获取网卡IPv4地址

package main

import (
	"fmt"
	"net"
)

func main() {
	ifname := "ens33"
	netIf, err := net.InterfaceByName(ifname)
	if err != nil {
		fmt.Printf("get netIf by name %s failed, err is %v\n", ifname, err)
		return
	}

	addrs, err := netIf.Addrs()
	if err != nil {
		fmt.Printf("get addrs by name %s failed, err is %v\n", ifname, err)
		return
	}

	for _, addr := range addrs {
		ipNet, ok := addr.(*net.IPNet)
		if ok && ipNet.IP.To4() != nil {
			fmt.Printf("ipv4 addr is %s\n", ipNet.IP.String())
			return
		}
	}
}

IP整型和字符串互转

package main

import (
	"fmt"
	"net"
)

func IPv4StringToUint32(ip string) (uint32, error) {
	p := net.ParseIP(ip).To4()
	if p == nil {
		return 0, fmt.Errorf("invalid ipv4 format")
	}

	return uint32(p[3])<<24 | uint32(p[2])<<16 | uint32(p[1])<<8 | uint32(p[0]), nil
}

func IPv4Uint32ToString(ipUint32 uint32) (string, error) {
	ip := make(net.IP, net.IPv4len)
	ip[3] = byte(ipUint32 >> 24)
	ip[2] = byte(ipUint32 >> 16)
	ip[1] = byte(ipUint32 >> 8)
	ip[0] = byte(ipUint32)

	return ip.String(), nil
}

func main() {
	ip := "100.101.102.103"

	ipUint32, err := IPv4StringToUint32(ip)
	if err != nil {
		fmt.Printf("get ipv4 uint32 from string %s failed, err is %v", ip, err)
		return
	}
	fmt.Println(ipUint32)

	ipString, err := IPv4Uint32ToString(ipUint32)
	if err != nil {
		fmt.Printf("get ipv4 string from uint32 %d failed, err is %v", ipUint32, err)
		return
	}
	fmt.Println(ipString)
}

解析cidr子网

package main

import (
	"fmt"
	"net"
)

func main() {
	cidrs := []string{"100.101.102.1/16", "100.101.102.1"}

	for _, cidr := range cidrs {
		_, ipNet, err := net.ParseCIDR(cidr)
		if err != nil {
			fmt.Printf("parse cidr %s failed, err is %v\n", cidr, err)
			continue
		}

		mask, _ := ipNet.Mask.Size()
		fmt.Printf("parse cidr %s result is %s/%d\n", cidr, ipNet.IP.String(), mask)
	}
}