[Exim] Long lookup time

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著者: Marcin Owsiany
日付:  
To: exim-users
題目: [Exim] Long lookup time
Hi!

The problem is with connecting to exim from some hosts. It takes a
(relatively) long time between

- the connection is accepted (e.g. telnet skynet.skynet.com.pl smtp says
Connected to skynet.skynet.com.pl. Escape character is '^]'.)

and

- the initial smtp 220 banner is displayed.

Here is a session of exim -d9 -bh 149.156.124.14

host in host_lookup? yes (*)
looking up host name for 149.156.124.14
IP address lookup yielded plus.ds14.agh.edu.pl

<<<< there is a long (about 1 minute) pause here >>>>

Actual local interface address is 127.0.0.1
Actual local interface address is 213.25.173.230
plus.ds14.agh.edu.pl 149.156.124.14 -1
sender_fullhost = plus.ds14.agh.edu.pl [149.156.124.14]
sender_rcvhost = plus.ds14.agh.edu.pl ([149.156.124.14])
set_process_info: 21796 3.12 handling incoming connection from
plus.ds14.agh.edu.pl [149.156.124.14]
host in host_reject? no (option unset)
host in host_reject_recipients? no (option unset)
host in auth_hosts? no (option unset)
host in sender_unqualified_hosts? no (option unset)
host in receiver_unqualified_hosts? no (option unset)
host in helo_verify? no (option unset)
host in helo_accept_junk_hosts? no (option unset)
220 skynet.skynet.com.pl ESMTP Exim 3.12 #1 Mon, 06 Nov 2000 14:22:32 +0100
220 skynet.skynet.com.pl ESMTP Exim 3.12 #1 Mon, 06 Nov 2000 14:22:32 +0100
smtp_setup_msg entered

And here are some preprocessed sniplets from tcpdump's output

[1],[2],[3] and [4] are dns servers. ([1] and [3] are in my
/etc/resolv.conf)
[@] is the connecting host and [#] is the mail server running exim in
question.

22:44:27.437154 [@].1114 > [#].25: S 2272180203:2272180203(0) win 16060 <mss 1460,sackOK,timestamp 539165[|tcp]> (DF) [tos 0x10]
22:44:27.437238 [#].25 > [@].1114: S 2142220085:2142220085(0) ack 2272180204 win 16060 <mss 1460,sackOK,timestamp 19619743[|tcp]> (DF)
22:44:27.577739 [@].1114 > [#].25: . ack 1 win 16060 <nop,nop,timestamp 539180 19619743> (DF) [tos 0x10]

22:44:27.579821 [#].1687 > [@].113: S 2139594957:2139594957(0) win 16060 <mss 1460,sackOK,timestamp 19619757[|tcp]> (DF)
22:44:27.714685 [@].113 > [#].1687: R 0:0(0) ack 2139594958 win 0

22:44:27.719925 [#].1302 > [1].53: 61856 (55)
22:44:31.010130 [#].1302 > [2].53: 61856 (55)
22:44:32.730162 [#].1710 > [3].53: 10142+ (55)

22:44:34.572712 [3].53   > [#].1706: 10142 ServFail 0/0/0 (55)
22:44:34.572778 [#]      > [3]: icmp: [#] udp port 1706 unreachable [tos 0xc0]


22:44:35.000133 [#].1302 > [1].53: 61856 (55)
22:44:37.740111 [#].1710 > [4].53: 10142+ (55)
22:44:43.000118 [#].1302 > [2].53: 61856 (55)

22:44:45.572473 [3].53   > [#].1709: 10142 ServFail 0/0/0 (55)
22:44:45.572524 [#]      > [3]: icmp: [#] udp port 1709 unreachable [tos 0xc0]


22:44:45.760088 [#].1710 > [3].53: 10142+ (55)

22:44:46.273201 [4].53 > [#].1710: 10142 ServFail 0/0/0 (55) (DF)

22:44:46.273424 [#].1710 > [4].53: 10142+ (55)
22:44:51.000118 [#].1302 > [1].53: 61856 (55)
22:44:55.290100 [#].1710 > [4].53: 10142+ (55)
22:45:07.000187 [#].1302 > [2].53: 61856 (55)

22:45:10.571461 [3].53 > [#].1710: 10142 ServFail 0/0/0 (55)

22:45:10.571756 [#].1710 > [4].53: 10142+ (55)



This seems to be some dns related problem, although all other services (e.g.
POP3) work almost immediately.

I have
host_lookup = *
host_accept_relay = localhost:213.25.173.224/24:*.pl
in /etc/exim.conf

There is probably something wrong with that dns lookup, but I don't know
what. It seems that only one nameserver responds to the query, and it
returns some kind of an error? Might that be some bug in resolver? Or in the
way Exim uses it? Commenting-out 'host_lookup' heals the situation, but i'm
not sure I want to skip hostname validation. What does exim try to look up
after it already knows the host name of the connecting host?

I'm using a Debian potato system: exim 3.12-10, libc 2.1.3-13 Linux kernel
2.2.17.

Has anyone had similar problem? How to fix that? Any pointers to some
information that could help me?

regards

Marcin

-- 
+--------------------------------+ The reason we come up with new versions
|Marcin Owsiany                  | is not to fix bugs. It's the stupidest
|porridge@???| reason to buy a new version
+--------------------------------+ I ever heard.            - Bill Gates