[Bug libc/11156] DNS name resolution issue when the answer does not allow recursion

[Bug libc/11156] DNS name resolution issue when the answer does not allow recursion

[pasky at suse dot cz]

http://sourceware.org/bugzilla/show_bug.cgi?id=11156

Petr Baudis <pasky at suse dot cz> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |RESOLVED
                 CC|                            |pasky at suse dot cz
         Resolution|                            |WORKSFORME

--- Comment #2 from Petr Baudis <pasky at suse dot cz> 2011-02-04 01:30:26 UTC ---
Unfortunately, there has been no update so we need to close this incomplete
bugreport.

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[Bug libc/11156] DNS name resolution issue when the answer does not allow recursion

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=11156

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
              Flags|                            |security-

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[Bug libc/11156] DNS name resolution issue when the answer does not allow recursion

[akshay.moghe+sourceware at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=11156

Akshay <akshay.moghe+sourceware at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |akshay.moghe+sourceware@gma
                   |                            |il.com

--- Comment #3 from Akshay <akshay.moghe+sourceware at gmail dot com> ---
This seems to occur repeatedly with vcc.healthdirect.org.au

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[Bug libc/11156] DNS name resolution issue when the answer does not allow recursion

[akshay.moghe+sourceware at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=11156

--- Comment #4 from Akshay <akshay.moghe+sourceware at gmail dot com> ---
Some additional information:

1. First ping

akshay@spitfire:~$ ping vcc.healthdirect.org.au 
ping: unknown host vcc.healthdirect.org.au


2. Next, dig

akshay@spitfire:~$ dig vcc.healthdirect.org.au @127.0.1.1

; <<>> DiG 9.10.3-P4-Ubuntu <<>> vcc.healthdirect.org.au @127.0.1.1
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 59265
;; flags: qr rd ra; QUERY: 1, ANSWER: 4, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
;; QUESTION SECTION:
;vcc.healthdirect.org.au.       IN      A

;; ANSWER SECTION:
vcc.healthdirect.org.au. 299    IN      CNAME   _aliased.coviu.com.
_aliased.coviu.com.     299     IN      CNAME  
production-ui-alb-975266950.ap-southeast-2.elb.amazonaws.com.
production-ui-alb-975266950.ap-southeast-2.elb.amazonaws.com. 59 IN A
52.65.119.14
production-ui-alb-975266950.ap-southeast-2.elb.amazonaws.com. 59 IN A
13.237.79.63

;; Query time: 62 msec
;; SERVER: 127.0.1.1#53(127.0.1.1)
;; WHEN: Fri Mar 13 00:19:51 PDT 2020
;; MSG SIZE  rcvd: 187

3. Strace `ping`

access("/etc/ld.so.nohwcap", F_OK)      = -1 ENOENT (No such file or directory)
open("/lib/x86_64-linux-gnu/libresolv.so.2", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0P9\0\0\0\0\0\0"..., 832)
= 832
fstat(3, {st_mode=S_IFREG|0644, st_size=101200, ...}) = 0
mmap(NULL, 2206280, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) =
0x7fa57db7d000
mprotect(0x7fa57db94000, 2097152, PROT_NONE) = 0
mmap(0x7fa57dd94000, 8192, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x17000) = 0x7fa57dd94000
mmap(0x7fa57dd96000, 6728, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7fa57dd96000
close(3)                                = 0
mprotect(0x7fa57dd94000, 4096, PROT_READ) = 0
mprotect(0x7fa57df9d000, 4096, PROT_READ) = 0
munmap(0x7fa57eb8d000, 110815)          = 0
stat("/etc/resolv.conf", {st_mode=S_IFREG|0644, st_size=183, ...}) = 0
socket(PF_INET, SOCK_DGRAM|SOCK_NONBLOCK, IPPROTO_IP) = 3
connect(3, {sa_family=AF_INET, sin_port=htons(53),
sin_addr=inet_addr("127.0.1.1")}, 16) = 0
poll([{fd=3, events=POLLOUT}], 1, 0)    = 1 ([{fd=3, revents=POLLOUT}])
sendto(3, "\211P\1\0\0\1\0\0\0\0\0\0\3vcc\fhealthdirect\3or"..., 41,
MSG_NOSIGNAL, NULL, 0) = 41
poll([{fd=3, events=POLLIN}], 1, 5000)  = 1 ([{fd=3, revents=POLLIN}])
ioctl(3, FIONREAD, [176])               = 0
recvfrom(3, "\211P\201\200\0\1\0\4\0\0\0\0\3vcc\fhealthdirect\3or"..., 1024, 0,
{sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("127.0.1.1")}, [16])
= 176
close(3)                                = 0
write(2, "ping: unknown host vcc.healthdir"..., 43ping: unknown host
vcc.healthdirect.org.au
) = 43
exit_group(2)                           = ?


