[Bug network/14212] New: getaddrinfo() with multiple results from /etc/hosts and AF_INET6 in hints fails when /etc/hosts.conf:multi=off

[Bug network/14212] New: getaddrinfo() with multiple results from /etc/hosts and AF_INET6 in hints fails when /etc/hosts.conf:multi=off

[vapier at gentoo dot org]

http://sourceware.org/bugzilla/show_bug.cgi?id=14212

             Bug #: 14212
           Summary: getaddrinfo() with multiple results from /etc/hosts
                    and AF_INET6 in hints fails when
                    /etc/hosts.conf:multi=off
           Product: glibc
           Version: 2.15
            Status: NEW
          Severity: normal
          Priority: P2
         Component: network
        AssignedTo: unassigned@sourceware.org
        ReportedBy: vapier@gentoo.org
    Classification: Unclassified


Created attachment 6444
  --> http://sourceware.org/bugzilla/attachment.cgi?id=6444
getaddrinfo test

i have these /etc settings:

$ cat /etc/hosts
127.0.0.1   localhost
::1         localhost

$ cat /etc/host.conf 
order hosts, bind
multi off

trying to do getaddrinfo("localhost") when hints is just set to
ai_family=AF_INET6 fails with EAI_NODATA when it should have returned ::1

if i change multi on, then i get back ::1 as expected

if i also use ai_flags=AI_V4MAPPED, then multi off gives me ::ffff:127.0.0.1 --
which is correct, just pointing out that it seems to be matching the first
result and then aborting because the hints didn't line up

see attached code:
$ gcc getaddrinfo.c && ./a.out localhost

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[Bug network/14212] getaddrinfo() with multiple results from /etc/hosts and AF_INET6 in hints fails when /etc/hosts.conf:multi=off

[siddhesh at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=14212

Siddhesh Poyarekar <siddhesh at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |siddhesh at redhat dot com

--- Comment #1 from Siddhesh Poyarekar <siddhesh at redhat dot com> 2013-04-15 13:11:27 UTC ---
I cannot reproduce this with latest master.

$ cat /etc/hosts
127.0.0.1   localhost
::1         localhost

$ cat /etc/host.conf
order hosts, bind
multi off

$ ./a.out localhost
this is an IPv6 result
this is an IPv6 result
this is an IPv6 result

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[Bug network/14212] getaddrinfo() with multiple results from /etc/hosts and AF_INET6 in hints fails when /etc/hosts.conf:multi=off

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=14212

Florian Weimer <fweimer at redhat dot com> changed:

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

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[Bug network/14212] getaddrinfo() with multiple results from /etc/hosts and AF_INET6 in hints fails when /etc/hosts.conf:multi=off

[aoliva at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=14212

Alexandre Oliva <aoliva at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |aoliva at sourceware dot org
         Resolution|---                         |FIXED

--- Comment #2 from Alexandre Oliva <aoliva at sourceware dot org> ---
This was fixed, apparently by accident, with the patch for bug 14505, commit
8479f23aa1.  It disabled the use of the nss gethostbyname4 interface for
non-AF_UNSPEC queries.  Without the patch, we'd use gethostbyname4, get only
the
IPv4 address from the hosts plugin (because multi is off, and gethostbyname4
doesn't know what address family we're looking for), and discard that address
as unsuitable.  With the patch, we use gethostbyname2 to look up IPv6 addresses
only.  It doesn't perform V4MAPPED conversions, for the hconf flag that would
do so is explicitly cleared by getaddrinfo, that would look up IPv4 addresses
separately afterwards in case of no IPv6 matches.

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