[PATCH] 7006496: Use modern Windows API to retrieve OS DNS servers

Anuraag Agrawal anuraaga at gmail.com
Thu Jan 9 15:22:45 UTC 2020


Hi all,

Apologies for the spam. I made one more tweak to follow up the previous,
and removed the default value of -1 for lastRefresh. Now that there is no
semantic meaning to -1, I think unspecified default (effectively zero) is
more appropriate and easy to reason about.

Inline patch follows

diff --git
a/src/java.base/windows/classes/sun/net/dns/ResolverConfigurationImpl.java
b/src/java.base/windows/classes/sun/net/dns/ResolverConfigurationImpl.java
index 2250b3158e..aefe44e9b3 100644
---
a/src/java.base/windows/classes/sun/net/dns/ResolverConfigurationImpl.java
+++
b/src/java.base/windows/classes/sun/net/dns/ResolverConfigurationImpl.java
@@ -25,9 +25,9 @@

 package sun.net.dns;

+import java.util.ArrayList;
 import java.util.List;
-import java.util.LinkedList;
-import java.util.StringTokenizer;
+import java.util.concurrent.TimeUnit;

 /*
  * An implementation of sun.net.ResolverConfiguration for Windows.
@@ -42,38 +42,64 @@ public class ResolverConfigurationImpl
     // Resolver options
     private final Options opts;

-    // Addresses have changed
-    private static boolean changed = false;
+    // Addresses have changed. We default to true to make sure we
+    // resolve the first time it is requested.
+    private static boolean changed = true;

     // Time of last refresh.
-    private static long lastRefresh = -1;
+    private static long lastRefresh;

     // Cache timeout (120 seconds) - should be converted into property
     // or configured as preference in the future.
-    private static final int TIMEOUT = 120000;
+    private static final long TIMEOUT_NANOS =
TimeUnit.SECONDS.toNanos(120);

     // DNS suffix list and name servers populated by native method
     private static String os_searchlist;
     private static String os_nameservers;

     // Cached lists
-    private static LinkedList<String> searchlist;
-    private static LinkedList<String> nameservers;
-
-    // Parse string that consists of token delimited by space or commas
-    // and return LinkedHashMap
-    private LinkedList<String> stringToList(String str) {
-        LinkedList<String> ll = new LinkedList<>();
-
-        // comma and space are valid delimiters
-        StringTokenizer st = new StringTokenizer(str, ", ");
-        while (st.hasMoreTokens()) {
-            String s = st.nextToken();
-            if (!ll.contains(s)) {
-                ll.add(s);
+    private static ArrayList<String> searchlist;
+    private static ArrayList<String> nameservers;
+
+    // Parse string that consists of token delimited by comma
+    // and return ArrayList. Refer to ResolverConfigurationImpl.c and
+    // strappend to see how the string is created.
+    private ArrayList<String> stringToList(String str) {
+        // String is delimited by comma.
+        String[] tokens = str.split(",");
+        ArrayList<String> l = new ArrayList<>(tokens.length);
+        for (String s : tokens) {
+            if (!s.isEmpty() && !l.contains(s)) {
+                l.add(s);
             }
         }
-        return ll;
+        l.trimToSize();
+        return l;
+    }
+
+    // Parse string that consists of token delimited by comma
+    // and return ArrayList.  Refer to ResolverConfigurationImpl.c and
+    // strappend to see how the string is created.
+    // In addition to splitting the string, converts IPv6 addresses to
+    // BSD-style.
+    private ArrayList<String> addressesToList(String str) {
+        // String is delimited by comma
+        String[] tokens = str.split(",");
+        ArrayList<String> l = new ArrayList<>(tokens.length);
+
+        for (String s : tokens) {
+            if (!s.isEmpty()) {
+                if (s.indexOf(':') >= 0 && s.charAt(0) != '[') {
+                    // Not BSD style
+                    s = '[' + s + ']';
+                }
+                if (!s.isEmpty() && !l.contains(s)) {
+                    l.add(s);
+                }
+            }
+        }
+        l.trimToSize();
+        return l;
     }

     // Load DNS configuration from OS
@@ -81,28 +107,34 @@ public class ResolverConfigurationImpl
     private void loadConfig() {
         assert Thread.holdsLock(lock);

-        // if address have changed then DNS probably changed as well;
-        // otherwise check if cached settings have expired.
-        //
+        // A change in the network address of the machine usually indicates
+        // a change in DNS configuration too so we always refresh the
config
+        // after such a change.
         if (changed) {
             changed = false;
         } else {
-            if (lastRefresh >= 0) {
-                long currTime = System.currentTimeMillis();
-                if ((currTime - lastRefresh) < TIMEOUT) {
-                    return;
-                }
+            // Otherwise we refresh if TIMEOUT_NANOS has passed since last
+            // load.
+            long currTime = System.nanoTime();
+            // lastRefresh will always have been set once because we start
with
+            // changed = true.
+            if ((currTime - lastRefresh) < TIMEOUT_NANOS) {
+                return;
             }
         }

