resolv: Mirror the entire resolver configuration in struct resolv_conf

This commit adds the remaining unchanging members (which are loaded
from /etc/resolv.conf) to struct resolv_conf.

The extended name server list is currently not used by the stub
resolver.  The switch depends on a cleanup: The _u._ext.nssocks
array stores just a single socket, and needs to be replaced with
a single socket value.

(The compatibility gethostname implementation does not use the
extended addres sort list, either.  Updating the compat code is
not worthwhile.)

6 files changed, 536 insertions, 116 deletions

diff --git a/resolv/nss_dns/dns-host.c b/resolv/nss_dns/dns-host.c
index 9d7ceb1691..7cd54ab504 100644
--- a/resolv/nss_dns/dns-host.c
+++ b/resolv/nss_dns/dns-host.c
@@ -108,7 +108,8 @@ typedef union querybuf
   u_char buf[MAXPACKET];
 } querybuf;
 
-static enum nss_status getanswer_r (const querybuf *answer, int anslen,
+static enum nss_status getanswer_r (struct resolv_context *ctx,
+				    const querybuf *answer, int anslen,
 				    const char *qname, int qtype,
 				    struct hostent *result, char *buffer,
 				    size_t buflen, int *errnop, int *h_errnop,
@@ -264,8 +265,9 @@ gethostbyname3_context (struct resolv_context *ctx,
       result->h_length = INADDRSZ;
     }
 
-  status = getanswer_r (host_buffer.buf, n, name, type, result, buffer, buflen,
-			errnop, h_errnop, map, ttlp, canonp);
+  status = getanswer_r
+    (ctx, host_buffer.buf, n, name, type, result, buffer, buflen,
+     errnop, h_errnop, map, ttlp, canonp);
   if (host_buffer.buf != orig_host_buffer)
     free (host_buffer.buf);
   return status;
@@ -522,8 +524,9 @@ _nss_dns_gethostbyaddr2_r (const void *addr, socklen_t len, int af,
       return errno == ECONNREFUSED ? NSS_STATUS_UNAVAIL : NSS_STATUS_NOTFOUND;
     }
 
-  status = getanswer_r (host_buffer.buf, n, qbuf, T_PTR, result, buffer, buflen,
-			errnop, h_errnop, 0 /* XXX */, ttlp, NULL);
+  status = getanswer_r
+    (ctx, host_buffer.buf, n, qbuf, T_PTR, result, buffer, buflen,
+     errnop, h_errnop, 0 /* XXX */, ttlp, NULL);
   if (host_buffer.buf != orig_host_buffer)
     free (host_buffer.buf);
   if (status != NSS_STATUS_SUCCESS)
@@ -553,25 +556,27 @@ _nss_dns_gethostbyaddr_r (const void *addr, socklen_t len, int af,
 				    errnop, h_errnop, NULL);
 }
 
-static void addrsort (char **ap, int num);
-
 static void
-addrsort (char **ap, int num)
+addrsort (struct resolv_context *ctx, char **ap, int num)
 {
   int i, j;
   char **p;
   short aval[MAX_NR_ADDRS];
   int needsort = 0;
+  size_t nsort = __resolv_context_sort_count (ctx);
 
   p = ap;
   if (num > MAX_NR_ADDRS)
     num = MAX_NR_ADDRS;
   for (i = 0; i < num; i++, p++)
     {
-      for (j = 0 ; (unsigned)j < _res.nsort; j++)
-	if (_res.sort_list[j].addr.s_addr ==
-	    (((struct in_addr *)(*p))->s_addr & _res.sort_list[j].mask))
-	  break;
+      for (j = 0 ; (unsigned)j < nsort; j++)
+	{
+	  struct resolv_sortlist_entry e
+	    = __resolv_context_sort_entry (ctx, j);
+	  if (e.addr.s_addr == (((struct in_addr *)(*p))->s_addr & e.mask))
+	    break;
+	}
       aval[i] = j;
       if (needsort == 0 && i > 0 && j < aval[i-1])
 	needsort = i;
@@ -598,7 +603,8 @@ addrsort (char **ap, int num)
 }
 
 static enum nss_status
-getanswer_r (const querybuf *answer, int anslen, const char *qname, int qtype,
+getanswer_r (struct resolv_context *ctx,
+	     const querybuf *answer, int anslen, const char *qname, int qtype,
 	     struct hostent *result, char *buffer, size_t buflen,
 	     int *errnop, int *h_errnop, int map, int32_t *ttlp, char **canonp)
 {
@@ -961,8 +967,9 @@ getanswer_r (const querybuf *answer, int anslen, const char *qname, int qtype,
        * in its return structures - should give it the "best"
        * address in that case, not some random one
        */
-      if (_res.nsort && haveanswer > 1 && qtype == T_A)
-	addrsort (host_data->h_addr_ptrs, haveanswer);
+      if (haveanswer > 1 && qtype == T_A
+	  && __resolv_context_sort_count (ctx) > 0)
+	addrsort (ctx, host_data->h_addr_ptrs, haveanswer);
 
       if (result->h_name == NULL)
 	{
diff --git a/resolv/res_init.c b/resolv/res_init.c
index 5941d37f32..80a21fb90d 100644
--- a/resolv/res_init.c
+++ b/resolv/res_init.c
@@ -104,7 +104,6 @@
 #include <errno.h>
 #include <resolv_conf.h>
 
-static void res_setoptions (res_state, const char *);
 static uint32_t net_mask (struct in_addr);
 
 unsigned long long int __res_initstamp;
@@ -124,28 +123,70 @@ is_sort_mask (char ch)
   return ch == '/' || ch == '&';
 }
 
