Extend NetUtils for network range scanning

bundles/org.openhab.core/src/main/java/org/openhab/core/net/NetUtil.java

@@ -34,6 +34,7 @@
 import java.util.concurrent.ScheduledFuture;
 import java.util.concurrent.TimeUnit;
 import java.util.regex.Pattern;
+import java.util.stream.Collectors;
 
 import org.eclipse.jdt.annotation.NonNullByDefault;
 import org.eclipse.jdt.annotation.Nullable;
@@ -55,6 +56,7 @@
  * @author Stefan Triller - Converted to OSGi service with primary ipv4 conf
  * @author Gary Tse - Network address change listener
  * @author Tim Roberts - Added primary address change to network address change listener
+ * @author Leo Siepel - Added methods to improve support for network scanning
  */
 @Component(configurationPid = "org.openhab.network", property = { "service.pid=org.openhab.network",
         "service.config.description.uri=system:network", "service.config.label=Network Settings",
@@ -595,4 +597,116 @@ private boolean getConfigParameter(Map<String, Object> parameters, String parame
             return defaultValue;
         }
     }
+
+    /**
+     * For all network interfaces (except loopback) all Ipv4 addresses are returned.
+     * This list can for example, be used to scan the network for available devices.
+     * 
+     * @return A full list of IP {@link InetAddress} (except network and broadcast)
+     */
+    public static List<InetAddress> getFullRangeOfAddressesToScan() {
+        List<InetAddress> addressesToScan = List.of();
+        List<CidrAddress> ipV4InterfaceAddresses = NetUtil.getAllInterfaceAddresses().stream()
+                .filter(a -> a.getAddress() instanceof Inet4Address).collect(Collectors.toList());
+
+        for (CidrAddress i : ipV4InterfaceAddresses) {
+            addressesToScan.addAll(getAddressesRangeByCidrAddress(i, i.getPrefix()));
+        }
+        return addressesToScan;
+    }
+
+    /**
+     * For the given {@link CidrAddress} all Ipv4 addresses are returned.
+     * This list can for example, be used to scan the network for available devices.
+     * 
+     * @param iFaceAddress The {@link CidrAddress} of the network interface
+     * @param maxPrefixLength Control the prefix length of the network (e.g. 24 for class C)
+     * @return A full list of IP {@link InetAddress} (except network and broadcast)
+     */
+    public static List<InetAddress> getAddressesRangeByCidrAddress(CidrAddress iFaceAddress, int maxPrefixLength) {
+        if (!(iFaceAddress.getAddress() instanceof Inet4Address) || iFaceAddress.getPrefix() < maxPrefixLength) {
+            return List.of();
+        }
+
+        List<byte[]> addresses = getAddressesInSubnet(iFaceAddress.getAddress().getAddress(), iFaceAddress.getPrefix(),
+                true);
+        if (addresses.size() > 2) {
+            addresses.remove(0); // remove network address
+            addresses.remove(addresses.size() - 1); // remove broadcast address
+        }
+
+        return addresses.stream().map(m -> {
+            try {
+                return InetAddress.getByAddress(m);
+            } catch (UnknownHostException e) {
+                return null;
+            }
+        }).filter(f -> f != null).sorted((a, b) -> {
+            byte[] aOct = a.getAddress();
+            byte[] bOct = b.getAddress();
+            int r = 0;
+            for (int i = 0; i < aOct.length && i < bOct.length; i++) {
+                r = Integer.compare(aOct[i] & 0xff, bOct[i] & 0xff);
+                if (r != 0) {
+                    return r;
+                }
+            }
+            return r;
+        }).collect(Collectors.toList());
+    }
+
+    /**
+     * Recursively calculate each IP address within a subnet
+     * 
+     * @param address IP address in byte array form (i.e. 127.0.0.1 = 01111111 00000000 00000000 00000001)
+     * @param maskLength Network mask length (i.e. the number after the forward-slash, '/', in CIDR notation)
+     * @param scrub Whether or not to scrub the unmasked bits of the address
+     * @return All possible IP addresses
+     * 
+     * @author: https://gist.github.com/ssttevee/b0e2b431f4b23d289537
+     */
+    private static List<byte[]> getAddressesInSubnet(byte[] address, int maskLength, boolean scrub) {
+        if (scrub) {
+            scrubAddress(address, maskLength);
+        }
+
+        if (maskLength >= address.length * 8) {
+            return Collections.singletonList(address);
+        }
+
+        List<byte[]> addresses = new ArrayList<byte[]>();
+
+        int set = maskLength / 8;
+        int pos = maskLength % 8;
+
+        byte[] addressLeft = address.clone();
+        addressLeft[set] |= 1 << pos;
+        addresses.addAll(getAddressesInSubnet(addressLeft, maskLength + 1, false));
+
+        byte[] addressRight = address.clone();
+        addressRight[set] &= ~(1 << pos);
+        addresses.addAll(getAddressesInSubnet(addressRight, maskLength + 1, false));
+
+        return addresses;
+    }
+
+    /**
+     * Set the unmasked bits of the IP address to 0
+     * 
+     * @param address IP address in byte array form (i.e. 127.0.0.1 = 01111111 00000000 00000000 00000001)
+     * @param maskLength Network mask length (i.e. the number after the forward-slash, '/', in CIDR notation)
+     * @return The scrubbed IP address
+     * 
+     * @author: https://gist.github.com/ssttevee/b0e2b431f4b23d289537
+     */
+    private static byte[] scrubAddress(byte[] address, int maskLength) {
+        for (int i = 0; i < address.length * 8; i++) {
+            if (i < maskLength)
+                continue;
+
+            address[i / 8] &= ~(1 << (i % 8));
+        }
+
+        return address;
+    }
 }

