hostinfo, tailcfg: split Hostinfo.OSVersion into separate fields

Stop jamming everything into one string.

Fixes #5578

Change-Id: I7dec8d6c073bddc7dc5f653e3baf2b4bf6b68378
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

hostinfo/hostinfo_linux.go

@@ -9,7 +9,6 @@ package hostinfo
 
 import (
 	"bytes"
-	"fmt"
 	"io/ioutil"
 	"os"
 	"strings"
@@ -21,14 +20,39 @@ import (
 )
 
 func init() {
-	osVersion = osVersionLinux
+	osVersion = lazyOSVersion.Get
 	packageType = packageTypeLinux
-
+	distroName = distroNameLinux
+	distroVersion = distroVersionLinux
+	distroCodeName = distroCodeNameLinux
 	if v := linuxDeviceModel(); v != "" {
 		SetDeviceModel(v)
 	}
 }
 
+var (
+	lazyVersionMeta = &lazyAtomicValue[versionMeta]{f: ptrTo(linuxVersionMeta)}
+	lazyOSVersion   = &lazyAtomicValue[string]{f: ptrTo(osVersionLinux)}
+)
+
+type versionMeta struct {
+	DistroName     string
+	DistroVersion  string
+	DistroCodeName string // "jammy", etc (VERSION_CODENAME from /etc/os-release)
+}
+
+func distroNameLinux() string {
+	return lazyVersionMeta.Get().DistroName
+}
+
+func distroVersionLinux() string {
+	return lazyVersionMeta.Get().DistroVersion
+}
+
+func distroCodeNameLinux() string {
+	return lazyVersionMeta.Get().DistroCodeName
+}
+
 func linuxDeviceModel() string {
 	for _, path := range []string{
 		// First try the Synology-specific location.
@@ -52,15 +76,22 @@ func linuxDeviceModel() string {
 func getQnapQtsVersion(versionInfo string) string {
 	for _, field := range strings.Fields(versionInfo) {
 		if suffix, ok := strs.CutPrefix(field, "QTSFW_"); ok {
-			return "QTS " + suffix
+			return suffix
 		}
 	}
 	return ""
 }
 
 func osVersionLinux() string {
-	// TODO(bradfitz,dgentry): cache this, or make caller(s) cache it.
+	var un unix.Utsname
+	unix.Uname(&un)
+	return unix.ByteSliceToString(un.Release[:])
+}
+
+func linuxVersionMeta() (meta versionMeta) {
 	dist := distro.Get()
+	meta.DistroName = string(dist)
+
 	propFile := "/etc/os-release"
 	switch dist {
 	case distro.Synology:
@@ -69,10 +100,12 @@ func osVersionLinux() string {
 		propFile = "/etc/openwrt_release"
 	case distro.WDMyCloud:
 		slurp, _ := ioutil.ReadFile("/etc/version")
-		return fmt.Sprintf("%s", string(bytes.TrimSpace(slurp)))
+		meta.DistroVersion = string(bytes.TrimSpace(slurp))
+		return
 	case distro.QNAP:
 		slurp, _ := ioutil.ReadFile("/etc/version_info")
-		return getQnapQtsVersion(string(slurp))
+		meta.DistroVersion = getQnapQtsVersion(string(slurp))
+		return
 	}
 
 	m := map[string]string{}
@@ -86,50 +119,45 @@ func osVersionLinux() string {
 		return nil
 	})
 
-	var un unix.Utsname
-	unix.Uname(&un)
-
-	var attrBuf strings.Builder
-	attrBuf.WriteString("; kernel=")
-	attrBuf.WriteString(unix.ByteSliceToString(un.Release[:]))
-	if inContainer() {
-		attrBuf.WriteString("; container")
+	if v := m["VERSION_CODENAME"]; v != "" {
+		meta.DistroCodeName = v
 	}
-	if env := GetEnvType(); env != "" {
-		fmt.Fprintf(&attrBuf, "; env=%s", env)
+	if v := m["VERSION_ID"]; v != "" {
+		meta.DistroVersion = v
 	}
-	attr := attrBuf.String()
-
 	id := m["ID"]
-
+	if id != "" {
+		meta.DistroName = id
+	}
 	switch id {
 	case "debian":
+		// Debian's VERSION_ID is just like "11". But /etc/debian_version has "11.5" normally.
+		// Or "bookworm/sid" on sid/testing.
 		slurp, _ := ioutil.ReadFile("/etc/debian_version")
-		return fmt.Sprintf("Debian %s (%s)%s", bytes.TrimSpace(slurp), m["VERSION_CODENAME"], attr)
-	case "ubuntu":
-		return fmt.Sprintf("Ubuntu %s%s", m["VERSION"], attr)
+		if v := string(bytes.TrimSpace(slurp)); v != "" {
+			if '0' <= v[0] && v[0] <= '9' {
+				meta.DistroVersion = v
+			} else if meta.DistroCodeName == "" {
+				meta.DistroCodeName = v
+			}
+		}
 	case "", "centos": // CentOS 6 has no /etc/os-release, so its id is ""
-		if cr, _ := ioutil.ReadFile("/etc/centos-release"); len(cr) > 0 { // "CentOS release 6.10 (Final)
-			return fmt.Sprintf("%s%s", bytes.TrimSpace(cr), attr)
-		}
-		fallthrough
-	case "fedora", "rhel", "alpine", "nixos":
-		// Their PRETTY_NAME is fine as-is for all versions I tested.
-		fallthrough
-	default:
-		if v := m["PRETTY_NAME"]; v != "" {
-			return fmt.Sprintf("%s%s", v, attr)
+		if meta.DistroVersion == "" {
+			if cr, _ := ioutil.ReadFile("/etc/centos-release"); len(cr) > 0 { // "CentOS release 6.10 (Final)
+				meta.DistroVersion = string(bytes.TrimSpace(cr))
+			}
 		}
 	}
+	if v := m["PRETTY_NAME"]; v != "" && meta.DistroVersion == "" && !strings.HasSuffix(v, "/sid") {
+		meta.DistroVersion = v
+	}
 	switch dist {
 	case distro.Synology:
-		return fmt.Sprintf("Synology %s%s", m["productversion"], attr)
+		meta.DistroVersion = m["productversion"]
 	case distro.OpenWrt:
-		return fmt.Sprintf("OpenWrt %s%s", m["DISTRIB_RELEASE"], attr)
-	case distro.Gokrazy:
-		return fmt.Sprintf("Gokrazy%s", attr)
+		meta.DistroVersion = m["DISTRIB_RELEASE"]
 	}
-	return fmt.Sprintf("Other%s", attr)
+	return
 }
 
 func packageTypeLinux() string {