+/* Array of name server addresses.  */
+#define DYNARRAY_STRUCT nameserver_list
+#define DYNARRAY_ELEMENT const struct sockaddr *
+#define DYNARRAY_ELEMENT_FREE(e) free ((struct sockaddr *) *(e))
+#define DYNARRAY_INITIAL_SIZE 3
+#define DYNARRAY_PREFIX nameserver_list_
+#include <malloc/dynarray-skeleton.c>
+
 /* Array of strings for the search array.  The backing store is
    managed separately.  */
 #define DYNARRAY_STRUCT search_list
 #define DYNARRAY_ELEMENT const char *
-#define DYNARRAY_INITIAL_SIZE 4
+#define DYNARRAY_INITIAL_SIZE 6
 #define DYNARRAY_PREFIX search_list_
 #include <malloc/dynarray-skeleton.c>
 
+/* Array of name server addresses.  */
+#define DYNARRAY_STRUCT sort_list
+#define DYNARRAY_ELEMENT struct resolv_sortlist_entry
+#define DYNARRAY_INITIAL_SIZE 0
+#define DYNARRAY_PREFIX sort_list_
+#include <malloc/dynarray-skeleton.c>
+
 /* resolv.conf parser state and results.  */
 struct resolv_conf_parser
 {
   char *buffer;            /* Temporary buffer for reading lines.  */
+
+  struct nameserver_list nameserver_list; /* Nameserver addresses.  */
+
   char *search_list_store; /* Backing storage for search list entries.  */
   struct search_list search_list; /* Points into search_list_store.  */
+
+  struct sort_list sort_list;   /* Address preference sorting list.  */
+
+  /* Configuration template.  The non-array elements are filled in
+     directly.  The array elements are updated prior to the call to
+     __resolv_conf_attach.  */
+  struct resolv_conf template;
 };
 
 static void
-resolv_conf_parser_init (struct resolv_conf_parser *parser)
+resolv_conf_parser_init (struct resolv_conf_parser *parser,
+                         const struct __res_state *preinit)
 {
   parser->buffer = NULL;
   parser->search_list_store = NULL;
+  nameserver_list_init (&parser->nameserver_list);
   search_list_init (&parser->search_list);
+  sort_list_init (&parser->sort_list);
+
+  if (preinit != NULL)
+    {
+      parser->template.retrans = preinit->retrans;
+      parser->template.retry = preinit->retry;
+      parser->template.options = preinit->options | RES_INIT;
+    }
+  else
+    {
+      parser->template.retrans = RES_TIMEOUT;
+      parser->template.retry = RES_DFLRETRY;
+      parser->template.options = RES_DEFAULT | RES_INIT;
+    }
+  parser->template.ndots = 1;
 }
 
 static void
@@ -153,7 +194,23 @@ resolv_conf_parser_free (struct resolv_conf_parser *parser)
 {
   free (parser->buffer);
   free (parser->search_list_store);
+  nameserver_list_free (&parser->nameserver_list);
   search_list_free (&parser->search_list);
+  sort_list_free (&parser->sort_list);
+}
+
+/* Allocate a struct sockaddr_in object on the heap, with the
+   specified address and port.  */
+static struct sockaddr *
+allocate_address_v4 (struct in_addr a, uint16_t port)
+{
+  struct sockaddr_in *sa4 = malloc (sizeof (*sa4));
+  if (sa4 == NULL)
+    return NULL;
+  sa4->sin_family = AF_INET;
+  sa4->sin_addr = a;
+  sa4->sin_port = htons (port);
+  return (struct sockaddr *) sa4;
 }
 
 /* Try to obtain the domain name from the host name and store it in
@@ -181,40 +238,17 @@ domain_from_hostname (char **result)
   return true;
 }
 
+static void res_setoptions (struct resolv_conf_parser *, const char *options);
+
 /* Internal helper function for __res_vinit, to aid with resource
    deallocation and error handling.  Return true on success, false on
    failure.  */
 static bool
-res_vinit_1 (res_state statp, bool preinit, FILE *fp,
-             struct resolv_conf_parser *parser)
+res_vinit_1 (FILE *fp, struct resolv_conf_parser *parser)
 {
   char *cp;
   size_t buffer_size = 0;
-  int nserv = 0;    /* Number of nameservers read from file.  */
-  bool have_serv6 = false;
   bool haveenv = false;
-  int nsort = 0;
-  char *net;
-
-  if (!preinit)
-    {
-      statp->retrans = RES_TIMEOUT;
-      statp->retry = RES_DFLRETRY;
-      statp->options = RES_DEFAULT;
-      statp->id = res_randomid ();
-    }
-
-  statp->nscount = 0;
-  statp->defdname[0] = '\0';
-  statp->ndots = 1;
-  statp->pfcode = 0;
-  statp->_vcsock = -1;
-  statp->_flags = 0;
-  statp->__glibc_unused_qhook = NULL;
-  statp->__glibc_unused_rhook = NULL;
-  statp->_u._ext.nscount = 0;
-  for (int n = 0; n < MAXNS; n++)
-    statp->_u._ext.nsaddrs[n] = NULL;
 
   /* Allow user to override the local domain definition.  */
   if ((cp = getenv ("LOCALDOMAIN")) != NULL)
@@ -350,19 +384,19 @@ res_vinit_1 (res_state statp, bool preinit, FILE *fp,
               continue;
             }
           /* Read nameservers to query.  */
-          if (MATCH (parser->buffer, "nameserver") && nserv < MAXNS)
+          if (MATCH (parser->buffer, "nameserver"))
             {
               struct in_addr a;
 
