rss-tools/vendor/golang.org/x/sys/unix/sockcmsg_unix.go (view raw)
| 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 | |
| 7 | // Socket control messages |
| 8 | |
| 9 | package unix |
| 10 | |
| 11 | import ( |
| 12 | "unsafe" |
| 13 | ) |
| 14 | |
| 15 | // CmsgLen returns the value to store in the Len field of the Cmsghdr |
| 16 | // structure, taking into account any necessary alignment. |
| 17 | func CmsgLen(datalen int) int { |
| 18 | return cmsgAlignOf(SizeofCmsghdr) + datalen |
| 19 | } |
| 20 | |
| 21 | // CmsgSpace returns the number of bytes an ancillary element with |
| 22 | // payload of the passed data length occupies. |
| 23 | func CmsgSpace(datalen int) int { |
| 24 | return cmsgAlignOf(SizeofCmsghdr) + cmsgAlignOf(datalen) |
| 25 | } |
| 26 | |
| 27 | func (h *Cmsghdr) data(offset uintptr) unsafe.Pointer { |
| 28 | return unsafe.Pointer(uintptr(unsafe.Pointer(h)) + uintptr(cmsgAlignOf(SizeofCmsghdr)) + offset) |
| 29 | } |
| 30 | |
| 31 | // SocketControlMessage represents a socket control message. |
| 32 | type SocketControlMessage struct { |
| 33 | Header Cmsghdr |
| 34 | Data []byte |
| 35 | } |
| 36 | |
| 37 | // ParseSocketControlMessage parses b as an array of socket control |
| 38 | // messages. |
| 39 | func ParseSocketControlMessage(b []byte) ([]SocketControlMessage, error) { |
| 40 | var msgs []SocketControlMessage |
| 41 | i := 0 |
| 42 | for i+CmsgLen(0) <= len(b) { |
| 43 | h, dbuf, err := socketControlMessageHeaderAndData(b[i:]) |
| 44 | if err != nil { |
| 45 | return nil, err |
| 46 | } |
| 47 | m := SocketControlMessage{Header: *h, Data: dbuf} |
| 48 | msgs = append(msgs, m) |
| 49 | i += cmsgAlignOf(int(h.Len)) |
| 50 | } |
| 51 | return msgs, nil |
| 52 | } |
| 53 | |
| 54 | // ParseOneSocketControlMessage parses a single socket control message from b, returning the message header, |
| 55 | // message data (a slice of b), and the remainder of b after that single message. |
| 56 | // When there are no remaining messages, len(remainder) == 0. |
| 57 | func ParseOneSocketControlMessage(b []byte) (hdr Cmsghdr, data []byte, remainder []byte, err error) { |
| 58 | h, dbuf, err := socketControlMessageHeaderAndData(b) |
| 59 | if err != nil { |
| 60 | return Cmsghdr{}, nil, nil, err |
| 61 | } |
| 62 | if i := cmsgAlignOf(int(h.Len)); i < len(b) { |
| 63 | remainder = b[i:] |
| 64 | } |
| 65 | return *h, dbuf, remainder, nil |
| 66 | } |
| 67 | |
| 68 | func socketControlMessageHeaderAndData(b []byte) (*Cmsghdr, []byte, error) { |
| 69 | h := (*Cmsghdr)(unsafe.Pointer(&b[0])) |
| 70 | if h.Len < SizeofCmsghdr || uint64(h.Len) > uint64(len(b)) { |
| 71 | return nil, nil, EINVAL |
| 72 | } |
| 73 | return h, b[cmsgAlignOf(SizeofCmsghdr):h.Len], nil |
| 74 | } |
| 75 | |
| 76 | // UnixRights encodes a set of open file descriptors into a socket |
| 77 | // control message for sending to another process. |
| 78 | func UnixRights(fds ...int) []byte { |
| 79 | datalen := len(fds) * 4 |
| 80 | b := make([]byte, CmsgSpace(datalen)) |
| 81 | h := (*Cmsghdr)(unsafe.Pointer(&b[0])) |
| 82 | h.Level = SOL_SOCKET |
| 83 | h.Type = SCM_RIGHTS |
| 84 | h.SetLen(CmsgLen(datalen)) |
| 85 | for i, fd := range fds { |
| 86 | *(*int32)(h.data(4 * uintptr(i))) = int32(fd) |
| 87 | } |
| 88 | return b |
| 89 | } |
| 90 | |
| 91 | // ParseUnixRights decodes a socket control message that contains an |
| 92 | // integer array of open file descriptors from another process. |
| 93 | func ParseUnixRights(m *SocketControlMessage) ([]int, error) { |
| 94 | if m.Header.Level != SOL_SOCKET { |
| 95 | return nil, EINVAL |
| 96 | } |
| 97 | if m.Header.Type != SCM_RIGHTS { |
| 98 | return nil, EINVAL |
| 99 | } |
| 100 | fds := make([]int, len(m.Data)>>2) |
| 101 | for i, j := 0, 0; i < len(m.Data); i += 4 { |
| 102 | fds[j] = int(*(*int32)(unsafe.Pointer(&m.Data[i]))) |
| 103 | j++ |
| 104 | } |
| 105 | return fds, nil |
| 106 | } |