[04/13] resolv: Add the __ns_samebinaryname function

---
 include/arpa/nameser.h         |  6 ++++
 resolv/Makefile                |  5 +++
 resolv/ns_samebinaryname.c     | 55 ++++++++++++++++++++++++++++++
 resolv/tst-ns_samebinaryname.c | 62 ++++++++++++++++++++++++++++++++++
 4 files changed, 128 insertions(+)
 create mode 100644 resolv/ns_samebinaryname.c
 create mode 100644 resolv/tst-ns_samebinaryname.c

On 2022-08-10 05:30, Florian Weimer via Libc-alpha wrote:
> ---
>   include/arpa/nameser.h         |  6 ++++
>   resolv/Makefile                |  5 +++
>   resolv/ns_samebinaryname.c     | 55 ++++++++++++++++++++++++++++++
>   resolv/tst-ns_samebinaryname.c | 62 ++++++++++++++++++++++++++++++++++
>   4 files changed, 128 insertions(+)
>   create mode 100644 resolv/ns_samebinaryname.c
>   create mode 100644 resolv/tst-ns_samebinaryname.c

OK, but like 3/13, it would be nice to document in the commit log why 
this function is needed.

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

> 
> diff --git a/include/arpa/nameser.h b/include/arpa/nameser.h
> index 53f1dbc7c3..bb1dede187 100644
> --- a/include/arpa/nameser.h
> +++ b/include/arpa/nameser.h
> @@ -55,6 +55,12 @@ int __ns_name_ntop (const unsigned char *, char *, size_t) __THROW;
>   int __ns_name_unpack (const unsigned char *, const unsigned char *,
>   		      const unsigned char *, unsigned char *, size_t) __THROW;
>   
> +/* Like ns_samename, but for uncompressed binary names.  Return true
> +   if the two arguments compare are equal as case-insensitive domain
> +   names.  */
> +_Bool __ns_samebinaryname (const unsigned char *, const unsigned char *)
> +  attribute_hidden;
> +
>   #define ns_msg_getflag(handle, flag) \
>     (((handle)._flags & _ns_flagdata[flag].mask) >> _ns_flagdata[flag].shift)
>   
> diff --git a/resolv/Makefile b/resolv/Makefile
> index 0038bb7028..ec61ad07bd 100644
> --- a/resolv/Makefile
> +++ b/resolv/Makefile
> @@ -46,6 +46,7 @@ routines := \
>     ns_name_skip \
>     ns_name_uncompress \
>     ns_name_unpack \
> +  ns_samebinaryname \
>     ns_samename \
>     nsap_addr \
>     nss_dns_functions \
> @@ -106,6 +107,10 @@ tests += \
>   tests-internal += tst-resolv-txnid-collision
>   tests-static += tst-resolv-txnid-collision
>   
> +# Likewise for __ns_samebinaryname.
> +tests-internal += tst-ns_samebinaryname
> +tests-static += tst-ns_samebinaryname
> +
>   # These tests need libdl.
>   ifeq (yes,$(build-shared))
>   tests += \
> diff --git a/resolv/ns_samebinaryname.c b/resolv/ns_samebinaryname.c
> new file mode 100644
> index 0000000000..9a47d8e97a
> --- /dev/null
> +++ b/resolv/ns_samebinaryname.c
> @@ -0,0 +1,55 @@
> +/* Compare two binary domain names for quality.
> +   Copyright (C) 2022 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#include <arpa/nameser.h>
> +#include <stdbool.h>
> +
> +/* Convert ASCII letters to upper case.  */
> +static inline int
> +ascii_toupper (unsigned char ch)
> +{
> +  if (ch >= 'a' && ch <= 'z')
> +    return ch - 'a' + 'A';
> +  else
> +    return ch;
> +}
> +
> +bool
> +__ns_samebinaryname (const unsigned char *a, const unsigned char *b)
> +{
> +  while (*a != 0 && *b != 0)
> +    {
> +      if (*a != *b)
> +        /* Different label length.  */
> +        return false;
> +      int labellen = *a;
> +      ++a;
> +      ++b;
> +      for (int i = 0; i < labellen; ++i)
> +        {
> +          if (*a != *b && ascii_toupper (*a) != ascii_toupper (*b))
> +            /* Different character in label.  */
> +            return false;
> +          ++a;
> +          ++b;
> +        }
> +    }
> +
> +  /* Match if both names are at the root label.  */
> +  return *a == 0 && *b == 0;
> +}
> diff --git a/resolv/tst-ns_samebinaryname.c b/resolv/tst-ns_samebinaryname.c
> new file mode 100644
> index 0000000000..b06ac610b4
> --- /dev/null
> +++ b/resolv/tst-ns_samebinaryname.c
> @@ -0,0 +1,62 @@
> +/* Test the __ns_samebinaryname function.
> +   Copyright (C) 2022 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#include <arpa/nameser.h>
> +#include <array_length.h>
> +#include <stdbool.h>
> +#include <stdio.h>
> +#include <support/check.h>
> +
> +/* First character denotes the comparison group: All names with the
> +   same first character are expected to compare equal.  */
> +static const char *const cases[] =
> +  {
> +    " ",
> +    "1\001a", "1\001A",
> +    "2\002ab", "2\002aB", "2\002Ab", "2\002AB",
> +    "3\001a\002ab", "3\001A\002ab",
> +    "w\003www\007example\003com", "w\003Www\007Example\003Com",
> +    "w\003WWW\007EXAMPLE\003COM",
> +    "W\003WWW", "W\003www",
> +  };
> +
> +static int
> +do_test (void)
> +{
> +  for (int i = 0; i < array_length (cases); ++i)
> +    for (int j = 0; j < array_length (cases); ++j)
> +      {
> +        unsigned char *a = (unsigned char *) &cases[i][1];
> +        unsigned char *b = (unsigned char *) &cases[j][1];
> +        bool actual = __ns_samebinaryname (a, b);
> +        bool expected = cases[i][0] == cases[j][0];
> +        if (actual != expected)
> +          {
> +            char a1[NS_MAXDNAME];
> +            TEST_VERIFY (ns_name_ntop (a, a1, sizeof (a1)) > 0);
> +            char b1[NS_MAXDNAME];
> +            TEST_VERIFY (ns_name_ntop (b, b1, sizeof (b1)) > 0);
> +            printf ("error: \"%s\" \"%s\": expected %s\n",
> +                    a1, b1, expected ? "equal" : "unqueal");
> +            support_record_failure ();
> +          }
> +      }
> +  return 0;
> +}
> +
> +#include <support/test-driver.c>