Merge pull request #205 from ebiggers/autoselect-v2

Automatically enable policy_version 2 when kernel support is detected

2 files changed, 30 insertions, 0 deletions

diff --git a/util/util.go b/util/util.go
index 97ee33c..d97a7ae 100644
--- a/util/util.go
+++ b/util/util.go
@@ -25,10 +25,14 @@ package util
 
 import (
 	"bufio"
+	"fmt"
+	"log"
 	"os"
 	"os/user"
 	"strconv"
 	"unsafe"
+
+	"golang.org/x/sys/unix"
 )
 
 // Ptr converts a Go byte array to a pointer to the start of the array.
@@ -126,3 +130,22 @@ func EffectiveUser() (*user.User, error) {
 func IsUserRoot() bool {
 	return os.Geteuid() == 0
 }
+
+// IsKernelVersionAtLeast returns true if the Linux kernel version is at least
+// major.minor. If something goes wrong it assumes false.
+func IsKernelVersionAtLeast(major, minor int) bool {
+	var uname unix.Utsname
+	if err := unix.Uname(&uname); err != nil {
+		log.Printf("Uname failed [%v], assuming old kernel", err)
+		return false
+	}
+	release := string(uname.Release[:])
+	log.Printf("Kernel version is %s", release)
+	var actualMajor, actualMinor int
+	if n, _ := fmt.Sscanf(release, "%d.%d", &actualMajor, &actualMinor); n != 2 {
+		log.Printf("Unrecognized uname format %q, assuming old kernel", release)
+		return false
+	}
+	return actualMajor > major ||
+		(actualMajor == major && actualMinor >= minor)
+}
diff --git a/util/util_test.go b/util/util_test.go
index 7739edd..70e7070 100644
--- a/util/util_test.go
+++ b/util/util_test.go
@@ -91,3 +91,10 @@ func TestNeverErrorNoPanic(t *testing.T) {
 
 	NeverError(nil)
 }
+
+func TestIsKernelVersionAtLeast(t *testing.T) {
+	// Even just running Go requires at least v2.6.23, so...
+	if !IsKernelVersionAtLeast(2, 6) {
+		t.Error("IsKernelVersionAtLeast() is broken")
+	}
+}