[Bug network/16077] New: Get canonical name from /etc/hosts for AF_INET

[Bug network/16077] New: Get canonical name from /etc/hosts for AF_INET

[siddhesh at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=16077

            Bug ID: 16077
           Summary: Get canonical name from /etc/hosts for AF_INET
           Product: glibc
           Version: 2.18
            Status: NEW
          Severity: normal
          Priority: P2
         Component: network
          Assignee: siddhesh at redhat dot com
          Reporter: siddhesh at redhat dot com

Currently, getaddrinfo does not return the actual ai_canonname when an AF_INET
lookup is satisfied from /etc/hosts.  Instead, the requested name is simply
copied back.

How Reproducible:

Always

Steps to reproduce:

1. Add the following entry to /etc/hosts

10.10.10.1 foo.test.com foo

2. Build and run the following program:


#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>

int main(int argc, char *argv[])
{
  int rc, i;
  struct addrinfo hints, *res;

  for(i=1; i < argc; i++)
    {
      memset(&hints,0,sizeof(hints));
      memset(&res,0,sizeof(res));

      hints.ai_family = AF_INET;
      hints.ai_socktype = SOCK_STREAM;
      hints.ai_protocol = IPPROTO_TCP;
      hints.ai_flags = AI_CANONNAME;

      rc = getaddrinfo("foo", NULL, &hints, &res);
      if (rc==0 && res && res->ai_canonname)
        printf("res->ai_canonname=%s\n",res->ai_canonname);
      else
        {
          printf("res=%p\n", res);
          if (res)
            printf("res->ai_canonname=%p\n",res->ai_canonname);
        }
    }
}

Actual Result:

res->ai_canonname=foo

Expected Result:

res->ai_canonname=foo.test.com

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[Bug network/16077] Get canonical name from /etc/hosts for AF_INET

[siddhesh at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=16077

--- Comment #2 from Siddhesh Poyarekar <siddhesh at redhat dot com> ---
(In reply to Rich Felker from comment #1)
> How do you define "canonical" for entries from the hosts file? The first
> hostname on the matching line? For DNS, "canonical" is defined clearly by

Yes, because the hosts man page defines a hosts entry as:

  IP_address canonical_hostname [aliases...]

I understand that it's not a standard definition, but I don't think there's any
such standard definition for a hosts file entry anyway.

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[Bug network/16077] Get canonical name from /etc/hosts for AF_INET

[siddhesh at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=16077

Siddhesh Poyarekar <siddhesh at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #3 from Siddhesh Poyarekar <siddhesh at redhat dot com> ---
Fixed in master:

commit 5a4c6d53f50b264d60cf6453576ca2810c7890b7
Author: Siddhesh Poyarekar <siddhesh@redhat.com>
Date:   Thu Nov 28 17:18:12 2013 +0530

    Get canonical name in getaddrinfo from hosts file for AF_INET (fixes 16077)

    AF_INET lookup in hosts file uses _nss_files_gethostbyname2_r, which
    is not capable of returning a canonical name if it has found one.
    This change adds _nss_files_gethostbyname3_r, which wraps around
    _nss_files_gethostbyname2_r and then returns result.h_name as the
    canonical name.

 ChangeLog                   |  12 ++++
 NEWS                        |   4 +-
 nss/Versions                |   1 +
 nss/nss_files/files-hosts.c | 507
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++----------------------------------------------------------------------
 4 files changed, 272 insertions(+), 252 deletions(-)

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[Bug network/16077] Get canonical name from /etc/hosts for AF_INET

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=16077

Florian Weimer <fweimer at redhat dot com> changed:

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

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