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

Anuraag Agrawal anuraaga at gmail.com
Wed Dec 11 16:49:51 UTC 2019


Hi Aleksei,

Thanks for the feedback. I had thought about it but felt that it might be
better to leave as much business logic to Java vs native as possible as a
general principle. But if it makes more sense to do it native here happy to
make the change :)

Thanks,
- Anuraag

On Thu, Dec 12, 2019, 01:18 Aleks Efimov <aleksej.efimov at oracle.com> wrote:

> Hi Anuraag,
>
> The webrev with the latest patch can be viewed here:
> http://cr.openjdk.java.net/~aefimov/anuraaga/7006496/02
>
> Thanks for replacing FirstDnsSuffix usages with DnsSuffix. I've double
> checked it with native application and can confirm that on my test host
> (Microsoft Windows Server 2016 Standard) the DnsSuffix contains correct
> information while the FirstDnsSuffix list is empty:
>         DNS Suffix (From DnsSuffix field):  test.domain.com
>         Number of IP Adapter DNS suffix entries: 0
>
>         DNS Suffix (From DnsSuffix field):
>         Number of IP Adapter DNS suffix entries: 0
>
>         DNS Suffix (From DnsSuffix field):
>         Number of IP Adapter DNS suffix entries: 0
>
>         DNS Suffix (From DnsSuffix field):
>         Number of IP Adapter DNS suffix entries: 0
>
>         DNS Suffix (From DnsSuffix field):  test.domain.com
>         Number of IP Adapter DNS suffix entries: 0
>
> About site-local addresses: Maybe we can move the site-local address check
> to native code? i.e. analyze dnsServer->Address.lpSockaddr and filter out
> site-local addresses.
>
> Testing:
> Run your latest patch though our CI system -  no issues detected.
>
> -Aleksei
>
> On 10/12/2019 06:59, Anuraag Agrawal wrote:
>
> Hi Aleksei,
>
> Thanks for running the test. I had checked the global search list, but
> realize I didn't check connection-specific suffixes which were causing the
> issue you see. While the documentation states that FirstDnsSuffix is
> populated on Vista+, amazingly it doesn't seem to be
>
>
> https://docs.microsoft.com/en-us/windows/win32/api/iptypes/ns-iptypes-ip_adapter_addresses_lh
>
>
> Chromium has run into the same issue and just doesn't use the field
>
>
> https://cs.chromium.org/chromium/src/net/dns/dns_config_service_win.cc?q=firstdnssuffix&sq=package:chromium&dr=C&l=532
>
> So I have gone ahead and switched to using the normal DnsSuffix field.
> DnsSuffix and looking up the search list in the registry should generally
> give a full list.
>
> During this testing, other issues I found are that the search list returns
> a comma-separated list. So to keep the string list parsing simple, I
> changed the delimiter from space to comma. Also, on my machine I would
> always have DNS servers like fec0:0:0:ffff:1 on some adapters. At first, I
> assumed it is ok to return these, since they are configured by the OS and
> should be valid, but I learnt that these are deprecated IPv6 site-local
> addresses and should not be used.
>
> https://en.wikipedia.org/wiki/Unique_local_address
>
> I used the same check for site-local as Inet6Address, which just sees if
> the first bytes are fec0.
>
> Thanks again - 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..b9a06461ab 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.
> @@ -50,30 +50,65 @@ public class ResolverConfigurationImpl
>
>      // 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 (!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) {
> +                    // IPv6
> +                    if (s.charAt(0) != '[') {
> +                        // Not BSD style
> +                        s = '[' + s + ']';
> +                    }
> +                    if (s.startsWith("[fec0:")) {
> +                        // Deprecated site-local address. Windows adds
> +                        // such addresses to IPv6 adapters without DNS
> +                        // configured, but these should not actually be
> +                        // used for queries.
> +                        continue;
> +                    }
> +                }
> +                if (!l.contains(s)) {
> +                    l.add(s);
> +                }
> +            }
> +        }
> +        l.trimToSize();
> +        return l;
>      }
>
>      // Load DNS configuration from OS
> @@ -81,28 +116,34 @@ 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 {
> +            // Otherwise we refresh if TIMEOUT_NANOS has passed since last
> +            // load.
>              if (lastRefresh >= 0) {
> -                long currTime = System.currentTimeMillis();
> -                if ((currTime - lastRefresh) < TIMEOUT) {
> +                long currTime = System.nanoTime();