               cp = parser->buffer + sizeof ("nameserver") - 1;
               while (*cp == ' ' || *cp == '\t')
                 cp++;
+              struct sockaddr *sa;
               if ((*cp != '\0') && (*cp != '\n') && __inet_aton (cp, &a))
                 {
-                  statp->nsaddr_list[nserv].sin_addr = a;
-                  statp->nsaddr_list[nserv].sin_family = AF_INET;
-                  statp->nsaddr_list[nserv].sin_port = htons (NAMESERVER_PORT);
-                  nserv++;
+                  sa = allocate_address_v4 (a, NAMESERVER_PORT);
+                  if (sa == NULL)
+                    return false;
                 }
               else
                 {
@@ -392,13 +426,18 @@ res_vinit_1 (res_state statp, bool preinit, FILE *fp,
                            compatibility.  */
                         __inet6_scopeid_pton
                           (&a6, el + 1, &sa6->sin6_scope_id);
-
-                      statp->nsaddr_list[nserv].sin_family = 0;
-                      statp->_u._ext.nsaddrs[nserv] = sa6;
-                      statp->_u._ext.nssocks[nserv] = -1;
-                      have_serv6 = true;
-                      nserv++;
+                      sa = (struct sockaddr *) sa6;
                     }
+                  else
+                    /* IPv6 address parse failure.  */
+                    sa = NULL;
+                }
+              if (sa != NULL)
+                {
+                  const struct sockaddr **p = nameserver_list_emplace
+                    (&parser->nameserver_list);
+                  if (p != NULL)
+                    *p = sa;
                 }
               continue;
             }
@@ -407,21 +446,22 @@ res_vinit_1 (res_state statp, bool preinit, FILE *fp,
               struct in_addr a;
 
               cp = parser->buffer + sizeof ("sortlist") - 1;
-              while (nsort < MAXRESOLVSORT)
+              while (true)
                 {
                   while (*cp == ' ' || *cp == '\t')
                     cp++;
                   if (*cp == '\0' || *cp == '\n' || *cp == ';')
                     break;
-                  net = cp;
+                  char *net = cp;
                   while (*cp && !is_sort_mask (*cp) && *cp != ';'
                          && isascii (*cp) && !isspace (*cp))
                     cp++;
                   char separator = *cp;
                   *cp = 0;
+                  struct resolv_sortlist_entry e;
                   if (__inet_aton (net, &a))
                     {
-                      statp->sort_list[nsort].addr = a;
+                      e.addr = a;
                       if (is_sort_mask (separator))
                         {
                           *cp++ = separator;
@@ -432,15 +472,13 @@ res_vinit_1 (res_state statp, bool preinit, FILE *fp,
                           separator = *cp;
                           *cp = 0;
                           if (__inet_aton (net, &a))
-                            statp->sort_list[nsort].mask = a.s_addr;
+                            e.mask = a.s_addr;
                           else
-                            statp->sort_list[nsort].mask
-                              = net_mask (statp->sort_list[nsort].addr);
+                            e.mask = net_mask (e.addr);
                         }
                       else
-                        statp->sort_list[nsort].mask
-                          = net_mask (statp->sort_list[nsort].addr);
-                      nsort++;
+                        e.mask = net_mask (e.addr);
+                      sort_list_add (&parser->sort_list, e);
                     }
                   *cp = separator;
                 }
@@ -448,23 +486,22 @@ res_vinit_1 (res_state statp, bool preinit, FILE *fp,
             }
           if (MATCH (parser->buffer, "options"))
             {
-              res_setoptions (statp, parser->buffer + sizeof ("options") - 1);
+              res_setoptions (parser, parser->buffer + sizeof ("options") - 1);
               continue;
             }
         }
-      statp->nscount = nserv;
-      if (have_serv6)
-        /* We try IPv6 servers again.  */
-        statp->ipv6_unavail = false;
-      statp->nsort = nsort;
       fclose (fp);
     }
-  if (__glibc_unlikely (statp->nscount == 0))
+  if (__glibc_unlikely (nameserver_list_size (&parser->nameserver_list) == 0))
     {
-      statp->nsaddr.sin_addr = __inet_makeaddr (IN_LOOPBACKNET, 1);
-      statp->nsaddr.sin_family = AF_INET;
-      statp->nsaddr.sin_port = htons (NAMESERVER_PORT);
-      statp->nscount = 1;
+      const struct sockaddr **p
+        = nameserver_list_emplace (&parser->nameserver_list);
+      if (p == NULL)
+        return false;
+      *p = allocate_address_v4 (__inet_makeaddr (IN_LOOPBACKNET, 1),
+                                NAMESERVER_PORT);
+      if (*p == NULL)
+        return false;
     }
 
   if (search_list_size (&parser->search_list) == 0)
@@ -481,15 +518,16 @@ res_vinit_1 (res_state statp, bool preinit, FILE *fp,
     }
 
   if ((cp = getenv ("RES_OPTIONS")) != NULL)
-    res_setoptions (statp, cp);
+    res_setoptions (parser, cp);
 
-  if (search_list_has_failed (&parser->search_list))
+  if (nameserver_list_has_failed (&parser->nameserver_list)
+      || search_list_has_failed (&parser->search_list)
+      || sort_list_has_failed (&parser->sort_list))
     {
       __set_errno (ENOMEM);
       return false;
     }
 
-  statp->options |= RES_INIT;
   return true;
 }
 
@@ -525,17 +563,27 @@ __res_vinit (res_state statp, int preinit)
       }
 
   struct resolv_conf_parser parser;
-  resolv_conf_parser_init (&parser);
-  bool ok = res_vinit_1 (statp, preinit, fp, &parser);
+  if (preinit)
+    {
+      resolv_conf_parser_init (&parser, statp);
+      statp->id = res_randomid ();
+    }
+  else
+    resolv_conf_parser_init (&parser, NULL);
 