-        // load DNS configuration, update timestamp, create
-        // new HashMaps from the loaded configuration
-        //
+        // Native code that uses Windows API to find out the DNS server
+        // addresses and search suffixes. It builds a comma-delimited
string
+        // of nameservers and domain suffixes and sets them to the static
+        // os_nameservers and os_searchlist. We then split these into Java
+        // Lists here.
         loadDNSconfig0();

-        lastRefresh = System.currentTimeMillis();
+        // Record the time of update and refresh the lists of addresses /
+        // domain suffixes.
+        lastRefresh = System.nanoTime();
         searchlist = stringToList(os_searchlist);
-        nameservers = stringToList(os_nameservers);
+        nameservers = addressesToList(os_nameservers);
         os_searchlist = null;                       // can be GC'ed
         os_nameservers = null;
     }
diff --git a/src/java.base/windows/native/libnet/NetworkInterface_winXP.c
b/src/java.base/windows/native/libnet/NetworkInterface_winXP.c
index f2368bafcb..297a1561ef 100644
--- a/src/java.base/windows/native/libnet/NetworkInterface_winXP.c
+++ b/src/java.base/windows/native/libnet/NetworkInterface_winXP.c
@@ -73,8 +73,8 @@ const int MAX_TRIES = 3;
  * for each adapter on the system. Returned in *adapters.
  * Buffer is malloc'd and must be freed (unless error returned)
  */
-static int getAdapters (JNIEnv *env, IP_ADAPTER_ADDRESSES **adapters) {
-    DWORD ret, flags;
+int getAdapters (JNIEnv *env, int flags, IP_ADAPTER_ADDRESSES **adapters) {
+    DWORD ret;
     IP_ADAPTER_ADDRESSES *adapterInfo;
     ULONG len;
     int try;
@@ -87,9 +87,6 @@ static int getAdapters (JNIEnv *env, IP_ADAPTER_ADDRESSES
**adapters) {
     }

     len = BUFF_SIZE;
-    flags = GAA_FLAG_SKIP_DNS_SERVER;
-    flags |= GAA_FLAG_SKIP_MULTICAST;
-    flags |= GAA_FLAG_INCLUDE_PREFIX;
     ret = GetAdaptersAddresses(AF_UNSPEC, flags, NULL, adapterInfo, &len);

     for (try = 0; ret == ERROR_BUFFER_OVERFLOW && try < MAX_TRIES; ++try) {
@@ -240,7 +237,7 @@ static int ipinflen = 2048;
  */
 int getAllInterfacesAndAddresses (JNIEnv *env, netif **netifPP)
 {
-    DWORD ret;
+    DWORD ret, flags;
     MIB_IPADDRTABLE *tableP;
     IP_ADAPTER_ADDRESSES *ptr, *adapters=NULL;
     ULONG len=ipinflen, count=0;
@@ -296,7 +293,11 @@ int getAllInterfacesAndAddresses (JNIEnv *env, netif
**netifPP)
         }
     }
     free(tableP);
-    ret = getAdapters (env, &adapters);
+
+    flags = GAA_FLAG_SKIP_DNS_SERVER;
+    flags |= GAA_FLAG_SKIP_MULTICAST;
+    flags |= GAA_FLAG_INCLUDE_PREFIX;
+    ret = getAdapters (env, flags, &adapters);
     if (ret != ERROR_SUCCESS) {
         goto err;
     }
diff --git
a/src/java.base/windows/native/libnet/ResolverConfigurationImpl.c
b/src/java.base/windows/native/libnet/ResolverConfigurationImpl.c
index 13b28044a5..e830b8e70b 100644
--- a/src/java.base/windows/native/libnet/ResolverConfigurationImpl.c
+++ b/src/java.base/windows/native/libnet/ResolverConfigurationImpl.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2013, Oracle and/or its affiliates. All rights
reserved.
+ * Copyright (c) 2002, 2019, Oracle and/or its affiliates. All rights
reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -24,17 +24,15 @@
  */

 #include <stdlib.h>
-#include <windows.h>
 #include <stdio.h>
 #include <stddef.h>
-#include <iprtrmib.h>
 #include <time.h>
 #include <assert.h>
-#include <iphlpapi.h>

+#include "net_util.h"
 #include "jni_util.h"

-#define MAX_STR_LEN         256
+#define MAX_STR_LEN         1024

 #define STS_NO_CONFIG       0x0             /* no configuration found */
 #define STS_SL_FOUND        0x1             /* search list found */
@@ -48,9 +46,11 @@
 static jfieldID searchlistID;
 static jfieldID nameserversID;

+extern int getAdapters(JNIEnv *env, int flags, IP_ADAPTER_ADDRESSES
**adapters);
+
 /*
- * Utility routine to append s2 to s1 with a space delimiter.
- *  strappend(s1="abc", "def")  => "abc def"
+ * Utility routine to append s2 to s1 with a comma delimiter.
+ *  strappend(s1="abc", "def")  => "abc,def"
  *  strappend(s1="", "def")     => "def
  */
 void strappend(char *s1, char *s2) {
@@ -60,41 +60,32 @@ void strappend(char *s1, char *s2) {
         return;

     len = strlen(s1)+1;
-    if (s1[0] != 0)                         /* needs space character */
+    if (s1[0] != 0)                         /* needs comma character */
         len++;
     if (len + strlen(s2) > MAX_STR_LEN)     /* insufficient space */
         return;

     if (s1[0] != 0) {
-        strcat(s1, " ");
+        strcat(s1, ",");
     }
     strcat(s1, s2);
 }

