[Bug libc/5790] strange behavior of getnameinfo on multiple PTR records

["jakub at redhat dot com" <sourceware-bugzilla@sourceware.org>]

------- Additional Comments From jakub at redhat dot com  2008-02-25 15:39 -------
The problem seems to be in resolv/nss_dns/dns-host.c.
The initial buffer is too small (1024 bytes), and getanswer_r will do:
      /* The buffer is too small.  */
    too_small:
      *errnop = ERANGE;
      *h_errnop = NETDB_INTERNAL;
      return NSS_STATUS_TRYAGAIN;
Which is the right thing that getnameinfo eventually expects:
                      while (__gethostbyaddr_r ((const char *) &in_addr,
                                                sizeof (struct in_addr),
                                                AF_INET, &th, tmpbuf,
                                                tmpbuflen, &h, &herror))
                        {
                          if (herror == NETDB_INTERNAL && errno == ERANGE)
                            tmpbuf = extend_alloca (tmpbuf, tmpbuflen,
                                                    2 * tmpbuflen);
                          else
                            break;
                        }
But, unlike _nss_dns_gethostbyname*_r, _nss_dns_gethostbyaddr*_r will overwrite
all the values:
  status = getanswer_r (host_buffer.buf, n, qbuf, T_PTR, result, buffer, buflen,
                        errnop, h_errnop, 0 /* XXX */, ttlp, NULL);
  if (host_buffer.buf != orig_host_buffer)
    free (host_buffer.buf);
  if (status != NSS_STATUS_SUCCESS)
    {
      *h_errnop = h_errno;
      *errnop = errno;
      return status;
    }
I guess nuking the *h_errnop = h_errno; *errnop = errno; could fix this.

-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=5790

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