9 messages in net.sourceforge.lists.courier-usersRe: [courier-users] Courier-MTA react...| From | Sent On | Attachments |
|---|---|---|
| Robert Penz | Aug 18, 2009 11:34 am | |
| Sam Varshavchik | Aug 18, 2009 4:29 pm | |
| Robert Penz | Aug 19, 2009 12:58 am | |
| Sam Varshavchik | Aug 19, 2009 4:02 am | |
| Robert Penz | Aug 19, 2009 8:08 am | |
| Aidas Kasparas | Aug 19, 2009 11:05 am | |
| Malcolm Weir | Aug 19, 2009 12:15 pm | |
| Sam Varshavchik | Aug 19, 2009 2:59 pm | |
| Alessandro Vesely | Aug 20, 2009 9:45 pm |
| Subject: | Re: [courier-users] Courier-MTA reacts badly if own DNS server goes down | |
|---|---|---|
| From: | Sam Varshavchik (mrs...@courier-mta.com) | |
| Date: | Aug 19, 2009 2:59:22 pm | |
| List: | net.sourceforge.lists.courier-users | |
Robert Penz writes:
I think you misunderstand me. dns using is ok, but it should use also hosts entries for A and PTR records, specially for its own hostname. To be specific I don't care about anything else accept its own hostname. Why does every Linux system have a /etc/hosts? because of the entry for loopback and its own hostname. If you use "ping" or any other program it checks the hosts file before it does a dns query.
Others have answered this already, I'll just emphasize. Neither ping nor telnet needs to look up MX or TXT records. Courier does. Furthermore, the system resolver functions, gethostbyname and gethostbyaddr, which search /etc/hosts, do not support IPv6. The newer replacements for these functions do, however getaddrinfo and getnameinfo were not widely implemented back when Courier has been originally written.
So, there was no choice but to implement DNS lookups, RFC 1035, directly. And to use a completely different mechanism for this specific case would've resulted in two different implementions of DNS resolution, which has its own problems.
Working DNS is fundamental. There's no way around it. A hosts file is fine for a closed LAN; however on the Internet you'll have to use DNS.
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