DCC suddenly fails on several servers

Vernon Schryver vjs@calcite.rhyolite.com
Fri Oct 15 17:11:23 UTC 2004

> From: "Dustin Puryear" 

> We had a small problem with a change that affected system IP addresses and
> DNS (/etc/resolv.conf). We fixed those problems. All servers again have the
> same information that they had previously. DCC then stopped working:

> dcc1.dcc-servers.net,-      RTT+0 ms    anon

That means that the DCC client library was unable to resolve the
name dcc1.dcc-servers.net.

> It was working fine before. Okay, so I looked at /var/dcc and found that
> /var/dcc/map had changed. Does this happen automatically every day? It
> appears so. 

/var/dcc/map contains the current estimates of the average round trip
time or RTT to known DCC servers.  Those estimates are updated after
every DCC operation via mmap().  /var/dcc/map also contains the host
names of DCC servers and up to a dozen IP addresses for those host
names.  The IP addresses are updated every hour or two.

>             Anyway, after some reading of manpages I decided to run 'cdcc
> "load map.txt"':
> # cd /var/dcc && cdcc "load map.txt"
> This worked, as you can see below:

Changing the host names, including rewriting them with their current
values, forces a check of IP addresses.

> Well, it worked for a while at least. The next day /var/dcc/map has changed
> again and DCC again fails.
> I did a strings on /var/dcc/map and found that the working version had more
> information than the non-working version:

Besides the RTT to servers, the /var/dcc/map file includes the "brand
name" that each server claims.  When you local DNS resolver is not
work, the file contains nothing about any DCC servers, including their
IP addresses, RTTs, brand names, and which of the last 32 DCC requests
were answered.

It sounds as if you still have problems with your DNS resolver.

Vernon Schryver    vjs@rhyolite.com

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