Avoid InetAddress.getHostName() (#64)

* InetAddress.getHostName()

---------

Co-authored-by: Tilmann Zäschke <tilmann.zaeschke@inf.ethz.ch>

CHANGELOG.md

@@ -9,12 +9,13 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ### Fixed
 - Fixed spurious CI failures, esp. Windows. [#61](https://github.com/tzaeschke/phtree-cpp/pull/61) 
 - Fix SCM references in pom file + clean up. [#60](https://github.com/tzaeschke/phtree-cpp/pull/60) 
-- DNS lookup caused by `InetAddress.getByName()`. [#63](https://github.com/tzaeschke/phtree-cpp/pull/63)
+- DNS lookup caused by `InetAddress.getByName()`. [#63](https://github.com/scionproto-contrib/jpan/pull/63)
+- DNS lookup caused by `InetAddress.getHostName()`. [#64](https://github.com/scionproto-contrib/jpan/pull/64)
 
 ## [0.1.0] - 2024-04-29
 
 ### Added
-- Code coverage. [#11](https://github.com/tzaeschke/phtree-cpp/pull/11)
+- Code coverage. [#11](https://github.com/netsec-ethz/scion-java-client/pull/11)
 - Global JUnit callback for initial setup. THis allows setting global properties before centrally
   before running any tests.
   [#38](https://github.com/netsec-ethz/scion-java-client/pull/38)

src/main/java/org/scion/jpan/ScionService.java

@@ -298,7 +298,8 @@ List<Daemon.Path> getPathListDaemon(long srcIsdAs, long dstIsdAs) {
    * @throws IOException if an errors occurs while querying paths.
    */
   public List<RequestPath> getPaths(InetSocketAddress dstAddress) throws IOException {
-    ScionAddress sa = getScionAddress(dstAddress.getHostName());
+    // Use getHostString() to avoid DNS reverse lookup.
+    ScionAddress sa = getScionAddress(dstAddress.getHostString());
     return getPaths(sa.getIsdAs(), sa.getInetAddress(), dstAddress.getPort());
   }
 

src/main/java/org/scion/jpan/internal/HostsFileParser.java

@@ -33,30 +33,25 @@ public class HostsFileParser {
 
   private static final Logger LOG = LoggerFactory.getLogger(HostsFileParser.class);
   private static final String PATH_LINUX = "/etc/scion/hosts";
-  private final String HOSTS_FILES =
+  private final String propHostsFiles =
       ScionUtil.getPropertyOrEnv(Constants.PROPERTY_HOSTS_FILES, Constants.ENV_HOSTS_FILES);
 
+  // We use hostName/addressString as key.
   private final Map<String, HostEntry> entries = new HashMap<>();
 
   public static class HostEntry {
     private final long isdAs;
-    private final String hostName;
     private final InetAddress address;
 
-    HostEntry(long isdAs, InetAddress address, String hostName) {
+    HostEntry(long isdAs, InetAddress address) {
       this.isdAs = isdAs;
-      this.hostName = hostName;
       this.address = address;
     }
 
     public long getIsdAs() {
       return isdAs;
     }
 
-    public String getHostName() {
-      return hostName;
-    }
-
     public InetAddress getAddress() {
       return address;
     }
@@ -69,8 +64,8 @@ public HostsFileParser() {
   private void init() {
     String hostsFiles;
     String os = System.getProperty("os.name");
-    if (HOSTS_FILES != null && !HOSTS_FILES.isEmpty()) {
-      hostsFiles = HOSTS_FILES;
+    if (propHostsFiles != null && !propHostsFiles.isEmpty()) {
+      hostsFiles = propHostsFiles;
     } else if ("Linux".equals(os)) {
       hostsFiles = PATH_LINUX;
     } else {
@@ -81,18 +76,18 @@ private void init() {
       Path path = Paths.get(file);
       // On Windows /etc/hosts is reported as ¨: not a file"
       if (!Files.exists(path) || !Files.isRegularFile(path)) {
-        LOG.info(PATH_LINUX + " not found.");
+        LOG.info("{} not found.", path);
         return;
       }
       try (Stream<String> lines = Files.lines(path)) {
-        lines.forEach(this::parseLine);
+        lines.forEach((line) -> parseLine(line, path));
       } catch (IOException e) {
         throw new ScionRuntimeException(e);
       }
     }
   }
 
-  private void parseLine(String line) {
+  private void parseLine(String line, Path path) {
     try {
       String s = line.trim();
       if (s.isEmpty() || s.startsWith("#")) {
@@ -109,27 +104,23 @@ private void parseLine(String line) {
       check(!addrStr.isEmpty(), "Address is empty");
 
       byte[] addrBytes = IPHelper.toByteArray(addrStr);
-
-      // TODO
-      // 4) Singleton ?!?!?!?!!!
-
+      check(addrBytes != null, "Address string is not a legal address");
       for (int i = 1; i < lineParts.length; i++) {
         String hostName = lineParts[i];
         if (hostName.startsWith("#")) {
           // ignore comments
           break;
         }
         InetAddress inetAddr = InetAddress.getByAddress(hostName, addrBytes);
-        entries.put(hostName, new HostEntry(isdIa, inetAddr, hostName));
+        entries.put(hostName, new HostEntry(isdIa, inetAddr));
       }
-      // The following may differ, e.g. for IPv6
-      // TODO find a better way, i.e. use InetAddress instances as keys?
       InetAddress inetAddr = InetAddress.getByAddress(addrStr, addrBytes);
-      entries.put(inetAddr.getHostName(), new HostEntry(isdIa, inetAddr, inetAddr.getHostName()));
-      entries.put(
-          inetAddr.getHostAddress(), new HostEntry(isdIa, inetAddr, inetAddr.getHostAddress()));
+      // Use original address string as key
+      entries.put(addrStr, new HostEntry(isdIa, inetAddr));
+      // Use "normalized" address string as key (these may differ fo IPv6)
+      entries.put(inetAddr.getHostAddress(), new HostEntry(isdIa, inetAddr));
     } catch (IndexOutOfBoundsException | IllegalArgumentException | UnknownHostException e) {
-      LOG.info("ERROR {} while parsing file {}: {}", e.getMessage(), PATH_LINUX, line);
+      LOG.info("ERROR parsing file {}: error=\"{}\" line=\"{}\"", path, e.getMessage(), line);
     }
   }
 

src/test/java/org/scion/jpan/testutil/JUnitSetUp.java

@@ -69,6 +69,7 @@ public void close() {
 
   @Override
   public void beforeEach(ExtensionContext context) {
+    System.setProperty(Constants.PROPERTY_HOSTS_FILES, "....some-invalid-file");
     Scion.closeDefault();
     if (failed) {
       System.exit(1);