+  bool ok = res_vinit_1 (fp, &parser);
   if (ok)
     {
-      struct resolv_conf init =
-        {
-          .search_list = search_list_begin (&parser.search_list),
-          .search_list_size = search_list_size (&parser.search_list),
-        };
-      struct resolv_conf *conf = __resolv_conf_allocate (&init);
+      parser.template.nameserver_list
+        = nameserver_list_begin (&parser.nameserver_list);
+      parser.template.nameserver_list_size
+        = nameserver_list_size (&parser.nameserver_list);
+      parser.template.search_list = search_list_begin (&parser.search_list);
+      parser.template.search_list_size
+        = search_list_size (&parser.search_list);
+      parser.template.sort_list = sort_list_begin (&parser.sort_list);
+      parser.template.sort_list_size = sort_list_size (&parser.sort_list);
+      struct resolv_conf *conf = __resolv_conf_allocate (&parser.template);
       if (conf == NULL)
         ok = false;
       else
@@ -547,18 +595,13 @@ __res_vinit (res_state statp, int preinit)
   resolv_conf_parser_free (&parser);
 
   if (!ok)
-    {
-      /* Deallocate the name server addresses which have been
-         allocated.  */
-      for (int n = 0; n < MAXNS; n++)
-        free (statp->_u._ext.nsaddrs[n]);
-      return -1;
-    }
-  return 0;
+    return -1;
+  else
+    return 0;
 }
 
 static void
-res_setoptions (res_state statp, const char *options)
+res_setoptions (struct resolv_conf_parser *parser, const char *options)
 {
   const char *cp = options;
 
@@ -572,25 +615,25 @@ res_setoptions (res_state statp, const char *options)
         {
           int i = atoi (cp + sizeof ("ndots:") - 1);
           if (i <= RES_MAXNDOTS)
-            statp->ndots = i;
+            parser->template.ndots = i;
           else
-            statp->ndots = RES_MAXNDOTS;
+            parser->template.ndots = RES_MAXNDOTS;
         }
       else if (!strncmp (cp, "timeout:", sizeof ("timeout:") - 1))
         {
           int i = atoi (cp + sizeof ("timeout:") - 1);
           if (i <= RES_MAXRETRANS)
-            statp->retrans = i;
+            parser->template.retrans = i;
           else
-            statp->retrans = RES_MAXRETRANS;
+            parser->template.retrans = RES_MAXRETRANS;
         }
       else if (!strncmp (cp, "attempts:", sizeof ("attempts:") - 1))
         {
           int i = atoi (cp + sizeof ("attempts:") - 1);
           if (i <= RES_MAXRETRY)
-            statp->retry = i;
+            parser->template.retry = i;
           else
-            statp->retry = RES_MAXRETRY;
+            parser->template.retry = RES_MAXRETRY;
         }
       else
         {
@@ -616,9 +659,9 @@ res_setoptions (res_state statp, const char *options)
             if (strncmp (cp, options[i].str, options[i].len) == 0)
               {
                 if (options[i].clear)
-                  statp->options &= options[i].flag;
+                  parser->template.options &= options[i].flag;
                 else
-                  statp->options |= options[i].flag;
+                  parser->template.options |= options[i].flag;
                 break;
               }
         }
diff --git a/resolv/resolv_conf.c b/resolv/resolv_conf.c
index 76d55fc32c..dd66523992 100644
--- a/resolv/resolv_conf.c
+++ b/resolv/resolv_conf.c
@@ -128,11 +128,80 @@ resolv_conf_get_1 (const struct __res_state *resp)
   return conf;
 }
 
+/* Return true if both IPv4 addresses are equal.  */
+static bool
+same_address_v4 (const struct sockaddr_in *left,
+                 const struct sockaddr_in *right)
+{
+  return left->sin_addr.s_addr == right->sin_addr.s_addr
+    && left->sin_port == right->sin_port;
+}
+
+/* Return true if both IPv6 addresses are equal.  This ignores the
+   flow label.  */
+static bool
+same_address_v6 (const struct sockaddr_in6 *left,
+                 const struct sockaddr_in6 *right)
+{
+  return memcmp (&left->sin6_addr, &right->sin6_addr,
+                 sizeof (left->sin6_addr)) == 0
+    && left->sin6_port == right->sin6_port
+    && left->sin6_scope_id == right->sin6_scope_id;
+}
+
+static bool
+same_address (const struct sockaddr *left, const struct sockaddr *right)
+{
+  if (left->sa_family != right->sa_family)
+    return false;
+  switch (left->sa_family)
+    {
+    case AF_INET:
+      return same_address_v4 ((const struct sockaddr_in *) left,
+                              (const struct sockaddr_in *) right);
+    case AF_INET6:
+      return same_address_v6 ((const struct sockaddr_in6 *) left,
+                              (const struct sockaddr_in6 *) right);
+    }
+  return false;
+}
+
 /* Check that *RESP and CONF match.  Used by __resolv_conf_get.  */
 static bool
 resolv_conf_matches (const struct __res_state *resp,
                      const struct resolv_conf *conf)
 {
+  /* NB: Do not compare the options, retrans, retry, ndots.  These can
+     be changed by applicaiton.  */
+
+  /* Check that the name servers in *RESP have not been modified by
+     the application.  */
+  {
+    size_t nserv = conf->nameserver_list_size;
+    if (nserv > MAXNS)
+      nserv = MAXNS;
+    /* _ext.nscount is 0 until initialized by res_send.c.  */
+    if (resp->nscount != nserv
+        && (resp->_u._ext.nscount != 0 && resp->_u._ext.nscount != nserv))
+      return false;
+    for (size_t i = 0; i < nserv; ++i)
+      {
+        if (resp->nsaddr_list[i].sin_family == 0)
+          {
+            if (resp->_u._ext.nsaddrs[i]->sin6_family != AF_INET6)
+              return false;
+            if (!same_address ((struct sockaddr *) resp->_u._ext.nsaddrs[i],
+                               conf->nameserver_list[i]))
+              return false;
+          }
+        else if (resp->nsaddr_list[i].sin_family != AF_INET)
+          return false;
+        else if (!same_address ((struct sockaddr *) &resp->nsaddr_list[i],
+                                conf->nameserver_list[i]))
+          return false;
+      }
+  }
+
   /* Check that the search list in *RESP has not been modified by the
      application.  */
   {
@@ -161,6 +230,18 @@ resolv_conf_matches (const struct __res_state *resp,
           }
       }
   }
+
+  /* Check that the sort list has not been modified.  */
+  {
+    size_t nsort = conf->sort_list_size;
+    if (nsort > MAXRESOLVSORT)
+      nsort = MAXRESOLVSORT;
+    for (size_t i = 0; i < nsort; ++i)
+      if (resp->sort_list[i].addr.s_addr != conf->sort_list[i].addr.s_addr
+          || resp->sort_list[i].mask != conf->sort_list[i].mask)
+        return false;
+  }
+
   return true;
 }
 
