control_pktinfo.go raw

   1  // Copyright 2014 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 darwin || linux || solaris
   6  
   7  package ipv4
   8  
   9  import (
  10  	"net"
  11  	"unsafe"
  12  
  13  	"golang.org/x/net/internal/iana"
  14  	"golang.org/x/net/internal/socket"
  15  
  16  	"golang.org/x/sys/unix"
  17  )
  18  
  19  func marshalPacketInfo(b []byte, cm *ControlMessage) []byte {
  20  	m := socket.ControlMessage(b)
  21  	m.MarshalHeader(iana.ProtocolIP, unix.IP_PKTINFO, sizeofInetPktinfo)
  22  	if cm != nil {
  23  		pi := (*inetPktinfo)(unsafe.Pointer(&m.Data(sizeofInetPktinfo)[0]))
  24  		if ip := cm.Src.To4(); ip != nil {
  25  			copy(pi.Spec_dst[:], ip)
  26  		}
  27  		if cm.IfIndex > 0 {
  28  			pi.setIfindex(cm.IfIndex)
  29  		}
  30  	}
  31  	return m.Next(sizeofInetPktinfo)
  32  }
  33  
  34  func parsePacketInfo(cm *ControlMessage, b []byte) {
  35  	pi := (*inetPktinfo)(unsafe.Pointer(&b[0]))
  36  	cm.IfIndex = int(pi.Ifindex)
  37  	if len(cm.Dst) < net.IPv4len {
  38  		cm.Dst = make(net.IP, net.IPv4len)
  39  	}
  40  	copy(cm.Dst, pi.Addr[:])
  41  }
  42