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Re: sudo slow on DNS lookup, with invalid resolv.conf entries

From "x9p" <debian-user@x9pneu.com>
Newsgroups linux.debian.user
Subject Re: sudo slow on DNS lookup, with invalid resolv.conf entries
Date 2017-09-15 23:10 +0200
Message-ID <uq627-8sF-55@gated-at.bofh.it> (permalink)
References <uq1lM-5ih-9@gated-at.bofh.it> <uq28a-5AW-5@gated-at.bofh.it> <uq4tj-7jR-1@gated-at.bofh.it> <uq4Wm-7vc-13@gated-at.bofh.it>
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> sudo(8) says:
>
>      sudo supports a plugin architecture for security policies and
> input/output logging.  Third parties can develop and distribute their
> own policy and I/O logging plugins to work seamlessly with the sudo
> front end.  The default security policy is sudoers, which is configured
> via the file /etc/sudoers, or via LDAP.
>
> And LDAP means TCP, and TCP usually mean DNS requests.
>
> So it's unusual (sudo does not exhibit such behavior here), but
> possible.
>

Agree there are situations where sudo does TCP. Disagree with that
occurring in my simplistic setup. sudo should not hang for X seconds if my
DNS servers are incorrect.

> A stray nameserver in resolv.conf, which can happen if resolvconf is
> used carelessly. Even more weird things are always possible with
> NetworkManager.

Am too old, I like /etc/resolv.conf being just a file. Am avoiding to turn
this into a systemd talk.

>> resolv.conf is not a symlink to systemd, just a plain file. I explicitly
>> removed the symlink and created a normal file.
>
> And of course one can never disregard a misconfigured VPN script.
>
>
>
>> > Specifically I'm interested with:
>> >
>> > grep hosts /etc/nsswitch.conf
>> >
>> > grep localhost /etc/hosts
>> >
>> > Reco
>> >
>>
>> Did not touched these, are the default from stretch:
>>
>> root@localhost:~# grep hosts /etc/nsswitch.conf
>> hosts:          files mdns4_minimal [NOTFOUND=return] dns myhostname
>> root@localhost:~# grep localhost /etc/hosts
>> 127.0.0.1       localhost
>> 127.0.1.1       localhost
>> ::1     localhost ip6-localhost ip6-loopback
>
> Curious. Can you reproduce the behaviour if sudo is run as root?
> I propose to simplify things a bit (needs to be run as root):
>

strace was already run as root (did "sudo su" as root to prove the point),
otherwise strace would fail with "effective uid is not 0".

x9p

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Thread

sudo slow on DNS lookup, with invalid resolv.conf entries "x9p" <debian-user@x9pneu.com> - 2017-09-15 18:10 +0200
  Re: sudo slow on DNS lookup, with invalid resolv.conf entries Reco <recoverym4n@gmail.com> - 2017-09-15 19:00 +0200
    Re: sudo slow on DNS lookup, with invalid resolv.conf entries "x9p" <debian-user@x9pneu.com> - 2017-09-15 21:30 +0200
      Re: sudo slow on DNS lookup, with invalid resolv.conf entries Reco <recoverym4n@gmail.com> - 2017-09-15 22:00 +0200
        Re: sudo slow on DNS lookup, with invalid resolv.conf entries "x9p" <debian-user@x9pneu.com> - 2017-09-15 23:10 +0200
          Re: sudo slow on DNS lookup, with invalid resolv.conf entries Reco <recoverym4n@gmail.com> - 2017-09-15 23:20 +0200
            Re: sudo slow on DNS lookup, with invalid resolv.conf entries "x9p" <debian-user@x9pneu.com> - 2017-09-15 23:40 +0200
              Re: sudo slow on DNS lookup, with invalid resolv.conf entries Reco <recoverym4n@gmail.com> - 2017-09-16 00:10 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries "x9p" <debian-user@x9pneu.com> - 2017-09-16 01:20 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries Gene Heskett <gheskett@shentel.net> - 2017-09-16 02:10 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries "x9p" <debian-user@x9pneu.com> - 2017-09-17 22:40 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries deloptes <deloptes@gmail.com> - 2017-09-17 23:00 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries Brian <ad44@cityscape.co.uk> - 2017-09-18 00:10 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries Gene Heskett <gheskett@shentel.net> - 2017-09-18 00:50 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries deloptes <deloptes@gmail.com> - 2017-09-18 01:00 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries Gene Heskett <gheskett@shentel.net> - 2017-09-18 01:10 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries deloptes <deloptes@gmail.com> - 2017-09-18 09:00 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries Reco <recoverym4n@gmail.com> - 2017-09-18 18:40 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries deloptes <deloptes@gmail.com> - 2017-09-18 20:20 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries Brian <ad44@cityscape.co.uk> - 2017-09-18 20:50 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries Reco <recoverym4n@gmail.com> - 2017-09-18 22:50 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries Brian <ad44@cityscape.co.uk> - 2017-09-19 00:00 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries "x9p" <debian-user@x9pneu.com> - 2017-09-18 22:50 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries Brian <ad44@cityscape.co.uk> - 2017-09-19 00:00 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries deloptes <deloptes@gmail.com> - 2017-09-18 23:00 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries Brian <ad44@cityscape.co.uk> - 2017-09-19 00:00 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries Gene Heskett <gheskett@shentel.net> - 2017-09-19 00:10 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries Gene Heskett <gheskett@shentel.net> - 2017-09-18 00:50 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries Brian <ad44@cityscape.co.uk> - 2017-09-18 01:20 +0200
  Re: sudo slow on DNS lookup, with invalid resolv.conf entries Dan Ritter <dsr@randomstring.org> - 2017-09-15 23:10 +0200
    Re: sudo slow on DNS lookup, with invalid resolv.conf entries "x9p" <debian-user@x9pneu.com> - 2017-09-15 23:40 +0200

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