@@ -190,7 +271,28 @@ __resolv_conf_put (struct resolv_conf *conf)
 struct resolv_conf *
 __resolv_conf_allocate (const struct resolv_conf *init)
 {
-  /* Space needed by the strings.  */
+  /* Allocate in decreasing order of alignment.  */
+  _Static_assert (__alignof__ (const char *const *)
+                  <= __alignof__ (struct resolv_conf), "alignment");
+  _Static_assert (__alignof__ (struct sockaddr_in6)
+                  <= __alignof__ (const char *const *), "alignment");
+  _Static_assert (__alignof__ (struct sockaddr_in)
+                  ==  __alignof__ (struct sockaddr_in6), "alignment");
+  _Static_assert (__alignof__ (struct resolv_sortlist_entry)
+                  <= __alignof__ (struct sockaddr_in), "alignment");
+
+  /* Space needed by the nameserver addresses.  */
+  size_t address_space = 0;
+  for (size_t i = 0; i < init->nameserver_list_size; ++i)
+    if (init->nameserver_list[i]->sa_family == AF_INET)
+      address_space += sizeof (struct sockaddr_in);
+    else
+      {
+        assert (init->nameserver_list[i]->sa_family == AF_INET6);
+        address_space += sizeof (struct sockaddr_in6);
+      }
+
+  /* Space needed by the search list strings.  */
   size_t string_space = 0;
   for (size_t i = 0; i < init->search_list_size; ++i)
     string_space += strlen (init->search_list[i]) + 1;
@@ -199,7 +301,10 @@ __resolv_conf_allocate (const struct resolv_conf *init)
   void *ptr;
   struct alloc_buffer buffer = alloc_buffer_allocate
     (sizeof (struct resolv_conf)
+     + init->nameserver_list_size * sizeof (init->nameserver_list[0])
+     + address_space
      + init->search_list_size * sizeof (init->search_list[0])
+     + init->sort_list_size * sizeof (init->sort_list[0])
      + string_space,
      &ptr);
   struct resolv_conf *conf
@@ -211,16 +316,57 @@ __resolv_conf_allocate (const struct resolv_conf *init)
 
   /* Initialize the contents.  */
   conf->__refcount = 1;
+  conf->retrans = init->retrans;
+  conf->retry = init->retry;
+  conf->options = init->options;
+  conf->ndots = init->ndots;
   conf->initstamp = __res_initstamp;
 
-  /* Allocate and fill the search list array.  */
+  /* Allocate the arrays with pointers.  These must come first because
+     they have the highets alignment.  */
+  conf->nameserver_list_size = init->nameserver_list_size;
+  const struct sockaddr **nameserver_array = alloc_buffer_alloc_array
+    (&buffer, const struct sockaddr *, init->nameserver_list_size);
+  conf->nameserver_list = nameserver_array;
+
+  conf->search_list_size = init->search_list_size;
+  const char **search_array = alloc_buffer_alloc_array
+    (&buffer, const char *, init->search_list_size);
+  conf->search_list = search_array;
+
+  /* Fill the name server list array.  */
+  for (size_t i = 0; i < init->nameserver_list_size; ++i)
+    if (init->nameserver_list[i]->sa_family == AF_INET)
+      {
+        struct sockaddr_in *sa = alloc_buffer_alloc
+          (&buffer, struct sockaddr_in);
+        *sa = *(struct sockaddr_in *) init->nameserver_list[i];
+        nameserver_array[i] = (struct sockaddr *) sa;
+      }
+    else
+      {
+        struct sockaddr_in6 *sa = alloc_buffer_alloc
+          (&buffer, struct sockaddr_in6);
+        *sa = *(struct sockaddr_in6 *) init->nameserver_list[i];
+        nameserver_array[i] = (struct sockaddr *) sa;
+      }
+
+  /* Allocate and fill the sort list array.  */
+  {
+    conf->sort_list_size = init->sort_list_size;
+    struct resolv_sortlist_entry *array = alloc_buffer_alloc_array
+      (&buffer, struct resolv_sortlist_entry, init->sort_list_size);
+    conf->sort_list = array;
+    for (size_t i = 0; i < init->sort_list_size; ++i)
+      array[i] = init->sort_list[i];
+  }
+
+  /* Fill the search list array.  This must come last because the
+     strings are the least aligned part of the allocation.  */
   {
-    conf->search_list_size = init->search_list_size;
-    const char **array = alloc_buffer_alloc_array
-      (&buffer, const char *, init->search_list_size);
-    conf->search_list = array;
     for (size_t i = 0; i < init->search_list_size; ++i)
-      array[i] = alloc_buffer_copy_string (&buffer, init->search_list[i]);
+      search_array[i] = alloc_buffer_copy_string
+        (&buffer, init->search_list[i]);
   }
 
