[sf-lug] resolver problem

Mon Aug 27 10:51:07 PDT 2012

Daniel G was kind enough to spend a lot of time with me at last Monday's LUG meeting trouble shooting this problem.  In the end he concluded that for reasons never made clear, resolver requests were being sent out using TCP instead of UDP and some servers honored that and some stuck to the rules and did not.  Changing /etc/resolv.conf to point to a server that did seemed to solve the problem (or should I say, 'circumvent' the problem, if that is indeed what it was. I can no longer reproduce the problem so can not investigate further.)
Nothing wrong with mail.easydns.com.  Everything works fine at present.  
If anyone is looking for a dns provider, I have been very well treated by easydns.com.  A fellow called Leandro and I had a long exchange before things were sorted out- clearly above and beyond the call of duty.
Tom: It's good to hear from you and know that you are still lurking:-)  I assume you are still in London? ak

a_kleider at yahoo.com

--- On Sat, 8/18/12, Alex Kleider <a_kleider at yahoo.com> wrote:

From: Alex Kleider <a_kleider at yahoo.com>
Subject: Re: [sf-lug] resolver problem
To: sf-lug at linuxmafia.com, "Tom Haddon" <tom at greenleaftech.net>
Date: Saturday, August 18, 2012, 6:50 PM

I'm not sure I completely understand but it appears that dig can be told to look for a specific service and your failure of dig -t mx indicates that mailout.easydns.com doesn't have the needed service. 
As it turns out, use of mailout.easydns.com works on another plug computer that I run on another network and the dig -t mx fails there as well.
The mystery remains unsolved. 
Here's the evidence:
alex at www:~$ dig -t mx mailout.easydns.com +short
alex at www:~$ dig  mailout.easydns.com +short
64.68.200.141
alex at www:~$ dig -p 2025 -t mx mailout.easydns.com +short

; <<>> DiG 9.7.3 <<>> -p 2025 -t mx mailout.easydns.com +short
;; global options: +cmd
;; connection timed out; no servers could be reached
alex at www:~$ dig mailout.easydns.com +short
64.68.200.141
alex at www:~$ dig -p2025
 mailout.easydns.com +short
; <<>> DiG 9.7.3 <<>> -p2025 mailout.easydns.com +short

;; global options: +cmd

;; connection timed out; no servers could be reached

I haven't mentioned that mailout.easydns.com listens on an unconventional port and I thought that might be an explanation for the dig -t mx failure but it seems not.
I have postfix running on both machines with the same /etc/postfix/main.cf file (except for the "mydestination=" line)

alex

--- On Sat, 8/18/12, Tom Haddon <tom at greenleaftech.net> wrote:

From: Tom Haddon <tom at greenleaftech.net>
Subject: Re: [sf-lug] resolver problem
To: sf-lug at linuxmafia.com
Date: Saturday, August 18, 2012, 9:10 AM

    You're mixing things that you're
      checking here. The host DNS entry for mailout.easydns.com may
      exist, but that doesn't mean there's an MX record for it.

      mthaddon at mallory:~$ dig mailout.easydns.com

      ; <<>> DiG 9.8.1-P1 <<>>
      mailout.easydns.com

      ;; global options: +cmd

      ;; Got answer:

      ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id:
      53568

      ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL:
      0

      ;; QUESTION SECTION:

      ;mailout.easydns.com.        IN    A

      ;; ANSWER SECTION:

      mailout.easydns.com.    300    IN    A    64.68.200.141

      ;; Query time: 12 msec

      ;; SERVER: 127.0.0.1#53(127.0.0.1)

      ;; WHEN: Sat Aug 18 17:09:43 2012

      ;; MSG SIZE  rcvd: 53

      mthaddon at mallory:~$
      dig -t mx mailout.easydns.com

      ; <<>> DiG 9.8.1-P1 <<>> -t mx
      mailout.easydns.com

      ;; global options: +cmd

      ;; Got answer:

      ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id:
      42943

      ;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL:
      0

      ;; QUESTION SECTION:

      ;mailout.easydns.com.        IN    MX

      ;; Query time: 13 msec

      ;; SERVER: 127.0.0.1#53(127.0.0.1)

      ;; WHEN: Sat Aug 18 17:04:57 2012

      ;; MSG SIZE  rcvd: 37

      Looks like you need to double check that that's what you should be
      trying to connect to.

