Comment by rvermeulen98

4 hours ago

Thanks, I am glad you like it! I couldn't find a Go API that just returns the OS "default" network interface, so struggled a bit with a correct implementation for that part.

When reading some blog posts, I found often a solution where it sends out an UDP dial to for example 8.8.8.8:53 because you can then get the network interface back from the connection it's local address. As fallback I implemented to pick the first non-loopback interface that is up.

Would be open to suggestions to do this in a better way!

3 comments

rvermeulen98

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.

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}'