Re: [PATCH 09/13] nss_dns: Remove remnants of IPv6 address mapping

[Siddhesh Poyarekar <siddhesh@gotplt.org>]

On 2022-08-10 05:30, Florian Weimer via Libc-alpha wrote:
> res_use_inet6 always returns false since commit 3f8b44be0a658266adff5
> ("resolv: Remove support for RES_USE_INET6 and the inet6 option").
> ---
>   resolv/README             |  3 --
>   resolv/mapv4v6addr.h      | 69 --------------------------------
>   resolv/mapv4v6hostent.h   | 84 ---------------------------------------
>   resolv/nss_dns/dns-host.c | 54 +++++--------------------
>   4 files changed, 9 insertions(+), 201 deletions(-)
>   delete mode 100644 resolv/mapv4v6addr.h
>   delete mode 100644 resolv/mapv4v6hostent.h

LGTM.

Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

> 
> diff --git a/resolv/README b/resolv/README
> index 514e9bb617..2146bc3b27 100644
> --- a/resolv/README
> +++ b/resolv/README
> @@ -146,6 +146,3 @@ res_libc.c is home-brewn, although parts of it are taken from res_data.c.
>   
>   res_hconf.c and res_hconf.h were contributed by David Mosberger, and
>   do not come from BIND.
> -
> -The files gethnamaddr.c, mapv4v6addr.h and mapv4v6hostent.h are
> -leftovers from BIND 4.9.7.
> diff --git a/resolv/mapv4v6addr.h b/resolv/mapv4v6addr.h
> deleted file mode 100644
> index 7f85f7d5e3..0000000000
> --- a/resolv/mapv4v6addr.h
> +++ /dev/null
> @@ -1,69 +0,0 @@
> -/*
> - * ++Copyright++ 1985, 1988, 1993
> - * -
> - * Copyright (c) 1985, 1988, 1993
> - *    The Regents of the University of California.  All rights reserved.
> - *
> - * Redistribution and use in source and binary forms, with or without
> - * modification, are permitted provided that the following conditions
> - * are met:
> - * 1. Redistributions of source code must retain the above copyright
> - *    notice, this list of conditions and the following disclaimer.
> - * 2. Redistributions in binary form must reproduce the above copyright
> - *    notice, this list of conditions and the following disclaimer in the
> - *    documentation and/or other materials provided with the distribution.
> - * 4. Neither the name of the University nor the names of its contributors
> - *    may be used to endorse or promote products derived from this software
> - *    without specific prior written permission.
> - *
> - * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
> - * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
> - * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
> - * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
> - * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
> - * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
> - * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
> - * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
> - * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
> - * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
> - * SUCH DAMAGE.
> - * -
> - * Portions Copyright (c) 1993 by Digital Equipment Corporation.
> - *
> - * Permission to use, copy, modify, and distribute this software for any
> - * purpose with or without fee is hereby granted, provided that the above
> - * copyright notice and this permission notice appear in all copies, and that
> - * the name of Digital Equipment Corporation not be used in advertising or
> - * publicity pertaining to distribution of the document or software without
> - * specific, written prior permission.
> - *
> - * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
> - * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
> - * OF MERCHANTABILITY AND FITNESS.   IN NO EVENT SHALL DIGITAL EQUIPMENT
> - * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
> - * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
> - * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
> - * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
> - * SOFTWARE.
> - * -
> - * --Copyright--
> - */
> -
> -#include <string.h>
> -#include <arpa/nameser.h>
> -
> -static void
> -map_v4v6_address (const char *src, char *dst)
> -{
> -  u_char *p = (u_char *) dst;
> -  int i;
> -
