resolv: Move dn_skipname to its own file and into libc

And reformat it to GNU style.

dn_skipname is used outside glibc, so do not deprecate it,
and export it as dn_skipname (not __dn_skipname).  Due to internal
users, provide a __libc_dn_skipname alias, and keep __dn_skipname
as a pure compatibility symbol.

__dn_skipname@GLIBC_2.0 was moved using the script, and
dn_skipname@@GLIBC_2.34 was added using make update-all-abi.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>

7 files changed, 110 insertions, 18 deletions

diff --git a/resolv/Makefile b/resolv/Makefile
index 9365185..e1a608f 100644
--- a/resolv/Makefile
+++ b/resolv/Makefile
@@ -30,6 +30,7 @@ headers	:= resolv.h bits/types/res_state.h \
 routines := \
   dn_comp \
   dn_expand \
+  dn_skipname \
   herror \
   inet_addr \
   inet_ntop \
diff --git a/resolv/Versions b/resolv/Versions
index e36cf45..634c783 100644
--- a/resolv/Versions
+++ b/resolv/Versions
@@ -1,6 +1,7 @@
 libc {
   GLIBC_2.0 {
     __dn_comp;
+    __dn_skipname;
     __h_errno_location;
     __res_randomid;
     _res;
@@ -45,6 +46,7 @@ libc {
 %endif
     dn_comp;
     dn_expand;
+    dn_skipname;
     ns_name_compress;
     ns_name_ntop;
     ns_name_pack;
@@ -61,6 +63,7 @@ libc {
     __inet_aton_exact;
     __inet_pton_length;
     __libc_dn_expand;
+    __libc_dn_skipname;
     __ns_name_compress;
     __ns_name_ntop;
     __ns_name_pack;
@@ -82,7 +85,6 @@ libresolv {
     __b64_ntop;
     __b64_pton;
     __dn_count_labels;
-    __dn_skipname;
     __fp_nquery;
     __fp_query;
     __fp_resstat;
diff --git a/resolv/dn_skipname.c b/resolv/dn_skipname.c
new file mode 100644
index 0000000..b9a587f
--- /dev/null
+++ b/resolv/dn_skipname.c
@@ -0,0 +1,103 @@
+/* Skipping over a compressed DNS domain name in wire format.
+   Copyright (C) 1995-2021 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/>.  */
+
+/*
+ * Copyright (c) 1985, 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.
+ */
+
+/*
+ * Portions Copyright (c) 1996-1999 by Internet Software Consortium.
+ *
+ * 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.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
+ * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
+ * CONSORTIUM 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.
+ */
+
+#include <arpa/nameser.h>
+#include <resolv.h>
+#include <shlib-compat.h>
+
+/* Skips over a compressed domain name. Returns the size or -1.  */
+int
+___dn_skipname (const unsigned char *ptr, const unsigned char *eom)
+{
+  const unsigned char *saveptr = ptr;
+  if (__ns_name_skip (&ptr, eom) < 0)
+    return -1;
+  return ptr - saveptr;
+}
+versioned_symbol (libc, ___dn_skipname, dn_skipname, GLIBC_2_34);
+versioned_symbol (libc, ___dn_skipname, __libc_dn_skipname, GLIBC_PRIVATE);
+libc_hidden_ver (___dn_skipname, __libc_dn_skipname)
+#if OTHER_SHLIB_COMPAT (libresolv, GLIBC_2_0, GLIBC_2_34)
+compat_symbol (libresolv, ___dn_skipname, __dn_skipname, GLIBC_2_0);
+#endif
diff --git a/resolv/nss_dns/dns-canon.c b/resolv/nss_dns/dns-canon.c
index b7340d7..c5718ce 100644
--- a/resolv/nss_dns/dns-canon.c
+++ b/resolv/nss_dns/dns-canon.c
@@ -90,7 +90,7 @@ _nss_dns_getcanonname_r (const char *name, char *buffer, size_t buflen,
 	  unsigned char *endptr = ansp.ptr + r;
 
 	  /* Skip over the query.  This is the name, type, and class.  */
-	  int s = __dn_skipname (ptr, endptr);
+	  int s = __libc_dn_skipname (ptr, endptr);
 	  if (s < 0)
 	    {
 	    unavail:
@@ -108,7 +108,7 @@ _nss_dns_getcanonname_r (const char *name, char *buffer, size_t buflen,
 		 then type, class, TTL, and the length of the RDATA.
 		 We remember the name start.  */
 	      unsigned char *namestart = ptr;
-	      s = __dn_skipname (ptr, endptr);
+	      s = __libc_dn_skipname (ptr, endptr);
 	      if (s < 0)
 		goto unavail;
 
diff --git a/resolv/nss_dns/dns-network.c b/resolv/nss_dns/dns-network.c
index 2be9bfe..801313c 100644
--- a/resolv/nss_dns/dns-network.c
+++ b/resolv/nss_dns/dns-network.c
@@ -322,7 +322,7 @@ getanswer_r (const querybuf *answer, int anslen, struct netent *result,
   /* Skip the question part.  */
   while (question_count-- > 0)
     {
-      int n = __dn_skipname (cp, end_of_message);
+      int n = __libc_dn_skipname (cp, end_of_message);
       if (n < 0 || end_of_message - (cp + n) < QFIXEDSZ)
        {
          __set_h_errno (NO_RECOVERY);
diff --git a/resolv/res_comp.c b/resolv/res_comp.c
index 1930f17..16f7e02 100644
--- a/resolv/res_comp.c
+++ b/resolv/res_comp.c
@@ -92,19 +92,6 @@
 #include <string.h>
 #include <unistd.h>
 
-/*
- * Skip over a compressed domain name. Return the size or -1.
- */
-int
-dn_skipname(const u_char *ptr, const u_char *eom) {
-	const u_char *saveptr = ptr;
-
-	if (ns_name_skip(&ptr, eom) == -1)
-		return (-1);
-	return (ptr - saveptr);
-}
-libresolv_hidden_def (dn_skipname)
-
 /* Return true if the string consists of printable ASCII characters
    only.  */
 static bool
diff --git a/resolv/resolv.h b/resolv/resolv.h
index 0e91801..a10ad99 100644
--- a/resolv/resolv.h
+++ b/resolv/resolv.h
@@ -211,7 +211,6 @@ __END_DECLS
 #define b64_ntop		__b64_ntop
 #define b64_pton		__b64_pton
 #define dn_count_labels		__dn_count_labels
-#define dn_skipname		__dn_skipname
 #define fp_resstat		__fp_resstat
 #define loc_aton		__loc_aton
 #define loc_ntoa		__loc_ntoa