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Merged
thaJeztah merged 2 commits into from
Jan 9, 2020
Merged

connhelper: use ssh multiplexing #2132

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c04dd6e
connhelper: add ssh multiplexing
tonistiigi Oct 10, 2019
4ecbef4
docs: document ssh multiplexing env
tonistiigi Jan 9, 2020
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21 changes: 20 additions & 1 deletion cli/connhelper/connhelper.go
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Expand Up@@ -5,7 +5,10 @@ import (
"context"
"net"
"net/url"
"os"
"strconv"

"github.com/docker/cli/cli/config"
"github.com/docker/cli/cli/connhelper/commandconn"
"github.com/docker/cli/cli/connhelper/ssh"
"github.com/pkg/errors"
Expand DownExpand Up@@ -34,7 +37,7 @@ func GetConnectionHelper(daemonURL string) (*ConnectionHelper, error) {
}
return &ConnectionHelper{
Dialer: func(ctx context.Context, network, addr string) (net.Conn, error) {
return commandconn.New(ctx, "ssh", append(sp.Args(), []string{"--", "docker", "system", "dial-stdio"}...)...)
return commandconn.New(ctx, "ssh", append(multiplexingArgs(), append(sp.Args(), []string{"--", "docker", "system", "dial-stdio"}...)...)...)
},
Host: "http://docker",
}, nil
Expand All@@ -53,3 +56,19 @@ func GetCommandConnectionHelper(cmd string, flags ...string) (*ConnectionHelper,
Host: "http://docker",
}, nil
}

func multiplexingArgs() []string {
if v := os.Getenv("DOCKER_SSH_NO_MUX"); v != "" {

@thaJeztahthaJeztahJan 9, 2020

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can you document the new environment variables in https://github.com/docker/cli/blob/master/docs/reference/commandline/cli.md#environment-variables ?

if b, err := strconv.ParseBool(v); err == nil && b {
return nil
}
}
if err := os.MkdirAll(config.Dir(), 0700); err != nil {

@AkihiroSudaAkihiroSudaOct 11, 2019

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Probably we should create a new directory, because when ~/.docker already exists with other permission bits, we can't guarantee the sockets are created under a directory with 0700.
On my Macintosh, ~/.docker was somehow created with 0755.

But it is more likely to hit UNIX_PATH_MAX (108)... 😢

@AkihiroSudaAkihiroSudaOct 11, 2019

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Probably we can let commandconn change working directory for avoiding 108 limit

@tonistiigitonistiigiOct 11, 2019

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The socket itself is created with 0600. This mkdir is to avoid the case where .docker does not exist.

return nil
}
args := []string{"-o", "ControlMaster=auto", "-o", "ControlPath=" + config.Dir() + "/%r@%h:%p"}

@AkihiroSudaAkihiroSudaOct 10, 2019

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What happens if .ssh/config already has this?

@tonistiigitonistiigiOct 10, 2019

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It overwrites afaik. This is the main reason I left a way to opt-out. If we want to be conservative about it, one way would be to use a different helper prefix.

if v := os.Getenv("DOCKER_SSH_MUX_PERSIST"); v != "" {
args = append(args, "-o", "ControlPersist="+v)

@justincormackjustincormackOct 29, 2019

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Is there any reason not to have a Docker config option for this as well?

@tonistiigitonistiigiDec 6, 2019

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If you would ever set them they would probably be more dependent on the actual DOCKER_HOST value, not a global client config. I'm not even sure we even want to document these, it should be very advanced usage if you want to set them.

@thaJeztahthaJeztahDec 12, 2019

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ping @justincormack pal ^

}
return args
}
2 changes: 2 additions & 0 deletions docs/reference/commandline/cli.md
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Expand Up@@ -86,6 +86,8 @@ by the `docker` command line:
* `DOCKER_TMPDIR` Location for temporary Docker files.
* `DOCKER_CONTEXT` Specify the context to use (overrides DOCKER_HOST env var and default context set with "docker context use")
* `DOCKER_DEFAULT_PLATFORM` Specify the default platform for the commands that take the `--platform` flag.
* `DOCKER_SSH_NO_MUX` If set will turn off SSH multiplexing when connecting to daemon through SSH.
* `DOCKER_SSH_MUX_PERSIST` Set a duration for keeping SSH multiplexing socket alive between commands (e.g `60s`).

Because Docker is developed using Go, you can also use any environment
variables used by the Go runtime. In particular, you may find these useful:
Expand Down