fc6: telnetd refuses connections if nameserver is down

[Dario Lesca]

Hi, in FC6, the telnetd service refuse the connection if the nameserver
is down. (see this bug):
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=223448

But in this tread:
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=221583

people say witch this problem is not a bug ....

In previous fc version, if the nameserver is down, the connection is
however accepted .

Someone can give me more information to this issue?.
It will be resolved (or not) in future?

Many thanks.

-- 
Dario Lesca <d.lesca(a)solinos.it&gt;

[Mikkel]

Dario Lesca wrote:
>  Hi, in FC6, the telnetd service refuse the connection if the
> nameserver
>  is down. (see this bug):
>  https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=223448
>  
>  But in this tread:
>  https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=221583
>  
>  people say witch this problem is not a bug ....
>  
>  In previous fc version, if the nameserver is down, the connection is
>  however accepted .
>  
>  Someone can give me more information to this issue?.
>  It will be resolved (or not) in future?
>  
>  Many thanks.
>   
I don't have telnetd installed, so I can not check it, but take a
look at /etc/xinetd.d/telnet and see if it has something like:

log_on_success  += HOST DURATION
log_on_failure  += HOST

I suspect you have something like the first line, and with DNS down,
it refuses connections, because it can not log the machine. Try
commenting out the line(s). You will have to restart xinetd.

Mikkel
-- 

  Do not meddle in the affairs of dragons,
for thou art crunchy and taste good with Ketchup!

[Dario Lesca]

Il giorno lun, 26/02/2007 alle 14.34 -0600, Mikkel L. Ellertson ha
scritto:

>  /etc/xinetd.d/telnet 
it contain only 'log_on_failure  +=
USERID'

but if I comment it none is change.

A workaround is delete the 'dns' keyword from /etc/nsswitch.conf from
'hosts:      files' line.

Thanks Mikkel.

-- 
Dario Lesca <d.lesca(a)solinos.it&gt;

[kalinix]

On Mon, 2007-02-26 at 22:00 +0100, Dario Lesca wrote:
>  Il giorno lun, 26/02/2007 alle 14.34 -0600, Mikkel L. Ellertson ha
>  scritto:
>  
>  > /etc/xinetd.d/telnet
>  it contain only 'log_on_failure  += USERID'
>  
>  but if I comment it none is change.
>  
>  A workaround is delete the 'dns' keyword from /etc/nsswitch.conf from
>  'hosts:      files' line.
>  
>  Thanks Mikkel.
>  
>  -- 
>  Dario Lesca <d.lesca(a)solinos.it&gt;
>   
Actually the "HOST" part is not in /etc/xinetd.d/telnet but
in /etc/xinetd.conf:


        log_on_failure  = HOST
        log_on_success  = PID HOST DURATION EXIT





Calin

=================================================
There is no proverb that is not true. -- Cervantes

[Mikkel]

kalinix wrote:
>  
>  Actually the "HOST" part is not in /etc/xinetd.d/telnet but
>  in /etc/xinetd.conf:
>  
>  
>          log_on_failure  = HOST
>          log_on_success  = PID HOST DURATION EXIT
>   
I guess I changed the default setup here. In any case, the settings
in /etc/xinetd.conf are the default settings, but they can be
overridden, or added to, by the individual service config files in
/etc/xinetd.d - take a look at any of the IMAP or POP entries...

Mikkel
-- 

  Do not meddle in the affairs of dragons,
for thou art crunchy and taste good with Ketchup!

[kalinix]

On Mon, 2007-02-26 at 17:10 -0600, Mikkel L. Ellertson wrote:
>  kalinix wrote:
>  > 
>  > Actually the "HOST" part is not in /etc/xinetd.d/telnet but
>  > in /etc/xinetd.conf:
>  > 
>  > 
>  >         log_on_failure  = HOST
>  >         log_on_success  = PID HOST DURATION EXIT
>  > 
>  I guess I changed the default setup here. In any case, the settings
>  in /etc/xinetd.conf are the default settings, but they can be
>  overridden, or added to, by the individual service config files in
>  /etc/xinetd.d - take a look at any of the IMAP or POP entries...
>  
>  Mikkel
>  -- 
>  
>    Do not meddle in the affairs of dragons,
>  for thou art crunchy and taste good with Ketchup!
>   
No doubt they can be override (as anything in linux world :) ), but I
was talking about FC6 default settings for xinetd and/or telnet, the
ones Dario uses on his system.


Calin

=================================================
Bucy's Law: Nothing is ever accomplished by a reasonable man.

