resolv: Introduce struct resolv_context [BZ #21668]

struct resolv_context objects provide a temporary resolver context
which does not change during a name lookup operation.  Only when the
outmost context is created, the stub resolver configuration is
verified to be current (at present, only against previous res_init
calls).  Subsequent attempts to obtain the context will reuse the
result of the initial verification operation.

struct resolv_context can also be extended in the future to store
data which needs to be deallocated during thread cancellation.

1 files changed, 8 insertions, 2 deletions

diff --git a/resolv/Versions b/resolv/Versions
index f528ed51e8..b05778d965 100644
--- a/resolv/Versions
+++ b/resolv/Versions
@@ -26,8 +26,12 @@ libc {
 
     __h_errno; __resp;
 
-    __res_maybe_init; __res_iclose;
+    __res_iclose;
     __inet_pton_length;
+    __resolv_context_get;
+    __resolv_context_get_preinit;
+    __resolv_context_get_override;
+    __resolv_context_put;
   }
 }
 
@@ -79,7 +83,9 @@ libresolv {
     # Needed in libnss_dns.
     __ns_name_unpack; __ns_name_ntop;
     __ns_get16; __ns_get32;
-    __libc_res_nquery; __libc_res_nsearch;
+    __res_context_query;
+    __res_context_search;
+    __res_context_hostalias;
   }
 }