如何检测两个Golang net.IPNet对象是否相交？

Question

How to detect if there is intersection between two Golang net.IPNet objects?

That is, how to check both if the first network is subnet of the second one OR if the second network is subnet of the first one.

Does Go provide any utility function ready for this specific task?

See test code below.

package main

import (
    "fmt"
    "net"
)

func main() {
    _, net1, _ := net.ParseCIDR("1.1.1.1/24")
    _, net2, _ := net.ParseCIDR("1.1.0.2/16")
    _, net3, _ := net.ParseCIDR("1.1.1.3/25")
    _, net4, _ := net.ParseCIDR("1.2.0.4/16")

    test(net1, net2, true)
    test(net2, net1, true)
    test(net1, net3, true)
    test(net3, net1, true)
    test(net1, net4, false)
    test(net4, net1, false)
}

func test(n1, n2 *net.IPNet, expect bool) {
    result := intersect(n1, n2)
    var label string
    if result == expect {
        label = "good"
    } else {
        label = "FAIL"
    }
    fmt.Printf("test intersect(%v,%v)=%v expected=%v => %s
", n1, n2, result, expect, label)
}

func intersect(n1, n2 *net.IPNet) bool {
    return false // FIXME WRITEME
}

Run it on Go Playground

Answer 1

If (as your test cases seem to imply) you don't care about which side contains which, but just that there's overlap, this should be sufficient.

func intersect(n1, n2 *net.IPNet) bool {
    return n2.Contains(n1.IP) || n1.Contains(n2.IP)
}