Comment by fellerts

3 hours ago

I think this package does exactly what you need: https://pkg.go.dev/github.com/google/gopacket/routing. Works on my machine (error handling left to the reader)

    router, _ := routing.New()
    iface, _, _, _ := router.Route(net.ParseIP("8.8.8.8"))
    fmt.Println(iface.Name)

this prints my Ethernet interface as expected. It doesn't make any requests, it just figures out where to route a packet. I guess it interfaces with the OS routing table.

2 comments

fellerts

rvermeulen98 3 hours ago

Thanks for sharing! This is definitely something I will look into, I am all in favor to simplify the current implementation of finding the "default" OS network interface.

contingencies 41 minutes ago

You'd better use the default route and not some random IP, particularly DNS IPs which people often meddle with.

  # IPv4 default route only
  uname
  Darwin$ route -n get 0.0.0.0 | grep interface | cut -d ':' -f2
  Linux$ route -nv  |grep ^0.0.0.0 | awk '{print $NF}'