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107 lines
3.1 KiB
Go
107 lines
3.1 KiB
Go
// Copyright 2011 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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//go:build aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd || solaris || zos
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// Socket control messages
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package unix
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import (
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"unsafe"
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)
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// CmsgLen returns the value to store in the Len field of the Cmsghdr
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// structure, taking into account any necessary alignment.
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func CmsgLen(datalen int) int {
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return cmsgAlignOf(SizeofCmsghdr) + datalen
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}
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// CmsgSpace returns the number of bytes an ancillary element with
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// payload of the passed data length occupies.
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func CmsgSpace(datalen int) int {
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return cmsgAlignOf(SizeofCmsghdr) + cmsgAlignOf(datalen)
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}
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func (h *Cmsghdr) data(offset uintptr) unsafe.Pointer {
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return unsafe.Pointer(uintptr(unsafe.Pointer(h)) + uintptr(cmsgAlignOf(SizeofCmsghdr)) + offset)
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}
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// SocketControlMessage represents a socket control message.
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type SocketControlMessage struct {
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Header Cmsghdr
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Data []byte
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}
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// ParseSocketControlMessage parses b as an array of socket control
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// messages.
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func ParseSocketControlMessage(b []byte) ([]SocketControlMessage, error) {
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var msgs []SocketControlMessage
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i := 0
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for i+CmsgLen(0) <= len(b) {
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h, dbuf, err := socketControlMessageHeaderAndData(b[i:])
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if err != nil {
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return nil, err
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}
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m := SocketControlMessage{Header: *h, Data: dbuf}
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msgs = append(msgs, m)
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i += cmsgAlignOf(int(h.Len))
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}
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return msgs, nil
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}
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// ParseOneSocketControlMessage parses a single socket control message from b, returning the message header,
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// message data (a slice of b), and the remainder of b after that single message.
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// When there are no remaining messages, len(remainder) == 0.
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func ParseOneSocketControlMessage(b []byte) (hdr Cmsghdr, data []byte, remainder []byte, err error) {
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h, dbuf, err := socketControlMessageHeaderAndData(b)
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if err != nil {
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return Cmsghdr{}, nil, nil, err
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}
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if i := cmsgAlignOf(int(h.Len)); i < len(b) {
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remainder = b[i:]
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}
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return *h, dbuf, remainder, nil
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}
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func socketControlMessageHeaderAndData(b []byte) (*Cmsghdr, []byte, error) {
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h := (*Cmsghdr)(unsafe.Pointer(&b[0]))
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if h.Len < SizeofCmsghdr || uint64(h.Len) > uint64(len(b)) {
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return nil, nil, EINVAL
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}
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return h, b[cmsgAlignOf(SizeofCmsghdr):h.Len], nil
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}
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// UnixRights encodes a set of open file descriptors into a socket
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// control message for sending to another process.
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func UnixRights(fds ...int) []byte {
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datalen := len(fds) * 4
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b := make([]byte, CmsgSpace(datalen))
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h := (*Cmsghdr)(unsafe.Pointer(&b[0]))
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h.Level = SOL_SOCKET
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h.Type = SCM_RIGHTS
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h.SetLen(CmsgLen(datalen))
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for i, fd := range fds {
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*(*int32)(h.data(4 * uintptr(i))) = int32(fd)
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}
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return b
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}
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// ParseUnixRights decodes a socket control message that contains an
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// integer array of open file descriptors from another process.
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func ParseUnixRights(m *SocketControlMessage) ([]int, error) {
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if m.Header.Level != SOL_SOCKET {
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return nil, EINVAL
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}
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if m.Header.Type != SCM_RIGHTS {
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return nil, EINVAL
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}
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fds := make([]int, len(m.Data)>>2)
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for i, j := 0, 0; i < len(m.Data); i += 4 {
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fds[j] = int(*(*int32)(unsafe.Pointer(&m.Data[i])))
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j++
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}
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return fds, nil
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}
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