 /*
- * Windows 2000/XP
- *
- * Use registry approach based on settings described in Appendix C
- * of "Microsoft Windows 2000 TCP/IP Implementation Details".
- *
- * DNS suffix list is obtained from SearchList registry setting. If
- * this is not specified we compile suffix list based on the
- * per-connection domain suffix.
- *
- * DNS name servers and domain settings are on a per-connection
- * basic. We therefore enumerate the network adapters to get the
- * names of each adapter and then query the corresponding registry
- * settings to obtain NameServer/DhcpNameServer and Domain/DhcpDomain.
+ * Use DNS server addresses returned by GetAdaptersAddresses for currently
+ * active interfaces.
  */
-static int loadConfig(char *sl, char *ns) {
-    IP_ADAPTER_INFO *adapterP;
-    ULONG size;
-    DWORD ret;
+static int loadConfig(JNIEnv *env, char *sl, char *ns) {
+    IP_ADAPTER_ADDRESSES *adapters, *adapter;
+    IP_ADAPTER_DNS_SERVER_ADDRESS *dnsServer;
+    WCHAR *suffix;
+    DWORD ret, flags;
     DWORD dwLen;
     ULONG ulType;
     char result[MAX_STR_LEN];
     HANDLE hKey;
-    int gotSearchList = 0;
+    SOCKADDR *sockAddr;
+    struct sockaddr_in6 *sockAddrIpv6;

     /*
      * First see if there is a global suffix list specified.
@@ -112,128 +103,74 @@ static int loadConfig(char *sl, char *ns) {
             assert(ulType == REG_SZ);
             if (strlen(result) > 0) {
                 strappend(sl, result);
-                gotSearchList = 1;
             }
         }
         RegCloseKey(hKey);
     }

-    /*
-     * Ask the IP Helper library to enumerate the adapters
-     */
-    size = sizeof(IP_ADAPTER_INFO);
-    adapterP = (IP_ADAPTER_INFO *)malloc(size);
-    if (adapterP == NULL) {
-        return STS_ERROR;
-    }
-    ret = GetAdaptersInfo(adapterP, &size);
-    if (ret == ERROR_BUFFER_OVERFLOW) {
-        IP_ADAPTER_INFO *newAdapterP = (IP_ADAPTER_INFO
*)realloc(adapterP, size);
-        if (newAdapterP == NULL) {
-            free(adapterP);
-            return STS_ERROR;
-        }
-        adapterP = newAdapterP;

-        ret = GetAdaptersInfo(adapterP, &size);
+    // We only need DNS server addresses so skip everything else.
+    flags = GAA_FLAG_SKIP_UNICAST;
+    flags |= GAA_FLAG_SKIP_ANYCAST;
+    flags |= GAA_FLAG_SKIP_MULTICAST;
+    flags |= GAA_FLAG_SKIP_FRIENDLY_NAME;
+    ret = getAdapters(env, flags, &adapters);
+
+    if (ret != ERROR_SUCCESS) {
+        return STS_ERROR;
     }

-    /*
-     * Iterate through the list of adapters as registry settings are
-     * keyed on the adapter name (GUID).
-     */
-    if (ret == ERROR_SUCCESS) {
-        IP_ADAPTER_INFO *curr = adapterP;
-        while (curr != NULL) {
-            char key[MAX_STR_LEN];
-
-            sprintf(key,
-
 "SYSTEM\\CurrentControlSet\\Services\\Tcpip\\Parameters\\Interfaces\\%s",
-                curr->AdapterName);
-
-            ret = RegOpenKeyEx(HKEY_LOCAL_MACHINE,
-                               key,
-                               0,
-                               KEY_READ,
-                               (PHKEY)&hKey);
-            if (ret == ERROR_SUCCESS) {
-                DWORD enableDhcp = 0;
-
-                /*
-                 * Is DHCP enabled on this interface
-                 */
-                dwLen = sizeof(enableDhcp);
-                ret = RegQueryValueEx(hKey, "EnableDhcp", NULL, &ulType,
-                                     (LPBYTE)&enableDhcp, &dwLen);
-
-                /*
-                 * If we don't have the suffix list when get the Domain
-                 * or DhcpDomain. If DHCP is enabled then Domain overides
-                 * DhcpDomain
-                 */
-                if (!gotSearchList) {
-                    result[0] = '\0';
-                    dwLen = sizeof(result);
-                    ret = RegQueryValueEx(hKey, "Domain", NULL, &ulType,
-                                         (LPBYTE)&result, &dwLen);
-                    if (((ret != ERROR_SUCCESS) || (strlen(result) == 0))
&&
-                        enableDhcp) {
-                        dwLen = sizeof(result);
-                        ret = RegQueryValueEx(hKey, "DhcpDomain", NULL,
&ulType,
-                                              (LPBYTE)&result, &dwLen);
-                    }
-                    if (ret == ERROR_SUCCESS) {
-                        assert(ulType == REG_SZ);
-                        strappend(sl, result);
+    adapter = adapters;
+    while (adapter != NULL) {
+        // Only load config from enabled adapters.
+        if (adapter->OperStatus == IfOperStatusUp) {
+            dnsServer = adapter->FirstDnsServerAddress;
+            while (dnsServer != NULL) {
+                sockAddr = dnsServer->Address.lpSockaddr;
+                if (sockAddr->sa_family == AF_INET6) {
+                    sockAddrIpv6 = (struct sockaddr_in6 *)sockAddr;
+                    if (sockAddrIpv6->sin6_scope_id != 0) {
+                        // An address with a scope is either link-local or
+                        // site-local, which aren't valid for DNS queries
so
+                        // we can skip them.
+                        dnsServer = dnsServer->Next;
+                        continue;
                     }
                 }

