diff options
Diffstat (limited to 'tunnel/src/main/java/com/wireguard/util')
-rw-r--r-- | tunnel/src/main/java/com/wireguard/util/Resolver.java | 134 |
1 files changed, 134 insertions, 0 deletions
diff --git a/tunnel/src/main/java/com/wireguard/util/Resolver.java b/tunnel/src/main/java/com/wireguard/util/Resolver.java new file mode 100644 index 00000000..f401b584 --- /dev/null +++ b/tunnel/src/main/java/com/wireguard/util/Resolver.java @@ -0,0 +1,134 @@ +/* + * Copyright © 2023 WireGuard LLC. All Rights Reserved. + * SPDX-License-Identifier: Apache-2.0 + */ + +package com.wireguard.util; + +import java.io.IOException; +import java.net.DatagramSocket; +import java.net.Inet4Address; +import java.net.Inet6Address; +import java.net.InetAddress; +import java.net.InetSocketAddress; +import java.net.SocketException; +import java.net.UnknownHostException; + +import android.net.IpPrefix; +import android.net.LinkProperties; +import android.net.Network; +import android.util.Log; + +import androidx.annotation.Nullable; + +@NonNullForAll +public class Resolver { + private static final String TAG = "WireGuard/Resolver"; + @Nullable private final Network network; + @Nullable private final LinkProperties linkProps; + @Nullable private IpPrefix nat64Prefix; + + public Resolver(Network network, LinkProperties linkProps) { + this.network = network; + this.linkProps = linkProps; + if (linkProps != null) { + this.nat64Prefix = linkProps.getNat64Prefix(); + } + } + + static boolean isULA(Inet6Address addr) { + byte[] raw = addr.getAddress(); + return ((raw[0] & 0xfe) == 0xfc); + } + + boolean isWithinNAT64Prefix(Inet6Address address) { + if (nat64Prefix == null) + return false; + + int prefixLength = nat64Prefix.getPrefixLength(); + byte[] rawAddr = address.getAddress(); + byte[] rawPrefix = nat64Prefix.getRawAddress(); + + for (int i=0; i < prefixLength/8; i++) { + if (rawAddr[i] != rawPrefix[i]) + return false; + } + + return true; + } + + boolean isPreferredIPv6(Inet6Address local, Inet6Address remote) { + if (linkProps == null) { + // Prefer IPv4 if there are not link properties that can + // be tested. + return false; + } + + // * Prefer IPv4 if local or remote address is ULA + // * Prefer IPv4 if remote IPv6 is within NAT64 prefix. + // * Otherwise prefer IPv6 + boolean isLocalULA = isULA(local); + boolean isRemoteULA = isULA(remote); + + if (isLocalULA || isRemoteULA) { + return false; + } + + if (isWithinNAT64Prefix(remote)) { + return false; + } + + return true; + } + + public InetAddress resolve(String host) throws UnknownHostException { + final InetAddress[] candidates = network != null ? network.getAllByName(host) : InetAddress.getAllByName(host); + InetAddress address = candidates[0]; + for (final InetAddress candidate : candidates) { + DatagramSocket sock; + + try { + sock = new DatagramSocket(); + if (network != null) { + network.bindSocket(sock); + } + } catch (SocketException e) { + // Return first candidate as fallback + Log.w(TAG, "DatagramSocket failed, fallback to: \"" + address); + return address; + } catch (IOException e) { + // Return first candidate as fallback + Log.w(TAG, "BindSocket failed, fallback to: \"" + address); + return address; + } + + sock.connect(candidate, 51820); + + if (sock.getLocalAddress().isAnyLocalAddress()) { + // Connect didn't find a local address. + Log.w(TAG, "No local address"); + continue; + } + + Log.w(TAG, "Local address: " + sock.getLocalAddress()); + + if (candidate instanceof Inet4Address) { + // Accept IPv4 as preferred address. + address = candidate; + break; + } + + Inet6Address local = (Inet6Address)sock.getLocalAddress(); + InetSocketAddress remoteSockAddr = (InetSocketAddress)sock.getRemoteSocketAddress(); + Inet6Address remote = (Inet6Address)remoteSockAddr.getAddress(); + sock.close(); + + if (isPreferredIPv6(local, remote)) { + address = candidate; + break; + } + } + Log.w(TAG, "Resolved \"" + host + "\" to: " + address); + return address; + } +} |