Subject: strange problem, perhaps involves with DNS?

From: Star Wang <[email-masked]>
Date: Sun, 30 Aug 1998 11:16:47 +0800

When using wuftpd2.4.2-beta18 for solaris 2.6, I have a problem!

The compling process is OK, and configuration is OK, too. The wuftpd is good.
But I still find a problem, when I ftp to the server from a host which didn't  have 
entry in the DNS server, the login process is slow(here the login process
means the time between I input "ftp ftpserver" and the prompt  information 
("User")appears.).

And if I put the client's name and IP address into the server's file /etc/hosts,
the login process is OK(this process time is half of the slow login process)

If someone knows the correct answer, please E-mail to me,
my email address: [email-masked]

---

From: Gregory A Lundberg <[email-masked]>
Date: Sat, 29 Aug 1998 23:37:14 -0400 (EDT)

On Sun, 30 Aug 1998, Star Wang wrote:

> when I ftp to the server from a host which didn't have entry in the DNS
> server, the login process is slow
> 
> if I put the client's name and IP address into the server's file
> /etc/hosts, the login process is OK
> 
> If someone knows the correct answer, please E-mail to me

Knee-jerk reaction: get a faster link.  This could be TCPwrappers (tcpd,
if you use it) preprocessing the connection to see if it's alright.  Or it
could be the ftp server checking the DNS for the connection.  In either
case, there's little to be done if the local DNS doesn't know the name and
the resolution takes a while.

----

Gregory A Lundberg		Senior Partner, VRnet Company
1441 Elmdale Drive              [email-masked]
Kettering, OH 45409-1615 USA    1-800-809-2195

---

From: Star Wang <[email-masked]>
Date: Sun, 30 Aug 1998 12:06:16 +0800

> the resolution takes a while.

I check my system, it doesn't has process such as "tcpd", and the
resolve process from the ftp server to DNS server is quite fast.

Another status is when I ftp to the ftp server from a host who has IN
entry in the DNS server, the login process is OK.

And I don't understand why  the ftp server looks for the client in the
DNS server.

---

From: Gregory A Lundberg <[email-masked]>
Date: Sun, 30 Aug 1998 11:23:13 -0400 (EDT)

> resolve process from the ftp server to DNS server is quite fast.

No problem there.  If you don't know what the tcpwrapper daemon is, and
want to learn more, check out Wieste Venema's security tools page at: 

  ftp://ftp.win.tue.nl/pub/security/index.html

> entry in the DNS server, the login process is OK.

If you mean that the client host must have an entry (probably an A or PTR
record, IN just means it's an Internet Name) on your _local_ DNS servers,
I'd take a look at the setup for your resolver (/etc/resolv.conf, man 5
resolver) to see if there's something bunged up there.  If everything's
OK, remember that the speed of a DNS lookup is controlled by several
things:  the speed of your DNS (sounds OK), the end-to-end speed of the
far DNS which holds the resource records, and the end-to-end speed of the
intermediate DNS which may be required such as root-servers.net and any
mid-level zones.

> And I don't understand why  the ftp server looks for the client in the

For security.  Most daemons these days check the name/number paring and
can limit or refuse services if there's a mis-match (which could indicate
spoofing).

----