> +                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..427d7c85eb 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
> @@ -30,6 +30,7 @@
>  #include <iprtrmib.h>
>  #include <time.h>
>  #include <assert.h>
> +#include <winsock2.h>
>  #include <iphlpapi.h>
>
>  #include "jni_util.h"
> @@ -48,8 +49,10 @@
>  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="", "def")     => "def
>   */
> @@ -60,41 +63,30 @@ 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;
>
>      /*
>       * First see if there is a global suffix list specified.
> @@ -112,122 +104,55 @@ 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);
> -                    }
> -                }
> -
> -                /*
> -                 * 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';
> +    adapter = adapters;
> +    while (adapter != NULL) {
> +        // Only load config from enabled adapters.
> +        if (adapter->OperStatus == IfOperStatusUp) {
> +            dnsServer = adapter->FirstDnsServerAddress;
> +            while (dnsServer != NULL) {
>                  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(dnsServer->Address.lpSockaddr,
> +                          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;
>  }
>
> @@ -260,7 +185,7 @@
> 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
>
> On Tue, Dec 10, 2019 at 1:29 AM Aleks Efimov <aleksej.efimov at oracle.com>
> wrote:
>
>> Hi Anuraag,
>>
>> The webrev with your latest changes can be found here:
>>     http://cr.openjdk.java.net/~aefimov/anuraaga/7006496/01
>>
>> The copyright changes looks good.
>>
>> The split by space also looks good with assumption that we will never get
>> string with two spaces between IP addresses/DNS suffixes.
>>
>> I've also performed one test on Windows machine and it shows an issue
>> with the retrieval of DNS suffixes:
>> Method to call:
>>      sun.net.dns.ResolverConfiguration.open().searchlist()
>>
>> Old implementation returns:
>>     [test.domain.com]
>>
>> With the latest patch the suffixes list (searchlist) is empty:
>>     []
>>
>> I've collected the following information on the test host that might help
>> you to fix the issue:
>>
>> The host OS: Microsoft Windows Server 2016 Standard
>>
>> Networking configuration (<---> is for masked addresses/info):
>> $ ipconfig /all
>>
>> Windows IP Configuration
>>
>>    Host Name . . . . . . . . . . . . : host-name-1
>>    Primary Dns Suffix  . . . . . . . :
>>    Node Type . . . . . . . . . . . . : Hybrid
>>    IP Routing Enabled. . . . . . . . : No
>>    WINS Proxy Enabled. . . . . . . . : No
>>    DNS Suffix Search List. . . . . . : test.domain.com
>>
>> Ethernet adapter Ethernet:
>>
>>    Connection-specific DNS Suffix  . : test.domain.com
>>    Description . . . . . . . . . . . : Broadcom NetXtreme-E Virtual
>> Function
>>    Physical Address. . . . . . . . . : <------------>
>>    DHCP Enabled. . . . . . . . . . . : Yes
>>    Autoconfiguration Enabled . . . . : Yes
>>    Link-local IPv6 Address . . . . . : <------------>
>>    IPv4 Address. . . . . . . . . . . : <------------>
>>    Subnet Mask . . . . . . . . . . . : <------------>
>>    Lease Obtained. . . . . . . . . . : <------------>
>>    Lease Expires . . . . . . . . . . : <------------>
>>    Default Gateway . . . . . . . . . : <------------>
>>    DHCP Server . . . . . . . . . . . : <------------>
>>    DHCPv6 Client DUID. . . . . . . . : <------------>
>>    DNS Servers . . . . . . . . . . . : <------------>
>>                                        <------------>
>>    NetBIOS over Tcpip. . . . . . . . : Disabled
>>
>> Tunnel adapter isatap.test.domain.com:
>>
>>    Media State . . . . . . . . . . . : Media disconnected
>>    Connection-specific DNS Suffix  . : test.domain.com
>>    Description . . . . . . . . . . . : Microsoft ISATAP Adapter #3
>>    Physical Address. . . . . . . . . : <------------>
>>    DHCP Enabled. . . . . . . . . . . : No
>>    Autoconfiguration Enabled . . . . : Yes
>>
>>
>> - Aleksei
>>
>>
>> On 07/12/2019 09:44, Anuraag Agrawal wrote:
>>
>> Hi all,
>>
>> Thanks for the reviews. I've fixed the formatting errors, and I hope I
>> fixed the copyright issue. I couldn't find documentation on the format of
>> the copyright header, but assume the second number is the year of
>> modification to update. I found ResolverConfigurationImpl.c to have an old
>> one and updated it to 2019.
>>
>> I also found the note in the docs that StringTokenizer is deprecated and
>> shouldn't be used - I agree it's a good time to replace it. As we have a
>> simple split by space, I have gone ahead and used the simpler String.split
