112 lines
3.1 KiB
Go
112 lines
3.1 KiB
Go
// Copyright 2011 The Go Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE file.
|
|
|
|
// +build darwin dragonfly freebsd linux netbsd openbsd solaris
|
|
|
|
// Socket control messages
|
|
|
|
package syscall
|
|
|
|
import (
|
|
"runtime"
|
|
"unsafe"
|
|
)
|
|
|
|
// Round the length of a raw sockaddr up to align it properly.
|
|
func cmsgAlignOf(salen int) int {
|
|
salign := int(sizeofPtr)
|
|
// NOTE: It seems like 64-bit Darwin and DragonFly BSD kernels
|
|
// still require 32-bit aligned access to network subsystem.
|
|
if darwin64Bit || dragonfly64Bit {
|
|
salign = 4
|
|
}
|
|
// NOTE: Solaris always uses 32-bit alignment,
|
|
// cf. _CMSG_DATA_ALIGNMENT in <sys/socket.h>.
|
|
if runtime.GOOS == "solaris" {
|
|
salign = 4
|
|
}
|
|
return (salen + salign - 1) & ^(salign - 1)
|
|
}
|
|
|
|
// CmsgLen returns the value to store in the Len field of the Cmsghdr
|
|
// structure, taking into account any necessary alignment.
|
|
func CmsgLen(datalen int) int {
|
|
return cmsgAlignOf(SizeofCmsghdr) + datalen
|
|
}
|
|
|
|
// CmsgSpace returns the number of bytes an ancillary element with
|
|
// payload of the passed data length occupies.
|
|
func CmsgSpace(datalen int) int {
|
|
return cmsgAlignOf(SizeofCmsghdr) + cmsgAlignOf(datalen)
|
|
}
|
|
|
|
func cmsgData(h *Cmsghdr) unsafe.Pointer {
|
|
return unsafe.Pointer(uintptr(unsafe.Pointer(h)) + uintptr(cmsgAlignOf(SizeofCmsghdr)))
|
|
}
|
|
|
|
// SocketControlMessage represents a socket control message.
|
|
type SocketControlMessage struct {
|
|
Header Cmsghdr
|
|
Data []byte
|
|
}
|
|
|
|
// ParseSocketControlMessage parses b as an array of socket control
|
|
// messages.
|
|
func ParseSocketControlMessage(b []byte) ([]SocketControlMessage, error) {
|
|
var msgs []SocketControlMessage
|
|
i := 0
|
|
for i+CmsgLen(0) <= len(b) {
|
|
h, dbuf, err := socketControlMessageHeaderAndData(b[i:])
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
m := SocketControlMessage{Header: *h, Data: dbuf}
|
|
msgs = append(msgs, m)
|
|
i += cmsgAlignOf(int(h.Len))
|
|
}
|
|
return msgs, nil
|
|
}
|
|
|
|
func socketControlMessageHeaderAndData(b []byte) (*Cmsghdr, []byte, error) {
|
|
h := (*Cmsghdr)(unsafe.Pointer(&b[0]))
|
|
if h.Len < SizeofCmsghdr || uint64(h.Len) > uint64(len(b)) {
|
|
return nil, nil, EINVAL
|
|
}
|
|
return h, b[cmsgAlignOf(SizeofCmsghdr):h.Len], nil
|
|
}
|
|
|
|
// UnixRights encodes a set of open file descriptors into a socket
|
|
// control message for sending to another process.
|
|
func UnixRights(fds ...int) []byte {
|
|
datalen := len(fds) * 4
|
|
b := make([]byte, CmsgSpace(datalen))
|
|
h := (*Cmsghdr)(unsafe.Pointer(&b[0]))
|
|
h.Level = SOL_SOCKET
|
|
h.Type = SCM_RIGHTS
|
|
h.SetLen(CmsgLen(datalen))
|
|
data := cmsgData(h)
|
|
for _, fd := range fds {
|
|
*(*int32)(data) = int32(fd)
|
|
data = unsafe.Pointer(uintptr(data) + 4)
|
|
}
|
|
return b
|
|
}
|
|
|
|
// ParseUnixRights decodes a socket control message that contains an
|
|
// integer array of open file descriptors from another process.
|
|
func ParseUnixRights(m *SocketControlMessage) ([]int, error) {
|
|
if m.Header.Level != SOL_SOCKET {
|
|
return nil, EINVAL
|
|
}
|
|
if m.Header.Type != SCM_RIGHTS {
|
|
return nil, EINVAL
|
|
}
|
|
fds := make([]int, len(m.Data)>>2)
|
|
for i, j := 0, 0; i < len(m.Data); i += 4 {
|
|
fds[j] = int(*(*int32)(unsafe.Pointer(&m.Data[i])))
|
|
j++
|
|
}
|
|
return fds, nil
|
|
}
|