better infinity mode implementation

utils.go

@@ -3,8 +3,11 @@ package main
 import (
 	"bufio"
 	"errors"
+	"fmt"
 	"io"
 	"log/slog"
+	"math"
+	"math/big"
 	"net"
 	"net/netip"
 	"regexp"
@@ -108,6 +111,67 @@ func ExistOnlyOne(arr []string) bool {
 	}
 	return exist
 }
+func IterateAddr(addr string) <-chan Host {
+	hostChan := make(chan Host)
+	_, _, err := net.ParseCIDR(addr)
+	if err == nil {
+		// is CIDR
+		return Iterate(strings.NewReader(addr))
+	}
+	ip := net.ParseIP(addr)
+	if ip == nil {
+		ip, err = LookupIP(addr)
+		if err != nil {
+			close(hostChan)
+			slog.Error("Not a valid IP, IP CIDR or domain", "addr", addr)
+			return hostChan
+		}
+	}
+	go func() {
+		slog.Info("Enable infinite mode", "init", ip.String())
+		lowIP := ip
+		highIP := ip
+		hostChan <- Host{
+			IP:     ip,
+			Origin: addr,
+			Type:   HostTypeIP,
+		}
+		for i := 0; i < math.MaxInt; i++ {
+			if i%2 == 0 {
+				lowIP = NextIP(lowIP, false)
+				hostChan <- Host{
+					IP:     lowIP,
+					Origin: lowIP.String(),
+					Type:   HostTypeIP,
+				}
+			} else {
+				highIP = NextIP(highIP, true)
+				hostChan <- Host{
+					IP:     highIP,
+					Origin: highIP.String(),
+					Type:   HostTypeIP,
+				}
+			}
+		}
+	}()
+	return hostChan
+}
+func LookupIP(addr string) (net.IP, error) {
+	ips, err := net.LookupIP(addr)
+	if err != nil {
+		return nil, fmt.Errorf("failed to lookup: %w", err)
+	}
+	var arr []net.IP
+	for _, ip := range ips {
+		if ip.To4() != nil || enableIPv6 {
+			arr = append(arr, ip)
+		}
+	}
+	if len(arr) == 0 {
+		return nil, errors.New("no IP found")
+	}
+	return arr[0], nil
+}
 func RemoveDuplicateStr(strSlice []string) []string {
 	allKeys := make(map[string]bool)
 	var list []string
@@ -128,3 +192,17 @@ func OutWriter(writer io.Writer) chan<- string {
 	}()
 	return ch
 }
+func NextIP(ip net.IP, increment bool) net.IP {
+	// Convert to big.Int and increment
+	ipb := big.NewInt(0).SetBytes(ip)
+	if increment {
+		ipb.Add(ipb, big.NewInt(1))
+	} else {
+		ipb.Sub(ipb, big.NewInt(1))
+	}
+
+	// Add leading zeros
+	b := ipb.Bytes()
+	b = append(make([]byte, len(ip)-len(b)), b...)
+	return b
+}