🐛 Support range decision on stream mode

pkg/ip/cidr.go

@@ -0,0 +1,48 @@
+package ip
+
+import (
+	"net"
+	"strconv"
+	"strings"
+)
+
+// CIDRKeys returns all possible CIDR prefixes of an IP, from the most specific (/32 for IPv4, /128 for IPv6) to the least specific (/0).
+func CIDRKeys(ipStr string) []string {
+	ip := net.ParseIP(ipStr)
+	if ip == nil {
+		return nil
+	}
+	ip4 := ip.To4()
+	if ip4 != nil {
+		keys := make([]string, 0, 33)
+		for bits := 32; bits >= 0; bits-- {
+			mask := net.CIDRMask(bits, 32)
+			n := make(net.IP, 4)
+			for i := 0; i < 4; i++ {
+				n[i] = ip4[i] & mask[i]
+			}
+			keys = append(keys, n.String()+"/"+strconv.Itoa(bits))
+		}
+		return keys
+	}
+	ip16 := ip.To16()
+	keys := make([]string, 0, 129)
+	for bits := 128; bits >= 0; bits-- {
+		mask := net.CIDRMask(bits, 128)
+		n := make(net.IP, 16)
+		for i := 0; i < 16; i++ {
+			n[i] = ip16[i] & mask[i]
+		}
+		keys = append(keys, n.String()+"/"+strconv.Itoa(bits))
+	}
+	return keys
+}
+
+// NormalizeCIDR parses a CIDR string and returns its normalized form, or an empty string if invalid.
+func NormalizeCIDR(cidrStr string) string {
+	_, ipNet, err := net.ParseCIDR(strings.TrimSpace(cidrStr))
+	if err != nil {
+		return ""
+	}
+	return ipNet.String()
+}