From e53cd07fcc3f5ea89b7806b84600f23bd6563301 Mon Sep 17 00:00:00 2001
From: Sebastiaan van Stijn <github@gone.nl>
Date: Fri, 27 Jun 2025 18:03:47 +0200
Subject: [PATCH] client: remove getDockerOS utility in favor of "Ostype"
 header

This utility was added in 83b5729f6452de6b40719b9485947eea0bd0eedd to
replace httputils.ParseServerHeader, which was added to print a warning
on Windows in 126529c6d0a20675de8f50939c57f23259d3e763. At the time, the
only available option to detect the daemon's OS was to parse the `Server`
header, which contained the version of Docker as well as the OS.

However, 7199522ea2e77c77bf931474eca92aa502ce0031 introduced an `OSType`
("Ostype") header that's included on all responses, and a later commit
e9dac5ef5e8a4b0ecce0c89d337fea90f2c6aef3 changed that to also be included
when producing an error for unsupported API versions.

Note that the casing in the midddleware was changed from `OSType` to
`Ostype` (normalized form) in 76a5ca1d4d97ad313b8f1f0deb1ae5563a158a40,
but headers are case-insensitive, and `header.Get()` should handle either
case in the response.

In short; every API response contains an "Ostype" header, which already
contains the OS ("windows" or "linux") that doesn't require any parsing,
so let's put that header to use.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
(cherry picked from commit fcf3ff1b2f04035ccdd5c53fd510f088f0784a13)
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
---
 client/container_stats.go  |  4 ++--
 client/image_build.go      |  2 +-
 client/image_build_test.go | 14 +-------------
 client/utils.go            | 13 -------------
 4 files changed, 4 insertions(+), 29 deletions(-)

diff --git a/client/container_stats.go b/client/container_stats.go
index 2244e0f4b9..076954f4c3 100644
--- a/client/container_stats.go
+++ b/client/container_stats.go
@@ -28,7 +28,7 @@ func (cli *Client) ContainerStats(ctx context.Context, containerID string, strea
 
 	return container.StatsResponseReader{
 		Body:   resp.Body,
-		OSType: getDockerOS(resp.Header.Get("Server")),
+		OSType: resp.Header.Get("Ostype"),
 	}, nil
 }
 
@@ -51,6 +51,6 @@ func (cli *Client) ContainerStatsOneShot(ctx context.Context, containerID string
 
 	return container.StatsResponseReader{
 		Body:   resp.Body,
-		OSType: getDockerOS(resp.Header.Get("Server")),
+		OSType: resp.Header.Get("Ostype"),
 	}, nil
 }
diff --git a/client/image_build.go b/client/image_build.go
index 66ca75e4af..1ed0878bfd 100644
--- a/client/image_build.go
+++ b/client/image_build.go
@@ -40,7 +40,7 @@ func (cli *Client) ImageBuild(ctx context.Context, buildContext io.Reader, optio
 
 	return build.ImageBuildResponse{
 		Body:   resp.Body,
-		OSType: getDockerOS(resp.Header.Get("Server")),
+		OSType: resp.Header.Get("Ostype"),
 	}, nil
 }
 
diff --git a/client/image_build_test.go b/client/image_build_test.go
index 5610391fdf..76c514962d 100644
--- a/client/image_build_test.go
+++ b/client/image_build_test.go
@@ -191,7 +191,7 @@ func TestImageBuild(t *testing.T) {
 				}
 
 				headers := http.Header{}
-				headers.Add("Server", "Docker/v1.23 (MyOS)")
+				headers.Add("Ostype", "MyOS")
 				return &http.Response{
 					StatusCode: http.StatusOK,
 					Body:       io.NopCloser(bytes.NewReader([]byte("body"))),
@@ -208,15 +208,3 @@ func TestImageBuild(t *testing.T) {
 		assert.Check(t, is.Equal(string(response), "body"))
 	}
 }
-
-func TestGetDockerOS(t *testing.T) {
-	cases := map[string]string{
-		"Docker/v1.22 (linux)":   "linux",
-		"Docker/v1.22 (windows)": "windows",
-		"Foo/v1.22 (bar)":        "",
-	}
-	for header, os := range cases {
-		g := getDockerOS(header)
-		assert.Check(t, is.Equal(g, os))
-	}
-}
diff --git a/client/utils.go b/client/utils.go
index 67e1e6934b..7b82f185ac 100644
--- a/client/utils.go
+++ b/client/utils.go
@@ -8,12 +8,9 @@ import (
 
 	cerrdefs "github.com/containerd/errdefs"
 	"github.com/docker/docker/api/types/filters"
-	"github.com/docker/docker/internal/lazyregexp"
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 )
 
-var headerRegexp = lazyregexp.New(`\ADocker/.+\s\((.+)\)\z`)
-
 type emptyIDError string
 
 func (e emptyIDError) InvalidParameter() {}
@@ -31,16 +28,6 @@ func trimID(objType, id string) (string, error) {
 	return id, nil
 }
 
-// getDockerOS returns the operating system based on the server header from the daemon.
-func getDockerOS(serverHeader string) string {
-	var osType string
-	matches := headerRegexp.FindStringSubmatch(serverHeader)
-	if len(matches) > 0 {
-		osType = matches[1]
-	}
-	return osType
-}
-
 // getFiltersQuery returns a url query with "filters" query term, based on the
 // filters provided.
 func getFiltersQuery(f filters.Args) (url.Values, error) {