From: Chip Davis <cdavis@codeweavers.com>
Subject: [PATCH] iphlpapi: Use res_getservers() if available to get the DNS server list.
Message-Id: <20191212231828.70104-1-cdavis@codeweavers.com>
Date: Thu, 12 Dec 2019 17:18:28 -0600

Signed-off-by: Chip Davis <cdavis@codeweavers.com>
---
 configure.ac                  | 15 +++++++++++++
 dlls/iphlpapi/iphlpapi_main.c | 42 +++++++++++++++++++++++++++++++++++
 2 files changed, 57 insertions(+)

diff --git a/configure.ac b/configure.ac
index d53321a8f7f..5b9a787e18a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1544,6 +1544,21 @@ then
         AC_DEFINE(HAVE_RESOLV, 1)
         AC_SUBST(RESOLV_LIBS,$ac_cv_have_resolv) ;;
     esac
+
+    if test "x$ac_cv_have_resolv" != "xnot found"
+    then
+        AC_CACHE_CHECK([for res_getservers],wine_cv_have_res_getservers,
+                       [ac_save_LIBS="$LIBS"
+                        test "x$ac_cv_have_resolv" = "xnone required" || \
+                             LIBS="$ac_cv_have_resolv $LIBS"
+                        AC_LINK_IFELSE([AC_LANG_PROGRAM(
+        [[#include <resolv.h>]],[[res_getservers(NULL, NULL, 0);]])],[wine_cv_have_res_getservers=yes],[wine_cv_have_res_getservers=no])
+	                 LIBS="$ac_save_LIBS"])
+        if test "$wine_cv_have_res_getservers" = "yes"
+        then
+          AC_DEFINE(HAVE_RES_GETSERVERS, 1, [Define to 1 if you have the `res_getservers' function.])
+        fi
+    fi
 fi
 
 dnl **** Check for LittleCMS ***
diff --git a/dlls/iphlpapi/iphlpapi_main.c b/dlls/iphlpapi/iphlpapi_main.c
index 8c7c9018c48..f90879e0523 100644
--- a/dlls/iphlpapi/iphlpapi_main.c
+++ b/dlls/iphlpapi/iphlpapi_main.c
@@ -1281,6 +1281,47 @@ static void initialise_resolver(void)
     LeaveCriticalSection(&res_init_cs);
 }
 
+#ifdef HAVE_RES_GETSERVERS
+static int get_dns_servers( SOCKADDR_STORAGE *servers, int num, BOOL ip4_only )
+{
+    struct __res_state *state = &_res;
+    int i, found = 0, total;
+    SOCKADDR_STORAGE *addr = servers;
+    union res_sockaddr_union *buf;
+
+    initialise_resolver();
+
+    total = res_getservers( state, NULL, 0 );
+
+    if ((!servers || !num) && !ip4_only) return total;
+
+    buf = HeapAlloc( GetProcessHeap(), 0, total * sizeof(union res_sockaddr_union) );
+    total = res_getservers( state, buf, total );
+
+    for (i = 0; i < total; i++)
+    {
+        if (buf[i].sin6.sin6_family == AF_INET6 && ip4_only) continue;
+        if (buf[i].sin.sin_family != AF_INET && buf[i].sin6.sin6_family != AF_INET6) continue;
+
+        found++;
+        if (!servers || !num) continue;
+
+        if (buf[i].sin6.sin6_family == AF_INET6)
+        {
+            sockaddr_in6_to_WS_storage( addr, &buf[i].sin6 );
+        }
+        else
+        {
+            sockaddr_in_to_WS_storage( addr, &buf[i].sin );
+        }
+        if (++addr >= servers + num) break;
+    }
+
+    HeapFree( GetProcessHeap(), 0, buf );
+    return found;
+}
+#else
+
 static int get_dns_servers( SOCKADDR_STORAGE *servers, int num, BOOL ip4_only )
 {
     int i, ip6_count = 0;
@@ -1316,6 +1357,7 @@ static int get_dns_servers( SOCKADDR_STORAGE *servers, int num, BOOL ip4_only )
     }
     return addr - servers;
 }
+#endif
 #elif defined(HAVE___RES_GET_STATE) && defined(HAVE___RES_GETSERVERS)
 
 static int get_dns_servers( SOCKADDR_STORAGE *servers, int num, BOOL ip4_only )

-- 
2.24.0