netlink link monitoring example

rtnetlink_monitor.go

package main

import (
	"log"
	"syscall"
)

func main(){
	fd,e1 := syscall.Socket(syscall.AF_NETLINK, syscall.SOCK_DGRAM, syscall.NETLINK_ROUTE)
	if e1 != nil {
		panic(e1)
	}
	e2 := syscall.Bind(fd, &syscall.SockaddrNetlink{
		Family: syscall.AF_NETLINK,
		Pid: uint32(syscall.Getpid()),
		Groups: syscall.RTNLGRP_LINK | syscall.RTNLGRP_NOTIFY,
	})
	if e2 != nil {
		panic(e2)
	}
	epfd, e3 := syscall.EpollCreate1(0)
	if e3 != nil {
		panic(e3)
	}
	ev := syscall.EpollEvent{ Events: syscall.EPOLLIN, Fd: int32(fd) }
	e4 := syscall.EpollCtl(epfd, syscall.EPOLL_CTL_ADD, fd, &ev)
	if e4 != nil {
		panic(e4)
	}
	defer func(){
		syscall.EpollCtl(epfd, syscall.EPOLL_CTL_DEL, fd, &ev)
	}()

	buf := make([]byte, syscall.Getpagesize())
	evs := make([]syscall.EpollEvent, 1)
	for {
		if n, err := syscall.EpollWait(epfd, evs, 10); err!=nil {
			panic(err)
		} else if n > 0 {
			nn,_,e5 := syscall.Recvfrom(fd, buf, syscall.MSG_TRUNC)
			if e5 != nil {
				panic(e5)
			}
			msgs, e6 := syscall.ParseNetlinkMessage(buf[:nn])
			if e6 != nil {
				panic(e6)
			}
			log.Print(msgs)
		}
	}
}