Pass upstream client's user agent through to registry on image pulls

Changes how the Engine interacts with Registry servers on image pull.
Previously, Engine sent a User-Agent string to the Registry server
that included only the Engine's version information.  This commit
appends to that string the fields from the User-Agent sent by the
client (e.g., Compose) of the Engine.  This allows Registry server
operators to understand what tools are actually generating pulls on
their registries.

Signed-off-by: Mike Goelzer <mgoelzer@docker.com>

integration-cli/docker_cli_registry_user_agent_test.go

@@ -0,0 +1,90 @@
+package main
+
+import (
+	"fmt"
+	"net/http"
+	"regexp"
+
+	"github.com/go-check/check"
+)
+
+// unescapeBackslashSemicolonParens unescapes \;()
+func unescapeBackslashSemicolonParens(s string) string {
+	re := regexp.MustCompile("\\\\;")
+	ret := re.ReplaceAll([]byte(s), []byte(";"))
+
+	re = regexp.MustCompile("\\\\\\(")
+	ret = re.ReplaceAll([]byte(ret), []byte("("))
+
+	re = regexp.MustCompile("\\\\\\)")
+	ret = re.ReplaceAll([]byte(ret), []byte(")"))
+
+	re = regexp.MustCompile("\\\\\\\\")
+	ret = re.ReplaceAll([]byte(ret), []byte("\\"))
+
+	return string(ret)
+}
+
+func regexpCheckUA(c *check.C, ua string) {
+	re := regexp.MustCompile("(?P<dockerUA>.+) UpstreamClient(?P<upstreamUA>.+)")
+	substrArr := re.FindStringSubmatch(ua)
+
+	c.Assert(substrArr, check.HasLen, 3, check.Commentf("Expected 'UpstreamClient()' with upstream client UA"))
+	dockerUA := substrArr[1]
+	upstreamUAEscaped := substrArr[2]
+
+	// check dockerUA looks correct
+	reDockerUA := regexp.MustCompile("^docker/[0-9A-Za-z+]")
+	bMatchDockerUA := reDockerUA.MatchString(dockerUA)
+	c.Assert(bMatchDockerUA, check.Equals, true, check.Commentf("Docker Engine User-Agent malformed"))
+
+	// check upstreamUA looks correct
+	// Expecting something like:  Docker-Client/1.11.0-dev (linux)
+	upstreamUA := unescapeBackslashSemicolonParens(upstreamUAEscaped)
+	reUpstreamUA := regexp.MustCompile("^\\(Docker-Client/[0-9A-Za-z+]")
+	bMatchUpstreamUA := reUpstreamUA.MatchString(upstreamUA)
+	c.Assert(bMatchUpstreamUA, check.Equals, true, check.Commentf("(Upstream) Docker Client User-Agent malformed"))
+}
+
+// TestUserAgentPassThroughOnPull verifies that when an image is pulled from
+// a registry, the registry should see a User-Agent string of the form
+//   [docker engine UA] UptreamClientSTREAM-CLIENT([client UA])
+func (s *DockerRegistrySuite) TestUserAgentPassThroughOnPull(c *check.C) {
+	reg, err := newTestRegistry(c)
+	c.Assert(err, check.IsNil)
+	expectUpstreamUA := false
+
+	reg.registerHandler("/v2/", func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(404)
+		var ua string
+		for k, v := range r.Header {
+			if k == "User-Agent" {
+				ua = v[0]
+			}
+		}
+		c.Assert(ua, check.Not(check.Equals), "", check.Commentf("No User-Agent found in request"))
+		if r.URL.Path == "/v2/busybox/manifests/latest" {
+			if expectUpstreamUA {
+				regexpCheckUA(c, ua)
+			}
+		}
+	})
+
+	repoName := fmt.Sprintf("%s/busybox", reg.hostport)
+	err = s.d.Start("--insecure-registry", reg.hostport, "--disable-legacy-registry=true")
+	c.Assert(err, check.IsNil)
+
+	dockerfileName, cleanup, err := makefile(fmt.Sprintf("FROM %s/busybox", reg.hostport))
+	c.Assert(err, check.IsNil, check.Commentf("Unable to create test dockerfile"))
+	defer cleanup()
+
+	s.d.Cmd("build", "--file", dockerfileName, ".")
+
+	s.d.Cmd("run", repoName)
+	s.d.Cmd("login", "-u", "richard", "-p", "testtest", "-e", "testuser@testdomain.com", reg.hostport)
+	s.d.Cmd("tag", "busybox", repoName)
+	s.d.Cmd("push", repoName)
+
+	expectUpstreamUA = true
+	s.d.Cmd("pull", repoName)
+}