github.com/graybobo/golang.org-package-offline-cache@v0.0.0-20200626051047-6608995c132f/x/net/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 6 7 package ipv4 8 9 import ( 10 "syscall" 11 "unsafe" 12 13 "golang.org/x/net/internal/iana" 14 ) 15 16 func marshalPacketInfo(b []byte, cm *ControlMessage) []byte { 17 m := (*syscall.Cmsghdr)(unsafe.Pointer(&b[0])) 18 m.Level = iana.ProtocolIP 19 m.Type = sysIP_PKTINFO 20 m.SetLen(syscall.CmsgLen(sysSizeofInetPktinfo)) 21 if cm != nil { 22 pi := (*sysInetPktinfo)(unsafe.Pointer(&b[syscall.CmsgLen(0)])) 23 if ip := cm.Src.To4(); ip != nil { 24 copy(pi.Spec_dst[:], ip) 25 } 26 if cm.IfIndex > 0 { 27 pi.setIfindex(cm.IfIndex) 28 } 29 } 30 return b[syscall.CmsgSpace(sysSizeofInetPktinfo):] 31 } 32 33 func parsePacketInfo(cm *ControlMessage, b []byte) { 34 pi := (*sysInetPktinfo)(unsafe.Pointer(&b[0])) 35 cm.IfIndex = int(pi.Ifindex) 36 cm.Dst = pi.Addr[:] 37 }