BUG: Zoiper ignore OpenVPN pushed DNS causing registration failures

Question

Hello,

This is apparently the only way to signal bugs in Zoiper, hoping someone in the dev team reads it...

Scenario:

- Android 5 (connected to any network, receiving y.y.y.y as network's DNS server IP)

- OpenVPN Connect 1.1.17

- Zoiper 1.51

- openvpn tunnel (layer 3 / tun, routed), server pushes DNS configuration (push "dhcp-option DNS x.x.x.x") (x.x.x.x being the IP address of the tun device on the server)

Current result / BUG:

- Zoiper sends/tries to send DNS queries to y.y.y.y (network's DNS).

- OpenVPN routing profile routes packets to y.y.y.y through the VPN

- y.y.y.y is unknown by the VPN server, thus DNS fails, thus registration is simply impossible

Expected result:

- Zoiper sends DNS queries to x.x.x.x (openvpn-pushed-DNS) (as do all other applications)

The problem can be reproduced as often as necessary, tcpdump on the server shows DNS queries for SIP servers sent to the wrong DNS server.

I'm happy to help with testing if necessary.

Best Regards

Comments

Zoiper is taking the DNS data from the Android OS itself. Try to first activate your VPN, check if other applications are able to successfully use the new DNS data and then try launching Zoiper.

---

Thanks, but it really looks like zoiper is taking the "wrong" (wifi/network-DHCP-provided) DNS servers.

This can be worked around on the OpenVPN server by adding a rule like

iptables -t nat -A PREROUTING -i tun_interface -p udp --dport 53 -j DNAT --to-destination tun_server_endpoint

(where tun_interface is usually something like tun0, and tun_server_endpoint is the in-tunnel-IP of the openvpn server)

So there is a workaround, and it really only seems to affect Zoiper on my terminal.

Answer 1

Actually, I can confirm that this bug still exists with actual Zoiper version and on Android 8.

Zoiper is the only App which does not use correct DNS Servers not even after closing and restarting the App.

Comments

Try the beta please: 

https://play.google.com/store/apps/details?id=com.zoiper.android.zoiperbeta.app&hl=en

That version should be using the vpn dns.

Let us know how it works for you.