7006496: Use modern Windows API to retrieve OS DNS servers

Reviewed-by: dfuchs, chegar, aefimov

src/java.base/windows/classes/sun/net/dns/ResolverConfigurationImpl.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2020, 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
@@ -25,9 +25,9 @@
 
 package sun.net.dns;
 
+import java.util.ArrayList;
 import java.util.List;
-import java.util.LinkedList;
+import java.util.concurrent.TimeUnit;
-import java.util.StringTokenizer;
 
 /*
  * An implementation of sun.net.ResolverConfiguration for Windows.
@@ -42,38 +42,64 @@ public class ResolverConfigurationImpl
     // Resolver options
     private final Options opts;
 
-    // Addresses have changed
+    // Addresses have changed. We default to true to make sure we
-    private static boolean changed = false;
+    // 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 ArrayList<String> searchlist;
-    private static LinkedList<String> nameservers;
+    private static ArrayList<String> nameservers;
 
-    // Parse string that consists of token delimited by space or commas
+    // Parse string that consists of token delimited by comma
-    // and return LinkedHashMap
+    // and return ArrayList. Refer to ResolverConfigurationImpl.c and
-    private LinkedList<String> stringToList(String str) {
+    // strappend to see how the string is created.
-        LinkedList<String> ll = new LinkedList<>();
+    private ArrayList<String> stringToList(String str) {
-
+        // String is delimited by comma.
-        // comma and space are valid delimiters
+        String[] tokens = str.split(",");
-        StringTokenizer st = new StringTokenizer(str, ", ");
+        ArrayList<String> l = new ArrayList<>(tokens.length);
-        while (st.hasMoreTokens()) {
+        for (String s : tokens) {
-            String s = st.nextToken();
+            if (!s.isEmpty() && !l.contains(s)) {
-            if (!ll.contains(s)) {
+                l.add(s);
-                ll.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;
+        // A change in the network address of the machine usually indicates
-        // otherwise check if cached settings have expired.
+        // a change in DNS configuration too so we always refresh the config
-        //
+        // after such a change.
         if (changed) {
             changed = false;
         } else {
-            if (lastRefresh >= 0) {
+            // Otherwise we refresh if TIMEOUT_NANOS has passed since last
-                long currTime = System.currentTimeMillis();
+            // load.
-                if ((currTime - lastRefresh) < TIMEOUT) {
+            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
+        // Native code that uses Windows API to find out the DNS server
-        // new HashMaps from the loaded configuration
+        // 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;
     }

src/java.base/windows/native/libnet/NetworkInterface_winXP.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2020, 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
@@ -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) {
+int getAdapters (JNIEnv *env, int flags, IP_ADAPTER_ADDRESSES **adapters) {
-    DWORD ret, flags;
+    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;
     }

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, 2020, 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.
+ * Utility routine to append s2 to s1 with a comma delimiter.
- *  strappend(s1="abc", "def")  => "abc def"
+ *  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 DNS server addresses returned by GetAdaptersAddresses for currently
- *
+ * active interfaces.
- * 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.
  */
-static int loadConfig(char *sl, char *ns) {
+static int loadConfig(JNIEnv *env, char *sl, char *ns) {
-    IP_ADAPTER_INFO *adapterP;
+    IP_ADAPTER_ADDRESSES *adapters, *adapter;
-    ULONG size;
+    IP_ADAPTER_DNS_SERVER_ADDRESS *dnsServer;
-    DWORD ret;
+    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
+    // We only need DNS server addresses so skip everything else.
-     */
+    flags = GAA_FLAG_SKIP_UNICAST;
-    size = sizeof(IP_ADAPTER_INFO);
+    flags |= GAA_FLAG_SKIP_ANYCAST;
-    adapterP = (IP_ADAPTER_INFO *)malloc(size);
+    flags |= GAA_FLAG_SKIP_MULTICAST;
-    if (adapterP == NULL) {
+    flags |= GAA_FLAG_SKIP_FRIENDLY_NAME;
+    ret = getAdapters(env, flags, &adapters);
+
+    if (ret != ERROR_SUCCESS) {
         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);
+    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;
+                    }
                 }
 
-    /*
-     * 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,
+                ret = WSAAddressToStringA(sockAddr,
-                                         (LPBYTE)&result, &dwLen);
+                          dnsServer->Address.iSockaddrLength, NULL,
-                    if (((ret != ERROR_SUCCESS) || (strlen(result) == 0)) &&
+                          result, &dwLen);
-                        enableDhcp) {
+                if (ret == 0) {
-                        dwLen = sizeof(result);
-                        ret = RegQueryValueEx(hKey, "DhcpDomain", NULL, &ulType,
-                                              (LPBYTE)&result, &dwLen);
-                    }
-                    if (ret == ERROR_SUCCESS) {
-                        assert(ulType == REG_SZ);
-                        strappend(sl, result);
-                    }
-                }
-
-                /*
-                 * 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);
                     strappend(ns, result);
                 }
 
-                /*
+                dnsServer = dnsServer->Next;
-                 * Finished with this registry key
-                 */
-                RegCloseKey(hKey);
             }
 
-            /*
+            // Add connection-specific search domains in addition to global one.
-             * Onto the next adapeter
+            suffix = adapter->DnsSuffix;
-             */
+            if (suffix != NULL) {
-            curr = curr->Next;
+                ret = WideCharToMultiByte(CP_UTF8, 0, suffix, -1,
+                    result, sizeof(result), NULL, NULL);
+                if (ret != 0) {
+                    strappend(sl, result);
+                }
             }
         }
 
-    /*
+        adapter = adapter->Next;
-     * Free the adpater structure
-     */
-    if (adapterP) {
-        free(adapterP);
     }
 
+    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");
     }
 }