$SSH_AUTH_SOCK is not being forwarded to docker #410
Description
Expected behavior
OSX ssh-agent socket is available (for mount) in containers
$ docker run -it -v ${SSH_AUTH_SOCK}:${SSH_AUTH_SOCK} -e SSH_AUTH_SOCK="${SSH_AUTH_SOCK}" --rm alpine:3.4 /bin/sh -c "apk update && apk add dropbear-ssh && ssh -T git@github.com"
fetch http://dl-cdn.alpinelinux.org/alpine/v3.4/main/x86_64/APKINDEX.tar.gz
fetch http://dl-cdn.alpinelinux.org/alpine/v3.4/community/x86_64/APKINDEX.tar.gz
v3.4.3-7-g2f47d74 [http://dl-cdn.alpinelinux.org/alpine/v3.4/main]
v3.4.2-11-g9b41a63 [http://dl-cdn.alpinelinux.org/alpine/v3.4/community]
OK: 5968 distinct packages available
(1/2) Installing dropbear (2016.74-r0)
(2/2) Installing dropbear-ssh (2016.74-r0)
Executing busybox-1.24.2-r9.trigger
OK: 5 MiB in 13 packages
Host 'github.com' is not in the trusted hosts file.
(ssh-rsa fingerprint md5 16:27:ac:a5:76:28:2d:36:63:1b:56:4d:eb:df:a6:48)
Do you want to continue connecting? (y/n) yes
Hi <githubusername>! You've successfully authenticated, but GitHub does not provide shell access.
Actual behavior
OSX ssh-agent socket is available, but does not work because it's a socket (unable to connect)
$ docker run -it -v ${SSH_AUTH_SOCK}:${SSH_AUTH_SOCK} -e SSH_AUTH_SOCK="${SSH_AUTH_SOCK}" --rm alpine:3.4 /bin/sh -c "apk update && apk add dropbear-ssh && ssh -T git@github.com"
fetch http://dl-cdn.alpinelinux.org/alpine/v3.4/main/x86_64/APKINDEX.tar.gz
fetch http://dl-cdn.alpinelinux.org/alpine/v3.4/community/x86_64/APKINDEX.tar.gz
v3.4.3-7-g2f47d74 [http://dl-cdn.alpinelinux.org/alpine/v3.4/main]
v3.4.2-11-g9b41a63 [http://dl-cdn.alpinelinux.org/alpine/v3.4/community]
OK: 5968 distinct packages available
(1/2) Installing dropbear (2016.74-r0)
(2/2) Installing dropbear-ssh (2016.74-r0)
Executing busybox-1.24.2-r9.trigger
OK: 5 MiB in 13 packages
Host 'github.com' is not in the trusted hosts file.
(ssh-rsa fingerprint md5 16:27:ac:a5:76:28:2d:36:63:1b:56:4d:eb:df:a6:48)
Do you want to continue connecting? (y/n) yes
ssh: Failed to connect to agent
ssh: Connection to git@github.com:22 exited: No auth methods could be used.
Information
https://forums.docker.com/t/can-we-re-use-the-osx-ssh-agent-socket-in-a-container/8152
It would be great if Docker for Mac would forward osx ssh-agent's socket into VM, just like how it does with docker.sock. Generic solution for socket would also help a lot.