vendor github.com/miekg/dns/internal

vendor/github.com/miekg/dns/internal/socket/controlmessage.go

@@ -0,0 +1,118 @@
+package socket
+
+import (
+	"errors"
+	"unsafe"
+)
+
+func controlHeaderLen() int {
+	return roundup(sizeofCmsghdr)
+}
+
+func controlMessageLen(dataLen int) int {
+	return roundup(sizeofCmsghdr) + dataLen
+}
+
+// returns the whole length of control message.
+func ControlMessageSpace(dataLen int) int {
+	return roundup(sizeofCmsghdr) + roundup(dataLen)
+}
+
+// A ControlMessage represents the head message in a stream of control
+// messages.
+//
+// A control message comprises of a header, data and a few padding
+// fields to conform to the interface to the kernel.
+//
+// See RFC 3542 for further information.
+type ControlMessage []byte
+
+// Data returns the data field of the control message at the head.
+func (m ControlMessage) Data(dataLen int) []byte {
+	l := controlHeaderLen()
+	if len(m) < l || len(m) < l+dataLen {
+		return nil
+	}
+	return m[l : l+dataLen]
+}
+
+// ParseHeader parses and returns the header fields of the control
+// message at the head.
+func (m ControlMessage) ParseHeader() (lvl, typ, dataLen int, err error) {
+	l := controlHeaderLen()
+	if len(m) < l {
+		return 0, 0, 0, errors.New("short message")
+	}
+	h := (*cmsghdr)(unsafe.Pointer(&m[0]))
+	return h.lvl(), h.typ(), int(uint64(h.len()) - uint64(l)), nil
+}
+
+// Next returns the control message at the next.
+func (m ControlMessage) Next(dataLen int) ControlMessage {
+	l := ControlMessageSpace(dataLen)
+	if len(m) < l {
+		return nil
+	}
+	return m[l:]
+}
+
+// MarshalHeader marshals the header fields of the control message at
+// the head.
+func (m ControlMessage) MarshalHeader(lvl, typ, dataLen int) error {
+	if len(m) < controlHeaderLen() {
+		return errors.New("short message")
+	}
+	h := (*cmsghdr)(unsafe.Pointer(&m[0]))
+	h.set(controlMessageLen(dataLen), lvl, typ)
+	return nil
+}
+
+// Marshal marshals the control message at the head, and returns the next
+// control message.
+func (m ControlMessage) Marshal(lvl, typ int, data []byte) (ControlMessage, error) {
+	l := len(data)
+	if len(m) < ControlMessageSpace(l) {
+		return nil, errors.New("short message")
+	}
+	h := (*cmsghdr)(unsafe.Pointer(&m[0]))
+	h.set(controlMessageLen(l), lvl, typ)
+	if l > 0 {
+		copy(m.Data(l), data)
+	}
+	return m.Next(l), nil
+}
+
+// Parse parses as a single or multiple control messages.
+func (m ControlMessage) Parse() ([]ControlMessage, error) {
+	var ms []ControlMessage
+	for len(m) >= controlHeaderLen() {
+		h := (*cmsghdr)(unsafe.Pointer(&m[0]))
+		l := h.len()
+		if l <= 0 {
+			return nil, errors.New("invalid header length")
+		}
+		if uint64(l) < uint64(controlHeaderLen()) {
+			return nil, errors.New("invalid message length")
+		}
+		if uint64(l) > uint64(len(m)) {
+			return nil, errors.New("short buffer")
+		}
+		ms = append(ms, ControlMessage(m[:l]))
+		ll := l - controlHeaderLen()
+		if len(m) >= ControlMessageSpace(ll) {
+			m = m[ControlMessageSpace(ll):]
+		} else {
+			m = m[controlMessageLen(ll):]
+		}
+	}
+	return ms, nil
+}
+
+// NewControlMessage returns a new stream of control messages.
+func NewControlMessage(dataLen []int) ControlMessage {
+	var l int
+	for i := range dataLen {
+		l += ControlMessageSpace(dataLen[i])
+	}
+	return make([]byte, l)
+}