On 7/30/18 3:40 AM, Alexey Brodkin wrote:
> Some proxy DNS servers might not resolve IPv6 names to addresses.
> Instead they reply with NOERROR while passing no real data.
> That combination of NOERROR and EAI_NODATA happen because the DNS
> server has a recored for requested name (example.net in our case)
> but that record is not of AAAA type which was requested.
>
> That's what Wireshark sees in that case:
> ---------------------------------->8-----------------------------
> Domain Name System (response)
> Transaction ID: 0x6e2e
> Flags: 0x8180 Standard query response, No error
> 1... .... .... .... = Response: Message is a response
> .000 0... .... .... = Opcode: Standard query (0)
> .... .0.. .... .... = Authoritative: Server is not an authority for domain
> .... ..0. .... .... = Truncated: Message is not truncated
> .... ...1 .... .... = Recursion desired: Do query recursively
> .... .... 1... .... = Recursion available: Server can do recursive queries
> .... .... .0.. .... = Z: reserved (0)
> .... .... ..0. .... = Answer authenticated: Answer/authority portion was not authenticated by the server
> .... .... ...0 .... = Non-authenticated data: Unacceptable
> .... .... .... 0000 = Reply code: No error (0)
> Questions: 1
> Answer RRs: 0
> Authority RRs: 0
> Additional RRs: 0
> Queries
> example.net: type AAAA, class IN
> Name: example.net
> [Name Length: 11]
> [Label Count: 2]
> Type: AAAA (IPv6 Address) (28)
> Class: IN (0x0001)
> ---------------------------------->8-----------------------------
>
> And that's what we see if Google DNS server (8.8.8.8) is used instead:
> ---------------------------------->8-----------------------------
> Domain Name System (response)
> Transaction ID: 0x3cd4
> Flags: 0x8180 Standard query response, No error
> 1... .... .... .... = Response: Message is a response
> .000 0... .... .... = Opcode: Standard query (0)
> .... .0.. .... .... = Authoritative: Server is not an authority for domain
> .... ..0. .... .... = Truncated: Message is not truncated
> .... ...1 .... .... = Recursion desired: Do query recursively
> .... .... 1... .... = Recursion available: Server can do recursive queries
> .... .... .0.. .... = Z: reserved (0)
> .... .... ..0. .... = Answer authenticated: Answer/authority portion was not authenticated by the server
> .... .... ...0 .... = Non-authenticated data: Unacceptable
> .... .... .... 0000 = Reply code: No error (0)
> Questions: 1
> Answer RRs: 1
> Authority RRs: 0
> Additional RRs: 0
> Queries
> example.net: type AAAA, class IN
> Name: example.net
> [Name Length: 11]
> [Label Count: 2]
> Type: AAAA (IPv6 Address) (28)
> Class: IN (0x0001)
> Answers
> example.net: type AAAA, class IN, addr 2606:2800:220:1:248:1893:25c8:1946
> ---------------------------------->8-----------------------------
> ---
> posix/tst-getaddrinfo4.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/posix/tst-getaddrinfo4.c b/posix/tst-getaddrinfo4.c
> index dc9e423448af..0139dee777a1 100644
> --- a/posix/tst-getaddrinfo4.c
> +++ b/posix/tst-getaddrinfo4.c
> @@ -39,6 +39,7 @@ try (const char *service, int family, int flags)
> case 0:
> case EAI_AGAIN:
> case EAI_NONAME:
> + case EAI_NODATA:
> printf ("SUCCESS getaddrinfo(service=%s, family=%d, flags=%d): %s: %m\n",
> service ?: "NULL", family, flags, gai_strerror (res));
> return 0;
>
Ping !
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