Improve rendering of remote Solr admin URLs

- properly handle IPv6 loopback address replacement
 - replace loopback address or host only when accessing peer remotely
 - replace loopback part with the peer hostname as requested rather than
with its seed public IP as this works better for Intranet mode and when
peer is behind a reverse proxy.

htroot/IndexFederated_p.java

@@ -189,7 +189,18 @@ public class IndexFederated_p {
             prop.put("table", 1);
             final SolrConnector solr = sb.index.fulltext().getDefaultRemoteSolrConnector();
             final long[] size = new long[]{((RemoteSolrConnector) solr).getSize()};
-            final ArrayList<String> urls = ((ShardInstance) ((RemoteSolrConnector) solr).getInstance()).getAdminInterfaces();
+            
+            final boolean toExternalAddress = !header.accessFromLocalhost();
+            String externalHost = null;
+            if(toExternalAddress) {
+            	/* The request does not come from the same computer than this peer : we get the external address used to reach it from the request headers, and we will use  
+            	 * it if some remote solr instance(s) URLs are configured with loopback address alias (such as 'localhost', '127.0.0.1', '[::1]')
+            	 * to render the externally reachable Solr instance(s) admin URLs */
+            	externalHost = header.getServerName();
+            }
+            
+			final ArrayList<String> urls = ((ShardInstance) ((RemoteSolrConnector) solr).getInstance())
+					.getAdminInterfaces(toExternalAddress, externalHost);
             boolean dark = false;
             for (int i = 0; i < size.length; i++) {
                 prop.put("table_list_" + i + "_dark", dark ? 1 : 0); dark = !dark;

source/net/yacy/cora/document/id/MultiProtocolURL.java

@@ -482,6 +482,33 @@ public class MultiProtocolURL implements Serializable, Comparable<MultiProtocolU
         identSearchpart();
         escape();
     }
+    
+    /**
+     * @param host the new host to apply to the copy
+     * @return an exact copy of this URL instance but with a new host. The original instance remains unchanged.
+     * @throws IllegalArgumentException when the host parameter is null or empty.
+     */
+    public MultiProtocolURL ofNewHost(final String host) throws IllegalArgumentException {
+    	if(host == null || host.trim().isEmpty()) {
+    		throw new IllegalArgumentException("Host parameter must not be null");
+    	}
+    	MultiProtocolURL copy = new MultiProtocolURL(this);
+    	
+    	if (host.indexOf(':') >= 0 && host.charAt(0) != '[') {
+    		copy.host = '[' + host + ']'; // IPv6 host must be enclosed in square brackets
+    	} else {
+        	copy.host = host;	
+    	}
+    	
+        if (!Punycode.isBasic(this.host)) try {
+            this.host = toPunycode(this.host);
+        } catch (final PunycodeException e) {
+        	ConcurrentLog.logException(e);
+        }
+    	
+    	return copy;
+    	
+    }
 
     /**
      * Resolve '..' segments in the path.

source/net/yacy/cora/federate/solr/instance/RemoteInstance.java

@@ -21,7 +21,6 @@
 package net.yacy.cora.federate.solr.instance;
 
 import java.io.IOException;
-import java.net.InetAddress;
 import java.net.MalformedURLException;
 import java.util.ArrayList;
 import java.util.Collection;
@@ -58,7 +57,6 @@ import org.apache.solr.client.solrj.SolrClient;
 import org.apache.solr.client.solrj.impl.ConcurrentUpdateSolrClient;
 
 import net.yacy.cora.document.id.MultiProtocolURL;
-import net.yacy.cora.protocol.Domains;
 import net.yacy.cora.protocol.HeaderFramework;
 import net.yacy.cora.util.CommonPattern;
 import net.yacy.cora.util.ConcurrentLog;
@@ -284,19 +282,35 @@ public class RemoteInstance implements SolrInstance {
         return o instanceof RemoteInstance && ((RemoteInstance) o).solrurl.equals(this.solrurl);
     }
 
-    /**
-     * @return the administration URL of the remote Solr instance
-     */
-    public String getAdminInterface() {
-        final InetAddress localhostExternAddress = Domains.myPublicLocalIP();
-        final String localhostExtern = localhostExternAddress == null ? "127.0.0.1" : localhostExternAddress.getHostAddress();
-        String u = this.solrurl;
-        int p = u.indexOf("localhost",0);
-        if (p < 0) p = u.indexOf("127.0.0.1",0);
-        if (p < 0) p = u.indexOf("0:0:0:0:0:0:0:1",0);
-        if (p >= 0) u = u.substring(0, p) + localhostExtern + u.substring(p + 9);
-        return u;
-    }
+	/**
+	 * @param toExternalAddress
+	 *            when true, try to replace the eventual loopback host part of the
+	 *            Solr URL with the external host name of the hosting machine
+	 * @param externalHost
+	 *            the eventual external host name or address to use when
+	 *            toExternalAddress is true
+	 * @return the administration URL of the remote Solr instance
+	 */
+	public String getAdminInterface(final boolean toExternalAddress, final String externalHost) {
+		String u = this.solrurl;
+		if (toExternalAddress && externalHost != null && !externalHost.trim().isEmpty()) {
+			try {
+				MultiProtocolURL url = new MultiProtocolURL(u);
+
+				if(url.isLocal()) {
+					url = url.ofNewHost(externalHost);
+					u = url.toString();
+				}
+
+			} catch (final MalformedURLException ignored) {
+				/*
+				 * This should not happen as the solrurl attribute has already been parsed in
+				 * the constructor
+				 */
+			}
+		}
+		return u;
+	}
 
     @Override
     public String getDefaultCoreName() {

source/net/yacy/cora/federate/solr/instance/ShardInstance.java

@@ -81,9 +81,18 @@ public class ShardInstance implements SolrInstance {
         for (RemoteInstance instance: instances) instance.close();
     }
     
-    public ArrayList<String> getAdminInterfaces() {
+	/**
+	 * @param toExternalAddress
+	 *            when true, try to replace the eventual loopback host part of the
+	 *            Solr instances URLs with the external host name of the hosting machine
+	 * @param externalHost
+	 *            the eventual external host name or address to use when
+	 *            toExternalAddress is true
+	 * @return the administration URLs of the Solr instances
+	 */
+    public ArrayList<String> getAdminInterfaces(final boolean toExternalAddress, final String externalHost) {
         ArrayList<String> a = new ArrayList<String>();
-        for (RemoteInstance i: this.instances) a.add(i.getAdminInterface());
+        for (RemoteInstance i: this.instances) a.add(i.getAdminInterface(toExternalAddress, externalHost));
         return a;
     }
 }