vpnkit impact on Windows TCP Stack ?

[chriscamicas]

I'm having an issue with a specific database engine (proprietary) inside a docker container on windows (LCOW). I've managed to narrow it down to the use of vpnkit.

Here is the situation: I start the container with few ports forwarded -p 6000:6000 -p 6001:6001 -p 1025-1035:1025-1035 I spawn an ODBC client on my Windows host, connect it to localhost, and query this db (multiple insert, approx. 4000 ). At some point the connection is closed, with a generic ODBC exception. Neither the db engine, nor the odbc client logs explains the situation, it seems related to a network issue.

Tail of the last TCP exchanges using localhost/vpnkit

When I do the same thing but connect the ODBC client to the hyper-v VM (MobyLinux) ip (in my case 10.0.75.2), everything works fine.

I'm guessing vpnkit has an impact on the network between the db engine and the odbc client, but it's not clear what exactly. I've read vpnkit has some sort of protocol over-the-top to handle connection close. Is there an impact on packet size ? MTU ? or anything else. I also suppose the db engine or the odbc client is not quite resilient to network perturbation.

docker version

Client:
 Version:           18.06.1-ce
 API version:       1.38
 Go version:        go1.10.3
 Git commit:        e68fc7a
 Built:             Tue Aug 21 17:21:34 2018
 OS/Arch:           windows/amd64
 Experimental:      false

Server:
 Engine:
  Version:          18.06.1-ce
  API version:      1.38 (minimum version 1.12)
  Go version:       go1.10.3
  Git commit:       e68fc7a
  Built:            Tue Aug 21 17:29:02 2018
  OS/Arch:          linux/amd64
  Experimental:     false

docker info

Containers: 1
 Running: 1
 Paused: 0
 Stopped: 0
Images: 28
Server Version: 18.06.1-ce
Storage Driver: overlay2
 Backing Filesystem: extfs
 Supports d_type: true
 Native Overlay Diff: true
Logging Driver: json-file
Cgroup Driver: cgroupfs
Plugins:
 Volume: local
 Network: bridge host macvlan null overlay
 Log: awslogs fluentd gcplogs gelf journald json-file logentries splunk syslog
Swarm: inactive
Runtimes: runc
Default Runtime: runc
Init Binary: docker-init
containerd version: 468a545b9edcd5932818eb9de8e72413e616e86e
runc version: 69663f0bd4b60df09991c08812a60108003fa340
init version: fec3683
Security Options:
 seccomp
  Profile: default
Kernel Version: 4.9.93-linuxkit-aufs
Operating System: Docker for Windows
OSType: linux
Architecture: x86_64
CPUs: 2
Total Memory: 1.934GiB
Name: linuxkit-00155d4b0153
ID: HGXK:WEF3:L5GZ:NIOG:MSZI:UB4T:YLNV:67ZA:QFUI:VIDD:WOVI:LK6C
Docker Root Dir: /var/lib/docker
Debug Mode (client): false
Debug Mode (server): true
 File Descriptors: 30
 Goroutines: 62
 System Time: 2018-09-28T14:58:48.1464452Z
 EventsListeners: 1
Registry: https://index.docker.io/v1/
Labels:
Experimental: false
Insecure Registries:
 127.0.0.0/8
Live Restore Enabled: false

Thank you

[chriscamicas]

I also tried with the latest Docker Edge version and still have the same issue.

[cforce]

related to https://github.com/docker/for-win/issues/1900