commit 4d2e67d6e5c910114dbccd17d9b93f06552c0024
Author: Florian Weimer <fweimer@redhat.com>
Date:   Tue Aug 30 10:02:49 2022 +0200

    resolv: Add internal __res_binary_hnok function
    
    During package parsing, only the binary representation is available,
    and it is convenient to check that directly for conformance with host
    name requirements.
    
    Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
    (cherry picked from commit c79327bf00a4be6d60259227acc78ef80ead3622)

diff --git a/include/resolv.h b/include/resolv.h
index 3590b6f496d47710..4dbbac3800b7ef30 100644
--- a/include/resolv.h
+++ b/include/resolv.h
@@ -70,5 +70,8 @@ libc_hidden_proto (__libc_res_nameinquery)
 extern __typeof (__res_queriesmatch) __libc_res_queriesmatch;
 libc_hidden_proto (__libc_res_queriesmatch)
 
+/* Variant of res_hnok which operates on binary (but uncompressed) names.  */
+bool __res_binary_hnok (const unsigned char *dn) attribute_hidden;
+
 # endif /* _RESOLV_H_ && !_ISOMAC */
 #endif
diff --git a/resolv/res-name-checking.c b/resolv/res-name-checking.c
index 2c603494fa3ca992..513ddb5f6b12ccb0 100644
--- a/resolv/res-name-checking.c
+++ b/resolv/res-name-checking.c
@@ -138,6 +138,12 @@ binary_leading_dash (const unsigned char *dn)
   return dn[0] > 0 && dn[1] == '-';
 }
 
+bool
+__res_binary_hnok (const unsigned char *dn)
+{
+  return !binary_leading_dash (dn) && binary_hnok (dn);
+}
+
 /* Return 1 if res_hnok is a valid host name.  Labels must only
    contain [0-9a-zA-Z_-] characters, and the name must not start with
    a '-'.  The latter is to avoid confusion with program options.  */
@@ -145,11 +151,9 @@ int
 ___res_hnok (const char *dn)
 {
   unsigned char buf[NS_MAXCDNAME];
-  if (!printable_string (dn)
-      || __ns_name_pton (dn, buf, sizeof (buf)) < 0
-      || binary_leading_dash (buf))
-    return 0;
-  return binary_hnok (buf);
+  return (printable_string (dn)
+	  && __ns_name_pton (dn, buf, sizeof (buf)) >= 0
+	  && __res_binary_hnok (buf));
 }
 versioned_symbol (libc, ___res_hnok, res_hnok, GLIBC_2_34);
 versioned_symbol (libc, ___res_hnok, __libc_res_hnok, GLIBC_PRIVATE);