github.com/Andyfoo/golang/x/net@v0.0.0-20190901054642-57c1bf301704/ipv4/control_pktinfo.go (about)

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