diff mbox

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

Message ID 20180730104036.4016-1-abrodkin@synopsys.com
State New, archived
Headers

Commit Message

Alexey Brodkin July 30, 2018, 10:40 a.m. UTC 
  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. UTC | #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. UTC | #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. UTC | #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. UTC | #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
Florian Weimer April 24, 2019, 12:50 p.m. UTC | #5 
* Alexey Brodkin:

> 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.

The test was added for this bug:

  getaddrinfo returns EAI_SYSTEM instead of EAI_NONAME when the network is down
  <https://sourceware.org/bugzilla/show_bug.cgi?id=15339>

So I think the return code from getaddrinfo matters here.

We could switch to a namespace with disabled networking; this way, the
test would perhaps be more reliable.

I also think the test is wrong.  EAI_NONAME indicates (negative)
success, something that should not happen if networking is disabled.

Thanks,
Florian
Alexey Brodkin April 24, 2019, 1:27 p.m. UTC | #6 
Hi Florian,

> -----Original Message-----
> From: linux-snps-arc <linux-snps-arc-bounces@lists.infradead.org> On Behalf Of Florian Weimer
> Sent: Wednesday, April 24, 2019 3:50 PM
> To: Alexey Brodkin <abrodkin@synopsys.com>
> Cc: linux-snps-arc@lists.infradead.org; libc-alpha@sourceware.org
> Subject: Re: [PATCH] posix/tst-getaddrinfo4: Consider EAI_NODATA as an expected result
> 
> * Alexey Brodkin:
> 
> > 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.
> 
> The test was added for this bug:
> 
>   getaddrinfo returns EAI_SYSTEM instead of EAI_NONAME when the network is down
>   <https://urldefense.proofpoint.com/v2/url?u=https-3A__sourceware.org_bugzilla_show-5Fbug.cgi-3Fid-
> 3D15339&d=DwICAg&c=DPL6_X_6JkXFx7AXWqB0tg&r=lqdeeSSEes0GFDDl656eViXO7breS55ytWkhpk5R81I&m=sC1flmdXCo0K
> _9eK__8gRyau_7kSpT32orktcQ2LNeQ&s=TlbAE45sBJja6y8F5OAcODgAOWc1Lx9MYQLP0_iOQSQ&e=>
> 
> So I think the return code from getaddrinfo matters here.
> 
> We could switch to a namespace with disabled networking; this way, the
> test would perhaps be more reliable.
> 
> I also think the test is wrong.  EAI_NONAME indicates (negative)
> success, something that should not happen if networking is disabled.

That makes perfect sense, thanks for explanation.
So I guess there's no point in spending any more time on that test now.

-Alexey
diff mbox

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;