lib/upgrade: Send OS version header to upgrade server (#9663)

This adds a header with the operating system version, verbatim in
whatever format the operating system reports it, to the upgrade check.
The intention is that the upgrade server can use this information to
filter out (or maybe just mark) potentially unsupported upgrades.

lib/config/folderconfiguration.go

@@ -17,7 +17,7 @@ import (
 	"strings"
 	"time"
 
-	"github.com/shirou/gopsutil/v3/disk"
+	"github.com/shirou/gopsutil/v4/disk"
 
 	"github.com/syncthing/syncthing/lib/build"
 	"github.com/syncthing/syncthing/lib/db"

lib/fs/basicfs.go

@@ -15,7 +15,7 @@ import (
 	"strings"
 	"time"
 
-	"github.com/shirou/gopsutil/v3/disk"
+	"github.com/shirou/gopsutil/v4/disk"
 	"github.com/syncthing/syncthing/lib/build"
 )
 

lib/upgrade/upgrade_supported.go

@@ -28,6 +28,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/shirou/gopsutil/v4/host"
 	"github.com/syncthing/syncthing/lib/dialer"
 	"github.com/syncthing/syncthing/lib/signature"
 	"golang.org/x/net/http2"
@@ -76,8 +77,12 @@ var insecureHTTP = &http.Client{
 	},
 }
 
+var osVersion string
+
 func init() {
 	_ = http2.ConfigureTransport(insecureHTTP.Transport.(*http.Transport))
+	osVersion, _ = host.KernelVersion()
+	osVersion = strings.TrimSpace(osVersion)
 }
 
 func insecureGet(url, version string) (*http.Response, error) {
@@ -87,6 +92,9 @@ func insecureGet(url, version string) (*http.Response, error) {
 	}
 
 	req.Header.Set("User-Agent", fmt.Sprintf(`syncthing %s (%s %s-%s)`, version, runtime.Version(), runtime.GOOS, runtime.GOARCH))
+	if osVersion != "" {
+		req.Header.Set("Syncthing-Os-Version", osVersion)
+	}
 	return insecureHTTP.Do(req)
 }
 
@@ -118,9 +126,11 @@ type SortByRelease []Release
 func (s SortByRelease) Len() int {
 	return len(s)
 }
+
 func (s SortByRelease) Swap(i, j int) {
 	s[i], s[j] = s[j], s[i]
 }
+
 func (s SortByRelease) Less(i, j int) bool {
 	return CompareVersions(s[i].Tag, s[j].Tag) > 0
 }
@@ -428,7 +438,7 @@ func writeBinary(dir string, inFile io.Reader) (filename string, err error) {
 		return "", err
 	}
 
-	err = os.Chmod(outFile.Name(), os.FileMode(0755))
+	err = os.Chmod(outFile.Name(), os.FileMode(0o755))
 	if err != nil {
 		os.Remove(outFile.Name())
 		return "", err