[Dario Lesca]

Il giorno mar, 27/02/2007 alle 00.51 +0200, kalinix ha scritto:
>  Actually the "HOST" part is not in /etc/xinetd.d/telnet
> but
>  in /etc/xinetd.conf:
>          log_on_failure  = HOST
>          log_on_success  = PID HOST DURATION EXIT
>   
Also comment out this line (this is my file part of xinetd.conf after
comment)
>  
>  # Define general logging characteristics.
>          log_type        = SYSLOG daemon info
>  #       log_on_failure  = HOST
>  #       log_on_success  = PID HOST DURATION EXIT 
and restart xinetd the problem persist.

Probably the problem is into resolver function, called from xinetd, like
bugzilla https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=221583
say

>  Comment #6
>  From Jakub
>  Jelinek 
>  on 2007-01-05
>  13:17 EST
>  [reply]
>   
>   
>  nsswitch.conf containing hosts: ... dns and missing resolv.conf is an admin
>  error, either you should remove dns from nsswitch.conf, or supply a valid
>  resolv.conf.  The missing resolv.conf is the same as resolv.conf containing no
>  nameserver lines and that causes libresolv to return TRY_AGAIN, the same as if
>  a DNS is unreachable.  For that EAI_AGAIN is the correct answer, instead of
>  silently pretending DNS replied, but said there is no DNS entry for that IP
>  address. 
Many thanks Kalinix

-- 
Dario Lesca <d.lesca(a)solinos.it&gt;

[kalinix]

On Tue, 2007-02-27 at 00:40 +0100, Dario Lesca wrote:
>  Il giorno mar, 27/02/2007 alle 00.51 +0200, kalinix ha scritto:
>  > Actually the "HOST" part is not in /etc/xinetd.d/telnet but
>  > in /etc/xinetd.conf:
>  >         log_on_failure  = HOST
>  >         log_on_success  = PID HOST DURATION EXIT
>  > 
>  
>  Also comment out this line (this is my file part of xinetd.conf after
>  comment)
>  > 
>  > # Define general logging characteristics.
>  >         log_type        = SYSLOG daemon info
>  > #       log_on_failure  = HOST
>  > #       log_on_success  = PID HOST DURATION EXIT
>  
>  and restart xinetd the problem persist.
>  
>  Probably the problem is into resolver function, called from xinetd, like
>  bugzilla https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=221583
>  say
>  
>  > Comment #6
>  > From Jakub
>  > Jelinek 
>  > on 2007-01-05
>  > 13:17 EST
>  > [reply]
>  >  
>  >  
>  > nsswitch.conf containing hosts: ... dns and missing resolv.conf is an admin
>  > error, either you should remove dns from nsswitch.conf, or supply a valid
>  > resolv.conf.  The missing resolv.conf is the same as resolv.conf containing no
>  > nameserver lines and that causes libresolv to return TRY_AGAIN, the same as if
>  > a DNS is unreachable.  For that EAI_AGAIN is the correct answer, instead of
>  > silently pretending DNS replied, but said there is no DNS entry for that IP
>  > address.
>  
>  Many thanks Kalinix
>  
>  -- 
>  Dario Lesca <d.lesca(a)solinos.it&gt;
>   
Dario,


from bug 221583:


"Sorry you are correct if a nameserver is configured correctly it return
the IP address as expected...

and 
... nsswitch.conf containing hosts: ... dns and missing resolv.conf is
an admin error, either you should remove dns from nsswitch.conf, or
supply a valid resolv.conf."


Do you have a nameserver configured (defined in /etc/resolv.conf) on
your telnet server?



Calin

=================================================
You will gain money by an illegal action.

[Dario Lesca]

Il giorno mar, 27/02/2007 alle 02.03 +0200, kalinix ha scritto:
>  Do you have a nameserver configured (defined in /etc/resolv.conf) on
>  your telnet server?  
Yes, but some time it is down, or the nameserver into resolv.conf is not
set.

Is a internal DNS, the local network in not property configured, the DNS
is not use. In this scenario the version fc[1-5] work great.

Now I have check (on telnet server) to point the nameserver to 127.0.0.1
and start bind (whitout configure it). The connection from a telnet
client now work (without the nsswitch.conf modify). The problem is
disappeared.

Then:

On fc6 the nameserver must set, and must point to a existent nameserver.
If nameserver is NOT set, or is set to a IP down or a generic host (not
a nameserver) the xinetd connection (like telnet ) do not work.

It is therefore? Is this right?

Thanks to all

-- 
Dario Lesca <d.lesca(a)solinos.it&gt;

[Tim]

On Tue, 2007-02-27 at 01:49 +0100, Dario Lesca wrote:
>  On fc6 the nameserver must set, and must point to a existent
>  nameserver. 
Or, there must be a name server on the same machine:

man resolv.conf

      "On a normally configured system this file should not be necessary.  The
       only name server to be queried will be on the local machine; the domain
       name is determined from the host name and the domain search path is
       constructed from the domain name."

-- 
(This box runs FC6, my others run FC4 & FC5, in case that's
 important to the thread.)

Don't send private replies to my address, the mailbox is ignored.
I read messages from the public lists.