>> instead of regex, hope that makes sense. While in many code I'd be a little
>> concerned with the array allocation, this is only run very infrequently so
>> I think it should be ok.
>>
>> Inline diff 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..47065e805e 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.
>> @@ -50,30 +50,55 @@ public class ResolverConfigurationImpl
>>
>>      // 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 space
>> +    // 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 space.
>> +        String[] tokens = str.split(" ");
>> +        ArrayList<String> l = new ArrayList<>(tokens.length);
>> +        for (String s : tokens) {
>> +            if (!l.contains(s)) {
>> +                l.add(s);
>>              }
>>          }
>> -        return ll;
>> +        l.trimToSize();
>> +        return l;
>> +    }
>> +
>> +    // Parse string that consists of token delimited by space
>> +    // 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 space
>> +        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 (!l.contains(s)) {
>> +                    l.add(s);
>> +                }
>> +            }
>> +        }
>> +        l.trimToSize();
>> +        return l;
>>      }
>>
>>      // Load DNS configuration from OS
>> @@ -81,28 +106,34 @@ 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 {
>> +            // Otherwise we refresh if TIMEOUT_NANOS has passed since
>> last
>> +            // load.
>>              if (lastRefresh >= 0) {
>> -                long currTime = System.currentTimeMillis();
>> -                if ((currTime - lastRefresh) < TIMEOUT) {
>> +                long currTime = System.nanoTime();
>> +                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 space-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..85a7935314 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
>> @@ -30,6 +30,7 @@
>>  #include <iprtrmib.h>
>>  #include <time.h>
>>  #include <assert.h>
>> +#include <winsock2.h>
>>  #include <iphlpapi.h>
>>
>>  #include "jni_util.h"
>> @@ -48,6 +49,8 @@
>>  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"
>> @@ -72,29 +75,19 @@ void strappend(char *s1, char *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;
>> +    SOCKADDR *address;
>> +    IP_ADAPTER_DNS_SUFFIX *suffix;
>> +    DWORD ret, flags;
>>      DWORD dwLen;
>>      ULONG ulType;
>>      char result[MAX_STR_LEN];
>>      HANDLE hKey;
>> -    int gotSearchList = 0;
>>
>>      /*
>>       * First see if there is a global suffix list specified.
>> @@ -112,122 +105,58 @@ 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);
>> -                    }
>> -                }
>> -
>> -                /*
>> -                 * 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';
>> +    adapter = adapters;
>> +    while (adapter != NULL) {
>> +        // Only load config from enabled adapters.
>> +        if (adapter->OperStatus == IfOperStatusUp) {
>> +            dnsServer = adapter->FirstDnsServerAddress;
>> +            while (dnsServer != NULL) {
>> +                address = dnsServer->Address.lpSockaddr;
>>                  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(dnsServer->Address.lpSockaddr,
>> +                          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->FirstDnsSuffix;
>> +            while (suffix != NULL) {
>> +                ret = WideCharToMultiByte(CP_UTF8, 0, suffix->String, -1,
>> +                    result, sizeof(result), NULL, NULL);
>> +                if (ret != 0) {
>> +                    strappend(sl, result);
>> +                }
>> +
>> +                suffix = suffix->Next;
>> +            }
>>          }
>> -    }
>>
>> -    /*
>> -     * Free the adpater structure
>> -     */
>> -    if (adapterP) {
>> -        free(adapterP);
>> +        adapter = adapter->Next;
>>      }
>>
>> +    free(adapters);
>> +
>>      return STS_SL_FOUND & STS_NS_FOUND;
>>  }
>>
>> @@ -260,7 +189,7 @@
>> 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
>>
>> On Sat, Dec 7, 2019 at 12:41 AM Alan Bateman <Alan.Bateman at oracle.com>
>> wrote:
>>
>>> On 06/12/2019 15:34, Aleks Efimov wrote:
>>> > :
>>> >
>>> > I've created webrev with your latest changes - it could be convenient
>>> > for other reviewers:
>>> > http://cr.openjdk.java.net/~aefimov/anuraaga/7006496/00
>>> >
>>> > I will happily sponsor this change once it gets necessary approvals
>>> This could be split into two issues but since the code using
>>> StringTokenizer is changing significantly then we should replace it with
>>> regex while we there.
>>>
>>> -Alan
>>>
>>
>>
>
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