Added logic to find next available IP address

ipaddresses.go

@@ -0,0 +1,100 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"net"
+	"os"
+)
+
+func getInterfaceIPAndMask(interfaceName string) (ip net.IP, mask net.IPMask, err error) {
+	iface, err := net.InterfaceByName(interfaceName)
+	if err != nil {
+		return nil, nil, fmt.Errorf("failed to get interface %s: %w", interfaceName, err)
+	}
+
+	addrs, err := iface.Addrs()
+	if err != nil {
+		return nil, nil, fmt.Errorf("failed to get addresses for %s: %w", interfaceName, err)
+	}
+
+	for _, addr := range addrs {
+		ipNet, ok := addr.(*net.IPNet)
+		if !ok || ipNet.IP.IsLoopback() || ipNet.IP.To4() == nil {
+			continue
+		}
+
+		return ipNet.IP, ipNet.Mask, nil
+	}
+
+	return nil, nil, fmt.Errorf("no valid IPv4 address found for interface %s", interfaceName)
+}
+
+func getNextFreeIP() (net.IP, error) {
+	var wg string = os.Getenv("WIREGUARD_INTERFACE")
+	ip, mask, err := getInterfaceIPAndMask(wg)
+	if err != nil {
+		log.Fatal(err)
+	}
+	used, err := parseUsedIPsFromConfigs("./configs")
+	if err != nil {
+		fmt.Println("Error:", err)
+		return nil, fmt.Errorf("Unkown err: %s", err)
+	}
+
+	for _, ip := range used {
+		fmt.Println("Used IP:", ip)
+	}
+	// used := []net.IP{
+	// 	net.ParseIP("10.200.34.1"),
+	// 	net.ParseIP("10.200.34.2"),
+	// 	net.ParseIP("10.200.34.3"),
+	// 	net.ParseIP("10.200.34.4"),
+	// 	net.ParseIP("10.200.34.5"),
+	// 	net.ParseIP("10.200.34.6"),
+	// 	net.ParseIP("10.200.34.225"),
+	// 	net.ParseIP("10.200.34.226"),
+	// 	net.ParseIP("10.200.34.227"),
+	// }
+
+	network := ip.Mask(mask)
+	ipNet := &net.IPNet{IP: network, Mask: mask}
+
+	// Turn the used list into a map for fast lookup
+	usedMap := make(map[string]bool)
+	for _, u := range used {
+		usedMap[u.String()] = true
+	}
+
+	// Get network boundaries
+	start := ipToUint32(network) + 1
+	end := ipToUint32(lastIP(ipNet)) - 1 // Skip broadcast
+
+	for i := start; i <= end; i++ {
+		candidate := uint32ToIP(i)
+		if !usedMap[candidate.String()] {
+			return candidate, nil
+		}
+	}
+
+	return nil, fmt.Errorf("no free IPs in subnet %s", ipNet.String())
+}
+
+func ipToUint32(ip net.IP) uint32 {
+	ip = ip.To4()
+	return uint32(ip[0])<<24 | uint32(ip[1])<<16 | uint32(ip[2])<<8 | uint32(ip[3])
+}
+
+func uint32ToIP(n uint32) net.IP {
+	return net.IPv4(byte(n>>24), byte(n>>16), byte(n>>8), byte(n))
+}
+
+func lastIP(ipNet *net.IPNet) net.IP {
+	ip := ipNet.IP.To4()
+	mask := ipNet.Mask
+	broadcast := make(net.IP, len(ip))
+	for i := range ip {
+		broadcast[i] = ip[i] | ^mask[i]
+	}
+	return broadcast
+}