These 3 results align perfectly with the referenced blog post, hence I'm
drawing attention here once again

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[Bug network/11156] DNS name resolution issue when the answer does not allow recursion

[fw at deneb dot enyo.de]

https://sourceware.org/bugzilla/show_bug.cgi?id=11156

Florian Weimer <fw at deneb dot enyo.de> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |fw at deneb dot enyo.de
           Assignee|drepper.fsp at gmail dot com       |unassigned at sourceware dot org
          Component|libc                        |network

--- Comment #5 from Florian Weimer <fw at deneb dot enyo.de> ---
(In reply to Akshay from comment #3)
> This seems to occur repeatedly with vcc.healthdirect.org.au

Please ask for help on the libc-help list
<https://sourceware.org/mailman/listinfo/libc-help> or use your distribution
channels.

Most likely, what you are encountering is a completely different issue. The dig
and strace output show that your stub resolver advertises the RA flag.

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[Bug network/11156] DNS name resolution issue when the answer does not allow recursion

[akshay.moghe+sourceware at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=11156

--- Comment #6 from Akshay <akshay.moghe+sourceware at gmail dot com> ---
This issue seems to be due to underscores in the CNAME.

bash#> nslookup vcc.healthdirect.org.au
Server:         127.0.1.1
Address:        127.0.1.1#53

Non-authoritative answer:
vcc.healthdirect.org.au canonical name = _aliased.coviu.com.
_aliased.coviu.com      canonical name =
production-ui-alb-975266950.ap-southeast-2.elb.amazonaws.com.
Name:   production-ui-alb-975266950.ap-southeast-2.elb.amazonaws.com
Address: 52.65.119.14
Name:   production-ui-alb-975266950.ap-southeast-2.elb.amazonaws.com
Address: 13.237.79.63


Now try resolving the canonical name:

akshay@spitfire:~$ nslookup _aliased.coviu.com
Server:         127.0.1.1
Address:        127.0.1.1#53

Non-authoritative answer:
_aliased.coviu.com      canonical name =
production-ui-alb-975266950.ap-southeast-2.elb.amazonaws.com.
Name:   production-ui-alb-975266950.ap-southeast-2.elb.amazonaws.com
Address: 13.237.79.63
Name:   production-ui-alb-975266950.ap-southeast-2.elb.amazonaws.com
Address: 52.65.119.14


But try it thru libc

akshay@spitfire:~$ getent hosts _aliased.coviu.com
akshay@spitfire:~$ 

... returns nothing

So the root cause for the case I reported seems to be that underscores are not
liked by the getaddrinfo implementation?

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[Bug network/11156] DNS name resolution issue when the answer does not allow recursion

[fw at deneb dot enyo.de]

https://sourceware.org/bugzilla/show_bug.cgi?id=11156

--- Comment #7 from Florian Weimer <fw at deneb dot enyo.de> ---
The underscore issue was fixed in glibc 2.27, via bug 22409.

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[Bug libc/11156] DNS name resolution issue when the answer does not allow recursion

[drepper at redhat dot com]

------- Additional Comments From drepper at redhat dot com  2010-04-04 19:16 -------
You have to me much more details.  Show me the protocol capture (wireshark). 
Show me a server which shows this behavior or explain how to set it up.

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