logic for finding next available ip

Author: jhrv

apiserver/database/cidr.go

@@ -0,0 +1,62 @@
+package database
+
+import (
+	"fmt"
+	"net"
+	"strings"
+)
+
+//func main() {
+//	ips := []string{"10.255.248.1", "10.255.248.3", "10.255.248.2"}
+//	allocated := make(map[string]struct{})
+//	for _, allocatedIP := range ips {
+//		allocated[allocatedIP] = struct{}{}
+//	}
+//
+//	next, err := FindAvailableIP("10.255.248.0/31", allocated)
+//	if err != nil {
+//		panic(err)
+//	}
+//	fmt.Println(next)
+//}
+
+func FindAvailableIP(cidr string, allocated map[string]struct{}) (string, error) {
+	ips, _ := cidrIPs(cidr)
+	for _, ip := range ips {
+		fmt.Println(ip)
+		if _, found := allocated[ip]; !found {
+			return ip, nil
+		}
+	}
+	return "", fmt.Errorf("no available IPs in range %v", cidr)
+}
+
+func cidrIPs(cidr string) ([]string, error) {
+	ip, ipnet, err := net.ParseCIDR(cidr)
+
+	if err != nil {
+		return nil, err
+	}
+
+	var ips []string
+	for ip := ip.Mask(ipnet.Mask); ipnet.Contains(ip); inc(ip) {
+		ips = append(ips, ip.String())
+	}
+
+	if strings.HasSuffix(cidr, "/32") {
+		return ips, nil
+	} else {
+		//remove network address and broadcast address
+		return ips[1 : len(ips)-1], nil
+	}
+}
+
+func inc(ip net.IP) {
+	fmt.Println([]byte(ip))
+	for j := len(ip) - 1; j >= 0; j-- {
+		ip[j]++
+		if ip[j] > 0 {
+			break
+		}
+	}
+}