From dcf9f73bcbaa68a3d6613ececc5502c1c089ed0c Mon Sep 17 00:00:00 2001
From: Brian Picciano <mediocregopher@gmail.com>
Date: Thu, 9 Aug 2018 12:34:09 -0600
Subject: [PATCH] mnet: implement IsReservedIP

---
 mnet/mnet.go      | 67 +++++++++++++++++++++++++++++++++++++++++++++++
 mnet/mnet_test.go | 33 +++++++++++++++++++++++
 2 files changed, 100 insertions(+)
 create mode 100644 mnet/mnet.go
 create mode 100644 mnet/mnet_test.go

diff --git a/mnet/mnet.go b/mnet/mnet.go
new file mode 100644
index 0000000..c8a4523
--- /dev/null
+++ b/mnet/mnet.go
@@ -0,0 +1,67 @@
+// Package mnet extends the standard package with extra functionality which is
+// commonly useful
+package mnet
+
+import (
+	"net"
+)
+
+func mustGetCIDRNetwork(cidr string) *net.IPNet {
+	_, n, err := net.ParseCIDR(cidr)
+	if err != nil {
+		panic(err)
+	}
+	return n
+}
+
+// https://en.wikipedia.org/wiki/Reserved_IP_addresses
+
+var reservedCIDRs4 = []*net.IPNet{
+	mustGetCIDRNetwork("0.0.0.0/8"),          // current network
+	mustGetCIDRNetwork("10.0.0.0/8"),         // private network
+	mustGetCIDRNetwork("100.64.0.0/10"),      // private network
+	mustGetCIDRNetwork("127.0.0.0/8"),        // localhost
+	mustGetCIDRNetwork("169.254.0.0/16"),     // link-local
+	mustGetCIDRNetwork("172.16.0.0/12"),      // private network
+	mustGetCIDRNetwork("192.0.0.0/24"),       // IETF protocol assignments
+	mustGetCIDRNetwork("192.0.2.0/24"),       // documentation and examples
+	mustGetCIDRNetwork("192.88.99.0/24"),     // 6to4 Relay
+	mustGetCIDRNetwork("192.168.0.0/16"),     // private network
+	mustGetCIDRNetwork("198.18.0.0/15"),      // private network
+	mustGetCIDRNetwork("198.51.100.0/24"),    // documentation and examples
+	mustGetCIDRNetwork("203.0.113.0/24"),     // documentation and examples
+	mustGetCIDRNetwork("224.0.0.0/4"),        // IP multicast
+	mustGetCIDRNetwork("240.0.0.0/4"),        // reserved
+	mustGetCIDRNetwork("255.255.255.255/32"), // limited broadcast address
+}
+
+var reservedCIDRs6 = []*net.IPNet{
+	mustGetCIDRNetwork("::/128"),        // unspecified address
+	mustGetCIDRNetwork("::1/128"),       // loopback address
+	mustGetCIDRNetwork("100::/64"),      // discard prefix
+	mustGetCIDRNetwork("2001::/32"),     // Teredo tunneling
+	mustGetCIDRNetwork("2001:20::/28"),  // ORCHID v2
+	mustGetCIDRNetwork("2001:db8::/32"), // documentation and examples
+	mustGetCIDRNetwork("2002::/16"),     // 6to4 addressing
+	mustGetCIDRNetwork("fc00::/7"),      // unique local
+	mustGetCIDRNetwork("fe80::/10"),     // link local
+	mustGetCIDRNetwork("ff00::/8"),      // multicast
+}
+
+// IsReservedIP returns true if the given valid IP is part of a reserved IP
+// range.
+func IsReservedIP(ip net.IP) bool {
+	containedBy := func(cidrs []*net.IPNet) bool {
+		for _, cidr := range cidrs {
+			if cidr.Contains(ip) {
+				return true
+			}
+		}
+		return false
+	}
+
+	if ip.To4() != nil {
+		return containedBy(reservedCIDRs4)
+	}
+	return containedBy(reservedCIDRs6)
+}
diff --git a/mnet/mnet_test.go b/mnet/mnet_test.go
new file mode 100644
index 0000000..64fc7fe
--- /dev/null
+++ b/mnet/mnet_test.go
@@ -0,0 +1,33 @@
+package mnet
+
+import (
+	"net"
+	. "testing"
+
+	"github.com/mediocregopher/mediocre-go-lib/mtest/massert"
+)
+
+func TestIsReservedIP(t *T) {
+	assertReserved := func(ipStr string) massert.Assertion {
+		ip := net.ParseIP(ipStr)
+		if ip == nil {
+			panic("ip:" + ipStr + " not valid")
+		}
+		return massert.Comment(massert.Equal(true, IsReservedIP(ip)),
+			"ip:%q", ipStr)
+	}
+
+	massert.Fatal(t, massert.All(
+		assertReserved("127.0.0.1"),
+		assertReserved("::ffff:127.0.0.1"),
+		assertReserved("192.168.40.50"),
+		assertReserved("::1"),
+		assertReserved("100::1"),
+	))
+
+	massert.Fatal(t, massert.None(
+		assertReserved("8.8.8.8"),
+		assertReserved("::ffff:8.8.8.8"),
+		assertReserved("2600:1700:7580:6e80:21c:25ff:fe97:44df"),
+	))
+}