OpenVPN on Android TCP retransmissions after OpenVPN server reboot

Posted by anogaki on Server Fault See other posts from Server Fault or by anogaki
Published on 2013-06-30T23:57:42Z Indexed on 2013/07/01 4:22 UTC
Read the original article Hit count: 523

Filed under:

linux

|

networking

|

openvpn

|

android

I raised OpenVPN on server for the first time. It worked fine until the server rebooted. The firewall configuration is unchanged. When I tcpdump from tun interface on the server, I always get TCP retransmissions on all TCP packets larger than a few bytes in Android.

Using a similar(read: same) configuration on my Linux box from where I'm posting this message now works just fine; no retransmissions, no loss.

It did work just fine before the server rebooted. What could possibly cause this? I already tried rebooting Android, it didn't help.

Client configuration, used on both Linux PC and Android tablet:

dev tun
client
remote 192.168.0.1
persist-key
persist-tun
nobind
pkcs12 user.p12
mssfix 1480
cipher AES-256-CBC
verb 3

1480 is below the mtu of uplink connection on server which is 1492.

I tried adding tun-mtu 1480 to Android but that didn't help either.

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