This is the mail archive of the cygwin mailing list for the Cygwin project.

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

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

On 2016-01-13 10:03, Andy Hall wrote:
-----Original Message-----
From: cygwin
On Behalf Of Brian Inglis
Corinna Vinschen writes:
On Jan  7 15:39, Brian Inglis wrote:
getaddrinfo fails with err 7 EAI_NODATA for some valid hosts
with A records. Err 7 EAI_NODATA is mapped from WSANO_DATA err
11004 in Windows. Can anyone reproduce failure with problem
host name below?

Yes, I can reproduce it, and it's a total surprise.
I have no idea why Windows' getaddrinfo chokes on at all.

Especially when after just one getaddrinfo call, the DNS cache is
populated with:
Record Name . . . . . :
Record Type . . . . . : 1
Time To Live  . . . . : 600
Data Length . . . . . : 4
Section . . . . . . . : Answer
A (Host) Record . . . :
so the DNS server is being contacted and responding normally, but
it would appear Windows GAI is failing to use that info. Has this
been reproduced on W10 so we can report this upstream? Is there any
support without an account for upstream W7 reports?

DNS just translates URLs to IP addresses.  It is no surprise that
works.   However, addresses in the range -
are reserved.   Windows is probably blocking that as a "favor".
Net Range - CIDR Name
Net Type	IANA Special Use Origin AS Organization	Internet Assigned
Numbers Authority (IANA) Registration Date Last Updated	2013-08-30
Comments	Addresses starting with 240 or a higher number have not been
allocated and should not be used, apart from, which
is used for "limited broadcast" on a local network.
This block was reserved by the IETF, the organization that develops
Internet protocols, in the Standard document and in RFC 1112. The
documents can be found at:
RESTful Link See Also
Related organization's POC records. See Also	Related delegations.

See also IANA services and ports reservations which have been ignored
since Windows devs got a connection to the world outside their PC
(cough Citrix!)

Reserved just means it won't be assigned, but as illustrated by my
OP and Linux tests, it has been usable since CIDR/VLSM came in RFCs
1517-1519 in 1993, and routable since RFC 1812 in 1995 supported
Classless Inter Domain Routing and Variable Length Subnet Masking.

The private reserved address ranges are bogon territory for routers;
the most that can be said about 240/8 is possible bogosity: that
space is available for global internet use without any guarantees
what devices, hosts, protocols, and services will interoperate.

IANA considered releasing the 248M addresses for assignment a few
years ago but decided it was not worth it, as it would only delay
exhaustion of IP V4 space for 18 months, and some crufty old gear
and stacks (cough Windows!) may not support it (as we saw and you
said) for some functions.

Regardless of that, the DNS lookup function should operate normally:
implementing mechanism not policy; if some higher layer wants to
apply a policy on use of those addresses, *THAT*'s what we have
filters for.

Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada

Problem reports:
Unsubscribe info:

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]