control_pktinfo.go

Documentation: golang.org/x/net/ipv4

     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
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