      Thanks, Tom

      On 18/08/12 16:55, Alex Kleider wrote:

            I've got postfix
              installed on my DreamPlug and am trying to get it

              configured to be able to send mail out to a "smart host."
              The smart host is

              mailout.easydns.com.  Mail doesn't get out; the following
              is reported

              in /var/log/mail.info:

              """

              Aug 18 08:34:59 dp4 postfix/pickup[25907]: 36C8229CE7:
              uid=0 from=<root>

              Aug 18 08:34:59 dp4 postfix/cleanup[26005]: 36C8229CE7:

              message-id=<20120818153459.GA25992 at kleider.ca>

              Aug 18 08:34:59 dp4 postfix/qmgr[17065]: 36C8229CE7:

              from=<root at kleider.ca>, size=416, nrcpt=1 (queue
              active)

              Aug 18 08:35:15 dp4 postfix/smtp[26008]: 36C8229CE7:

              to=<akleider at sonic.net>, relay=none, delay=16,
              delays=0.1/0.03/16/0,

              dsn=4.4.3, status=deferred (Host or domain name not found.
              Name service

              error for name=mailout.easydns.com type=MX: Host not
              found, try again)

              """

              Investigation of name resolution gives what seem to be
              conflicting

              results (ping and dig work but traceroute and mtr don't):

              root at dp4:/var/log# ping mailout.easydns.com

              PING mailout.easydns.com (64.68.200.141) 56(84) bytes of
              data.

              64 bytes from mailout.easydns.com (64.68.200.141):
              icmp_req=1 ttl=50

              time=81.9 ms

              64 bytes from mailout.easydns.com (64.68.200.141):
              icmp_req=2 ttl=50

              time=79.9 ms

              64 bytes from mailout.easydns.com (64.68.200.141):
              icmp_req=3 ttl=50

              time=81.3 ms

              ^C64 bytes from mailout.easydns.com (64.68.200.141):
              icmp_req=4 ttl=50

              time=80.3 ms

              --- mailout.easydns.com ping statistics ---

              4 packets transmitted, 4 received, 0% packet loss, time
              13907ms

              rtt min/avg/max/mdev = 79.989/80.931/81.988/0.788 ms

              root at dp4:/var/log# traceroute mailout.easydns.com

              mailout.easydns.com: No address associated with hostname

              Cannot handle "host" cmdline arg `mailout.easydns.com' on
              position 1 (argc

              1)

              root at dp4:/var/log# dig @127.0.0.1 mailout.easydns.com

              ; <<>> DiG 9.7.3 <<>> @127.0.0.1
              mailout.easydns.com

              ; (1 server found)

              ;; global options: +cmd

              ;; Got answer:

              ;; ->>HEADER<<- opcode: QUERY, status:
              NOERROR, id: 47312

              ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0,
              ADDITIONAL: 0

              ;; QUESTION SECTION:

              ;mailout.easydns.com.           IN      A

              ;; ANSWER SECTION:

              mailout.easydns.com.    191     IN      A      
              64.68.200.141

              ;; Query time: 4016 msec

              ;; SERVER: 127.0.0.1#53(127.0.0.1)

              ;; WHEN: Sat Aug 18 08:27:38 2012

              ;; MSG SIZE  rcvd: 53

              root at dp4:/var/log# mtr mailout.easydns.com

              No address associated with hostname: Success

              Other commands that require resolver success (wget, w3m)
              work fine.

              Any thoughts?

              Alex

              ~           

              a_kleider at yahoo.com

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