   assert (!alloc_buffer_has_failed (&buffer));
@@ -231,6 +377,56 @@ __resolv_conf_allocate (const struct resolv_conf *init)
 static __attribute__ ((nonnull (1, 2), warn_unused_result)) bool
 update_from_conf (struct __res_state *resp, const struct resolv_conf *conf)
 {
+  resp->defdname[0] = '\0';
+  resp->pfcode = 0;
+  resp->_vcsock = -1;
+  resp->_flags = 0;
+  resp->ipv6_unavail = false;
+  resp->__glibc_unused_qhook = NULL;
+  resp->__glibc_unused_rhook = NULL;
+
+  resp->retrans = conf->retrans;
+  resp->retry = conf->retry;
+  resp->options = conf->options;
+  resp->ndots = conf->ndots;
+
+  /* Copy the name server addresses.  */
+  {
+    resp->nscount = 0;
+    resp->_u._ext.nscount = 0;
+    size_t nserv = conf->nameserver_list_size;
+    if (nserv > MAXNS)
+      nserv = MAXNS;
+    for (size_t i = 0; i < nserv; i++)
+      {
+        if (conf->nameserver_list[i]->sa_family == AF_INET)
+          {
+            resp->nsaddr_list[i]
+              = *(struct sockaddr_in *)conf->nameserver_list[i];
+            resp->_u._ext.nsaddrs[i] = NULL;
+          }
+        else
+          {
+            assert (conf->nameserver_list[i]->sa_family == AF_INET6);
+            resp->nsaddr_list[i].sin_family = 0;
+            /* Make a defensive copy of the name server address, in
+               case the application overwrites it.  */
+            struct sockaddr_in6 *sa = malloc (sizeof (*sa));
+            if (sa == NULL)
+              {
+                for (size_t j = 0; j < i; ++j)
+                  free (resp->_u._ext.nsaddrs[j]);
+                return false;
+              }
+            *sa = *(struct sockaddr_in6 *)conf->nameserver_list[i];
+            resp->_u._ext.nsaddrs[i] = sa;
+          }
+        resp->_u._ext.nssocks[i] = -1;
+      }
+    resp->nscount = nserv;
+    /* Leave resp->_u._ext.nscount at 0.  res_send.c handles this.  */
+  }
+
   /* Fill in the prefix of the search list.  It is truncated either at
      MAXDNSRCH, or if reps->defdname has insufficient space.  */
   {
@@ -249,6 +445,19 @@ update_from_conf (struct __res_state *resp, const struct resolv_conf *conf)
     resp->dnsrch[i] = NULL;
   }
 
+  /* Copy the sort list.  */
+  {
+    size_t nsort = conf->sort_list_size;
+    if (nsort > MAXRESOLVSORT)
+      nsort = MAXRESOLVSORT;
+    for (size_t i = 0; i < nsort; ++i)
+      {
+        resp->sort_list[i].addr = conf->sort_list[i].addr;
+        resp->sort_list[i].mask = conf->sort_list[i].mask;
+      }
+    resp->nsort = nsort;
+  }
+
   /* The overlapping parts of both configurations should agree after
      initialization.  */
   assert (resolv_conf_matches (resp, conf));
diff --git a/resolv/resolv_conf.h b/resolv/resolv_conf.h
index 80a0b93f94..7ca80cdeba 100644
--- a/resolv/resolv_conf.h
+++ b/resolv/resolv_conf.h
@@ -19,9 +19,17 @@
 #ifndef RESOLV_STATE_H
 #define RESOLV_STATE_H
 
+#include <netinet/in.h>
 #include <stdbool.h>
 #include <stddef.h>
 
+/* This type corresponds to members of the _res.sort_list array.  */
+struct resolv_sortlist_entry
+{
+  struct in_addr addr;
+  uint32_t mask;
+};
+
 /* Extended resolver state associated with res_state objects.  Client
    code can reach this state through a struct resolv_context
    object.  */
@@ -36,9 +44,24 @@ struct resolv_conf
      zero.  For internal use within resolv_conf only.  */
   size_t __refcount;
 
+  /* List of IPv4 and IPv6 name server addresses.  */
+  const struct sockaddr **nameserver_list;
+  size_t nameserver_list_size;
+
   /* The domain names forming the search list.  */
   const char *const *search_list;
   size_t search_list_size;
+
+  /* IPv4 address preference rules.  */
+  const struct resolv_sortlist_entry *sort_list;
+  size_t sort_list_size;
+
+  /* _res.options has type unsigned long, but we can only use 32 bits
+     for portability across all architectures.  */
+  unsigned int options;
+  unsigned int retrans;         /* Timeout.  */
+  unsigned int retry;           /* Number of times to retry.  */
+  unsigned int ndots; /* Dots needed for initial non-search query.  */
 };
 
 /* The functions below are for use by the res_init resolv.conf parser
diff --git a/resolv/resolv_context.h b/resolv/resolv_context.h
index 0f4d47d26d..e2f7ad6645 100644
--- a/resolv/resolv_context.h
+++ b/resolv/resolv_context.h
@@ -112,6 +112,67 @@ __resolv_context_search_list (const struct resolv_context *ctx, size_t index)
   return NULL;
 }
 
