Hi!

I tested again with latest Wireguard (.35) and Windows 2019 (.914) and the 
problem remains easy to reproduce.

In short, after restarting a Windows that is doing NAT for a peer behind a 
Wireguard tunnel, the tunnel stops correctly moving packets. I can see the 
Wiregurad "sent" and "received" counts increment to some degree but the end 
result is that pings do not work after some restarts of the tunnel/server).

I remain ready to assist in further diagnosis if a more informed person can 
guide me to what data might be useful.


Cheers,

Sander Saares, Advisor, Axinom
phone: +49 911 80109-54 | [email protected]

-----Original Message-----
From: Sander Saares 
Sent: esmaspäev, 5. august 2019 10:55
To: '[email protected]' <[email protected]>
Subject: Windows tunnel shows established but traffic sometimes does not move 
after recycling tunnel

Hi!

I submit a report on a problem encountered attempting to use WireGuard in a 
Windows-to-Windows "VPN gateway/proxy" deployment. I have a test deployment 
available in case I can provide further data for ease of debugging.

Scenario:
* Server A set up as WireGuard server, accepting connections from server B.
* Traffic from WireGuard network is forwarded and NATed by server A using 
built-in Windows networking features.
* Server B connects through WireGuard tunnel to access the internet.

For purpose of experimentation, the internet is defined as 8.8.8.8/32.

Expected result: tunnel is successfully established, internet traffic of server 
B is forwarded through server A.
Actual result: tunnel is successfully established (at least as shown in 
WireGuard GUI) but sometimes the expected traffic flows do not occur.
Occasionally, actual result matches expected result.

Method of observation: mutual ping on private IP address; ping from server B 
(WG client) to 8.8.8.8.
In failure case:
* both pings time out (server A and server B cannot ping each other on private 
IP)
* ping to 8.8.8.8 times out, EXCEPT for the first ping after tunnel is 
re-established (server B always seems to get 1 response before connectivity 
vanishes; possibly this is a ping not routed through the VPN, so it just goes 
directly out from server B to the internet?)
In success case, all pings work fine and get expected responses.

I suspect some startup/lifecycle/timing issue disrupting proper operation of 
the tunnel and/or associated routing configuration. If I can provide more data 
that may prove useful, I am happy to do so when instructed on how to collect it.

Configuration and experiment log follows.

Both systems are Windows 2019 (17763.652) running in clean Azure VMs, fully 
patched. WireGuard 0.0.19.

WireGuard server (server A)
=======================
[Interface]
PrivateKey = 
ListenPort = 9000
Address = 172.16.16.1/24

[Peer]
PublicKey = 
AllowedIPs = 172.16.16.0/24

WireGuard client (server B)
=======================
[Interface]
PrivateKey = 
Address = 172.16.16.2/24

[Peer]
PublicKey = 
AllowedIPs = 172.16.16.0/24, 8.8.8.8/32
Endpoint = xxx:9000

Forward+NAT setup (server A)
=================
PS C:\Users\saares> $interfaces = Get-NetIPInterface
PS C:\Users\saares> $interfaces[4]

ifIndex InterfaceAlias                  AddressFamily NlMtu(Bytes) 
InterfaceMetric Dhcp     ConnectionState PolicyStore
------- --------------                  ------------- ------------ 
--------------- ----     --------------- -----------
3       wg-test                         IPv4                  1420              
 5 Disabled Connected       ActiveStore

PS C:\Users\saares> $interfaces[4] | Set-NetIPInterface -Forwarding Enabled
PS C:\Users\saares> New-NetNat -Name NAT -InternalIPInterfaceAddressPrefix 
"172.16.16.0/24"

Name                             : NAT
ExternalIPInterfaceAddressPrefix :
InternalIPInterfaceAddressPrefix : 172.16.16.0/24
IcmpQueryTimeout                 : 30
TcpEstablishedConnectionTimeout  : 1800
TcpTransientConnectionTimeout    : 120
TcpFilteringBehavior             : AddressDependentFiltering
UdpFilteringBehavior             : AddressDependentFiltering
UdpIdleSessionTimeout            : 120
UdpInboundRefresh                : False
Store                            : Local
Active                           : True

Experiment log
===============
Immediate after setup -> all OK
Recycle tunnel on server -> all OK
Restart server PC -> tunnel reestablished but traffic does not move
Recycle tunnel on server -> all OK
Recycle tunnel on server -> all OK
Recycle tunnel on server -> all OK
Recycle tunnel on server -> all OK
Recycle tunnel on server -> all OK
Recycle tunnel on server -> all OK
Restart server PC -> all OK
Restart server PC -> tunnel reestablished but traffic does not move
Recycle tunnel on server -> tunnel reestablished but traffic does not move
Recycle tunnel on server -> tunnel reestablished but traffic does not move
Recycle tunnel on server -> tunnel reestablished but traffic does not move
Recycle tunnel on server -> tunnel reestablished but traffic does not move
Recycle tunnel on server -> all OK
Recycle tunnel on server -> tunnel reestablished but traffic does not move
Recycle tunnel on server -> tunnel reestablished but traffic does not move
Recycle tunnel on server -> tunnel reestablished but traffic does not move



Cheers,

Sander Saares
Advisor 
 
Axinom | Soola 8 | 51004 Tartu | Estonia
phone: +49 911 80109-54
[email protected] | www.axinom.com 
 
Managing Directors: Sergei Gussev, Oleg Knut
Tartu Circuit Court, Reg. 11046287

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