-                /*
-                 * Get DNS servers based on NameServer or DhcpNameServer
-                 * registry setting. If NameServer is set then it overrides
-                 * DhcpNameServer (even if DHCP is enabled).
-                 */
-                result[0] = '\0';
                 dwLen = sizeof(result);
-                ret = RegQueryValueEx(hKey, "NameServer", NULL, &ulType,
-                                     (LPBYTE)&result, &dwLen);
-                if (((ret != ERROR_SUCCESS) || (strlen(result) == 0)) &&
-                    enableDhcp) {
-                    dwLen = sizeof(result);
-                    ret = RegQueryValueEx(hKey, "DhcpNameServer", NULL,
&ulType,
-                                          (LPBYTE)&result, &dwLen);
-                }
-                if (ret == ERROR_SUCCESS) {
-                    assert(ulType == REG_SZ);
+                ret = WSAAddressToStringA(sockAddr,
+                          dnsServer->Address.iSockaddrLength, NULL,
+                          result, &dwLen);
+                if (ret == 0) {
                     strappend(ns, result);
                 }

-                /*
-                 * Finished with this registry key
-                 */
-                RegCloseKey(hKey);
+                dnsServer = dnsServer->Next;
             }

-            /*
-             * Onto the next adapeter
-             */
-            curr = curr->Next;
+            // Add connection-specific search domains in addition to
global one.
+            suffix = adapter->DnsSuffix;
+            if (suffix != NULL) {
+                ret = WideCharToMultiByte(CP_UTF8, 0, suffix, -1,
+                    result, sizeof(result), NULL, NULL);
+                if (ret != 0) {
+                    strappend(sl, result);
+                }
+            }
         }
-    }

-    /*
-     * Free the adpater structure
-     */
-    if (adapterP) {
-        free(adapterP);
+        adapter = adapter->Next;
     }

+    free(adapters);
+
     return STS_SL_FOUND & STS_NS_FOUND;
 }


 /*
- * Initialize JNI field IDs.
+ * Initialize JNI field IDs and classes.
  */
 JNIEXPORT void JNICALL
 Java_sun_net_dns_ResolverConfigurationImpl_init0(JNIEnv *env, jclass cls)
@@ -260,7 +197,7 @@
Java_sun_net_dns_ResolverConfigurationImpl_loadDNSconfig0(JNIEnv *env,
jclass cl
     searchlist[0] = '\0';
     nameservers[0] = '\0';

-    if (loadConfig(searchlist, nameservers) != STS_ERROR) {
+    if (loadConfig(env, searchlist, nameservers) != STS_ERROR) {

         /*
          * Populate static fields in sun.net.DefaultResolverConfiguration
@@ -272,8 +209,6 @@
Java_sun_net_dns_ResolverConfigurationImpl_loadDNSconfig0(JNIEnv *env,
jclass cl
         obj = (*env)->NewStringUTF(env, nameservers);
         CHECK_NULL(obj);
         (*env)->SetStaticObjectField(env, cls, nameserversID, obj);
-    } else {
-        JNU_ThrowOutOfMemoryError(env, "native memory allocation failed");
     }
 }



On Fri, Jan 10, 2020 at 12:17 AM Anuraag Agrawal <anuraaga at gmail.com> wrote:

