docker cp to a target file on host fails if target file is in a symlinked directory.

[florianlaws]

Description

docker cp from a file in the container to a target file on the host fails if target filename is in a symlinked directory.

Steps to reproduce the issue:

1. Start a container
2. Try to copy a file from the running container to the host.
   On MacOS try e.g. docker cp containerid:/bin/bash /tmp/dockerbash (on MacOS /tmp is a symlink to private/tmp
   On Linux try ln -s /tmp sl docker cp containerid:/bin/bash sl/dockerbash

Describe the results you received:

Error message: not a directory, file was not created.

Describe the results you expected:

File should be copied into /tmp/dockerbash or sl/dockerbask

Output of docker version:

$ docker version
Client:
 Version:      17.03.0-ce
 API version:  1.24 (downgraded from 1.26)
 Go version:   go1.8
 Git commit:   60ccb22
 Built:        
 OS/Arch:      darwin/amd64

Server:
 Version:      1.12.3
 API version:  1.24 (minimum version )
 Go version:   go1.6.3
 Git commit:   6b644ec
 Built:        Wed Oct 26 23:26:11 2016
 OS/Arch:      linux/amd64
 Experimental: false

Output of docker info:

Containers: 47
 Running: 3
 Paused: 0
 Stopped: 44
Images: 147
Server Version: 1.12.3
Storage Driver: aufs
 Root Dir: /mnt/sda1/var/lib/docker/aufs
 Backing Filesystem: extfs
 Dirs: 288
 Dirperm1 Supported: true
Logging Driver: json-file
Cgroup Driver: cgroupfs
Plugins: 
 Volume: local
 Network: host overlay bridge null
Swarm: inactive
Runtimes: runc
Default Runtime: runc
Init Binary: 
containerd version: 
runc version: 
init version: 
Security Options:
 seccomp
Kernel Version: 4.4.27-boot2docker
Operating System: Boot2Docker 1.12.3 (TCL 7.2); HEAD : 7fc7575 - Thu Oct 27 17:23:17 UTC 2016
OSType: linux
Architecture: x86_64
CPUs: 1
Total Memory: 995.8 MiB
Name: default
ID: 52NW:N6TU:3SBB:GXQ2:PHYI:IAW3:5AUC:ZUAA:G6LS:BH4Y:EB52:ACEZ
Docker Root Dir: /mnt/sda1/var/lib/docker
Debug Mode (client): false
Debug Mode (server): true
 File Descriptors: 28
 Goroutines: 43
 System Time: 2017-03-14T10:58:01.490570974Z
 EventsListeners: 0
Registry: https://index.docker.io/v1/
Labels:
 provider=virtualbox
Experimental: false
Insecure Registries:
 127.0.0.0/8
Live Restore Enabled: false```

**Additional environment details (AWS, VirtualBox, physical, etc.):**

Above on MacOs Sierra with docker-machine 0.10.0, but reproducible with Linux too. 

[dccurtis]

#dibs

[thaJeztah]

Thanks @dccurtis let us know if you need help 👍

[dccurtis]

Will do, so far so good!

[dccurtis]

The root cause of this problem is that os.Lstat -> FileInfo.IsDir() returns false for a symlink directory in CopyInfoDestinationPath.

not a directory is thrown whenever you copy a file from a container to a host symlink directory with a new target filename.

I have a fix for this. I'm finishing up my testing and will have a PR out soon!

[karanguptak9]

#dibs

[dccurtis]

@karanguptak9 Just a heads up; my fix was already approved for this. Just waiting on it to be merged.

[JBYoshi]

The PR for this was merged, so I think this can be closed.