CLI help (#20)

* CLI help

---------

Co-authored-by: Tilmann Zäschke <[email protected]>

Author: tzaeschke

CHANGELOG.md

@@ -9,6 +9,11 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 -- Nothing yet
 
+### Added
+
+- Added command line `--help` and several options to multi-ping.
+  [#20](https://github.com/netsec-ethz/scion-java-multiping/pull/20)
+
 ## [0.5.0] - 2025-09-09
 
 ### Added

README.md

@@ -23,6 +23,15 @@ java -jar scion-multiping-0.5.0-executable.jar [tool-command]
 Some tools require configuration files, see below in the tool description sections.   
 See also the troubleshooting section below in case of issues.
 
+# Help
+
+To get command line help, the tool can be executed with:
+
+```
+java -jar scion-multiping-0.5.0-executable.jar --help
+```
+
+
 # Download Assignments
 
 The tool
@@ -34,7 +43,9 @@ Note: the `isd-as-assignments.csv` output file can be directly used as input fil
 
 The tool
 parses [Anapayas ISD/AS assignment website](https://docs.anapaya.net/en/latest/resources/isd-as-assignments/),
-identifies the shortest path to each AS and sends a traceroute to each AS.
+identifies the shortest or fastest path to each AS and sends a traceroute to each AS.
+By default is will use the fastest path (determined by a traceroute over all paths), but it can be
+configured to use the shortest path (`--shortest`).
 It reports the number of paths to each AS as well as the shortest path with latency, remote IP, hop
 count and remote IP.
 

src/main/java/org/scion/multiping/Main.java

@@ -22,30 +22,35 @@
 public class Main {
 
   public static void main(String[] args) throws IOException {
-    if (args.length != 1) {
-      printUsage();
-      System.exit(1);
-    }
+    checkArgs(args, 1, Integer.MAX_VALUE);
     String mode = args[0].toLowerCase(Locale.ROOT);
     String[] newArgs = Arrays.copyOfRange(args, 1, args.length);
     switch (mode) {
       case "download-assignments":
         {
+          checkArgs(args, 1, 1);
           DownloadAssignments.main(newArgs);
           return;
         }
+      case "help":
+        {
+          printHelp(args.length == 1 ? "" : args[1]);
+          return;
+        }
       case "ping-all":
         {
           PingAll.main(newArgs);
           return;
         }
       case "ping-repeat":
         {
+          checkArgs(args, 1, 1);
           PingRepeat.main(newArgs);
           return;
         }
       case "ping-responder":
         {
+          checkArgs(args, 1, 1);
           PingResponder.main(newArgs);
           return;
         }
@@ -55,6 +60,33 @@ public static void main(String[] args) throws IOException {
     }
   }
 
+  private static void checkArgs(String[] args, int minArgs, int maxArgs) {
+    if (args.length < minArgs || args.length > maxArgs) {
+      Util.println("Invalid number of arguments.");
+      printUsage();
+      System.exit(1);
+    }
+  }
+
+  private static void printHelp(String mode) {
+    switch (mode) {
+      case "download-assignments":
+        printUsageDownloadAssignments();
+        return;
+      case "ping-all":
+        printUsagePingAll();
+        return;
+      case "ping-repeat":
+        printUsagePingRepeat();
+        return;
+      case "ping-responder":
+        printUsagePingResponder();
+        return;
+      default:
+        printUsage();
+    }
+  }
+
   private static void printUsage() {
     Util.println("Usage: scion-multiping [MODE]");
     Util.println("where MODE is one of: ");
@@ -65,6 +97,53 @@ private static void printUsage() {
         "    - `ping-repeat` for repeatedly probing (traceroute) multiple paths to multiple ASes.");
     Util.println(
         "    - `ping-responder` for starting a server that responds to incoming echo requests.");
+    Util.println("    - `help [MODE]` for getting more help for a given mode.");
+    Util.println("");
+  }
+
+  private static void printUsageDownloadAssignments() {
+    Util.println("Usage: scion-multiping download-assignments");
+    Util.println();
+    Util.println(
+        "  This tool downloads a list of known ISD/AS assignments and saves it to a file.");
+    Util.println("  The output file is called `isd-as-assignments.csv`.");
+    Util.println("");
+  }
+
+  static void printUsagePingAll() {
+    Util.println(
+        "Usage: ping-all [--help] [--fastest|--shortest|--shortest_echo|--fastest_sync] [--port <port>] [--shim]");
+    Util.println("  --help              Show this help message.");
+    Util.println("  --fastest           Use fastest path with SCMP traceroute (default).");
+    Util.println(
+        "                      The fastest path is determined by running a single traceroute on all path.");
+    // Util.println("  --fastest_sync      Use fastest path with SCMP traceroute (synchronous)");
+    Util.println("  --shortest          Use shortest path (fewest hops) with SCMP traceroute.");
+    // Util.println("  --shortest_echo     Use shortest path with SCMP echo");
+    Util.println(
+        "  --port <port>       Use specified local port (default " + PingAll.localPort + ").");
+    Util.println("  --shim              Start with SHIM enabled (default disabled).");
+    Util.println("");
+  }
+
+  private static void printUsagePingRepeat() {
+    Util.println("Usage: scion-multiping ping-repeat");
+    Util.println();
+    Util.println(
+        "  This tool is used for repeatedly probing (traceroute) multiple paths to multiple ASes.");
+    Util.println("  The destination ASes are read from a file `isd-as-assignments.csv`.");
+    Util.println("  Other configuration options can be defined in `ping-repeat-config.json`.");
+    Util.println("  Results are written to a CSV file `ping-results.csv`.");
+    Util.println("  See README.md for more information.");
+    Util.println("");
+  }
+
+  private static void printUsagePingResponder() {
+    Util.println("Usage: scion-multiping ping-responder");
+    Util.println();
+    Util.println("  This command starts a server that responds to incoming echo requests.");
+    Util.println("  It takes a configuration file `ping-responder-config.json` as input.");
+    Util.println("  See README.md for more information.");
     Util.println("");
   }
 }