+/* Return the number of name servers.  */
+static __attribute__ ((nonnull (1), unused)) size_t
+__resolv_context_nameserver_count (const struct resolv_context *ctx)
+{
+  if (ctx->conf != NULL)
+    return ctx->conf->nameserver_list_size;
+  else
+    return ctx->resp->nscount;
+}
+
+/* Return a pointer to the socket address of the name server INDEX, or
+   NULL if the index is out of bounds.  */
+static __attribute__ ((nonnull (1), unused)) const struct sockaddr *
+__resolv_context_nameserver (const struct resolv_context *ctx, size_t index)
+{
+  if (ctx->conf != NULL)
+    {
+      if (index < ctx->conf->nameserver_list_size)
+        return ctx->conf->nameserver_list[index];
+    }
+  else
+    if (index < ctx->resp->nscount)
+      {
+        if (ctx->resp->nsaddr_list[index].sin_family != 0)
+          return (const struct sockaddr *) &ctx->resp->nsaddr_list[index];
+        else
+          return (const struct sockaddr *) &ctx->resp->_u._ext.nsaddrs[index];
+      }
+  return NULL;
+}
+
+/* Return the number of sort list entries.  */
+static __attribute__ ((nonnull (1), unused)) size_t
+__resolv_context_sort_count (const struct resolv_context *ctx)
+{
+  if (ctx->conf != NULL)
+    return ctx->conf->sort_list_size;
+  else
+    return ctx->resp->nsort;
+}
+
+/* Return the sort list entry at INDEX.  */
+static __attribute__ ((nonnull (1), unused)) struct resolv_sortlist_entry
+__resolv_context_sort_entry (const struct resolv_context *ctx, size_t index)
+{
+  if (ctx->conf != NULL)
+    {
+      if (index < ctx->conf->sort_list_size)
+        return ctx->conf->sort_list[index];
+      /* Fall through.  */
+    }
+  else if (index < ctx->resp->nsort)
+    return (struct resolv_sortlist_entry)
+      {
+        .addr = ctx->resp->sort_list[index].addr,
+        .mask = ctx->resp->sort_list[index].mask,
+      };
+
+  return (struct resolv_sortlist_entry) { .mask = 0, };
+}
+
 /* Called during thread shutdown to free the associated resolver
    context (mostly in response to cancellation, otherwise the
    __resolv_context_get/__resolv_context_put pairing will already have
diff --git a/resolv/tst-resolv-res_init-skeleton.c b/resolv/tst-resolv-res_init-skeleton.c
index cea14569b8..f98e9f4030 100644
--- a/resolv/tst-resolv-res_init-skeleton.c
+++ b/resolv/tst-resolv-res_init-skeleton.c
@@ -242,6 +242,46 @@ print_resp (FILE *fp, res_state resp)
         }
     }
 
+  /* The extended name server list.  */
+  {
+    size_t i = 0;
+    while (true)
+      {
+        const struct sockaddr *addr = __resolv_context_nameserver (ctx, i);
+        if (addr == NULL)
+          break;
+        size_t addrlen;
+        switch (addr->sa_family)
+          {
+          case AF_INET:
+            addrlen = sizeof (struct sockaddr_in);
+            break;
+          case AF_INET6:
+            addrlen = sizeof (struct sockaddr_in6);
+            break;
+          default:
+            FAIL_EXIT1 ("invalid address family %d", addr->sa_family);
+          }
+
+        char host[NI_MAXHOST];
+        char service[NI_MAXSERV];
+        int ret = getnameinfo (addr, addrlen,
+                               host, sizeof (host), service, sizeof (service),
+                               NI_NUMERICHOST | NI_NUMERICSERV);
+
+        if (ret != 0)
+          {
+            if (ret == EAI_SYSTEM)
+              fprintf (fp, "; error: getnameinfo: %m\n");
+            else
+              fprintf (fp, "; error: getnameinfo: %s\n", gai_strerror (ret));
+          }
+        else
+          fprintf (fp, "; nameserver[%zu]: [%s]:%s\n", i, host, service);
+        ++i;
+      }
+  }
+
   TEST_VERIFY (!ferror (fp));
 
