1 // Copyright 2011 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
5 // +build aix darwin dragonfly freebsd linux netbsd openbsd solaris
7 // Socket control messages
16 // Round the length of a raw sockaddr up to align it properly.
17 func cmsgAlignOf(salen int) int {
21 case "darwin", "dragonfly", "solaris":
22 // NOTE: It seems like 64-bit Darwin, DragonFly BSD and
23 // Solaris kernels still require 32-bit aligned access to
28 case "netbsd", "openbsd":
29 // NetBSD and OpenBSD armv7 require 64-bit alignment.
30 if runtime.GOARCH == "arm" {
35 return (salen + salign - 1) & ^(salign - 1)
38 // CmsgLen returns the value to store in the Len field of the Cmsghdr
39 // structure, taking into account any necessary alignment.
40 func CmsgLen(datalen int) int {
41 return cmsgAlignOf(SizeofCmsghdr) + datalen
44 // CmsgSpace returns the number of bytes an ancillary element with
45 // payload of the passed data length occupies.
46 func CmsgSpace(datalen int) int {
47 return cmsgAlignOf(SizeofCmsghdr) + cmsgAlignOf(datalen)
50 func cmsgData(h *Cmsghdr) unsafe.Pointer {
51 return unsafe.Pointer(uintptr(unsafe.Pointer(h)) + uintptr(cmsgAlignOf(SizeofCmsghdr)))
54 // SocketControlMessage represents a socket control message.
55 type SocketControlMessage struct {
60 // ParseSocketControlMessage parses b as an array of socket control
62 func ParseSocketControlMessage(b []byte) ([]SocketControlMessage, error) {
63 var msgs []SocketControlMessage
65 for i+CmsgLen(0) <= len(b) {
66 h, dbuf, err := socketControlMessageHeaderAndData(b[i:])
70 m := SocketControlMessage{Header: *h, Data: dbuf}
71 msgs = append(msgs, m)
72 i += cmsgAlignOf(int(h.Len))
77 func socketControlMessageHeaderAndData(b []byte) (*Cmsghdr, []byte, error) {
78 h := (*Cmsghdr)(unsafe.Pointer(&b[0]))
79 if h.Len < SizeofCmsghdr || uint64(h.Len) > uint64(len(b)) {
80 return nil, nil, EINVAL
82 return h, b[cmsgAlignOf(SizeofCmsghdr):h.Len], nil
85 // UnixRights encodes a set of open file descriptors into a socket
86 // control message for sending to another process.
87 func UnixRights(fds ...int) []byte {
88 datalen := len(fds) * 4
89 b := make([]byte, CmsgSpace(datalen))
90 h := (*Cmsghdr)(unsafe.Pointer(&b[0]))
93 h.SetLen(CmsgLen(datalen))
95 for _, fd := range fds {
96 *(*int32)(data) = int32(fd)
97 data = unsafe.Pointer(uintptr(data) + 4)
102 // ParseUnixRights decodes a socket control message that contains an
103 // integer array of open file descriptors from another process.
104 func ParseUnixRights(m *SocketControlMessage) ([]int, error) {
105 if m.Header.Level != SOL_SOCKET {
108 if m.Header.Type != SCM_RIGHTS {
111 fds := make([]int, len(m.Data)>>2)
112 for i, j := 0, 0; i < len(m.Data); i += 4 {
113 fds[j] = int(*(*int32)(unsafe.Pointer(&m.Data[i])))