> Hi Daniel,
>
> Thanks for the review!
>
> On Thu, Jan 9, 2020 at 9:04 PM Daniel Fuchs <daniel.fuchs at oracle.com>
> wrote:
>
>> Hi,
>>
>> Two small remarks:
>>
>> ResolverConfigurationImpl.java:
>>
>>    71             if (!l.contains(s)) {
>>
>> Maybe empty strings should be skipped here too.
>>
>
> Makes sense, added the check.
>
>
>>
>> I believe it would be more correct to change this line:
>>
>>   117             if (lastRefresh >= 0) {
>>
>> to
>>
>>   117             if (lastRefresh != -1) {
>>
>> as System.nanoTime() can return negative values.
>>
>
> Had never realized nanoTime can return negative values, I have to check
> all my other code for bugs now ;) I have gone ahead and removed this check
> altogether, instead defaulting "changed" to true so we always load on the
> first time through. I think this should be the most precise.
>
> Inline patch follows
>
> diff --git
> a/src/java.base/windows/classes/sun/net/dns/ResolverConfigurationImpl.java
> b/src/java.base/windows/classes/sun/net/dns/ResolverConfigurationImpl.java
> index 2250b3158e..0f161ea4a8 100644
> ---
> a/src/java.base/windows/classes/sun/net/dns/ResolverConfigurationImpl.java
> +++
> b/src/java.base/windows/classes/sun/net/dns/ResolverConfigurationImpl.java
> @@ -25,9 +25,9 @@
>
>  package sun.net.dns;
>
> +import java.util.ArrayList;
>  import java.util.List;
> -import java.util.LinkedList;
> -import java.util.StringTokenizer;
> +import java.util.concurrent.TimeUnit;
>
>  /*
>   * An implementation of sun.net.ResolverConfiguration for Windows.
> @@ -42,38 +42,64 @@ public class ResolverConfigurationImpl
>      // Resolver options
>      private final Options opts;
>
> -    // Addresses have changed
> -    private static boolean changed = false;
> +    // Addresses have changed. We default to true to make sure we
> +    // resolve the first time it is requested.
> +    private static boolean changed = true;
>
>      // Time of last refresh.
>      private static long lastRefresh = -1;
>
>      // Cache timeout (120 seconds) - should be converted into property
>      // or configured as preference in the future.
> -    private static final int TIMEOUT = 120000;
> +    private static final long TIMEOUT_NANOS =
> TimeUnit.SECONDS.toNanos(120);
>
>      // DNS suffix list and name servers populated by native method
>      private static String os_searchlist;
>      private static String os_nameservers;
>
>      // Cached lists
> -    private static LinkedList<String> searchlist;
> -    private static LinkedList<String> nameservers;
> -
> -    // Parse string that consists of token delimited by space or commas
> -    // and return LinkedHashMap
> -    private LinkedList<String> stringToList(String str) {
> -        LinkedList<String> ll = new LinkedList<>();
> -
> -        // comma and space are valid delimiters
> -        StringTokenizer st = new StringTokenizer(str, ", ");
> -        while (st.hasMoreTokens()) {
> -            String s = st.nextToken();
> -            if (!ll.contains(s)) {
> -                ll.add(s);
> +    private static ArrayList<String> searchlist;
> +    private static ArrayList<String> nameservers;
> +
> +    // Parse string that consists of token delimited by comma
> +    // and return ArrayList. Refer to ResolverConfigurationImpl.c and
> +    // strappend to see how the string is created.
> +    private ArrayList<String> stringToList(String str) {
> +        // String is delimited by comma.
> +        String[] tokens = str.split(",");
> +        ArrayList<String> l = new ArrayList<>(tokens.length);
> +        for (String s : tokens) {
> +            if (!s.isEmpty() && !l.contains(s)) {
> +                l.add(s);
>              }
>          }
> -        return ll;
> +        l.trimToSize();
> +        return l;
> +    }
> +
> +    // Parse string that consists of token delimited by comma
> +    // and return ArrayList.  Refer to ResolverConfigurationImpl.c and
> +    // strappend to see how the string is created.
> +    // In addition to splitting the string, converts IPv6 addresses to
> +    // BSD-style.
> +    private ArrayList<String> addressesToList(String str) {
> +        // String is delimited by comma
> +        String[] tokens = str.split(",");
> +        ArrayList<String> l = new ArrayList<>(tokens.length);
> +
> +        for (String s : tokens) {
> +            if (!s.isEmpty()) {
> +                if (s.indexOf(':') >= 0 && s.charAt(0) != '[') {
> +                    // Not BSD style
> +                    s = '[' + s + ']';
> +                }
> +                if (!s.isEmpty() && !l.contains(s)) {
> +                    l.add(s);
> +                }
> +            }
> +        }
> +        l.trimToSize();
> +        return l;
>      }
>
>      // Load DNS configuration from OS
> @@ -81,28 +107,34 @@ public class ResolverConfigurationImpl
>      private void loadConfig() {
>          assert Thread.holdsLock(lock);
>
> -        // if address have changed then DNS probably changed as well;
