# Overview
After setting up OpenVPN, we are able to connect over SSH (e.g. to 10.8.0.9), but the SSH connection hangs/stalls, usually after about 2-minutes. The SSH connection is from Ubuntu 18 on WSL to Ubuntu 18 on Digital Ocean.
# What have we tried?
We have done the following on the server and all the clients.
* Since many suggest this is an MTU problem, we adjusted `fragment` and `mssfix` down to `1200`.
* We used `ping`, `traceroute`, and `tracepath` to check the MTU between hosts; the MTU comes in at around `1500`.
* We set the `tun0` MTU at `1400` with `sudo ip link set dev tun0 mtu 1400`.
* We disabled window scaling with `sysctl -w net.ipv4.tcp_window_scaling=0`.
* To rule out Firewall causes, we have (temporarily) disabled the Firewall.
None of this is resolving the stalls/hangs. With all of the above changes, we can still connect over SSH, but within minutes, the SSH connection hangs/stalls.
# Question
We have set our local VPN client's `verb` to `11`. This is the output when the VPN is actively stalling/hanging. What hints, if any, does that output give us about what is causing the hang?
us=52848 UDP write returned 112
us=52924 PO_CTL rwflags=0x0001 ev=5 arg=0x55f0cef4c168
us=53000 PO_CTL rwflags=0x0001 ev=6 arg=0x55f0cef4c068
us=53032 I/O WAIT TR|Tw|SR|Sw [4/92829]
us=91180 PO_WAIT[1,0] fd=6 rev=0x00000001 rwflags=0x0001 arg=0x55f0cef4c068
us=91300 event_wait returned 1
us=91313 I/O WAIT status=0x0004
us=91325 read from TUN/TAP returned 84
us=91377 TUN READ [84]
us=91414 FRAG_OUT len=84 type=0 seq_id=0 frag_id=0 frag_size=0 flags=0x00000000
us=91427 TLS: tls_pre_encrypt: key_id=0
us=91471 tls_prepend_opcode_v2
us=91503 ENCRYPT IV: 000001ca c1f70e33 9b725bd5
us=91611 ENCRYPT FROM: 00000000 45000054 e8fe4000 40013d85 0a080005 0a080011 080071f2 0c2d000[more...]
us=91677 ENCRYPT AD: 48000008 000001ca
us=91787 ENCRYPT TO: 48000008 000001ca fda00e43 93938a26 d2f6b551 a96d0ced 95ce1caf cb4b087[more...]
us=91899 PO_CTL rwflags=0x0003 ev=5 arg=0x55f0cef4c168
us=91999 PO_CTL rwflags=0x0000 ev=6 arg=0x55f0cef4c068
us=92101 I/O WAIT Tr|Tw|SR|SW [3/92829]
us=92197 PO_WAIT[0,0] fd=5 rev=0x00000004 rwflags=0x0002 arg=0x55f0cef4c168
us=92287 event_wait returned 1
us=92358 I/O WAIT status=0x0002
us=92525 UDP WRITE [112] to [AF_INET]xxx.xxx.xxx.xxx:1194: P_DATA_V2 kid=0 DATA 00000800 0001cafd a00e4393 938a26d2 f6b551a9 6d0ced95 ce1cafcb 4b0874b[more...]
The hang usually lasts for upwards of five minutes, during which time `ping` no longer returns results and SSH is frozen. Once the hang resolves itself, both the `ping` and the SSH connection start working too.
This is the related question on ServerFault:
https://serverfault.com/q/1010959/179158
