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

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

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;