sendmail and the resolver

D

ducu_00

I have 2 freebsd systems....but let the commands speak for themselves:

[root@fbsd6-c:/usr/ports]# uname -a
FreeBSD fbsd6-c.bdux.dsdis.ro 6.4-RELEASE FreeBSD 6.4-RELEASE #0: Wed Nov 26 11:43:51 UTC 2008 root@dessler.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC i386
[root@fbsd6-c:/usr/ports]# cat /etc/resolv.conf
search bdux.dsdis.ro
nameserver 10.32.0.1
[root@fbsd6-c:/usr/ports]# cat /dev/null | sendmail -d0.1
Version 8.14.3
Compiled with: DNSMAP LOG MAP_REGEX MATCHGECOS MILTER MIME7TO8 MIME8TO7
NAMED_BIND NETINET NETINET6 NETUNIX NEWDB NIS PIPELINING SCANF
STARTTLS TCPWRAPPERS USERDB XDEBUG
.....
[root@fbsd6-c:/usr/ports]# mail postmaster@kvm0.bdux.dsdis.ro
Subject: test2
EOT
Null message body; hope that's ok
Click to expand...

[root@fbsd71:~/tmp/ducu]# uname -a
FreeBSD fbsd71.bdux.dsdis.ro 7.1-RELEASE FreeBSD 7.1-RELEASE #0: Thu Jan 1 14:37:25 UTC 2009 root@logan.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC i386
[root@fbsd71:~/tmp/ducu]# cat /etc/resolv.conf
search bdux.dsdis.ro
nameserver 10.32.0.1
[root@fbsd71:~/tmp/ducu]# cat /dev/null | sendmail -d0.1
Version 8.14.3
Compiled with: DNSMAP LOG MAP_REGEX MATCHGECOS MILTER MIME7TO8 MIME8TO7
NAMED_BIND NETINET NETINET6 NETUNIX NEWDB NIS PIPELINING SCANF
STARTTLS TCPWRAPPERS USERDB XDEBUG
......
[root@fbsd71:~/tmp/ducu]# mail postmaster@kvm0.bdux.dsdis.ro
Subject: test1
EOT
Null message body; hope that's ok
Click to expand...


The mailers configurations are the default ones (from the base system), the nsswitch.conf file too (^host: files dns). Didn't touch /etc/hosts either.

