route: fix case statement complexity

Author: hurricanehrndz

route/address.go

@@ -396,6 +396,12 @@ func marshalAddrs(b []byte, as []Addr) (uint, error) {
 func parseAddrs(attrs uint, fn func(int, []byte) (int, Addr, error), b []byte) ([]Addr, error) {
 	var as [syscall.RTAX_MAX]Addr
 	af := int(syscall.AF_UNSPEC)
+	isInet := func(fam int) bool {
+		return fam == syscall.AF_INET || fam == syscall.AF_INET6
+	}
+	isMask := func(addrType uint) bool {
+		return addrType == syscall.RTAX_NETMASK || addrType == syscall.RTAX_GENMASK
+	}
 	for i := uint(0); i < syscall.RTAX_MAX && len(b) >= roundup(0); i++ {
 		if attrs&(1<<i) == 0 {
 			continue
@@ -413,8 +419,8 @@ func parseAddrs(attrs uint, fn func(int, []byte) (int, Addr, error), b []byte) (
 					return nil, errMessageTooShort
 				}
 				b = b[l:]
-			case ((b[1] == syscall.AF_INET || b[1] == syscall.AF_INET6) || ((i == syscall.RTAX_NETMASK || i == syscall.RTAX_GENMASK) && (af == syscall.AF_INET || af == syscall.AF_INET6))):
-				if (i != syscall.RTAX_NETMASK && i != syscall.RTAX_GENMASK) {
+			case isInet(int(b[1])) || (isMask(i) && isInet(af)):
+				if !isMask(i){
 					af = int(b[1])
 				}
 				a, err := parseInetAddr(af, b)

route/example_darwin_test.go

@@ -1,3 +1,7 @@
+// Copyright 2025 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
 package route_test
 
 import (