   __resolv_context_put (ctx);
@@ -391,12 +431,14 @@ struct test_case test_cases[] =
      .expected = "search example.com\n"
      "; search[0]: example.com\n"
      "nameserver 127.0.0.1\n"
+     "; nameserver[0]: [127.0.0.1]:53\n"
     },
     {.name = "empty file with LOCALDOMAIN",
      .conf = "",
      .expected = "search example.net\n"
      "; search[0]: example.net\n"
-     "nameserver 127.0.0.1\n",
+     "nameserver 127.0.0.1\n"
+     "; nameserver[0]: [127.0.0.1]:53\n",
      .localdomain = "example.net",
     },
     {.name = "empty file with RES_OPTIONS",
@@ -404,7 +446,8 @@ struct test_case test_cases[] =
      .expected = "options attempts:5 edns0\n"
      "search example.com\n"
      "; search[0]: example.com\n"
-     "nameserver 127.0.0.1\n",
+     "nameserver 127.0.0.1\n"
+     "; nameserver[0]: [127.0.0.1]:53\n",
      .res_options = "edns0 attempts:5",
     },
     {.name = "empty file with RES_OPTIONS and LOCALDOMAIN",
@@ -412,7 +455,8 @@ struct test_case test_cases[] =
      .expected = "options attempts:5 edns0\n"
      "search example.org\n"
      "; search[0]: example.org\n"
-     "nameserver 127.0.0.1\n",
+     "nameserver 127.0.0.1\n"
+     "; nameserver[0]: [127.0.0.1]:53\n",
      .localdomain = "example.org",
      .res_options = "edns0 attempts:5",
     },
@@ -424,6 +468,7 @@ struct test_case test_cases[] =
      "; search[0]: corp.example.com\n"
      "; search[1]: example.com\n"
      "nameserver 192.0.2.1\n"
+     "; nameserver[0]: [192.0.2.1]:53\n"
     },
     {.name = "whitespace",
      .conf = "# This test covers comment and whitespace processing "
@@ -440,6 +485,8 @@ struct test_case test_cases[] =
      "; search[1]: example.com\n"
      "nameserver 192.0.2.1\n"
      "nameserver 192.0.2.2\n"
+     "; nameserver[0]: [192.0.2.1]:53\n"
+     "; nameserver[1]: [192.0.2.2]:53\n"
     },
     {.name = "domain",
      .conf = "domain example.net\n"
@@ -447,6 +494,7 @@ struct test_case test_cases[] =
      .expected = "search example.net\n"
      "; search[0]: example.net\n"
      "nameserver 192.0.2.1\n"
+     "; nameserver[0]: [192.0.2.1]:53\n"
     },
     {.name = "domain space",
      .conf = "domain example.net \n"
@@ -454,6 +502,7 @@ struct test_case test_cases[] =
      .expected = "search example.net\n"
      "; search[0]: example.net\n"
      "nameserver 192.0.2.1\n"
+     "; nameserver[0]: [192.0.2.1]:53\n"
     },
     {.name = "domain tab",
      .conf = "domain example.net\t\n"
@@ -461,6 +510,7 @@ struct test_case test_cases[] =
      .expected = "search example.net\n"
      "; search[0]: example.net\n"
      "nameserver 192.0.2.1\n"
+     "; nameserver[0]: [192.0.2.1]:53\n"
     },
     {.name = "domain override",
      .conf = "search example.com example.org\n"
@@ -469,6 +519,7 @@ struct test_case test_cases[] =
      .expected = "search example.net\n"
      "; search[0]: example.net\n"
      "nameserver 192.0.2.1\n"
+     "; nameserver[0]: [192.0.2.1]:53\n"
     },
     {.name = "option values, multiple servers",
      .conf = "options\tinet6\tndots:3 edns0\tattempts:5\ttimeout:19\n"
@@ -485,6 +536,9 @@ struct test_case test_cases[] =
      "nameserver 192.0.2.1\n"
      "nameserver ::1\n"
      "nameserver 192.0.2.2\n"
+     "; nameserver[0]: [192.0.2.1]:53\n"
+     "; nameserver[1]: [::1]:53\n"
+     "; nameserver[2]: [192.0.2.2]:53\n"
     },
     {.name = "out-of-range option vales",
      .conf = "options use-vc timeout:999 attempts:999 ndots:99\n"
@@ -493,6 +547,7 @@ struct test_case test_cases[] =
      "search example.com\n"
      "; search[0]: example.com\n"
      "nameserver 127.0.0.1\n"
+     "; nameserver[0]: [127.0.0.1]:53\n"
     },
     {.name = "repeated directives",
      .conf = "options ndots:3 use-vc\n"
@@ -505,6 +560,7 @@ struct test_case test_cases[] =
      "search example.org\n"
      "; search[0]: example.org\n"
      "nameserver 127.0.0.1\n"
+     "; nameserver[0]: [127.0.0.1]:53\n"
     },
     {.name = "many name servers, sortlist",
      .conf = "options single-request\n"
@@ -528,6 +584,14 @@ struct test_case test_cases[] =
      "nameserver 192.0.2.1\n"
      "nameserver 192.0.2.2\n"
      "nameserver 192.0.2.3\n"
+     "; nameserver[0]: [192.0.2.1]:53\n"
+     "; nameserver[1]: [192.0.2.2]:53\n"
+     "; nameserver[2]: [192.0.2.3]:53\n"
+     "; nameserver[3]: [192.0.2.4]:53\n"
+     "; nameserver[4]: [192.0.2.5]:53\n"
+     "; nameserver[5]: [192.0.2.6]:53\n"
+     "; nameserver[6]: [192.0.2.7]:53\n"
+     "; nameserver[7]: [192.0.2.8]:53\n"
     },
     {.name = "IPv4 and IPv6 nameservers",
      .conf = "options single-request\n"
@@ -554,6 +618,14 @@ struct test_case test_cases[] =
      "nameserver 192.0.2.1\n"
      "nameserver 2001:db8::2\n"
      "nameserver 192.0.2.3\n"
+     "; nameserver[0]: [192.0.2.1]:53\n"
+     "; nameserver[1]: [2001:db8::2]:53\n"
+     "; nameserver[2]: [192.0.2.3]:53\n"
+     "; nameserver[3]: [2001:db8::4]:53\n"
+     "; nameserver[4]: [192.0.2.5]:53\n"
+     "; nameserver[5]: [2001:db8::6]:53\n"
+     "; nameserver[6]: [192.0.2.7]:53\n"
+     "; nameserver[7]: [2001:db8::8]:53\n",
     },
     {.name = "garbage after nameserver",
      .conf = "nameserver 192.0.2.1 garbage\n"
@@ -563,6 +635,8 @@ struct test_case test_cases[] =
      "; search[0]: example.com\n"
      "nameserver 192.0.2.1\n"
      "nameserver 192.0.2.3\n"
+     "; nameserver[0]: [192.0.2.1]:53\n"
+     "; nameserver[1]: [192.0.2.3]:53\n"
     },
     {.name = "RES_OPTIONS is cummulative",
      .conf = "options timeout:7 ndots:2 use-vc\n"
@@ -570,7 +644,8 @@ struct test_case test_cases[] =
      .expected = "options ndots:3 timeout:7 attempts:5 use-vc edns0\n"
      "search example.com\n"
      "; search[0]: example.com\n"
-     "nameserver 192.0.2.1\n",
+     "nameserver 192.0.2.1\n"
+     "; nameserver[0]: [192.0.2.1]:53\n",
      .res_options = "attempts:5 ndots:3 edns0 ",
     },
     {.name = "many search list entries (bug 19569)",
@@ -588,7 +663,8 @@ struct test_case test_cases[] =
      "; search[5]: example.com\n"
      "; search[6]: example.org\n"
      "; search[7]: example.net\n"
-     "nameserver 192.0.2.1\n",
+     "nameserver 192.0.2.1\n"
+     "; nameserver[0]: [192.0.2.1]:53\n"
     },
     {.name = "very long search list entries (bug 21475)",
      .conf = "nameserver 192.0.2.1\n"
@@ -603,7 +679,8 @@ struct test_case test_cases[] =
      "; search[2]: " H63 "." D63 ".example.net\n"
 #undef H63
 #undef D63
-     "nameserver 192.0.2.1\n",
+     "nameserver 192.0.2.1\n"
+     "; nameserver[0]: [192.0.2.1]:53\n"
     },
     { NULL }
   };