> -        // otherwise check if cached settings have expired.
> -        //
> +        // A change in the network address of the machine usually
> indicates
> +        // a change in DNS configuration too so we always refresh the
> config
> +        // after such a change.
>          if (changed) {
>              changed = false;
>          } else {
> -            if (lastRefresh >= 0) {
> -                long currTime = System.currentTimeMillis();
> -                if ((currTime - lastRefresh) < TIMEOUT) {
> -                    return;
> -                }
> +            // Otherwise we refresh if TIMEOUT_NANOS has passed since last
> +            // load.
> +            long currTime = System.nanoTime();
> +            // lastRefresh will always have been set once because we
> start with
> +            // changed = true.
> +            if ((currTime - lastRefresh) < TIMEOUT_NANOS) {
> +                return;
>              }
>          }
>
> -        // load DNS configuration, update timestamp, create
> -        // new HashMaps from the loaded configuration
> -        //
> +        // Native code that uses Windows API to find out the DNS server
> +        // addresses and search suffixes. It builds a comma-delimited
> string
> +        // of nameservers and domain suffixes and sets them to the static
> +        // os_nameservers and os_searchlist. We then split these into Java
> +        // Lists here.
>          loadDNSconfig0();
>
> -        lastRefresh = System.currentTimeMillis();
> +        // Record the time of update and refresh the lists of addresses /
> +        // domain suffixes.
> +        lastRefresh = System.nanoTime();
>          searchlist = stringToList(os_searchlist);
> -        nameservers = stringToList(os_nameservers);
> +        nameservers = addressesToList(os_nameservers);
>          os_searchlist = null;                       // can be GC'ed
>          os_nameservers = null;
>      }
> diff --git a/src/java.base/windows/native/libnet/NetworkInterface_winXP.c
> b/src/java.base/windows/native/libnet/NetworkInterface_winXP.c
> index f2368bafcb..297a1561ef 100644
> --- a/src/java.base/windows/native/libnet/NetworkInterface_winXP.c
> +++ b/src/java.base/windows/native/libnet/NetworkInterface_winXP.c
> @@ -73,8 +73,8 @@ const int MAX_TRIES = 3;
>   * for each adapter on the system. Returned in *adapters.
>   * Buffer is malloc'd and must be freed (unless error returned)
>   */
> -static int getAdapters (JNIEnv *env, IP_ADAPTER_ADDRESSES **adapters) {
> -    DWORD ret, flags;
> +int getAdapters (JNIEnv *env, int flags, IP_ADAPTER_ADDRESSES **adapters)
> {
> +    DWORD ret;
>      IP_ADAPTER_ADDRESSES *adapterInfo;
>      ULONG len;
>      int try;
> @@ -87,9 +87,6 @@ static int getAdapters (JNIEnv *env,
> IP_ADAPTER_ADDRESSES **adapters) {
>      }
>
>      len = BUFF_SIZE;
> -    flags = GAA_FLAG_SKIP_DNS_SERVER;
> -    flags |= GAA_FLAG_SKIP_MULTICAST;
> -    flags |= GAA_FLAG_INCLUDE_PREFIX;
>      ret = GetAdaptersAddresses(AF_UNSPEC, flags, NULL, adapterInfo, &len);
>
>      for (try = 0; ret == ERROR_BUFFER_OVERFLOW && try < MAX_TRIES; ++try)
> {
> @@ -240,7 +237,7 @@ static int ipinflen = 2048;
>   */
>  int getAllInterfacesAndAddresses (JNIEnv *env, netif **netifPP)
>  {
> -    DWORD ret;
> +    DWORD ret, flags;
>      MIB_IPADDRTABLE *tableP;
>      IP_ADAPTER_ADDRESSES *ptr, *adapters=NULL;
>      ULONG len=ipinflen, count=0;
> @@ -296,7 +293,11 @@ int getAllInterfacesAndAddresses (JNIEnv *env, netif
> **netifPP)
>          }
>      }
>      free(tableP);
> -    ret = getAdapters (env, &adapters);
> +
> +    flags = GAA_FLAG_SKIP_DNS_SERVER;
> +    flags |= GAA_FLAG_SKIP_MULTICAST;
> +    flags |= GAA_FLAG_INCLUDE_PREFIX;
> +    ret = getAdapters (env, flags, &adapters);
>      if (ret != ERROR_SUCCESS) {
>          goto err;
>      }
> diff --git
> a/src/java.base/windows/native/libnet/ResolverConfigurationImpl.c
> b/src/java.base/windows/native/libnet/ResolverConfigurationImpl.c
> index 13b28044a5..e830b8e70b 100644
> --- a/src/java.base/windows/native/libnet/ResolverConfigurationImpl.c
> +++ b/src/java.base/windows/native/libnet/ResolverConfigurationImpl.c
> @@ -1,5 +1,5 @@
>  /*
> - * Copyright (c) 2002, 2013, Oracle and/or its affiliates. All rights
> reserved.
> + * Copyright (c) 2002, 2019, Oracle and/or its affiliates. All rights
> reserved.
>   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
>   *
>   * This code is free software; you can redistribute it and/or modify it
> @@ -24,17 +24,15 @@
>   */
>
>  #include <stdlib.h>
> -#include <windows.h>
>  #include <stdio.h>
>  #include <stddef.h>
> -#include <iprtrmib.h>
>  #include <time.h>
>  #include <assert.h>
> -#include <iphlpapi.h>
>
> +#include "net_util.h"
>  #include "jni_util.h"
>
> -#define MAX_STR_LEN         256
> +#define MAX_STR_LEN         1024
>
>  #define STS_NO_CONFIG       0x0             /* no configuration found */
>  #define STS_SL_FOUND        0x1             /* search list found */
