diff options
Diffstat (limited to 'vendor/github.com/cilium/ebpf/internal/feature.go')
-rw-r--r-- | vendor/github.com/cilium/ebpf/internal/feature.go | 138 |
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 +} |