> -  /* Move the IPv4 part to the right position.  */
> -  memcpy (dst + 12, src, INADDRSZ);
> -
> -  /* Mark this ipv6 addr as a mapped ipv4. */
> -  for (i = 0; i < 10; i++)
> -    *p++ = 0x00;
> -  *p++ = 0xff;
> -  *p = 0xff;
> -}
> diff --git a/resolv/mapv4v6hostent.h b/resolv/mapv4v6hostent.h
> deleted file mode 100644
> index c11038adf3..0000000000
> --- a/resolv/mapv4v6hostent.h
> +++ /dev/null
> @@ -1,84 +0,0 @@
> -/*
> - * ++Copyright++ 1985, 1988, 1993
> - * -
> - * Copyright (c) 1985, 1988, 1993
> - *    The Regents of the University of California.  All rights reserved.
> - *
> - * Redistribution and use in source and binary forms, with or without
> - * modification, are permitted provided that the following conditions
> - * are met:
> - * 1. Redistributions of source code must retain the above copyright
> - *    notice, this list of conditions and the following disclaimer.
> - * 2. Redistributions in binary form must reproduce the above copyright
> - *    notice, this list of conditions and the following disclaimer in the
> - *    documentation and/or other materials provided with the distribution.
> - * 4. Neither the name of the University nor the names of its contributors
> - *    may be used to endorse or promote products derived from this software
> - *    without specific prior written permission.
> - *
> - * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
> - * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
> - * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
> - * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
> - * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
> - * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
> - * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
> - * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
> - * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
> - * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
> - * SUCH DAMAGE.
> - * -
> - * Portions Copyright (c) 1993 by Digital Equipment Corporation.
> - *
> - * Permission to use, copy, modify, and distribute this software for any
> - * purpose with or without fee is hereby granted, provided that the above
> - * copyright notice and this permission notice appear in all copies, and that
> - * the name of Digital Equipment Corporation not be used in advertising or
> - * publicity pertaining to distribution of the document or software without
> - * specific, written prior permission.
> - *
> - * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
> - * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
> - * OF MERCHANTABILITY AND FITNESS.   IN NO EVENT SHALL DIGITAL EQUIPMENT
> - * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
> - * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
> - * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
> - * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
> - * SOFTWARE.
> - * -
> - * --Copyright--
> - */
> -
> -#include <arpa/nameser.h>
> -#include <sys/socket.h>
> -
> -typedef union {
> -    int32_t al;
> -    char ac;
> -} align;
> -
> -static int
> -map_v4v6_hostent (struct hostent *hp, char **bpp, int *lenp)
> -{
> -  char **ap;
> -
> -  if (hp->h_addrtype != AF_INET || hp->h_length != INADDRSZ)
> -    return 0;
> -  hp->h_addrtype = AF_INET6;
> -  hp->h_length = IN6ADDRSZ;
> -  for (ap = hp->h_addr_list; *ap; ap++)
> -    {
> -      int i = sizeof (align) - ((u_long) *bpp % sizeof (align));
> -
> -      if (*lenp < (i + IN6ADDRSZ))
> -	/* Out of memory.  */
> -	return 1;
> -      *bpp += i;
> -      *lenp -= i;
> -      map_v4v6_address (*ap, *bpp);
> -      *ap = *bpp;
> -      *bpp += IN6ADDRSZ;
> -      *lenp -= IN6ADDRSZ;
> -    }
> -  return 0;
> -}
> diff --git a/resolv/nss_dns/dns-host.c b/resolv/nss_dns/dns-host.c
> index cd26399b7e..8e38583e15 100644
> --- a/resolv/nss_dns/dns-host.c
> +++ b/resolv/nss_dns/dns-host.c
> @@ -87,10 +87,6 @@
>   #include <resolv/resolv-internal.h>
>   #include <resolv/resolv_context.h>
>   
> -/* Get implementations of some internal functions.  */
> -#include <resolv/mapv4v6addr.h>