bundles/org.openhab.core/src/test/java/org/openhab/core/net/NetUtilTest.java

@@ -14,6 +14,11 @@
 
 import static org.hamcrest.CoreMatchers.is;
 import static org.hamcrest.MatcherAssert.assertThat;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.net.InetAddress;
+import java.net.UnknownHostException;
+import java.util.List;
 
 import org.eclipse.jdt.annotation.NonNullByDefault;
 import org.junit.jupiter.api.Test;
@@ -116,4 +121,35 @@ public void testBroadcastAddress() {
             assertThat(iae.getMessage(), is("IP 'SOME_TEXT' is not a valid IPv4 address"));
         }
     }
+
+    @Test
+    public void checkValidRangeCount() throws UnknownHostException {
+        InetAddress testableAddress = InetAddress.getByName("192.168.1.0");
+        List<InetAddress> addresses = NetUtil
+                .getAddressesRangeByCidrAddress(new CidrAddress(testableAddress, (short) 24), 24);
+
+        assertEquals(254, addresses.size());
+        assertEquals("192.168.1.1", addresses.get(0).getHostAddress());
+        assertEquals("192.168.1.254", addresses.get(253).getHostAddress());
+    }
+
+    @Test
+    public void checkValidLargeRangeCount() throws UnknownHostException {
+        InetAddress testableAddress = InetAddress.getByName("127.0.0.0");
+        List<InetAddress> addresses = NetUtil
+                .getAddressesRangeByCidrAddress(new CidrAddress(testableAddress, (short) 16), 16);
+
+        assertEquals(65534, addresses.size());
+        assertEquals("127.0.0.1", addresses.get(0).getHostAddress());
+        assertEquals("127.0.255.254", addresses.get(65533).getHostAddress());
+    }
+
+    @Test
+    public void checkInvalidPrefixLength() throws UnknownHostException {
+        InetAddress testableAddress = InetAddress.getByName("192.168.1.0");
+        List<InetAddress> addresses = NetUtil
+                .getAddressesRangeByCidrAddress(new CidrAddress(testableAddress, (short) 16), 24);
+
+        assertEquals(0, addresses.size());
+    }
 }