IP_PKTINFO usage in Go

udp_ip_pktinfo.go

package main
 
import (
        "bytes"
        "encoding/binary"
        "fmt"
        "net"
        "syscall"
)
 
func main() {
        serverAddr, _ := net.ResolveUDPAddr("udp", ":1025")
        sConn, _ := net.ListenUDP("udp", serverAddr)
        file, _ := sConn.File()
 
        syscall.SetsockoptInt(int(file.Fd()), syscall.IPPROTO_IP, syscall.IP_PKTINFO, 1)
 
        data := make([]byte, 1024)
        oob := make([]byte, 1024)
        bytes_read, oob_bytes_read, _, _, _ := sConn.ReadMsgUDP(data, oob)
 
        fmt.Println(data[:bytes_read], oob[:oob_bytes_read])
 
        oob_buffer := bytes.NewBuffer(oob)
 
        msg := syscall.Cmsghdr{}
        binary.Read(oob_buffer, binary.LittleEndian, &msg)
        fmt.Println(msg)
 
        if msg.Level == syscall.IPPROTO_IP && msg.Type == syscall.IP_PKTINFO {
                packet_info := syscall.Inet4Pktinfo{}
                binary.Read(oob_buffer, binary.LittleEndian, &packet_info)
                fmt.Println(packet_info)
        }
}

For anyone running into this gist, the OSX (Darwin) implementation is broken because of a bug.
See https://code.google.com/p/go/issues/detail?id=8329&thanks=8329&ts=1404510948