Elia Battiston | be9edc1 | 2022-03-09 11:35:58 +0100 | [diff] [blame^] | 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. |
| 4 | |
| 5 | //go:build aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd || solaris || zos |
| 6 | // +build aix darwin dragonfly freebsd linux netbsd openbsd solaris zos |
| 7 | |
| 8 | // Socket control messages |
| 9 | |
| 10 | package unix |
| 11 | |
| 12 | import ( |
| 13 | "unsafe" |
| 14 | ) |
| 15 | |
| 16 | // CmsgLen returns the value to store in the Len field of the Cmsghdr |
| 17 | // structure, taking into account any necessary alignment. |
| 18 | func CmsgLen(datalen int) int { |
| 19 | return cmsgAlignOf(SizeofCmsghdr) + datalen |
| 20 | } |
| 21 | |
| 22 | // CmsgSpace returns the number of bytes an ancillary element with |
| 23 | // payload of the passed data length occupies. |
| 24 | func CmsgSpace(datalen int) int { |
| 25 | return cmsgAlignOf(SizeofCmsghdr) + cmsgAlignOf(datalen) |
| 26 | } |
| 27 | |
| 28 | func (h *Cmsghdr) data(offset uintptr) unsafe.Pointer { |
| 29 | return unsafe.Pointer(uintptr(unsafe.Pointer(h)) + uintptr(cmsgAlignOf(SizeofCmsghdr)) + offset) |
| 30 | } |
| 31 | |
| 32 | // SocketControlMessage represents a socket control message. |
| 33 | type SocketControlMessage struct { |
| 34 | Header Cmsghdr |
| 35 | Data []byte |
| 36 | } |
| 37 | |
| 38 | // ParseSocketControlMessage parses b as an array of socket control |
| 39 | // messages. |
| 40 | func ParseSocketControlMessage(b []byte) ([]SocketControlMessage, error) { |
| 41 | var msgs []SocketControlMessage |
| 42 | i := 0 |
| 43 | for i+CmsgLen(0) <= len(b) { |
| 44 | h, dbuf, err := socketControlMessageHeaderAndData(b[i:]) |
| 45 | if err != nil { |
| 46 | return nil, err |
| 47 | } |
| 48 | m := SocketControlMessage{Header: *h, Data: dbuf} |
| 49 | msgs = append(msgs, m) |
| 50 | i += cmsgAlignOf(int(h.Len)) |
| 51 | } |
| 52 | return msgs, nil |
| 53 | } |
| 54 | |
| 55 | func socketControlMessageHeaderAndData(b []byte) (*Cmsghdr, []byte, error) { |
| 56 | h := (*Cmsghdr)(unsafe.Pointer(&b[0])) |
| 57 | if h.Len < SizeofCmsghdr || uint64(h.Len) > uint64(len(b)) { |
| 58 | return nil, nil, EINVAL |
| 59 | } |
| 60 | return h, b[cmsgAlignOf(SizeofCmsghdr):h.Len], nil |
| 61 | } |
| 62 | |
| 63 | // UnixRights encodes a set of open file descriptors into a socket |
| 64 | // control message for sending to another process. |
| 65 | func UnixRights(fds ...int) []byte { |
| 66 | datalen := len(fds) * 4 |
| 67 | b := make([]byte, CmsgSpace(datalen)) |
| 68 | h := (*Cmsghdr)(unsafe.Pointer(&b[0])) |
| 69 | h.Level = SOL_SOCKET |
| 70 | h.Type = SCM_RIGHTS |
| 71 | h.SetLen(CmsgLen(datalen)) |
| 72 | for i, fd := range fds { |
| 73 | *(*int32)(h.data(4 * uintptr(i))) = int32(fd) |
| 74 | } |
| 75 | return b |
| 76 | } |
| 77 | |
| 78 | // ParseUnixRights decodes a socket control message that contains an |
| 79 | // integer array of open file descriptors from another process. |
| 80 | func ParseUnixRights(m *SocketControlMessage) ([]int, error) { |
| 81 | if m.Header.Level != SOL_SOCKET { |
| 82 | return nil, EINVAL |
| 83 | } |
| 84 | if m.Header.Type != SCM_RIGHTS { |
| 85 | return nil, EINVAL |
| 86 | } |
| 87 | fds := make([]int, len(m.Data)>>2) |
| 88 | for i, j := 0, 0; i < len(m.Data); i += 4 { |
| 89 | fds[j] = int(*(*int32)(unsafe.Pointer(&m.Data[i]))) |
| 90 | j++ |
| 91 | } |
| 92 | return fds, nil |
| 93 | } |