MiniDns ignore response without the "recursion available" flag set

Smack Smack Support
,
1

Hi,

We are using smack for our Android app. We noticed that for some French mobile networks operators, we have a DNS resolution error.

However the query DNS succeed to resolve DNS but the response doesn’t contains RA flags.

Query :

DnsMessage(40048 QUERY NO_ERROR query[qr=0] rd)
[Q: xmpp-02.x. IN A]
[X: EDNS: version: 0, flags:; udp: 1024]

Response :

DnsMessage(40048 QUERY NO_ERROR resp[qr=1] rd)
[Q: xmpp-02.x. IN A]
[A: xmpp-02.x. x IN A x.x.x.x]
[X: EDNS: version: 0, flags:; udp: 4096]

Log:

Could not resolve DNS SRV resource records for _xmpp-client._tcp.x. Consider adding those.
The DNS server /x.x.x.x returned a response without the "recursion available" (RA) flag set. This likely indicates a misconfiguration because the server is not suitable for DNS resolution. 
The DNS server /8.8.8.8 returned a response without the "recursion available" (RA) flag set. This likely indicates a misconfiguration because the server is not suitable for DNS resolution.

DNSClient.java line 155:

                responseMessage = query(q, dns);
                if (responseMessage == null) {
                    continue;
                }

                if (!responseMessage.recursionAvailable) {
                    boolean newRaServer = nonRaServers.add(dns);
                    if (newRaServer) {
                        LOGGER.warning("The DNS server "
                                + dns
                                + " returned a response without the \"recursion available\" (RA) flag set. This likely indicates a misconfiguration because the server is not suitable for DNS resolution");
                    }
                    continue;
                }

Why MiniDns ignore response if recursion isn’t available even though response contains the IP ?

Thanks in advance for your help,

Louis

Smack version : 4.3.4

2

It is interesting how french mobile network operators often come up regarding non-standard or detrimental behavior, like extremely short NAT timeouts (2-3 minutes).

While we could add an extra check for this, the response is contradictory: The server says it won’t do recursion for you, but then it does. Eventually MiniDNS will use the hardcoded fall back DNS services, so it shouldn’t be a big issue.

I would still suggest to inform the french mobile network operator about their misbehaving DNS server.

3

Why do you mean with “The server says it won’t do recursion for you, but then it does” - Unless I’m mistaken, the server can resolve the IP without recursion ? If so why exclude it ?

Besides, the hardcoded fall back doesn’t seem to work :

The DNS server /8.8.8.8 returned a response without the "recursion available" (RA) flag set. This likely indicates a misconfiguration because the server is not suitable for DNS resolution
The DNS server /2001:4860:4860::8888 returned a response without the "recursion available" (RA) flag set. This likely indicates a misconfiguration because the server is not suitable for DNS resolution

We can’t connect at all with some french operators :smiley:

4

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