1 files changed, 138 insertions, 0 deletions
diff --git a/vendor/github.com/cilium/ebpf/internal/feature.go b/vendor/github.com/cilium/ebpf/internal/feature.go
new file mode 100644
index 000000000..ec62ed39b
--- /dev/null
+++ b/vendor/github.com/cilium/ebpf/internal/feature.go
@@ -0,0 +1,138 @@
+package internal
+
+import (
+	"errors"
+	"fmt"
+	"sync"
+)
+
+// ErrNotSupported indicates that a feature is not supported by the current kernel.
+var ErrNotSupported = errors.New("not supported")
+
+// UnsupportedFeatureError is returned by FeatureTest() functions.
+type UnsupportedFeatureError struct {
+	// The minimum Linux mainline version required for this feature.
+	// Used for the error string, and for sanity checking during testing.
+	MinimumVersion Version
+
+	// The name of the feature that isn't supported.
+	Name string
+}
+
+func (ufe *UnsupportedFeatureError) Error() string {
+	if ufe.MinimumVersion.Unspecified() {
+		return fmt.Sprintf("%s not supported", ufe.Name)
+	}
+	return fmt.Sprintf("%s not supported (requires >= %s)", ufe.Name, ufe.MinimumVersion)
+}
+
+// Is indicates that UnsupportedFeatureError is ErrNotSupported.
+func (ufe *UnsupportedFeatureError) Is(target error) bool {
+	return target == ErrNotSupported
+}
+
+type featureTest struct {
+	sync.RWMutex
+	successful bool
+	result     error
+}
+
+// FeatureTestFn is used to determine whether the kernel supports
+// a certain feature.
+//
+// The return values have the following semantics:
+//
+//   err == ErrNotSupported: the feature is not available
+//   err == nil: the feature is available
+//   err != nil: the test couldn't be executed
+type FeatureTestFn func() error
+
+// FeatureTest wraps a function so that it is run at most once.
+//
+// name should identify the tested feature, while version must be in the
+// form Major.Minor[.Patch].
+//
+// Returns an error wrapping ErrNotSupported if the feature is not supported.
+func FeatureTest(name, version string, fn FeatureTestFn) func() error {
+	v, err := NewVersion(version)
+	if err != nil {
+		return func() error { return err }
+	}
+
+	ft := new(featureTest)
+	return func() error {
+		ft.RLock()
+		if ft.successful {
+			defer ft.RUnlock()
+			return ft.result
+		}
+		ft.RUnlock()
+		ft.Lock()
+		defer ft.Unlock()
+		// check one more time on the off
+		// chance that two go routines
+		// were able to call into the write
+		// lock
+		if ft.successful {
+			return ft.result
+		}
+		err := fn()
+		switch {
+		case errors.Is(err, ErrNotSupported):
+			ft.result = &UnsupportedFeatureError{
+				MinimumVersion: v,
+				Name:           name,
+			}
+			fallthrough
+
+		case err == nil:
+			ft.successful = true
+
+		default:
+			// We couldn't execute the feature test to a point
+			// where it could make a determination.
+			// Don't cache the result, just return it.
+			return fmt.Errorf("detect support for %s: %w", name, err)
+		}
+
+		return ft.result
+	}
+}
+
+// A Version in the form Major.Minor.Patch.
+type Version [3]uint16
+
+// NewVersion creates a version from a string like "Major.Minor.Patch".
+//
+// Patch is optional.
+func NewVersion(ver string) (Version, error) {
+	var major, minor, patch uint16
+	n, _ := fmt.Sscanf(ver, "%d.%d.%d", &major, &minor, &patch)
+	if n < 2 {
+		return Version{}, fmt.Errorf("invalid version: %s", ver)
+	}
+	return Version{major, minor, patch}, nil
+}
+
+func (v Version) String() string {
+	if v[2] == 0 {
+		return fmt.Sprintf("v%d.%d", v[0], v[1])
+	}
+	return fmt.Sprintf("v%d.%d.%d", v[0], v[1], v[2])
+}
+
+// Less returns true if the version is less than another version.
+func (v Version) Less(other Version) bool {
+	for i, a := range v {
+		if a == other[i] {
+			continue
+		}
+		return a < other[i]
+	}
+	return false
+}
+
+// Unspecified returns true if the version is all zero.
+func (v Version) Unspecified() bool {
+	return v[0] == 0 && v[1] == 0 && v[2] == 0
+}