github.com/akashshinde/docker@v1.9.1/api/server/middleware.go

package server

import (
	"net/http"
	"runtime"
	"strings"

	"github.com/Sirupsen/logrus"
	"github.com/docker/docker/api"
	"github.com/docker/docker/api/server/httputils"
	"github.com/docker/docker/autogen/dockerversion"
	"github.com/docker/docker/errors"
	"github.com/docker/docker/pkg/version"
	"golang.org/x/net/context"
)

// middleware is an adapter to allow the use of ordinary functions as Docker API filters.
// Any function that has the appropriate signature can be register as a middleware.
type middleware func(handler httputils.APIFunc) httputils.APIFunc

// loggingMiddleware logs each request when logging is enabled.
func (s *Server) loggingMiddleware(handler httputils.APIFunc) httputils.APIFunc {
	return func(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error {
		if s.cfg.Logging {
			logrus.Infof("%s %s", r.Method, r.RequestURI)
		}
		return handler(ctx, w, r, vars)
	}
}

// userAgentMiddleware checks the User-Agent header looking for a valid docker client spec.
func (s *Server) userAgentMiddleware(handler httputils.APIFunc) httputils.APIFunc {
	return func(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error {
		if strings.Contains(r.Header.Get("User-Agent"), "Docker-Client/") {
			dockerVersion := version.Version(s.cfg.Version)

			userAgent := strings.Split(r.Header.Get("User-Agent"), "/")

			// v1.20 onwards includes the GOOS of the client after the version
			// such as Docker/1.7.0 (linux)
			if len(userAgent) == 2 && strings.Contains(userAgent[1], " ") {
				userAgent[1] = strings.Split(userAgent[1], " ")[0]
			}

			if len(userAgent) == 2 && !dockerVersion.Equal(version.Version(userAgent[1])) {
				logrus.Debugf("Warning: client and server don't have the same version (client: %s, server: %s)", userAgent[1], dockerVersion)
			}
		}
		return handler(ctx, w, r, vars)
	}
}

// corsMiddleware sets the CORS header expectations in the server.
func (s *Server) corsMiddleware(handler httputils.APIFunc) httputils.APIFunc {
	return func(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error {
		// If "api-cors-header" is not given, but "api-enable-cors" is true, we set cors to "*"
		// otherwise, all head values will be passed to HTTP handler
		corsHeaders := s.cfg.CorsHeaders
		if corsHeaders == "" && s.cfg.EnableCors {
			corsHeaders = "*"
		}

		if corsHeaders != "" {
			writeCorsHeaders(w, r, corsHeaders)
		}
		return handler(ctx, w, r, vars)
	}
}

// versionMiddleware checks the api version requirements before passing the request to the server handler.
func versionMiddleware(handler httputils.APIFunc) httputils.APIFunc {
	return func(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error {
		apiVersion := version.Version(vars["version"])
		if apiVersion == "" {
			apiVersion = api.Version
		}

		if apiVersion.GreaterThan(api.Version) {
			return errors.ErrorCodeNewerClientVersion.WithArgs(apiVersion, api.Version)
		}
		if apiVersion.LessThan(api.MinVersion) {
			return errors.ErrorCodeOldClientVersion.WithArgs(apiVersion, api.Version)
		}

		w.Header().Set("Server", "Docker/"+dockerversion.VERSION+" ("+runtime.GOOS+")")
		ctx = context.WithValue(ctx, httputils.APIVersionKey, apiVersion)
		return handler(ctx, w, r, vars)
	}
}

// handleWithGlobalMiddlwares wraps the handler function for a request with
// the server's global middlewares. The order of the middlewares is backwards,
// meaning that the first in the list will be evaludated last.
//
// Example: handleWithGlobalMiddlewares(s.getContainersName)
//
//	s.loggingMiddleware(
//		s.userAgentMiddleware(
//			s.corsMiddleware(
//				versionMiddleware(s.getContainersName)
//			)
//		)
//	)
// )
func (s *Server) handleWithGlobalMiddlewares(handler httputils.APIFunc) httputils.APIFunc {
	middlewares := []middleware{
		versionMiddleware,
		s.corsMiddleware,
		s.userAgentMiddleware,
		s.loggingMiddleware,
	}

	h := handler
	for _, m := range middlewares {
		h = m(h)
	}
	return h
}