fff53afca7
CmsgLen() does not account for data alignment. Reviewed-by: Adrian Dewhurst <adrian@tailscale.com> Signed-off-by: Jordan Whited <jordan@tailscale.com> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
114 lines
2.8 KiB
Go
114 lines
2.8 KiB
Go
/* SPDX-License-Identifier: MIT
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*
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* Copyright (C) 2017-2023 WireGuard LLC. All Rights Reserved.
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*/
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package conn
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import (
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"net/netip"
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"unsafe"
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"golang.org/x/sys/unix"
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)
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// getSrcFromControl parses the control for PKTINFO and if found updates ep with
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// the source information found.
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func getSrcFromControl(control []byte, ep *StdNetEndpoint) {
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ep.ClearSrc()
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var (
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hdr unix.Cmsghdr
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data []byte
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rem []byte = control
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err error
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)
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for len(rem) > unix.SizeofCmsghdr {
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hdr, data, rem, err = unix.ParseOneSocketControlMessage(control)
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if err != nil {
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return
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}
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if hdr.Level == unix.IPPROTO_IP &&
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hdr.Type == unix.IP_PKTINFO {
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info := pktInfoFromBuf[unix.Inet4Pktinfo](data)
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ep.src.Addr = netip.AddrFrom4(info.Spec_dst)
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ep.src.ifidx = info.Ifindex
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return
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}
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if hdr.Level == unix.IPPROTO_IPV6 &&
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hdr.Type == unix.IPV6_PKTINFO {
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info := pktInfoFromBuf[unix.Inet6Pktinfo](data)
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ep.src.Addr = netip.AddrFrom16(info.Addr)
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ep.src.ifidx = int32(info.Ifindex)
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return
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}
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}
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}
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// pktInfoFromBuf returns type T populated from the provided buf via copy(). It
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// panics if buf is of insufficient size.
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func pktInfoFromBuf[T unix.Inet4Pktinfo | unix.Inet6Pktinfo](buf []byte) (t T) {
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size := int(unsafe.Sizeof(t))
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if len(buf) < size {
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panic("pktInfoFromBuf: buffer too small")
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}
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copy(unsafe.Slice((*byte)(unsafe.Pointer(&t)), size), buf)
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return t
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}
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// setSrcControl sets an IP{V6}_PKTINFO in control based on the source address
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// and source ifindex found in ep. control's len will be set to 0 in the event
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// that ep is a default value.
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func setSrcControl(control *[]byte, ep *StdNetEndpoint) {
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*control = (*control)[:cap(*control)]
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if len(*control) < int(unsafe.Sizeof(unix.Cmsghdr{})) {
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*control = (*control)[:0]
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return
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}
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if ep.src.ifidx == 0 && !ep.SrcIP().IsValid() {
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*control = (*control)[:0]
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return
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}
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if len(*control) < srcControlSize {
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*control = (*control)[:0]
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return
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}
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hdr := (*unix.Cmsghdr)(unsafe.Pointer(&(*control)[0]))
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if ep.SrcIP().Is4() {
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hdr.Level = unix.IPPROTO_IP
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hdr.Type = unix.IP_PKTINFO
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hdr.SetLen(unix.CmsgLen(unix.SizeofInet4Pktinfo))
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info := (*unix.Inet4Pktinfo)(unsafe.Pointer(&(*control)[unix.SizeofCmsghdr]))
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info.Ifindex = ep.src.ifidx
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if ep.SrcIP().IsValid() {
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info.Spec_dst = ep.SrcIP().As4()
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}
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*control = (*control)[:unix.CmsgSpace(unix.SizeofInet4Pktinfo)]
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} else {
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hdr.Level = unix.IPPROTO_IPV6
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hdr.Type = unix.IPV6_PKTINFO
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hdr.SetLen(unix.CmsgLen(unix.SizeofInet6Pktinfo))
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info := (*unix.Inet6Pktinfo)(unsafe.Pointer(&(*control)[unix.SizeofCmsghdr]))
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info.Ifindex = uint32(ep.src.ifidx)
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if ep.SrcIP().IsValid() {
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info.Addr = ep.SrcIP().As16()
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}
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*control = (*control)[:unix.CmsgSpace(unix.SizeofInet6Pktinfo)]
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}
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}
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var srcControlSize = unix.CmsgSpace(unix.SizeofInet6Pktinfo)
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