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I observe at least three installations of different Linux (Ubuntu 16.04, Antergos latest as per 2017-06-28, Debian 9.0) with the following behaviour:

  • IPv6 is deconfigured (no Address assigned)
  • The DNS server receives simultaneous A and AAAA queries for any resoultion to be performed.

I already messed around with nsswitch.conf (option ipnodes), resolv.conf (non-existing option no-ipv6), gai.conf, without any success.

The C program I took from this website does not perform AAAA queries.

This simple and stupid PHP program does perform both, AAAA and A DNS queries, simultaneously:

<?php
$ch = curl_init($argv[1]);
curl_exec($ch);

Since there may be dozens of clients (also within LXC containers) having this issue by throwing useless queries at the DNS server, I want to ask if there is a way to prevent AAAA DNS queries by these standard system calls (getaddrinfo and the like).

Note that these AAAA queries are performed via IPv4, since the clients and also the DNS server do not have IPv6 configured:

$ ip addr show dev venet0
2: venet0: <BROADCAST,POINTOPOINT,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN 
link/void 
inet 127.0.0.2/32 scope host venet0
inet 192.168.8.40/32 brd 192.168.8.40 scope global venet0:0
  • I fail to see your problem with AAAA records. Even if your DNS server has no IPv6 connectivity it can/could reply to queries with AAAA info. On the other hand, if your DNS server has no IPv6 connectivy, there should not be any AAAA record for itself (the DNS server). So what are you trying to achieve? – Patrick Mevzek Jun 30 '17 at 11:40
  • The server responses quickly and correctly, but in a network with two extremely busy database servers and two extremely busy web servers and dozens other services I am happy about everything I can shave off. – rexkogitans Jun 30 '17 at 13:16

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