Implement VPN over native AP

2018-01-05 00:25:56 +08:00
parent b86a9590fb
commit dc2db049c7
9 changed files with 271 additions and 135 deletions
--- a/mobile/src/main/java/be/mygod/vpnhotspot/Routing.kt
+++ b/mobile/src/main/java/be/mygod/vpnhotspot/Routing.kt
@@ -0,0 +1,77 @@
+package be.mygod.vpnhotspot
+
+import java.io.IOException
+import java.net.Inet4Address
+import java.net.InetAddress
+import java.net.NetworkInterface
+import java.util.*
+
+class Routing(private val upstream: String, val downstream: String, ownerAddress: InetAddress? = null) {
+    companion object {
+        fun clean() = noisySu(
+                "iptables -t nat -F PREROUTING",
+                "while iptables -D FORWARD -j vpnhotspot_fwd; do done",
+                "iptables -F vpnhotspot_fwd",
+                "iptables -X vpnhotspot_fwd",
+                "while ip rule del lookup 62; do done",
+                "ip route flush table 62",
+                "while ip rule del priority 17999; do done")
+    }
+
+    class InterfaceNotFoundException : IOException()
+
+    val hostAddress: String
+    private val subnetPrefixLength: Short
+    private val startScript = LinkedList<String>()
+    private val stopScript = LinkedList<String>()
+    init {
+        val address = NetworkInterface.getByName(downstream)?.interfaceAddresses
+                ?.singleOrNull { if (ownerAddress == null) it.address is Inet4Address else it.address == ownerAddress }
+                ?: throw InterfaceNotFoundException()
+        hostAddress = address.address.hostAddress
+        subnetPrefixLength = address.networkPrefixLength
+    }
+
+    fun p2pRule(): Routing {
+        startScript.add("echo 1 >/proc/sys/net/ipv4/ip_forward")    // Wi-Fi direct doesn't enable ip_forward
+        startScript.add("ip route add default dev $upstream scope link table 62")
+        startScript.add("ip route add $hostAddress/$subnetPrefixLength dev $downstream scope link table 62")
+        startScript.add("ip route add broadcast 255.255.255.255 dev $downstream scope link table 62")
+        startScript.add("ip rule add iif $downstream lookup 62")
+        stopScript.addFirst("ip route del default dev $upstream scope link table 62")
+        stopScript.addFirst("ip route del $hostAddress/$subnetPrefixLength dev $downstream scope link table 62")
+        stopScript.addFirst("ip route del broadcast 255.255.255.255 dev $downstream scope link table 62")
+        stopScript.addFirst("ip rule del iif $downstream lookup 62")
+        return this
+    }
+
+    /* Since Android 5.0, RULE_PRIORITY_TETHERING = 18000.
+     * https://android.googlesource.com/platform/system/netd/+/b9baf26/server/RouteController.cpp#65 */
+    fun apRule(): Routing {
+        startScript.add("ip rule add from all iif $downstream lookup $upstream priority 17999")
+        stopScript.addFirst("ip rule del from all iif $downstream lookup $upstream priority 17999")
+        return this
+    }
+
+    fun forward(): Routing {
+        startScript.add("iptables -N vpnhotspot_fwd")
+        startScript.add("iptables -A vpnhotspot_fwd -i $upstream -o $downstream -m state --state ESTABLISHED,RELATED -j ACCEPT")
+        startScript.add("iptables -A vpnhotspot_fwd -i $downstream -o $upstream -j ACCEPT")
+        startScript.add("iptables -I FORWARD -j vpnhotspot_fwd")
+        stopScript.addFirst("iptables -X vpnhotspot_fwd")
+        stopScript.addFirst("iptables -F vpnhotspot_fwd")
+        stopScript.addFirst("iptables -D FORWARD -j vpnhotspot_fwd")
+        return this
+    }
+
+    fun dnsRedirect(dns: String): Routing {
+        startScript.add("iptables -t nat -A PREROUTING -i $downstream -p tcp -d $hostAddress --dport 53 -j DNAT --to-destination $dns")
+        startScript.add("iptables -t nat -A PREROUTING -i $downstream -p udp -d $hostAddress --dport 53 -j DNAT --to-destination $dns")
+        stopScript.addFirst("iptables -t nat -D PREROUTING -i $downstream -p tcp -d $hostAddress --dport 53 -j DNAT --to-destination $dns")
+        stopScript.addFirst("iptables -t nat -D PREROUTING -i $downstream -p udp -d $hostAddress --dport 53 -j DNAT --to-destination $dns")
+        return this
+    }
+
+    fun start() = noisySu(startScript)
+    fun stop() = noisySu(stopScript)
+}