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Lorenz Bauer
8e5104632a
It's possible to control the source address of a UDP packet by passing a socket control message of type IP_PKTINFO or IPV6_PKTINFO. This is a somewhat esoteric feature of the network stack, but it's extremely useful feature when you really need it. Change-Id: I8300575f975679f6689d6f1282af253ba62e8f9d Reviewed-on: https://go-review.googlesource.com/c/sys/+/355610 Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com> TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org> Trust: Tobias Klauser <tobias.klauser@gmail.com>
59 lines
1.7 KiB
Go
59 lines
1.7 KiB
Go
// Copyright 2011 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Socket control messages
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package unix
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import "unsafe"
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// UnixCredentials encodes credentials into a socket control message
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// for sending to another process. This can be used for
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// authentication.
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func UnixCredentials(ucred *Ucred) []byte {
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b := make([]byte, CmsgSpace(SizeofUcred))
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h := (*Cmsghdr)(unsafe.Pointer(&b[0]))
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h.Level = SOL_SOCKET
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h.Type = SCM_CREDENTIALS
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h.SetLen(CmsgLen(SizeofUcred))
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*(*Ucred)(h.data(0)) = *ucred
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return b
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}
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// ParseUnixCredentials decodes a socket control message that contains
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// credentials in a Ucred structure. To receive such a message, the
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// SO_PASSCRED option must be enabled on the socket.
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func ParseUnixCredentials(m *SocketControlMessage) (*Ucred, error) {
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if m.Header.Level != SOL_SOCKET {
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return nil, EINVAL
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}
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if m.Header.Type != SCM_CREDENTIALS {
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return nil, EINVAL
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}
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ucred := *(*Ucred)(unsafe.Pointer(&m.Data[0]))
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return &ucred, nil
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}
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// PktInfo4 encodes Inet4Pktinfo into a socket control message of type IP_PKTINFO.
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func PktInfo4(info *Inet4Pktinfo) []byte {
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b := make([]byte, CmsgSpace(SizeofInet4Pktinfo))
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h := (*Cmsghdr)(unsafe.Pointer(&b[0]))
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h.Level = SOL_IP
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h.Type = IP_PKTINFO
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h.SetLen(CmsgLen(SizeofInet4Pktinfo))
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*(*Inet4Pktinfo)(h.data(0)) = *info
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return b
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}
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// PktInfo6 encodes Inet6Pktinfo into a socket control message of type IPV6_PKTINFO.
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func PktInfo6(info *Inet6Pktinfo) []byte {
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b := make([]byte, CmsgSpace(SizeofInet6Pktinfo))
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h := (*Cmsghdr)(unsafe.Pointer(&b[0]))
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h.Level = SOL_IPV6
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h.Type = IPV6_PKTINFO
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h.SetLen(CmsgLen(SizeofInet6Pktinfo))
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*(*Inet6Pktinfo)(h.data(0)) = *info
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return b
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}
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