get_interfaces.java

/*
Example code for the addr of Run called interfaces.
This code is not actually used directly by this repo.

Adapted from:

https://github.com/tailscale/tailscale-android/blob/51fc2e7030191d08b434758dbd70a3a90338ef48/android/src/main/java/com/tailscale/ipn/App.java#L350-L398
*/

import java.lang.StringBuilder;
import java.net.InterfaceAddress;
import java.net.NetworkInterface;
import java.util.Collections;
import java.util.List
import java.util.Locale;

public class Example {


    // Returns details of the interfaces in the system, encoded as a single string for ease
    // of transfer over to the Go environment.
    //
    // Example:
    // rmnet_data0 10 2000 true false false false false | fe80::4059:dc16:7ed3:9c6e%rmnet_data0/64
    // dummy0 3 1500 true false false false false | fe80::1450:5cff:fe13:f891%dummy0/64
    // wlan0 30 1500 true true false false true | fe80::2f60:2c82:4163:8389%wlan0/64 10.1.10.131/24
    // r_rmnet_data0 21 1500 true false false false false | fe80::9318:6093:d1ad:ba7f%r_rmnet_data0/64
    // rmnet_data2 12 1500 true false false false false | fe80::3c8c:44dc:46a9:9907%rmnet_data2/64
    // r_rmnet_data1 22 1500 true false false false false | fe80::b6cd:5cb0:8ae6:fe92%r_rmnet_data1/64
    // rmnet_data1 11 1500 true false false false false | fe80::51f2:ee00:edce:d68b%rmnet_data1/64
    // lo 1 65536 true false true false false | ::1/128 127.0.0.1/8
    // v4-rmnet_data2 68 1472 true true false true true | 192.0.0.4/32
    //
    // Where the fields are:
    // name ifindex mtu isUp hasBroadcast isLoopback isPointToPoint hasMulticast | ip1/N ip2/N ip3/N;
    String getInterfaces() {
        List<NetworkInterface> interfaces;
        try {
            interfaces = Collections.list(NetworkInterface.getNetworkInterfaces());
        } catch (Exception e) {
            return "";
        }

        StringBuilder sb = new StringBuilder("");
        for (NetworkInterface nif : interfaces) {
            try {
                // Android doesn't have a supportsBroadcast() but the Go net.Interface wants
                // one, so we say the interface has broadcast if it has multicast.
                sb.append(String.format(java.util.Locale.ROOT, "%s %d %d %b %b %b %b %b |", nif.getName(),
                                nif.getIndex(), nif.getMTU(), nif.isUp(), nif.supportsMulticast(),
                                nif.isLoopback(), nif.isPointToPoint(), nif.supportsMulticast()));

                for (InterfaceAddress ia : nif.getInterfaceAddresses()) {
                    // InterfaceAddress == hostname + "/" + IP
                    String[] parts = ia.toString().split("/", 0);
                    if (parts.length > 1) {
                        sb.append(String.format(java.util.Locale.ROOT, "%s/%d ", parts[1], ia.getNetworkPrefixLength()));
                    }
                }
            } catch (Exception e) {
                // TODO should log the exception not silently suppress it.
                continue;
            }
            sb.append("\n");
        }
        return sb.toString();
    }
    
}