posix/tst-getaddrinfo4: Consider EAI_NODATA as an expected result

Message ID 20180730104036.4016-1-abrodkin@synopsys.com
State New
Headers show
Series
  • posix/tst-getaddrinfo4: Consider EAI_NODATA as an expected result
Related show

Commit Message

Alexey Brodkin July 30, 2018, 10:40 a.m.
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(+)

Comments

Vineet Gupta Dec. 17, 2018, 6:54 p.m. | #1
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 !
Alexey Brodkin March 26, 2019, 8:01 p.m. | #2
Hello,

Any chance for this one to get reviewed?
It allows 1 more test to complete successfully in case of
certain (though seems to be valid) DNS server setups.

-Alexey

> -----Original Message-----
> From: Vineet Gupta <vgupta@synopsys.com>
> Sent: Monday, December 17, 2018 9:54 PM
> To: Alexey Brodkin <Alexey.Brodkin@synopsys.com>; libc-alpha@sourceware.org
> Cc: linux-snps-arc@lists.infradead.org
> Subject: Re: [PATCH] posix/tst-getaddrinfo4: Consider EAI_NODATA as an expected result
> 
> 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 !
Florian Weimer April 18, 2019, 12:07 p.m. | #3
* Alexey Brodkin:

> 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.

I think this invalidates the test to a large degree.  I don't think this
is a valid test environment.  You need to fix it.

Thanks,
Florian
Alexey Brodkin April 18, 2019, 4:58 p.m. | #4
Hi Florian,

> -----Original Message-----
> From: Florian Weimer <fweimer@redhat.com>
> Sent: Thursday, April 18, 2019 3:08 PM
> To: Alexey Brodkin <abrodkin@synopsys.com>
> Cc: libc-alpha@sourceware.org; linux-snps-arc@lists.infradead.org
> Subject: Re: [PATCH] posix/tst-getaddrinfo4: Consider EAI_NODATA as an expected result
> 
> * Alexey Brodkin:
> 
> > 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.
> 
> I think this invalidates the test to a large degree.  I don't think this
> is a valid test environment.  You need to fix it.

I think more interesting would be to figure out if behavior that I see
is valid or not and then decide which test is representative.

From my Googling I didn't find any data confirming that observed
behavior is incorrect, otherwise I would have asked our IT team to fix it.

Do you have a solid understanding that NOERROR && EIA_NODATA is not
valid combination?

-Alexey

Patch

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;