Little class for asynchronous DNS Blocklist lookups

src/cc/co/evenprime/bukkit/nocheat/checks/chat/dnsbl/DnsBlocklistChecker.java

@@ -0,0 +1,94 @@
+package cc.co.evenprime.bukkit.nocheat.checks.chat.dnsbl;
+
+import java.util.Hashtable;
+import java.util.LinkedList;
+import java.util.List;
+import javax.naming.Context;
+import javax.naming.NameNotFoundException;
+import javax.naming.NamingException;
+import javax.naming.directory.DirContext;
+import javax.naming.directory.InitialDirContext;
+import org.bukkit.Bukkit;
+import org.bukkit.entity.Player;
+import cc.co.evenprime.bukkit.nocheat.NoCheat;
+
+public class DnsBlocklistChecker {
+
+    private static final String[] attributes = {"A"};
+
+    private final NoCheat         plugin;
+    private final DirContext      context;
+    private final String[]        blocklistProviders;
+
+    public DnsBlocklistChecker(NoCheat plugin, int limit, String... providers) throws NamingException {
+
+        Hashtable<Object, String> environment = new Hashtable<Object, String>();
+        environment.put(Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.dns.DnsContextFactory");
+
+        context = new InitialDirContext(environment);
+        this.plugin = plugin;
+        this.blocklistProviders = providers;
+    }
+
+    public void check(final Player player, final String ip) {
+
+        // Invert IP
+        String[] parts = ip.split("\\.");
+        StringBuilder buffer = new StringBuilder();
+
+        for(int i = parts.length - 1; i >= 0; i--) {
+            buffer.append(parts[i]).append('.');
+        }
+
+        final String invertedIp = buffer.toString();
+
+        Runnable r = new CheckRunnable(invertedIp, player);
+
+        // We have time, therefore let the bukkit scheduler do this
+        Bukkit.getScheduler().scheduleAsyncDelayedTask(plugin, r);
+    }
+
+    public void finished(final Player player, final List<String> failures) {
+
+    }
+
+    /**
+     * Runnable that does the actual dns checking
+     *
+     */
+    public class CheckRunnable implements Runnable {
+
+        private final String       invertedIp;
+        private final Player       player;
+        private final List<String> failures = new LinkedList<String>();
+
+        public CheckRunnable(String invertedIp, Player player) {
+            this.invertedIp = invertedIp;
+            this.player = player;
+        }
+
+        @Override
+        public void run() {
+            for(String provider : blocklistProviders) {
+                String lookupHost = invertedIp + provider;
+                try {
+                    context.getAttributes(lookupHost, attributes);
+
+                    // If we got a response, the address is listed
+                    // so the player failed that one.
+                    failures.add(provider);
+
+                } catch(NameNotFoundException e) {
+                    // great, the player is not on the blacklist
+                    // e.printStackTrace();
+                } catch(NamingException e) {
+                    // not so great, but I don't care atm
+                    // e.printStackTrace();
+                }
+            }
+
+            // We are done, let's work with the results
+            finished(player, failures);
+        }
+    }
+}