src/main/java/org/scion/multiping/PingAll.java

@@ -52,8 +52,8 @@ public class PingAll {
   private static final boolean SHOW_ONLY_ICMP = false;
   private static final Config config = new Config();
 
-  private static final int LOCAL_PORT = 30041;
-  private static final boolean STOP_SHIM = true;
+  static int localPort = 30041;
+  private static boolean startShim = false;
 
   static {
     config.tryICMP = false;
@@ -88,21 +88,71 @@ enum Policy {
     this.service = service;
   }
 
-  public static void main(String[] args) throws IOException {
+  public static void main(String[] argsArray) throws IOException {
     PRINT = true;
-    // System.setProperty(Constants.PROPERTY_DNS_SEARCH_DOMAINS, "ethz.ch.");
-    System.setProperty(Constants.PROPERTY_SHIM, STOP_SHIM ? "false" : "true"); // disable SHIM
+
+    Policy policy = parseArgs(argsArray);
+
+    System.setProperty(Constants.PROPERTY_SHIM, startShim ? "true" : "false"); // disable SHIM
 
     println("Settings:");
-    println("  Path policy = " + DEFAULT_POLICY);
+    println("  Path policy = " + policy);
     println("  ICMP=" + config.tryICMP);
     println("  printOnlyICMP=" + SHOW_ONLY_ICMP);
 
-    PingAll pingAll = new PingAll(DEFAULT_POLICY, ScionProvider.defaultProvider(LOCAL_PORT));
+    PingAll pingAll = new PingAll(policy, ScionProvider.defaultProvider(localPort));
     pingAll.run();
     pingAll.summary.prettyPrint();
   }
 
+  private static Policy parseArgs(String[] argsArray) {
+    List<String> args = new ArrayList<>(Arrays.asList(argsArray));
+    Policy policy = DEFAULT_POLICY;
+    while (!args.isEmpty()) {
+      switch (args.get(0)) {
+        case "--fastest":
+          policy = Policy.FASTEST_TR_ASYNC;
+          break;
+        case "--shortest":
+          policy = Policy.SHORTEST_TR;
+          break;
+        case "--shortest_echo":
+          policy = Policy.SHORTEST_ECHO;
+          break;
+        case "--fastest_sync":
+          policy = Policy.FASTEST_TR;
+          break;
+        case "--help":
+          Main.printUsagePingAll();
+          System.exit(0);
+        case "--shim":
+          startShim = true;
+          break;
+        case "--port":
+          if (args.size() < 2) {
+            Util.println("Error: --port requires a port number");
+            Main.printUsagePingAll();
+            System.exit(1);
+          }
+          try {
+            localPort = Integer.parseInt(args.get(1));
+          } catch (NumberFormatException e) {
+            Util.println("Error: Invalid port number: " + args.get(1));
+            Main.printUsagePingAll();
+            System.exit(1);
+          }
+          args.remove(1);
+          break;
+        default:
+          Util.println("Unknown option: " + args.get(0));
+          Main.printUsagePingAll();
+          System.exit(1);
+      }
+      args.remove(0);
+    }
+    return policy;
+  }
+
   ResultSummary run() throws IOException {
     List<ParseAssignments.HostEntry> allASes = service.getIsdAsEntries();
     // remove entry for local AS