116 lines
2.8 KiB
Go
116 lines
2.8 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 freebsd linux netbsd openbsd
|
|
|
|
// Socket control messages
|
|
|
|
package syscall
|
|
|
|
import (
|
|
"unsafe"
|
|
)
|
|
|
|
// Round the length of a raw sockaddr up to align it propery.
|
|
func cmsgAlignOf(salen int) int {
|
|
salign := sizeofPtr
|
|
// NOTE: It seems like 64-bit Darwin kernel still requires 32-bit
|
|
// aligned access to BSD subsystem.
|
|
if darwinAMD64 {
|
|
salign = 4
|
|
}
|
|
if salen == 0 {
|
|
return salign
|
|
}
|
|
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(cmsg *Cmsghdr) unsafe.Pointer {
|
|
return unsafe.Pointer(uintptr(unsafe.Pointer(cmsg)) + SizeofCmsghdr)
|
|
}
|
|
|
|
type SocketControlMessage struct {
|
|
Header Cmsghdr
|
|
Data []byte
|
|
}
|
|
|
|
func ParseSocketControlMessage(buf []byte) ([]SocketControlMessage, error) {
|
|
var (
|
|
h *Cmsghdr
|
|
dbuf []byte
|
|
e error
|
|
cmsgs []SocketControlMessage
|
|
)
|
|
|
|
for len(buf) >= CmsgLen(0) {
|
|
h, dbuf, e = socketControlMessageHeaderAndData(buf)
|
|
if e != nil {
|
|
break
|
|
}
|
|
m := SocketControlMessage{}
|
|
m.Header = *h
|
|
m.Data = dbuf[:int(h.Len)-cmsgAlignOf(SizeofCmsghdr)]
|
|
cmsgs = append(cmsgs, m)
|
|
buf = buf[cmsgAlignOf(int(h.Len)):]
|
|
}
|
|
|
|
return cmsgs, e
|
|
}
|
|
|
|
func socketControlMessageHeaderAndData(buf []byte) (*Cmsghdr, []byte, error) {
|
|
h := (*Cmsghdr)(unsafe.Pointer(&buf[0]))
|
|
if h.Len < SizeofCmsghdr || int(h.Len) > len(buf) {
|
|
return nil, nil, EINVAL
|
|
}
|
|
return h, buf[cmsgAlignOf(SizeofCmsghdr):], 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
|
|
buf := make([]byte, CmsgSpace(datalen))
|
|
cmsg := (*Cmsghdr)(unsafe.Pointer(&buf[0]))
|
|
cmsg.Level = SOL_SOCKET
|
|
cmsg.Type = SCM_RIGHTS
|
|
cmsg.SetLen(CmsgLen(datalen))
|
|
|
|
data := uintptr(cmsgData(cmsg))
|
|
for _, fd := range fds {
|
|
*(*int32)(unsafe.Pointer(data)) = int32(fd)
|
|
data += 4
|
|
}
|
|
|
|
return buf
|
|
}
|
|
|
|
// ParseUnixRights decodes a socket control message that contains an
|
|
// integer array of open file descriptors from another process.
|
|
func ParseUnixRights(msg *SocketControlMessage) ([]int, error) {
|
|
if msg.Header.Level != SOL_SOCKET {
|
|
return nil, EINVAL
|
|
}
|
|
if msg.Header.Type != SCM_RIGHTS {
|
|
return nil, EINVAL
|
|
}
|
|
fds := make([]int, len(msg.Data)>>2)
|
|
for i, j := 0, 0; i < len(msg.Data); i += 4 {
|
|
fds[j] = int(*(*int32)(unsafe.Pointer(&msg.Data[i])))
|
|
j++
|
|
}
|
|
return fds, nil
|
|
}
|