| // 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 aix darwin dragonfly freebsd linux netbsd openbsd solaris |
| |
| // Socket control messages |
| |
| package unix |
| |
| import ( |
| "runtime" |
| "unsafe" |
| ) |
| |
| // Round the length of a raw sockaddr up to align it properly. |
| func cmsgAlignOf(salen int) int { |
| salign := SizeofPtr |
| |
| switch runtime.GOOS { |
| case "darwin", "dragonfly", "solaris": |
| // NOTE: It seems like 64-bit Darwin, DragonFly BSD and |
| // Solaris kernels still require 32-bit aligned access to |
| // network subsystem. |
| if SizeofPtr == 8 { |
| salign = 4 |
| } |
| case "netbsd", "openbsd": |
| // NetBSD and OpenBSD armv7 require 64-bit alignment. |
| if runtime.GOARCH == "arm" { |
| salign = 8 |
| } |
| } |
| |
| 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 |
| } |