gypsy wrote:
Simon,
I have read the man page but I still need assistance. Because dnsmasq
cannot reload the cache from a dump, this must be perfect before I stop
and restart dnsmasq, else I will again have Email messages backed up for
hours (a few deferred 4 days last time!) while the cache rebuilds.
I need MX. In dnsmasq.conf there are 4 lines; which do I set, please?
mx-host
(What is the meaning of "mx_name[, hostname][, preference#]"? Do I need
to set mx-host?)
mx-target
(mx-target seems inappropriate, if I read the man page correctly.)
selfmx
(???)
localmx
(???)
Here is the scenario:
eth1 EXTERNAL IP FQDN INTERNAL IP eth0
66.209.101.194 yesican.chsoft.biz 192.168.1.1
66.209.101.195 news.chsoft.biz 192.168.1.205
When "news" emails to "yesican", I need for dnsmasq to return
192.168.1.1 to the MX request. (? and the A request if there will be
one, and to return 1.1.168.192.in-addr.arpa to the PTR request if there
is one of those ?)
WBTH (What Bad Thing Happens):
The present configuration causes this
Aug 24 02:05:05 YesICan dnsmasq[123]: query[MX] yesican.chsoft.biz from
192.168.1.205
Aug 24 02:05:05 YesICan dnsmasq[123]: forwarded yesican.chsoft.biz to
207.178.128.21
--->>>^^^ This should not be forwarded! ^^^<<<---
Aug 24 02:05:05 YesICan dnsmasq[123]: query[A] yesican.chsoft.biz from
192.168.1.205
Aug 24 02:05:05 YesICan dnsmasq[123]: /etc/hosts yesican.chsoft.biz is
66.209.101.194
Aug 24 02:05:05 YesICan dnsmasq[123]: query[PTR]
195.101.209.66.in-addr.arpa from 127.0.0.1
Aug 24 02:05:05 YesICan dnsmasq[123]: cached 66.209.101.195 is
66-209-101-195.skyriver.net
Aug 24 02:05:05 YesICan dnsmasq[123]: query[A]
66-209-101-195.skyriver.net from 127.0.0.1
Aug 24 02:05:05 YesICan dnsmasq[123]: forwarded
66-209-101-195.skyriver.net to 207.178.128.21
Aug 24 02:05:05 YesICan dnsmasq[123]: reply 66-209-101-195.skyriver.net
is <NXDOMAIN>-IPv4
Aug 24 02:05:05 YesICan dnsmasq[123]: query[A]
66-209-101-195.skyriver.net.chsoft.biz from 127.0.0.1
Aug 24 02:05:05 YesICan dnsmasq[123]: forwarded
66-209-101-195.skyriver.net.chsoft.biz to 207.178.128.21
Aug 24 02:05:05 YesICan dnsmasq[123]: reply
66-209-101-195.skyriver.net.chsoft.biz is <NXDOMAIN>-IPv4
More generally, any MX request from an internal machine should return
the internal IP of the specified computer.
dnsmasq version 2.22 running on Slackware Linux version 10.0.
1) Your explanations in this mailing list are clear; please add some
(more) explanatory text to the man page so it too is clear. An example
in the config file would be a huge help as a supplement to the man page.
2) Please supply an external program to reload the cache from a SIGUSR1
dump for those of us who are in serious need of an equivalent to
dnscache's SlurpCache feature. If I had this, I could take the time to
work out the answer to my question for myself. I realize that the load
on my setup exceeds the "light weight" in the description of dnsmasq,
but except for this single lack, dnsmasq is ideal.
First, MX. You seem to believe that the result of an MX lookup is an IP
address; this is wrong. An MX lookup returns a domain name. A mailer
then has to do a A record lookup on that domain name to get to the IP
address it needs to talk to.
Actually an MX lookup returns a set of domain names, each of which has a
preference. A mailer will try each of the result in turn, in reverse
order of preference.
So for example.
scratchy:/usr/src/modules# dig mx thekelleys.org.uk
; <<>> DiG 9.3.1 <<>> mx thekelleys.org.uk
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 8732
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 5, ADDITIONAL: 5
;; QUESTION SECTION:
;thekelleys.org.uk. IN MX
;; ANSWER SECTION:
thekelleys.org.uk. 43200 IN MX 30 eyas.biff.org.uk.
thekelleys.org.uk. 43200 IN MX 5 thekelleys.org.uk.
A mailer would first attempt to deliver mail to
some...@thekelleys.org.uk to the machine called thekelleys.org.uk but it
will need another A record lookup to do that.
scratchy:/usr/src/modules# dig thekelleys.org.uk
; <<>> DiG 9.3.1 <<>> thekelleys.org.uk
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 15618
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 5, ADDITIONAL: 4
;; QUESTION SECTION:
;thekelleys.org.uk. IN A
;; ANSWER SECTION:
thekelleys.org.uk. 60 IN A 81.108.205.124
If that fails, then the mail will go to the backup, eyas.biff.org.uk
(after another DNS A record lookup to get the Ip address of that host.
The fields in mx-host are just these: so to get the MX records above, do
mx-host=thekelleys.org.uk,thekelleys.org.uk,5
mx-host=thekelleys.org.uk,eyas.biff.org.uk,30
> More generally, any MX request from an internal machine should return
> the internal IP of the specified computer.
That's not clear, but assuming you want an MX record which sends mail
addresses to each internal machine to itself, rather than a smarthost,
then just
selfmx
will do. That returns an MX record for each internal machine, pointing
to itself, with priority 1, so it's equivalent to doing
mx-host=hostname,hostname,1
for all hosts in /etc/hosts and named via DNS.
Second, Slurpcache. I'm sorry, but I don't understand how that would
help. Can you tell me?
Cheers,
Simon.
