resolv: Move __res_get_nsaddr to its own file and into libc

Eliminate the use of the EXT macro from it because it does not
add clarity.  The function was added to res_send.c in 2015, and
the copyright year reflects that.

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

resolv/Makefile

@@ -46,6 +46,7 @@ routines := \
   res-close \
   res-name-checking \
   res-state \
+  res_get_nsaddr \
   res_hconf \
   res_init \
   res_libc \

resolv/Versions

@@ -81,6 +81,7 @@ libc {
     __ns_name_skip;
     __ns_name_uncompress;
     __ns_name_unpack;
+    __res_get_nsaddr;
     __res_iclose;
     __resolv_context_get;
     __resolv_context_get_override;

resolv/res_get_nsaddr.c

@@ -0,0 +1,39 @@
+/* Name server address at specified index in res_state.
+   Copyright (C) 2015-2021 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/>.  */
+
+#include <assert.h>
+#include <resolv.h>
+#include <resolv-internal.h>
+
+struct sockaddr *
+__res_get_nsaddr (res_state statp, unsigned int n)
+{
+  assert (n < statp->nscount);
+
+  if (statp->nsaddr_list[n].sin_family == 0
+      && statp->_u._ext.nsaddrs[n] != NULL)
+    /* statp->_u._ext.nsaddrs[n] holds an address that is larger than
+       struct sockaddr, and user code did not update
+       statp->nsaddr_list[n].  */
+    return (struct sockaddr *) statp->_u._ext.nsaddrs[n];
+  else
+    /* User code updated statp->nsaddr_list[n], or statp->nsaddr_list[n]
+       has the same content as statp->_u._ext.nsaddrs[n].  */
+    return (struct sockaddr *) (void *) &statp->nsaddr_list[n];
+}
+libc_hidden_def (__res_get_nsaddr)

resolv/res_send.c

@@ -180,7 +180,6 @@ evNowTime(struct timespec *res) {
 
 /* Forward. */
 
-static struct sockaddr *get_nsaddr (res_state, unsigned int);
 static int		send_vc(res_state, const u_char *, int,
 				const u_char *, int,
 				u_char **, int *, int *, int, u_char **,
@@ -215,7 +214,7 @@ res_ourserver_p(const res_state statp, const struct sockaddr_in6 *inp)
 
 	    for (ns = 0;  ns < statp->nscount;  ns++) {
 		const struct sockaddr_in *srv =
-		    (struct sockaddr_in *) get_nsaddr (statp, ns);
+		    (struct sockaddr_in *) __res_get_nsaddr (statp, ns);
 
 		if ((srv->sin_family == AF_INET) &&
 		    (srv->sin_port == port) &&
@@ -226,7 +225,7 @@ res_ourserver_p(const res_state statp, const struct sockaddr_in6 *inp)
 	} else if (inp->sin6_family == AF_INET6) {
 	    for (ns = 0;  ns < statp->nscount;  ns++) {
 		const struct sockaddr_in6 *srv
-		  = (struct sockaddr_in6 *) get_nsaddr (statp, ns);
+		  = (struct sockaddr_in6 *) __res_get_nsaddr (statp, ns);
 		if ((srv->sin6_family == AF_INET6) &&
 		    (srv->sin6_port == inp->sin6_port) &&
 		    !(memcmp(&srv->sin6_addr, &in6addr_any,
@@ -608,22 +607,6 @@ res_send (const unsigned char *buf, int buflen, unsigned char *ans, int anssiz)
 
 /* Private */
 
-static struct sockaddr *
-get_nsaddr (res_state statp, unsigned int n)
-{
-  assert (n < statp->nscount);
-
-  if (statp->nsaddr_list[n].sin_family == 0 && EXT(statp).nsaddrs[n] != NULL)
-    /* EXT(statp).nsaddrs[n] holds an address that is larger than
-       struct sockaddr, and user code did not update
-       statp->nsaddr_list[n].  */
-    return (struct sockaddr *) EXT(statp).nsaddrs[n];
-  else
-    /* User code updated statp->nsaddr_list[n], or statp->nsaddr_list[n]
-       has the same content as EXT(statp).nsaddrs[n].  */
-    return (struct sockaddr *) (void *) &statp->nsaddr_list[n];
-}
-
 /* Close the resolver structure, assign zero to *RESPLEN2 if RESPLEN2
    is not NULL, and return zero.  */
 static int
@@ -717,7 +700,7 @@ send_vc(res_state statp,
 	const HEADER *hp = (HEADER *) buf;
 	const HEADER *hp2 = (HEADER *) buf2;
 	HEADER *anhp = (HEADER *) *ansp;
-	struct sockaddr *nsap = get_nsaddr (statp, ns);
+	struct sockaddr *nsap = __res_get_nsaddr (statp, ns);
 	int truncating, connreset, n;
 	/* On some architectures compiler might emit a warning indicating
 	   'resplen' may be used uninitialized.  However if buf2 == NULL
@@ -948,7 +931,7 @@ static int
 reopen (res_state statp, int *terrno, int ns)
 {
 	if (EXT(statp).nssocks[ns] == -1) {
-		struct sockaddr *nsap = get_nsaddr (statp, ns);
+		struct sockaddr *nsap = __res_get_nsaddr (statp, ns);
 		socklen_t slen;
 
 		/* only try IPv6 if IPv6 NS and if not failed before */

resolv/resolv-internal.h

@@ -103,4 +103,10 @@ void __res_thread_freeres (void) attribute_hidden;
    success, -1 on failure.  */
 int __res_enable_icmp (int family, int fd) attribute_hidden;
 
+
+/* Returns the name server address for the indicated index.  */
+struct sockaddr *__res_get_nsaddr (res_state statp, unsigned int n);
+libc_hidden_proto (__res_get_nsaddr)
+
+
 #endif  /* _RESOLV_INTERNAL_H */