hotfix(firewall): fix ip prefix parsing for ipv6 (again)

internal/firewall/parse.go

@@ -4,7 +4,6 @@ import (
 	"errors"
 	"fmt"
 	"net/netip"
-	"regexp"
 	"slices"
 	"strconv"
 	"strings"
@@ -153,11 +152,15 @@ func parseInstructionFlag(key, value string, instruction *iptablesInstruction) (
 	return nil
 }
 
-var regexCidrSuffix = regexp.MustCompile(`/[0-9][0-9]{0,2}$`)
-
 func parseIPPrefix(value string) (prefix netip.Prefix, err error) {
-	if !regexCidrSuffix.MatchString(value) {
-		value += "/32"
-	}
+	slashIndex := strings.Index(value, "/")
+	if slashIndex >= 0 {
 		return netip.ParsePrefix(value)
+	}
+
+	ip, err := netip.ParseAddr(value)
+	if err != nil {
+		return netip.Prefix{}, fmt.Errorf("parsing IP address: %w", err)
+	}
+	return netip.PrefixFrom(ip, ip.BitLen()), nil
 }

internal/firewall/parse_test.go

@@ -82,3 +82,57 @@ func Test_parseIptablesInstruction(t *testing.T) {
 		})
 	}
 }
+
+func Test_parseIPPrefix(t *testing.T) {
+	t.Parallel()
+
+	testCases := map[string]struct {
+		value      string
+		prefix     netip.Prefix
+		errMessage string
+	}{
+		"empty": {
+			errMessage: `parsing IP address: ParseAddr(""): unable to parse IP`,
+		},
+		"invalid": {
+			value:      "invalid",
+			errMessage: `parsing IP address: ParseAddr("invalid"): unable to parse IP`,
+		},
+		"valid_ipv4_with_bits": {
+			value:  "10.0.0.0/16",
+			prefix: netip.PrefixFrom(netip.AddrFrom4([4]byte{10, 0, 0, 0}), 16),
+		},
+		"valid_ipv4_without_bits": {
+			value:  "10.0.0.4",
+			prefix: netip.PrefixFrom(netip.AddrFrom4([4]byte{10, 0, 0, 4}), 32),
+		},
+		"valid_ipv6_with_bits": {
+			value: "2001:db8::/32",
+			prefix: netip.PrefixFrom(
+				netip.AddrFrom16([16]byte{0x20, 0x01, 0x0d, 0xb8}),
+				32),
+		},
+		"valid_ipv6_without_bits": {
+			value: "2001:db8::",
+			prefix: netip.PrefixFrom(
+				netip.AddrFrom16([16]byte{0x20, 0x01, 0x0d, 0xb8}),
+				128),
+		},
+	}
+
+	for name, testCase := range testCases {
+		testCase := testCase
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+
+			prefix, err := parseIPPrefix(testCase.value)
+
+			assert.Equal(t, testCase.prefix, prefix)
+			if testCase.errMessage != "" {
+				assert.EqualError(t, err, testCase.errMessage)
+			} else {
+				assert.NoError(t, err)
+			}
+		})
+	}
+}