> @@ -48,9 +46,11 @@
>  static jfieldID searchlistID;
>  static jfieldID nameserversID;
>
> +extern int getAdapters(JNIEnv *env, int flags, IP_ADAPTER_ADDRESSES
> **adapters);
> +
>  /*
> - * Utility routine to append s2 to s1 with a space delimiter.
> - *  strappend(s1="abc", "def")  => "abc def"
> + * Utility routine to append s2 to s1 with a comma delimiter.
> + *  strappend(s1="abc", "def")  => "abc,def"
>   *  strappend(s1="", "def")     => "def
>   */
>  void strappend(char *s1, char *s2) {
> @@ -60,41 +60,32 @@ void strappend(char *s1, char *s2) {
>          return;
>
>      len = strlen(s1)+1;
> -    if (s1[0] != 0)                         /* needs space character */
> +    if (s1[0] != 0)                         /* needs comma character */
>          len++;
>      if (len + strlen(s2) > MAX_STR_LEN)     /* insufficient space */
>          return;
>
>      if (s1[0] != 0) {
> -        strcat(s1, " ");
> +        strcat(s1, ",");
>      }
>      strcat(s1, s2);
>  }
>
>  /*
> - * Windows 2000/XP
> - *
> - * Use registry approach based on settings described in Appendix C
> - * of "Microsoft Windows 2000 TCP/IP Implementation Details".
> - *
> - * DNS suffix list is obtained from SearchList registry setting. If
> - * this is not specified we compile suffix list based on the
> - * per-connection domain suffix.
> - *
> - * DNS name servers and domain settings are on a per-connection
> - * basic. We therefore enumerate the network adapters to get the
> - * names of each adapter and then query the corresponding registry
> - * settings to obtain NameServer/DhcpNameServer and Domain/DhcpDomain.
> + * Use DNS server addresses returned by GetAdaptersAddresses for currently
> + * active interfaces.
>   */
> -static int loadConfig(char *sl, char *ns) {
> -    IP_ADAPTER_INFO *adapterP;
> -    ULONG size;
> -    DWORD ret;
> +static int loadConfig(JNIEnv *env, char *sl, char *ns) {
> +    IP_ADAPTER_ADDRESSES *adapters, *adapter;
> +    IP_ADAPTER_DNS_SERVER_ADDRESS *dnsServer;
> +    WCHAR *suffix;
> +    DWORD ret, flags;
>      DWORD dwLen;
>      ULONG ulType;
>      char result[MAX_STR_LEN];
>      HANDLE hKey;
> -    int gotSearchList = 0;
> +    SOCKADDR *sockAddr;
> +    struct sockaddr_in6 *sockAddrIpv6;
>
>      /*
>       * First see if there is a global suffix list specified.
> @@ -112,128 +103,74 @@ static int loadConfig(char *sl, char *ns) {
>              assert(ulType == REG_SZ);
>              if (strlen(result) > 0) {
>                  strappend(sl, result);
> -                gotSearchList = 1;
>              }
>          }
>          RegCloseKey(hKey);
>      }
>
> -    /*
> -     * Ask the IP Helper library to enumerate the adapters
> -     */
> -    size = sizeof(IP_ADAPTER_INFO);
> -    adapterP = (IP_ADAPTER_INFO *)malloc(size);
> -    if (adapterP == NULL) {
> -        return STS_ERROR;
> -    }
> -    ret = GetAdaptersInfo(adapterP, &size);
> -    if (ret == ERROR_BUFFER_OVERFLOW) {
> -        IP_ADAPTER_INFO *newAdapterP = (IP_ADAPTER_INFO
> *)realloc(adapterP, size);
> -        if (newAdapterP == NULL) {
> -            free(adapterP);
> -            return STS_ERROR;
> -        }
> -        adapterP = newAdapterP;
>
> -        ret = GetAdaptersInfo(adapterP, &size);
> +    // We only need DNS server addresses so skip everything else.
> +    flags = GAA_FLAG_SKIP_UNICAST;
> +    flags |= GAA_FLAG_SKIP_ANYCAST;
> +    flags |= GAA_FLAG_SKIP_MULTICAST;
> +    flags |= GAA_FLAG_SKIP_FRIENDLY_NAME;
> +    ret = getAdapters(env, flags, &adapters);
> +
> +    if (ret != ERROR_SUCCESS) {
> +        return STS_ERROR;
>      }
>
> -    /*
> -     * Iterate through the list of adapters as registry settings are
> -     * keyed on the adapter name (GUID).
> -     */
> -    if (ret == ERROR_SUCCESS) {
> -        IP_ADAPTER_INFO *curr = adapterP;
> -        while (curr != NULL) {
> -            char key[MAX_STR_LEN];
> -
> -            sprintf(key,
> -
>  "SYSTEM\\CurrentControlSet\\Services\\Tcpip\\Parameters\\Interfaces\\%s",
> -                curr->AdapterName);
> -
> -            ret = RegOpenKeyEx(HKEY_LOCAL_MACHINE,
> -                               key,
> -                               0,
> -                               KEY_READ,
> -                               (PHKEY)&hKey);
> -            if (ret == ERROR_SUCCESS) {
> -                DWORD enableDhcp = 0;
> -
> -                /*
> -                 * Is DHCP enabled on this interface
> -                 */
> -                dwLen = sizeof(enableDhcp);
> -                ret = RegQueryValueEx(hKey, "EnableDhcp", NULL, &ulType,
> -                                     (LPBYTE)&enableDhcp, &dwLen);
> -
> -                /*
> -                 * If we don't have the suffix list when get the Domain
> -                 * or DhcpDomain. If DHCP is enabled then Domain overides
> -                 * DhcpDomain
> -                 */
> -                if (!gotSearchList) {
> -                    result[0] = '\0';
