From 6d48f9c2ba66da3d98b0cd9251a8cc5d7394885e Mon Sep 17 00:00:00 2001
From: Quentin McGaw <quentin.mcgaw@gmail.com>
Date: Mon, 22 May 2023 05:56:27 +0000
Subject: [PATCH] fix(routing): net.IPNet to netip.Prefix conversion

---
 internal/routing/conversion.go      | 12 +++++++-
 internal/routing/conversion_test.go | 48 +++++++++++++++++++++++++++++
 2 files changed, 59 insertions(+), 1 deletion(-)

diff --git a/internal/routing/conversion.go b/internal/routing/conversion.go
index 439a114b..6e2f77cc 100644
--- a/internal/routing/conversion.go
+++ b/internal/routing/conversion.go
@@ -21,7 +21,17 @@ func NetipPrefixToIPNet(prefix *netip.Prefix) (ipNet *net.IPNet) {
 }
 
 func netIPNetToNetipPrefix(ipNet net.IPNet) (prefix netip.Prefix) {
-	return netip.MustParsePrefix(ipNet.String())
+	if len(ipNet.IP) != net.IPv4len && len(ipNet.IP) != net.IPv6len {
+		return prefix
+	}
+	var ip netip.Addr
+	if ipv4 := ipNet.IP.To4(); ipv4 != nil {
+		ip = netip.AddrFrom4([4]byte(ipv4))
+	} else {
+		ip = netip.AddrFrom16([16]byte(ipNet.IP))
+	}
+	bits, _ := ipNet.Mask.Size()
+	return netip.PrefixFrom(ip, bits)
 }
 
 func netIPToNetipAddress(ip net.IP) (address netip.Addr) {
diff --git a/internal/routing/conversion_test.go b/internal/routing/conversion_test.go
index a30dfbb5..53002956 100644
--- a/internal/routing/conversion_test.go
+++ b/internal/routing/conversion_test.go
@@ -8,6 +8,54 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
+func Test_netIPNetToNetipPrefix(t *testing.T) {
+	t.Parallel()
+
+	testCases := map[string]struct {
+		ipNet  net.IPNet
+		prefix netip.Prefix
+	}{
+		"empty ipnet": {},
+		"custom sized IP in ipnet": {
+			ipNet: net.IPNet{
+				IP: net.IP{1},
+			},
+		},
+		"IPv4 ipnet": {
+			ipNet: net.IPNet{
+				IP:   net.IP{1, 2, 3, 4},
+				Mask: net.IPMask{255, 255, 255, 0},
+			},
+			prefix: netip.PrefixFrom(netip.AddrFrom4([4]byte{1, 2, 3, 4}), 24),
+		},
+		"IPv4-in-IPv6 ipnet": {
+			ipNet: net.IPNet{
+				IP:   net.IPv4(1, 2, 3, 4),
+				Mask: net.IPMask{255, 255, 255, 0},
+			},
+			prefix: netip.PrefixFrom(netip.AddrFrom4([4]byte{1, 2, 3, 4}), 24),
+		},
+		"IPv6 ipnet": {
+			ipNet: net.IPNet{
+				IP:   net.IPv6loopback,
+				Mask: net.IPMask{0xff},
+			},
+			prefix: netip.PrefixFrom(netip.IPv6Loopback(), 8),
+		},
+	}
+
+	for name, testCase := range testCases {
+		testCase := testCase
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+
+			prefix := netIPNetToNetipPrefix(testCase.ipNet)
+
+			assert.Equal(t, testCase.prefix, prefix)
+		})
+	}
+}
+
 func Test_netIPToNetipAddress(t *testing.T) {
 	t.Parallel()