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Reduce probability of sending packets with private IPs

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When starting/stopping the VPNService, some packets with internal IP
addresses 10.215.173.1 and 10.215.173.2 may be sent over the LAN.
Based on trial and error, this patch reduces such events. In
particular we can see:

- At startup, DNS queries with internal DNS server 10.215.173.2
- At shutdown, some packets with source IP 10.215.173.1

The shutdown issue is more frequent when stopping the VPN from the
android VPN settings. This also happens with other VPN apps.
This commit is contained in:
emanuele-f 2021-02-08 00:51:15 +01:00
parent da531740f3
commit 1bb08e3b0c
2 changed files with 17 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
app/src/main/java/com/emanuelef/remote_capture/CaptureService.java
View File

@ -205,6 +205,17 @@ public class CaptureService extends VpnService implements Runnable {
private void stop() {
stopPacketLoop();
while((mThread != null) && (mThread.isAlive())) {
try {
Log.d(TAG, "Joining native thread...");
mThread.join();
} catch (InterruptedException e) {
Log.e(TAG, "Joining native thread failed");
}
}
mThread = null;
if(mParcelFileDescriptor != null) {
try {
mParcelFileDescriptor.close();
@ -258,7 +269,7 @@ public class CaptureService extends VpnService implements Runnable {
@Override
public void run() {
if(mParcelFileDescriptor != null) {
int fd = mParcelFileDescriptor.detachFd();
int fd = mParcelFileDescriptor.getFd();
if(fd > 0)
runPacketLoop(fd, this, Build.VERSION.SDK_INT);

7
app/src/main/jni/vpnproxy-jni/vpnproxy.c
View File

@ -976,7 +976,11 @@ static int run_tun(JNIEnv *env, jclass vpn, int tapfd, jint sdk) {
goto housekeeping;
}
check_dns_req_dnat(&proxy, &pkt, conn);
if((check_dns_req_dnat(&proxy, &pkt, conn) == 0)
&& (pkt.tuple.dst_ip == proxy.vpn_dns)) {
log_android(ANDROID_LOG_DEBUG, "ignoring packet directed to the virtual DNS server");
goto housekeeping;
}
if(proxy.tls_decryption.enabled)
check_tls_mitm(tun, &proxy, &pkt, conn);
@ -1065,7 +1069,6 @@ Java_com_emanuelef_remote_1capture_CaptureService_runPacketLoop(JNIEnv *env, jcl
jobject vpn, jint sdk) {
run_tun(env, vpn, tapfd, sdk);
close(tapfd);
}
JNIEXPORT void JNICALL