> -#include <resolv/mapv4v6hostent.h>
> -
>   #define RESOLVSORT
>   
>   #if PACKETSZ > 65536
> @@ -116,7 +112,7 @@ static enum nss_status getanswer_r (struct resolv_context *ctx,
>   				    const char *qname, int qtype,
>   				    struct hostent *result, char *buffer,
>   				    size_t buflen, int *errnop, int *h_errnop,
> -				    int map, int32_t *ttlp, char **canonp);
> +				    int32_t *ttlp, char **canonp);
>   static enum nss_status getanswer_ptr (unsigned char *packet, size_t packetlen,
>   				      struct alloc_buffer *abuf,
>   				      char **hnamep, int *errnop,
> @@ -197,7 +193,6 @@ gethostbyname3_context (struct resolv_context *ctx,
>     char tmp[NS_MAXDNAME];
>     int size, type, n;
>     const char *cp;
> -  int map = 0;
>     int olderr = errno;
>     enum nss_status status;
>   
> @@ -258,32 +253,12 @@ gethostbyname3_context (struct resolv_context *ctx,
>   	*errnop = EAGAIN;
>         else
>   	__set_errno (olderr);
> -
> -      /* If we are looking for an IPv6 address and mapping is enabled
> -	 by having the RES_USE_INET6 bit in _res.options set, we try
> -	 another lookup.  */
> -      if (af == AF_INET6 && res_use_inet6 ())
> -	n = __res_context_search (ctx, name, C_IN, T_A, host_buffer.buf->buf,
> -				  host_buffer.buf != orig_host_buffer
> -				  ? MAXPACKET : 1024, &host_buffer.ptr,
> -				  NULL, NULL, NULL, NULL);
> -
> -      if (n < 0)
> -	{
> -	  if (host_buffer.buf != orig_host_buffer)
> -	    free (host_buffer.buf);
> -	  return status;
> -	}
> -
> -      map = 1;
> -
> -      result->h_addrtype = AF_INET;
> -      result->h_length = INADDRSZ;
>       }
> +  else
> +    status = getanswer_r
> +      (ctx, host_buffer.buf, n, name, type, result, buffer, buflen,
> +       errnop, h_errnop, ttlp, canonp);
>   
> -  status = getanswer_r
> -    (ctx, host_buffer.buf, n, name, type, result, buffer, buflen,
> -     errnop, h_errnop, map, ttlp, canonp);
>     if (host_buffer.buf != orig_host_buffer)
>       free (host_buffer.buf);
>     return status;
> @@ -329,13 +304,8 @@ _nss_dns_gethostbyname_r (const char *name, struct hostent *result,
>         *h_errnop = NETDB_INTERNAL;
>         return NSS_STATUS_UNAVAIL;
>       }
> -  status = NSS_STATUS_NOTFOUND;
> -  if (res_use_inet6 ())
> -    status = gethostbyname3_context (ctx, name, AF_INET6, result, buffer,
> -				     buflen, errnop, h_errnop, NULL, NULL);
> -  if (status == NSS_STATUS_NOTFOUND)
> -    status = gethostbyname3_context (ctx, name, AF_INET, result, buffer,
> -				     buflen, errnop, h_errnop, NULL, NULL);
> +  status = gethostbyname3_context (ctx, name, AF_INET, result, buffer,
> +				   buflen, errnop, h_errnop, NULL, NULL);
>     __resolv_context_put (ctx);
>     return status;
>   }
> @@ -648,7 +618,7 @@ static enum nss_status
>   getanswer_r (struct resolv_context *ctx,
>   	     const querybuf *answer, int anslen, const char *qname, int qtype,
>   	     struct hostent *result, char *buffer, size_t buflen,
> -	     int *errnop, int *h_errnop, int map, int32_t *ttlp, char **canonp)
> +	     int *errnop, int *h_errnop, int32_t *ttlp, char **canonp)
>   {
>     struct host_data
>     {
> @@ -664,7 +634,6 @@ getanswer_r (struct resolv_context *ctx,
>     char *bp, **ap, **hap;
>     char tbuf[MAXDNAME];
>     u_char packtmp[NS_MAXCDNAME];
> -  int have_to_map = 0;
>     uintptr_t pad = -(uintptr_t) buffer % __alignof__ (struct host_data);
>     buffer += pad;
>     buflen = buflen > pad ? buflen - pad : 0;
> @@ -845,9 +814,7 @@ getanswer_r (struct resolv_context *ctx,
>   	  continue;
>   	}
>   
> -      if (type == T_A && qtype == T_AAAA && map)
> -	have_to_map = 1;
> -      else if (__glibc_unlikely (type != qtype))
> +      if (__glibc_unlikely (type != qtype))
>   	{
>   	  cp += n;
>   	  continue;			/* XXX - had_error++ ? */
> @@ -944,9 +911,6 @@ getanswer_r (struct resolv_context *ctx,
>   	  linebuflen -= n;
>   	}
>   
> -      if (have_to_map)
> -	if (map_v4v6_hostent (result, &bp, &linebuflen))
> -	  goto too_small;
>         *h_errnop = NETDB_SUCCESS;
>         return NSS_STATUS_SUCCESS;
>       }