resolv: Introduce struct resolv_conf with extended resolver state

This change provides additional resolver configuration state which
is not exposed through the _res ABI.  It reuses the existing
initstamp field in the supposedly-private part of _res.  Some effort
is undertaken to avoid memory safety issues introduced by applications
which directly patch the _res object.

With this commit, only the initstamp field is moved into struct
resolv_conf.  Additional members will be added later, eventually
migrating the entire resolver configuration.

1 files changed, 14 insertions, 1 deletions

diff --git a/resolv/res_init.c b/resolv/res_init.c
index 5d8b2c994d..659d3ea81f 100644
--- a/resolv/res_init.c
+++ b/resolv/res_init.c
@@ -102,6 +102,7 @@
 #include <sys/types.h>
 #include <inet/net-internal.h>
 #include <errno.h>
+#include <resolv_conf.h>
 
 static void res_setoptions (res_state, const char *);
 static uint32_t net_mask (struct in_addr);
@@ -137,7 +138,6 @@ res_vinit_1 (res_state statp, bool preinit, FILE *fp, char **buffer)
   bool havesearch = false;
   int nsort = 0;
   char *net;
-  statp->_u._ext.initstamp = __res_initstamp;
 
   if (!preinit)
     {
@@ -457,6 +457,19 @@ __res_vinit (res_state statp, int preinit)
   bool ok = res_vinit_1 (statp, preinit, fp, &buffer);
   free (buffer);
 
+  if (ok)
+    {
+      struct resolv_conf init = { 0 }; /* No data yet.  */
+      struct resolv_conf *conf = __resolv_conf_allocate (&init);
+      if (conf == NULL)
+        ok = false;
+      else
+        {
+          ok = __resolv_conf_attach (statp, conf);
+          __resolv_conf_put (conf);
+        }
+    }
+
   if (!ok)
     {
       /* Deallocate the name server addresses which have been