Re: getaddrinfo fails with EAI_NODATA for some valid hosts with A records

[Brian Inglis <Brian dot Inglis at SystematicSw dot ab dot ca>]

Andy Hall <fixpertise-consulting <at> comcast.net> writes:
>> On Jan  8 13:44, cyg Simple wrote:
>>> On 1/8/2016 6:14 AM, Corinna Vinschen wrote:
>>>> $ ./gai leapsecond.utcd.org
>>>> ret = 11004
>>>> I have no idea why Windows' getaddrinfo chokes on leapsecond.utcd.org
>>>> at all.
>>> utcd.org doesn't resolve for me.  So getaddrinfo has no info to get.
>> Why then does it work on Linux?
> nslookup works for me:
> Win7 64-bit
> $ nslookup leapsecond.utcd.org
> Non-authoritative answer:
> Server:  UnKnown
> Address:  192.168.1.1
> Name:    leapsecond.utcd.org
> Address:  244.34.36.97
> Win10 64-bit
> C:\Users\Andy>nslookup leapsecond.utcd.org
> Server:  UnKnown
> Address:  192.168.1.1
> Non-authoritative answer:
> Name:    leapsecond.utcd.org
> Address:  244.34.36.97
> However,  tracert and ping  yield this on both W7 & W10:
> $ tracert leapsecond.utcd.org
> Unable to resolve target system name leapsecond.utcd.org.
> $ tracert 244.34.36.97
> Tracing route to 244.34.36.97 over a maximum of 30 hops
>   1  Transmit error: code 1231.
> Trace complete.
> $ ping 244.34.36.97
> Pinging 244.34.36.97 with 32 bytes of data:
> PING: transmit failed. General failure.
> PING: transmit failed. General failure.
> PING: transmit failed. General failure.
> PING: transmit failed. General failure.
> Ping statistics for 244.34.36.97:
>     Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),
> Weird!

Everything works in my STC except Cygwin x86/x64 
"getent ahosts leapsecond.utcd.org" 
on Windows 7 x64 which uses Cygwin getaddrinfo. 
Windows getaddrinfo (ASCII names) in Corinna's STC; Cygwin getaddrinfo, and
Windows GetAddrInfoW (UCS2-LE names) used in the Cygwin implementations,
fail in my code. 
Identical code works from Linux via the same router, and Corinna's MinGW STC
indicates the problem is Windows code, not a BLODA, unless we define Windows
as a likely BLODA. ;^> 

Worked around the problem by falling back to trying gethostbyname when gai
returns 7 EAI_NODATA because GAIW returns 11004 WSANO_DATA. That error is
normally reported when there are no A (and/or AAAA, depending on family and
flags in the call) records for a domain name (most commonly only MX for mail
server, possibly CNAME misspelled or with missing associated A/AAAA, or
other DNS mis-configuration). 

Running whois utcd.org replies normally; whois, traceroute/tracert, and ping
all fail on the name and address as there is host at that address. 
The domain, name, address, SOA, NS, A, and PTR records were set up by P-HK
(phk.freebsd.dk) to provide leapsecond info from IERS Bulletin C encoded in
an address in the IP V4 global class E experimental 240/8 space, see code at
http://phk.freebsd.dk/time/20151122.html. 
An update is due next week for the end of June, when no change is expected,
except the date updated to be valid until after then. 



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