[Bug 792300] [NEW] getaddrinfo() AI_V4MAPPED flag doesn't work with hosts file

[Nick Tait]

Public bug reported:

When using getaddrinfo() with family=AF_INET6 and flags=AI_V4MAPPED to
resolve a host name that is in /etc/hosts with an IPv4 address only, it
returns EAI_NODATA, instead of converting the IPv4 address to an
IPv4-mapped IPv6 address.

I have attached a program which demonstrates the bug. When you run this
program you specify the host name to resolve as a command-line argument.
The lines below show the relevant contents of my hosts file, and the
output of the program when used with "localhost", "127.0.0.1",
"localhost6", and "::1". It is only "localhost" which isn't working
properly. I would have expected this to return the same result as
"127.0.0.1" (in other words "::ffff:127.0.0.1") since my hosts file
defines localhost as being 127.0.0.1. (Please note this behaviour is not
specific to loopback addresses - I have used these in my example because
they should be able to used to reproduce this fault on any machine.)

nick at freddo:~/workspace/v4mappedtest$ grep localhost /etc/hosts
127.0.0.1	localhost.localdomain	localhost
::1	freddo	localhost6.localdomain6	localhost6
::1     ip6-localhost ip6-loopback
nick at freddo:~/workspace/v4mappedtest$ ./a.out localhost
No address associated with hostname
nick at freddo:~/workspace/v4mappedtest$ ./a.out 127.0.0.1
The following addresses were returned:
::ffff:127.0.0.1
nick at freddo:~/workspace/v4mappedtest$ ./a.out localhost6
The following addresses were returned:
::1
nick at freddo:~/workspace/v4mappedtest$ ./a.out ::1
The following addresses were returned:
::1
nick at freddo:~/workspace/v4mappedtest$

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: libc6 2.13-0ubuntu13
ProcVersionSignature: Ubuntu 2.6.38-8.42-generic 2.6.38.2
Uname: Linux 2.6.38-8-generic i686
NonfreeKernelModules: nvidia
Architecture: i386
Date: Fri Jun  3 22:17:20 2011
ProcEnviron:
 LANGUAGE=en_NZ:en
 PATH=(custom, user)
 LANG=en_NZ.UTF-8
 SHELL=/bin/bash
SourcePackage: eglibc
UpgradeStatus: Upgraded to natty on 2011-04-29 (34 days ago)

** Affects: eglibc (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: apport-bug i386 natty

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https://bugs.launchpad.net/bugs/792300

Title:
  getaddrinfo() AI_V4MAPPED flag doesn't work with hosts file

Status in “eglibc” package in Ubuntu:
  New

Bug description:
  When using getaddrinfo() with family=AF_INET6 and flags=AI_V4MAPPED to
  resolve a host name that is in /etc/hosts with an IPv4 address only,
  it returns EAI_NODATA, instead of converting the IPv4 address to an
  IPv4-mapped IPv6 address.

  I have attached a program which demonstrates the bug. When you run
  this program you specify the host name to resolve as a command-line
  argument. The lines below show the relevant contents of my hosts file,
  and the output of the program when used with "localhost", "127.0.0.1",
  "localhost6", and "::1". It is only "localhost" which isn't working
  properly. I would have expected this to return the same result as
  "127.0.0.1" (in other words "::ffff:127.0.0.1") since my hosts file
  defines localhost as being 127.0.0.1. (Please note this behaviour is
  not specific to loopback addresses - I have used these in my example
  because they should be able to used to reproduce this fault on any
  machine.)

  nick at freddo:~/workspace/v4mappedtest$ grep localhost /etc/hosts
  127.0.0.1	localhost.localdomain	localhost
  ::1	freddo	localhost6.localdomain6	localhost6
  ::1     ip6-localhost ip6-loopback
  nick at freddo:~/workspace/v4mappedtest$ ./a.out localhost
  No address associated with hostname
  nick at freddo:~/workspace/v4mappedtest$ ./a.out 127.0.0.1
  The following addresses were returned:
  ::ffff:127.0.0.1
  nick at freddo:~/workspace/v4mappedtest$ ./a.out localhost6
  The following addresses were returned:
  ::1
  nick at freddo:~/workspace/v4mappedtest$ ./a.out ::1
  The following addresses were returned:
  ::1
  nick at freddo:~/workspace/v4mappedtest$

  ProblemType: Bug
  DistroRelease: Ubuntu 11.04
  Package: libc6 2.13-0ubuntu13
  ProcVersionSignature: Ubuntu 2.6.38-8.42-generic 2.6.38.2
  Uname: Linux 2.6.38-8-generic i686
  NonfreeKernelModules: nvidia
  Architecture: i386
  Date: Fri Jun  3 22:17:20 2011
  ProcEnviron:
   LANGUAGE=en_NZ:en
   PATH=(custom, user)
   LANG=en_NZ.UTF-8
   SHELL=/bin/bash
  SourcePackage: eglibc
  UpgradeStatus: Upgraded to natty on 2011-04-29 (34 days ago)