Let's see the name server conversations:
....for freebsd 6.4:
11:55:02.197484 IP 10.32.0.67.58879 > 10.32.0.1.domain: 46405+ AAAA? fbsd6-c.bdux.dsdis.ro. (39)
11:55:02.197777 IP 10.32.0.1.domain > 10.32.0.67.58879: 46405* 0/1/0 (83)
11:55:02.198303 IP 10.32.0.67.57464 > 10.32.0.1.domain: 46406+ AAAA? fbsd6-c.bdux.dsdis.ro.bdux.dsdis.ro. (53)
11:55:02.198397 IP 10.32.0.1.domain > 10.32.0.67.57464: 46406 NXDomain* 0/1/0 (97)
11:55:02.198892 IP 10.32.0.67.57943 > 10.32.0.1.domain: 46407+ A? fbsd6-c.bdux.dsdis.ro. (39)
11:55:02.199005 IP 10.32.0.1.domain > 10.32.0.67.57943: 46407* 1/1/1 A[|domain]
11:55:02.207142 IP 10.32.0.67.50757 > 10.32.0.1.domain: 46408+ AAAA? kvm0.bdux.dsdis.ro. (36)
11:55:02.207214 IP 10.32.0.1.domain > 10.32.0.67.50757: 46408* 0/1/0 (80)
11:55:02.207593 IP 10.32.0.67.50442 > 10.32.0.1.domain: 46409+ A? kvm0.bdux.dsdis.ro. (36)
11:55:02.207702 IP 10.32.0.1.domain > 10.32.0.67.50442: 46409* 1/1/1 A 10.32.0.10 (85)
11:55:02.223780 IP 10.32.0.67.51669 > 10.32.0.1.domain: 27977+ AAAA? fbsd6-c.bdux.dsdis.ro. (39)
11:55:02.223849 IP 10.32.0.1.domain > 10.32.0.67.51669: 27977* 0/1/0 (83)
11:55:02.224215 IP 10.32.0.67.64610 > 10.32.0.1.domain: 27978+ A? fbsd6-c.bdux.dsdis.ro. (39)
11:55:02.224306 IP 10.32.0.1.domain > 10.32.0.67.64610: 27978* 1/1/1 A[|domain]
11:55:02.226482 IP 10.32.0.67.55261 > 10.32.0.1.domain: 27979+ AAAA? kvm0.bdux.dsdis.ro. (36)
11:55:02.226548 IP 10.32.0.1.domain > 10.32.0.67.55261: 27979* 0/1/0 (80)
11:55:02.226935 IP 10.32.0.67.56008 > 10.32.0.1.domain: 27980+ A? kvm0.bdux.dsdis.ro. (36)
11:55:02.227004 IP 10.32.0.1.domain > 10.32.0.67.56008: 27980* 1/1/1 A 10.32.0.10 (85)
11:55:02.338078 IP 10.32.0.67.56597 > 10.32.0.1.domain: 27981+ MX? kvm0.bdux.dsdis.ro. (36)
11:55:02.338150 IP 10.32.0.1.domain > 10.32.0.67.56597: 27981* 0/1/0 (80)
11:55:02.339751 IP 10.32.0.67.64421 > 10.32.0.1.domain: 27982+ AAAA? kvm0.bdux.dsdis.ro. (36)
11:55:02.339816 IP 10.32.0.1.domain > 10.32.0.67.64421: 27982* 0/1/0 (80)
11:55:02.340549 IP 10.32.0.67.62620 > 10.32.0.1.domain: 27983+ A? kvm0.bdux.dsdis.ro. (36)
11:55:02.340619 IP 10.32.0.1.domain > 10.32.0.67.62620: 27983* 1/1/1 A 10.32.0.10 (85)
11:55:02.341952 IP 10.32.0.67.64621 > 10.32.0.1.domain: 27984+ AAAA? kvm0.bdux.dsdis.ro. (36)
11:55:02.342016 IP 10.32.0.1.domain > 10.32.0.67.64621: 27984* 0/1/0 (80)
11:55:02.345332 IP 10.32.0.67.51785 > 10.32.0.1.domain: 27985+ AAAA? kvm0.bdux.dsdis.ro. (36)
11:55:02.345397 IP 10.32.0.1.domain > 10.32.0.67.51785: 27985* 0/1/0 (80)
11:55:02.345766 IP 10.32.0.67.62973 > 10.32.0.1.domain: 27986+ AAAA? kvm0. (22)
11:55:02.345828 IP 10.32.0.1.domain > 10.32.0.67.62973: 27986 NXDomain 0/1/0 (97)
11:55:02.346214 IP 10.32.0.67.50473 > 10.32.0.1.domain: 27987+ AAAA? kvm0.bdux.dsdis.ro. (36)
11:55:02.346280 IP 10.32.0.1.domain > 10.32.0.67.50473: 27987* 0/1/0 (80)
11:55:02.346689 IP 10.32.0.67.61494 > 10.32.0.1.domain: 27988+ AAAA? kvm0. (22)
11:55:02.346746 IP 10.32.0.1.domain > 10.32.0.67.61494: 27988 NXDomain 0/1/0 (97)
11:55:02.347140 IP 10.32.0.67.54877 > 10.32.0.1.domain: 27989+ A? kvm0.bdux.dsdis.ro. (36)
11:55:02.347201 IP 10.32.0.1.domain > 10.32.0.67.54877: 27989* 1/1/1 A 10.32.0.10 (85)
11:55:02.348057 IP 10.32.0.67.59675 > 10.32.0.1.domain: 27990+ PTR? 67.0.32.10.in-addr.arpa. (41)
11:55:02.348139 IP 10.32.0.1.domain > 10.32.0.67.59675: 27990* 1/1/1 PTR[|domain]
Click to expand...

