0000660: getaddrinfo() queries are redundant and in odd order

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Category

Severity

Reproducibility

Date Submitted

Last Update

0000660

[uClibc] Networking Support

minor

always

01-25-06 16:52

11-01-08 16:26

Reporter

akvadrako

View Status

public

Assigned To

uClibc

Priority

normal

Resolution

open

Status

assigned

Product Version

0.9.28

Summary

0000660: getaddrinfo() queries are redundant and in odd order

Description

I have IPv6 support enabled and three DNS servers listed in /etc/resolv.conf. I'm looking up a hostname that only has an A record. uClibc's getaddrinfo() looks up the records by trying each nameserver in order then trying again two more times. When the family is AF_UNSPEC, it completes this process for AAAA records then A records.

So in my case, to get the A record, I have to wait for 9 queries to fail first. Since they timeout in ten seconds, this is unacceptably long if some of the DNS servers are down.

To make the situation worse, getaddrinfo() doesn't trust query responses with no answers. Instead it treats them as an error, and repeats the query, even to the same host.

RFC1035 recommends retransmissions (but not timeouts) every 2-5 seconds. I suggest three changes to the current lookup method:

  * trust the first response without an error, even if negative
  * ask for both type of records in each query (adds negligable size)
  * retransmit every 5 seconds, not every 10

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Notes
(0001005) vapier 01-25-06 19:04	can you try the patch in Bug 473: http://busybox.net/bugs/file_download.php?file_id=389&type=bug [^]

(0001006) akvadrako 01-25-06 21:10	Patch 389 is not relevant to this issue. This issue does not deal with search domains or invalid encoding of domain names. The problems discussed in this issue apply to queries of all domain names.

(0014804) vda 11-01-08 16:26	Revision 23895 contains a fix to not treat negative responses as errors.

Issue History
Date Modified	Username	Field	Change
01-25-06 16:52	akvadrako	New Issue
01-25-06 16:52	akvadrako	Status	new => assigned
01-25-06 16:52	akvadrako	Assigned To	=> uClibc
01-25-06 19:04	vapier	Note Added: 0001005
01-25-06 21:10	akvadrako	Note Added: 0001006
07-25-06 14:34	dcostako	Issue Monitored: dcostako
11-01-08 16:26	vda	Note Added: 0014804