[PATCH] 7006496: Use modern Windows API to retrieve OS DNS servers
Anuraag Agrawal
anuraaga at gmail.com
Sat Dec 7 09:44:13 UTC 2019
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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