> -                    dwLen = sizeof(result);
> -                    ret = RegQueryValueEx(hKey, "Domain", NULL, &ulType,
> -                                         (LPBYTE)&result, &dwLen);
> -                    if (((ret != ERROR_SUCCESS) || (strlen(result) == 0))
> &&
> -                        enableDhcp) {
> -                        dwLen = sizeof(result);
> -                        ret = RegQueryValueEx(hKey, "DhcpDomain", NULL,
> &ulType,
> -                                              (LPBYTE)&result, &dwLen);
> -                    }
> -                    if (ret == ERROR_SUCCESS) {
> -                        assert(ulType == REG_SZ);
> -                        strappend(sl, result);
> +    adapter = adapters;
> +    while (adapter != NULL) {
> +        // Only load config from enabled adapters.
> +        if (adapter->OperStatus == IfOperStatusUp) {
> +            dnsServer = adapter->FirstDnsServerAddress;
> +            while (dnsServer != NULL) {
> +                sockAddr = dnsServer->Address.lpSockaddr;
> +                if (sockAddr->sa_family == AF_INET6) {
> +                    sockAddrIpv6 = (struct sockaddr_in6 *)sockAddr;
> +                    if (sockAddrIpv6->sin6_scope_id != 0) {
> +                        // An address with a scope is either link-local or
> +                        // site-local, which aren't valid for DNS queries
> so
> +                        // we can skip them.
> +                        dnsServer = dnsServer->Next;
> +                        continue;
>                      }
>                  }
>
> -                /*
> -                 * Get DNS servers based on NameServer or DhcpNameServer
> -                 * registry setting. If NameServer is set then it
> overrides
> -                 * DhcpNameServer (even if DHCP is enabled).
> -                 */
> -                result[0] = '\0';
>                  dwLen = sizeof(result);
> -                ret = RegQueryValueEx(hKey, "NameServer", NULL, &ulType,
> -                                     (LPBYTE)&result, &dwLen);
> -                if (((ret != ERROR_SUCCESS) || (strlen(result) == 0)) &&
> -                    enableDhcp) {
> -                    dwLen = sizeof(result);
> -                    ret = RegQueryValueEx(hKey, "DhcpNameServer", NULL,
> &ulType,
> -                                          (LPBYTE)&result, &dwLen);
> -                }
> -                if (ret == ERROR_SUCCESS) {
> -                    assert(ulType == REG_SZ);
> +                ret = WSAAddressToStringA(sockAddr,
> +                          dnsServer->Address.iSockaddrLength, NULL,
> +                          result, &dwLen);
> +                if (ret == 0) {
>                      strappend(ns, result);
>                  }
>
> -                /*
> -                 * Finished with this registry key
> -                 */
> -                RegCloseKey(hKey);
> +                dnsServer = dnsServer->Next;
>              }
>
> -            /*
> -             * Onto the next adapeter
> -             */
> -            curr = curr->Next;
> +            // Add connection-specific search domains in addition to
> global one.
> +            suffix = adapter->DnsSuffix;
> +            if (suffix != NULL) {
> +                ret = WideCharToMultiByte(CP_UTF8, 0, suffix, -1,
> +                    result, sizeof(result), NULL, NULL);
> +                if (ret != 0) {
> +                    strappend(sl, result);
> +                }
> +            }
>          }
> -    }
>
> -    /*
> -     * Free the adpater structure
> -     */
> -    if (adapterP) {
> -        free(adapterP);
> +        adapter = adapter->Next;
>      }
>
> +    free(adapters);
> +
>      return STS_SL_FOUND & STS_NS_FOUND;
>  }
>
>
>  /*
> - * Initialize JNI field IDs.
> + * Initialize JNI field IDs and classes.
>   */
>  JNIEXPORT void JNICALL
>  Java_sun_net_dns_ResolverConfigurationImpl_init0(JNIEnv *env, jclass cls)
> @@ -260,7 +197,7 @@
> Java_sun_net_dns_ResolverConfigurationImpl_loadDNSconfig0(JNIEnv *env,
> jclass cl
>      searchlist[0] = '\0';
>      nameservers[0] = '\0';
>
> -    if (loadConfig(searchlist, nameservers) != STS_ERROR) {
> +    if (loadConfig(env, searchlist, nameservers) != STS_ERROR) {
>
>          /*
>           * Populate static fields in sun.net.DefaultResolverConfiguration
> @@ -272,8 +209,6 @@
> Java_sun_net_dns_ResolverConfigurationImpl_loadDNSconfig0(JNIEnv *env,
> jclass cl
>          obj = (*env)->NewStringUTF(env, nameservers);
>          CHECK_NULL(obj);
>          (*env)->SetStaticObjectField(env, cls, nameserversID, obj);
> -    } else {
> -        JNU_ThrowOutOfMemoryError(env, "native memory allocation failed");
>      }
>  }
>
>
>
>>
>>
>> best regards,
>>
>> -- daniel
>>
>>
>> On 09/01/2020 00:54, Aleks Efimov wrote:
>> > Got the testing results: the CI is happy with the last patch - no JNDI
>> > test failures observed
>> >
>> > Kind Regards,
>> > Aleksei
>>
>
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