.57.0-2
ii procps 2:3.3.12-3
Versions of packages cups recommends:
ii avahi-daemon 0.7-3
ii colord 1.3.3-2
ii cups-filters [ghostscript-cups] 1.16.4-1+b2
ii printer-driver-gutenprint 5.2.13-1
Versions of packages cups suggests:
ii cups-bsd 2.2.4-7
pn cups-pdf <none>
ii foomatic-db-compressed-ppds [foomatic-db] 20170723-1
ii hplip 3.17.7+repack0-3
ii printer-driver-hpcups 3.17.7+repack0-3
ii smbclient 2:4.6.7+dfsg-2
ii udev 234-3
- -- debconf information excluded
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--- Begin Message ---
Control: tags -1 +wontfix
Le jeudi, 12 octobre 2017, 19.03:33 h CEST Dominik George a écrit :
> > … ServerName is set from gethostname(2), which, by their manpages, return
> > the same value as hostname(1), aka uname(2)'s nodename, which you can
> > retrieve from $ uname -n.
>
> Right. Now read the man page:
>
> ServerName hostname
> Specifies the fully-qualified hostname of the server. The
> default is the value reported by the hostname(1) command.
>
> Neither gethopstname(2) nor hostname(1) nor uname(2) return the
> *fully-qualified hostname of the server*.
That's right. If I phrase differently what the manpage says: "ServerName is
the configuration stanza you _can_ use in cupsd.conf if you want to specify the
fully-qualified hostname of the server. If you don't, the default will be the
value reported by the hostname(1) command."
> So the default used is NOT the FQDN, while ServerName shall be set to the
> FQDN.
Exactly. The default is (and I think both the code and the documentation agree
here), whatever hostname(1) outputs.
> So: The code should be changed…
I disagree. You happen to disagree what the ServerName default should be and
that's fine. I, as maintainer, think it's a fine default.
> > ServerName is set around these lines and there are various heuristics
> > which
> > add ServerAliases to that configuration. All these are logged at the
> > 'debug' level. I've added a patch to log the ServerName cups takes:
> >
> > --- a/scheduler/conf.c
> > +++ b/scheduler/conf.c
> > @@ -891,6 +891,7 @@ cupsdReadConfiguration(void)
> >
> > }
> >
> > cupsdSetString(&ServerName, temp);
> >
> > + cupsdLogMessage(CUPSD_LOG_DEBUG, "Set ServerName %s", temp);
>
> …especially as these heuristics try to generate the base host name by
> stripping the domain part from the ServerName, expecting it to be the
> FQDN.
Well. No, they don't. Read the code again. Whatever is outputted by
gethostname(2) goes to temp which is then _set_ to ServerName. ServerAliases
is filled by other heuristics.
> > What is it that you get?
>
> $ hostname
> foo
> $ hostname -f
> foo.example.com
>
> Still, CUPS only responds to foo, not foo.example.com.
I think you're misreading the 'ServerName' documentation. The documentation
doesn't say that ServerName will have as default the system's FQDN, it says
that _if_ you don't define it, it will use the output of hostname(2).
hostname(2) says it uses gethostname(1) which itself says it will return the
output of uname -n.
The code does what the documentation says it does.
> (Please mind that your system seems to be misconfigured and does not
> return the FQDN with hostname -f!)
(I don't want my system to have a FQDN as it's not routeable anyway.)
> > And do you still think there's discrepancy between
> > code and documentation? If so, which one do you think is wrong?
>
> The code is wrong. It should use the FQDN, like reported by hostname -f,
> as default for ServerName, probably by resolving the name it got from
> gethostbyname() twice (like hostname -f does).
I disagree. In my reading of the code and documentation, they _do_ agree. If
you don't like the default (uname -n), `ServerName` is there for you; you can
specify a specific FQDN. Finally, I think ServerName defaulting to _not_ being
the FQDN is in line with CUPS listening on localhost by default only. You will
need to add both `Listen` _and_ `ServerName` stanzas to cupsd.conf if you want
it to listen to its FQDN, and I don't see a problem with that.
I'm hereby closing this bug, and tagging it as wontfix too. As I am _not_ going
to diverge from upstream on that, please feel free to bring your arguments to
upstream on their bugtracker (but don't hold your breath; this code is in CUPS
since 2009):
https://github.com/apple/cups/issues
With my best regards,
OdyX
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