...and for freebsd 7.1:
11:29:26.542430 IP 10.32.0.69.64982 > 10.32.0.1.domain: 51837+ AAAA? fbsd71.bdux.dsdis.ro. (38)
11:29:26.542614 IP 10.32.0.1.domain > 10.32.0.69.64982: 51837* 0/1/0 (82)
11:29:26.543198 IP 10.32.0.69.59456 > 10.32.0.1.domain: 51838+ AAAA? fbsd71.bdux.dsdis.ro.bdux.dsdis.ro. (52)
11:29:26.543318 IP 10.32.0.1.domain > 10.32.0.69.59456: 51838 NXDomain* 0/1/0 (96)
11:29:26.543639 IP 10.32.0.69.62847 > 10.32.0.1.domain: 51839+ A? fbsd71.bdux.dsdis.ro. (38)
11:29:26.543717 IP 10.32.0.1.domain > 10.32.0.69.62847: 51839* 1/1/1 A 10.32.0.69 (87)
11:29:26.554687 IP 10.32.0.69.53886 > 10.32.0.1.domain: 51840+ AAAA? kvm0.bdux.dsdis.ro. (36)
11:29:26.554794 IP 10.32.0.1.domain > 10.32.0.69.53886: 51840* 0/1/0 (80)
11:29:26.555157 IP 10.32.0.69.60804 > 10.32.0.1.domain: 51841+ A? kvm0.bdux.dsdis.ro. (36)
11:29:26.555228 IP 10.32.0.1.domain > 10.32.0.69.60804: 51841* 1/1/1 A 10.32.0.10 (85)
11:29:26.569798 IP 10.32.0.69.56145 > 10.32.0.1.domain: 4859+ AAAA? fbsd71.bdux.dsdis.ro. (38)
11:29:26.569902 IP 10.32.0.1.domain > 10.32.0.69.56145: 4859* 0/1/0 (82)
11:29:26.570281 IP 10.32.0.69.58469 > 10.32.0.1.domain: 4860+ A? fbsd71.bdux.dsdis.ro. (38)
11:29:26.570360 IP 10.32.0.1.domain > 10.32.0.69.58469: 4860* 1/1/1 A 10.32.0.69 (87)
11:29:26.572462 IP 10.32.0.69.64996 > 10.32.0.1.domain: 4861+ AAAA? kvm0.bdux.dsdis.ro. (36)
11:29:26.572565 IP 10.32.0.1.domain > 10.32.0.69.64996: 4861* 0/1/0 (80)
11:29:26.572865 IP 10.32.0.69.57071 > 10.32.0.1.domain: 4862+ A? kvm0.bdux.dsdis.ro. (36)
11:29:26.572935 IP 10.32.0.1.domain > 10.32.0.69.57071: 4862* 1/1/1 A 10.32.0.10 (85)
11:29:26.686465 IP 10.32.0.69.52608 > 10.32.0.1.domain: 4863+ MX? kvm0.bdux.dsdis.ro. (36)
11:29:26.686571 IP 10.32.0.1.domain > 10.32.0.69.52608: 4863* 0/1/0 (80)
11:29:26.687016 IP 10.32.0.69.54589 > 10.32.0.1.domain: 4864+ AAAA? kvm0.bdux.dsdis.ro. (36)
11:29:26.687086 IP 10.32.0.1.domain > 10.32.0.69.54589: 4864* 0/1/0 (80)
11:29:26.687455 IP 10.32.0.69.51550 > 10.32.0.1.domain: 4865+ A? kvm0.bdux.dsdis.ro. (36)
11:29:26.687565 IP 10.32.0.1.domain > 10.32.0.69.51550: 4865* 1/1/1 A 10.32.0.10 (85)
11:29:26.688676 IP 10.32.0.69.61240 > 10.32.0.1.domain: 4866+ AAAA? kvm0.bdux.dsdis.ro. (36)
11:29:26.688742 IP 10.32.0.1.domain > 10.32.0.69.61240: 4866* 0/1/0 (80)
11:29:26.689084 IP 10.32.0.69.51843 > 10.32.0.1.domain: 4867+ A? kvm0.bdux.dsdis.ro. (36)
11:29:26.689191 IP 10.32.0.1.domain > 10.32.0.69.51843: 4867* 1/1/1 A 10.32.0.10 (85)
11:29:26.689792 IP 10.32.0.69.52105 > 10.32.0.1.domain: 4868+ A? kvm0.bdux.dsdis.ro. (36)
11:29:26.689862 IP 10.32.0.1.domain > 10.32.0.69.52105: 4868* 1/1/1 A 10.32.0.10 (85)
11:29:26.694359 IP 10.32.0.69.61229 > 10.32.0.1.domain: 4869+ PTR? 69.0.32.10.in-addr.arpa. (41)
11:29:26.694472 IP 10.32.0.1.domain > 10.32.0.69.61229: 4869* 1/1/1 PTR[|domain]
11:46:37.890372 IP 10.32.0.69.53611 > 10.32.0.1.domain: 1191+ AAAA? fbsd71.bdux.dsdis.ro. (38)
11:46:37.890566 IP 10.32.0.1.domain > 10.32.0.69.53611: 1191* 0/1/0 (82)
11:46:37.891147 IP 10.32.0.69.50391 > 10.32.0.1.domain: 1192+ AAAA? fbsd71.bdux.dsdis.ro.bdux.dsdis.ro. (52)
11:46:37.891270 IP 10.32.0.1.domain > 10.32.0.69.50391: 1192 NXDomain* 0/1/0 (96)
11:46:37.891575 IP 10.32.0.69.62032 > 10.32.0.1.domain: 1193+ A? fbsd71.bdux.dsdis.ro. (38)
11:46:37.891653 IP 10.32.0.1.domain > 10.32.0.69.62032: 1193* 1/1/1 A 10.32.0.69 (87)
Click to expand...

See the red lines. The same behaviour for 6.3 and 5.5 releases. What is the reason for these queries?

It seems the questionable queries are harmfull, but they aren't in some network configurations where the name server is a M$ one (my situation) which, in the default configuration:
1. does not forward and
2. returns ServFail, not NXDomain, for the single label queries. For more information, see http://www.tomshardware.co.uk/forum/page-197182_36_0.html
In this setup, the mails stay in the queue and the sendmail logs are full of "stat=Deferred: Name server: kvm0.bdux.dsdis.ro.: host name lookup failure". Do I need to say that `host kvm0.bdux.dsdis.ro` returns the right ipv4 address?

Now, I know there are solutions (by the way, WorkAroundBrokenAAAA is _not_ working in this case), but one question still remains: why the single label queries?

Thank you. For reading the long post, in the first place ;)
 
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