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