commit bb8adbba4f5d9237a144786ba8e504039beff161

Author: Florian Weimer <fweimer@redhat.com>

Date:   Tue Aug 30 10:02:49 2022 +0200

    resolv: Add the __ns_samebinaryname function

    During packet parsing, only the binary name is available.  If the name

    equality check is performed before conversion to text, we can sometimes

    skip the last step.

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

    (cherry picked from commit 394085a34d25a51513019a4dc411acd3527fbd33)

diff --git a/include/arpa/nameser.h b/include/arpa/nameser.h

index 53f1dbc7c3f659e9..bb1dede187cf1500 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 567f4c2dcf5749df..0b4fa30716af3b8a 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 \

@@ -107,6 +108,10 @@ 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 0000000000000000..9a47d8e97a84c759

--- /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 0000000000000000..b06ac610b4cde8be

--- /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>