1 files changed, 48 insertions, 0 deletions
diff --git a/Sources/WireGuardKit/IPAddressRange.swift b/Sources/WireGuardKit/IPAddressRange.swift
index 67c3955..ecb888e 100644
--- a/Sources/WireGuardKit/IPAddressRange.swift
+++ b/Sources/WireGuardKit/IPAddressRange.swift
@@ -64,4 +64,52 @@ extension IPAddressRange {
 
         return (address, networkPrefixLength)
     }
+
+    public func subnetMask() -> IPAddress {
+        if address is IPv4Address {
+            let mask = networkPrefixLength > 0 ? ~UInt32(0) << (32 - networkPrefixLength) : UInt32(0)
+            let bytes = Data([
+                UInt8(truncatingIfNeeded: mask >> 24),
+                UInt8(truncatingIfNeeded: mask >> 16),
+                UInt8(truncatingIfNeeded: mask >> 8),
+                UInt8(truncatingIfNeeded: mask >> 0)
+            ])
+            return IPv4Address(bytes)!
+        }
+        if address is IPv6Address {
+            var bytes = Data(repeating: 0, count: 16)
+            for i in 0..<Int(networkPrefixLength/8) {
+                bytes[i] = 0xff
+            }
+            let nibble = networkPrefixLength % 32
+            if nibble != 0 {
+                let mask = ~UInt32(0) << (32 - nibble)
+                let i = Int(networkPrefixLength / 32 * 4)
+                bytes[i + 0] = UInt8(truncatingIfNeeded: mask >> 24)
+                bytes[i + 1] = UInt8(truncatingIfNeeded: mask >> 16)
+                bytes[i + 2] = UInt8(truncatingIfNeeded: mask >> 8)
+                bytes[i + 3] = UInt8(truncatingIfNeeded: mask >> 0)
+            }
+            return IPv6Address(bytes)!
+        }
+        fatalError()
+    }
+
+    public func maskedAddress() -> IPAddress {
+        let subnet = subnetMask().rawValue
+        var masked = Data(address.rawValue)
+        if subnet.count != masked.count {
+            fatalError()
+        }
+        for i in 0..<subnet.count {
+            masked[i] &= subnet[i]
+        }
+        if subnet.count == 4 {
+            return IPv4Address(masked)!
+        }
+        if subnet.count == 16 {
+            return IPv6Address(masked)!
+        }
+        fatalError()
+    }
 }