dotcloud/docker

package middleware // import "github.com/docker/docker/api/server/middleware"

import (
    "context"
    "fmt"
    "net/http"
    "runtime"

    "github.com/docker/docker/api"
    "github.com/docker/docker/api/server/httputils"
    "github.com/docker/docker/api/types/versions"
)

// VersionMiddleware is a middleware that
// validates the client and server versions.
type VersionMiddleware struct {
    serverVersion string

    // defaultAPIVersion is the default API version provided by the API server,
    // specified as "major.minor". It is usually configured to the latest API
    // version [github.com/docker/docker/api.DefaultVersion].
    //
    // API requests for API versions greater than this version are rejected by
    // the server and produce a [versionUnsupportedError].
    defaultAPIVersion string

    // minAPIVersion is the minimum API version provided by the API server,
    // specified as "major.minor".
    //
    // API requests for API versions lower than this version are rejected by
    // the server and produce a [versionUnsupportedError].
    minAPIVersion string
}

// NewVersionMiddleware creates a VersionMiddleware with the given versions.
func NewVersionMiddleware(serverVersion, defaultAPIVersion, minAPIVersion string) (*VersionMiddleware, error) {
    if versions.LessThan(defaultAPIVersion, api.MinSupportedAPIVersion) || versions.GreaterThan(defaultAPIVersion, api.DefaultVersion) {
        return nil, fmt.Errorf("invalid default API version (%s): must be between %s and %s", defaultAPIVersion, api.MinSupportedAPIVersion, api.DefaultVersion)
    }
    if versions.LessThan(minAPIVersion, api.MinSupportedAPIVersion) || versions.GreaterThan(minAPIVersion, api.DefaultVersion) {
        return nil, fmt.Errorf("invalid minimum API version (%s): must be between %s and %s", minAPIVersion, api.MinSupportedAPIVersion, api.DefaultVersion)
    }
    if versions.GreaterThan(minAPIVersion, defaultAPIVersion) {
        return nil, fmt.Errorf("invalid API version: the minimum API version (%s) is higher than the default version (%s)", minAPIVersion, defaultAPIVersion)
    }
    return &VersionMiddleware{
        serverVersion:     serverVersion,
        defaultAPIVersion: defaultAPIVersion,
        minAPIVersion:     minAPIVersion,
    }, nil
}

type versionUnsupportedError struct {
    version, minVersion, maxVersion string
}

func (e versionUnsupportedError) Error() string {
    if e.minVersion != "" {
        return fmt.Sprintf("client version %s is too old. Minimum supported API version is %s, please upgrade your client to a newer version", e.version, e.minVersion)
    }
    return fmt.Sprintf("client version %s is too new. Maximum supported API version is %s", e.version, e.maxVersion)
}

func (e versionUnsupportedError) InvalidParameter() {}

// WrapHandler returns a new handler function wrapping the previous one in the request chain.
func (v VersionMiddleware) WrapHandler(handler func(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error) func(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error {
    return func(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error {
        w.Header().Set("Server", fmt.Sprintf("Docker/%s (%s)", v.serverVersion, runtime.GOOS))
        w.Header().Set("API-Version", v.defaultAPIVersion)
        w.Header().Set("OSType", runtime.GOOS)

        apiVersion := vars["version"]
        if apiVersion == "" {
            apiVersion = v.defaultAPIVersion
        }
        if versions.LessThan(apiVersion, v.minAPIVersion) {
            return versionUnsupportedError{version: apiVersion, minVersion: v.minAPIVersion}
        }
        if versions.GreaterThan(apiVersion, v.defaultAPIVersion) {
            return versionUnsupportedError{version: apiVersion, maxVersion: v.defaultAPIVersion}
        }
        ctx = context.WithValue(ctx, httputils.APIVersionKey{}, apiVersion)
        return handler(ctx, w, r, vars)
    }
}