DnsQuery无法在某些特定的FQDN上获得有效地址

Question

When I using this code reference here: http://support.microsoft.com/kb/831226

I can complier success, but when i use it doing some dns query, the return address is weird, for example: 176.20.31.0 (this shouldn't be a valid address)

Here is my output:

C:\dnsq\Debug>dnsq.exe -n tw.media.blizzard.com -t A -s 8.8.8.8
The IP address of the host tw.media.blizzard.com is 176.20.31.0

But actually the tw.media.blizzard.com should be: (I query it by nslookup)

# nslookup tw.media.blizzard.com 8.8.8.8
Server:         8.8.8.8
Address:        8.8.8.8#53

Non-authoritative answer:
tw.media.blizzard.com   canonical name = tw.media.blizzard.com.edgesuite.net.
tw.media.blizzard.com.edgesuite.net     canonical name = a1479.g.akamai.net.
Name:   a1479.g.akamai.net
Address: 23.14.93.167
Name:   a1479.g.akamai.net
Address: 23.14.93.157

My question is why dnsquery doesn't work on some FQDN? Any suggestion would be appreciated :)

Answer 1

I found the problem.

For those FQDN which leading to invlid address, the common thing are all of their DNS record type are "DNS_TYPE_CNAME", not DNS_TYPE_A.

So we need to parse the whole PDNS_RECORD to get DNS_TYPE_A information.

---

I'll post my change here:

Original code from MS:

    if(wType == DNS_TYPE_A) {
        //convert the Internet network address into a string
        //in Internet standard dotted format.
        ipaddr.S_un.S_addr = (pDnsRecord->Data.A.IpAddress);
        printf("The IP address of the host %s is %s \n", pOwnerName,inet_ntoa(ipaddr));

        // Free memory allocated for DNS records. 
        DnsRecordListFree(pDnsRecord, freetype);
    }

My change here:

    if(wType == DNS_TYPE_A) {
        //convert the Internet network address into a string
        //in Internet standard dotted format.
        PDNS_RECORD cursor;

        for (cursor = pDnsRecord; cursor != NULL; cursor = cursor->pNext) {
            if (cursor->wType == DNS_TYPE_A) {
                ipaddr.S_un.S_addr = (cursor->Data.A.IpAddress);
                printf("The IP address of the host %s is %s \n", pOwnerName,inet_ntoa(ipaddr));                 
            }
        }

        // Free memory allocated for DNS records. 
        DnsRecordListFree(pDnsRecord, freetype);
    }       

Answer 2

PDNS_RECORD pQueryResults;

DNS_STATUS dResult = DnsQuery_A(
        "www.facebook.com",
        DNS_TYPE_A,
        DNS_QUERY_WIRE_ONLY, 
        NULL,
        (PDNS_RECORD*)&pQueryResults,
        NULL
    );

char* szActualHost = (char*) pQueryResults->Data.CNAME.pNameHost;

Thanks a lot for sharing this but I would like to add this for further clarification;

• Even if you call DNSQuery_A with DNS_TYPE_A as wType for some FQDN, it may still return you a record for wType as (0x5) DNS_TYPE_CNAME.

• In such cases you can find the actual host name by inspecting the actual CNAME part of the QueryResults and ofcourse call the DNSQuery_A() API for the new hostname again. Check the above Code snipette