From 7cf25970ded96df6ce3c6557c4e4deaac6f43989 Mon Sep 17 00:00:00 2001
From: Meow <197331664+Meo597@users.noreply.github.com>
Date: Sun, 26 Apr 2026 00:07:04 +0800
Subject: [PATCH] IPMatcher: Fix full CIDR issue (#5971)

Fixes https://github.com/XTLS/Xray-core/issues/5977
---
 common/geodata/ip_matcher.go      | 11 +++-
 common/geodata/ip_matcher_test.go | 84 +++++++++++++++++++++++++++++++
 2 files changed, 93 insertions(+), 2 deletions(-)

diff --git a/common/geodata/ip_matcher.go b/common/geodata/ip_matcher.go
index 315ce040..abacf109 100644
--- a/common/geodata/ip_matcher.go
+++ b/common/geodata/ip_matcher.go
@@ -915,24 +915,31 @@ func (f *IPSetFactory) createFrom(yield func(func(*CIDR)) error) (*IPSet, error)
 		return nil, errors.New("failed to build IPv6 set").Base(err)
 	}
 
+	var has4, has6 bool
 	var max4, max6 int
 
 	for _, p := range ipv4.Prefixes() {
+		has4 = true
 		if b := p.Bits(); b > max4 {
 			max4 = b
 		}
 	}
 	for _, p := range ipv6.Prefixes() {
+		has6 = true
 		if b := p.Bits(); b > max6 {
 			max6 = b
 		}
 	}
 
-	if max4 == 0 {
+	if !has4 {
 		max4 = 0xff
+	} else if max4 == 0 {
+		max4 = 0xfe
 	}
-	if max6 == 0 {
+	if !has6 {
 		max6 = 0xff
+	} else if max6 == 0 {
+		max6 = 0xfe
 	}
 
 	return &IPSet{ipv4: ipv4, ipv6: ipv6, max4: uint8(max4), max6: uint8(max6)}, nil
diff --git a/common/geodata/ip_matcher_test.go b/common/geodata/ip_matcher_test.go
index d1dc2de2..829c455d 100644
--- a/common/geodata/ip_matcher_test.go
+++ b/common/geodata/ip_matcher_test.go
@@ -97,6 +97,90 @@ func TestIPMatcher(t *testing.T) {
 	}
 }
 
+func TestIPMatcherFullCIDR4(t *testing.T) {
+	matcher := buildIPMatcher(
+		"0.0.0.0/0",
+	)
+
+	testCases := []struct {
+		Input  string
+		Output bool
+	}{
+		{
+			Input:  "192.168.1.1",
+			Output: true,
+		},
+		{
+			Input:  "0.0.0.0",
+			Output: true,
+		},
+		{
+			Input:  "255.255.255.255",
+			Output: true,
+		},
+		{
+			Input:  "2001:cdba::3257:9652",
+			Output: false,
+		},
+		{
+			Input:  "::0",
+			Output: false,
+		},
+		{
+			Input:  "ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff",
+			Output: false,
+		},
+	}
+
+	for _, test := range testCases {
+		if v := matcher.Match(xnet.ParseAddress(test.Input).IP()); v != test.Output {
+			t.Error("unexpected output: ", v, " for test case ", test)
+		}
+	}
+}
+
+func TestIPMatcherFullCIDR6(t *testing.T) {
+	matcher := buildIPMatcher(
+		"::0/0",
+	)
+
+	testCases := []struct {
+		Input  string
+		Output bool
+	}{
+		{
+			Input:  "192.168.1.1",
+			Output: false,
+		},
+		{
+			Input:  "0.0.0.0",
+			Output: false,
+		},
+		{
+			Input:  "255.255.255.255",
+			Output: false,
+		},
+		{
+			Input:  "2001:cdba::3257:9652",
+			Output: true,
+		},
+		{
+			Input:  "::0",
+			Output: true,
+		},
+		{
+			Input:  "ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff",
+			Output: true,
+		},
+	}
+
+	for _, test := range testCases {
+		if v := matcher.Match(xnet.ParseAddress(test.Input).IP()); v != test.Output {
+			t.Error("unexpected output: ", v, " for test case ", test)
+		}
+	}
+}
+
 func TestIPMatcherRegression(t *testing.T) {
 	matcher := buildIPMatcher(
 		"98.108.20.0/22",