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Re: [bug] nss resolver code doesn't stop at files lookup
- To: Ben Collins <bcollins at debian dot org>
- Subject: Re: [bug] nss resolver code doesn't stop at files lookup
- From: Thorsten Kukuk <kukuk at suse dot de>
- Date: Sat, 11 Nov 2000 07:24:11 +0100
- Cc: libc-alpha at sources dot redhat dot com
- Organization: SuSE GmbH, Nuernberg, Germany
- References: <20001110210106.F229@visi.net>
On Fri, Nov 10, Ben Collins wrote:
> This is pretty easy to reproduce. Basically what happens (and can be seen
> from an strace) is that that with getaddrinfo(), a success on a /etc/hosts
> lookup does not stop the NSS lookup process, and it continues to try and
> find it via DNS.
You forget to say one important thing: glibc tries to get the IPv6 address
> 127.0.0.1 localhost
Add the following:
# special IPv6 addresses
::1 localhost ipv6-localhost ipv6-loopback
> Now, if you do a name lookup for `localhost' under these conditions, I
> would expect that it would not attempt a DNS lookup. This is not the case
> with getaddrinfo(), but it is the case with gethostbyname().
I would expect a DNS lookup, since you have not specified the IPv6 address
SuSE solves this problem for a long time with a second libnss_dns Module.
Our standard libnss_dns Module does not make lookups for IPv6 addresses.
> getaddrinfo() continues to do a DNS lookup, even after it has read and
> parsed /etc/hosts. Now this would not be a major problem, if it did not
> cause the call to getaddrinfo to fail and return non-zero. IOW, any DNS
> failure (other than notfound) for a host in /etc/hosts, will cause a
> failure for the getaddrinfo call completely.
Strange, I never saw this. This sounds like a real bug.
Thorsten Kukuk http://www.suse.de/~kukuk/ email@example.com
SuSE GmbH Schanzaeckerstr. 10 90443 Nuernberg
Linux is like a Vorlon. It is incredibly powerful, gives terse,
cryptic answers and has a lot of things going on in the background.