api: add MinSupportedAPIVersion const

This const contains the minimum API version that can be supported by the
API server. The daemon is currently configured to use the same version,
but we may increment the _configured_ minimum version when deprecating
old API versions in future.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

api/common.go

@@ -2,9 +2,18 @@ package api // import "github.com/docker/docker/api"
 
 // Common constants for daemon and client.
 const (
-	// DefaultVersion of Current REST API
+	// DefaultVersion of the current REST API.
 	DefaultVersion = "1.45"
 
+	// MinSupportedAPIVersion is the minimum API version that can be supported
+	// by the API server, specified as "major.minor". Note that the daemon
+	// may be configured with a different minimum API version, as returned
+	// in [github.com/docker/docker/api/types.Version.MinAPIVersion].
+	//
+	// API requests for API versions lower than the configured version produce
+	// an error.
+	MinSupportedAPIVersion = "1.24"
+
 	// NoBaseImageSpecifier is the symbol used by the FROM
 	// command to specify that no base image is to be used.
 	NoBaseImageSpecifier = "scratch"

daemon/config/config.go

@@ -58,7 +58,7 @@ const (
 	// This version can be overridden through the "DOCKER_MIN_API_VERSION"
 	// environment variable. It currently defaults to the minimum API version
 	// supported by the API server.
-	defaultMinAPIVersion = "1.24"
+	defaultMinAPIVersion = api.MinSupportedAPIVersion
 	// SeccompProfileDefault is the built-in default seccomp profile.
 	SeccompProfileDefault = "builtin"
 	// SeccompProfileUnconfined is a special profile name for seccomp to use an