Support prt records

dns/dns_proxy.go

@@ -380,7 +380,7 @@ func (p *DNSProxy) handleDNSQuery(udpConn *gonet.UDPConn, queryData []byte, clie
 
 	// Check if we have local records for this query
 	var response *dns.Msg
-	if question.Qtype == dns.TypeA || question.Qtype == dns.TypeAAAA {
+	if question.Qtype == dns.TypeA || question.Qtype == dns.TypeAAAA || question.Qtype == dns.TypePTR {
 		response = p.checkLocalRecords(msg, question)
 	}
 
@@ -410,6 +410,34 @@ func (p *DNSProxy) handleDNSQuery(udpConn *gonet.UDPConn, queryData []byte, clie
 
 // checkLocalRecords checks if we have local records for the query
 func (p *DNSProxy) checkLocalRecords(query *dns.Msg, question dns.Question) *dns.Msg {
+	// Handle PTR queries
+	if question.Qtype == dns.TypePTR {
+		if ptrDomain, ok := p.recordStore.GetPTRRecord(question.Name); ok {
+			logger.Debug("Found local PTR record for %s -> %s", question.Name, ptrDomain)
+
+			// Create response message
+			response := new(dns.Msg)
+			response.SetReply(query)
+			response.Authoritative = true
+
+			// Add PTR answer record
+			rr := &dns.PTR{
+				Hdr: dns.RR_Header{
+					Name:   question.Name,
+					Rrtype: dns.TypePTR,
+					Class:  dns.ClassINET,
+					Ttl:    300, // 5 minutes
+				},
+				Ptr: ptrDomain,
+			}
+			response.Answer = append(response.Answer, rr)
+
+			return response
+		}
+		return nil
+	}
+
+	// Handle A and AAAA queries
 	var recordType RecordType
 	if question.Qtype == dns.TypeA {
 		recordType = RecordTypeA

dns/dns_records.go

@@ -1,6 +1,7 @@
 package dns
 
 import (
+	"fmt"
 	"net"
 	"strings"
 	"sync"
@@ -14,15 +15,17 @@ type RecordType uint16
 const (
 	RecordTypeA    RecordType = RecordType(dns.TypeA)
 	RecordTypeAAAA RecordType = RecordType(dns.TypeAAAA)
+	RecordTypePTR  RecordType = RecordType(dns.TypePTR)
 )
 
-// DNSRecordStore manages local DNS records for A and AAAA queries
+// DNSRecordStore manages local DNS records for A, AAAA, and PTR queries
 type DNSRecordStore struct {
 	mu            sync.RWMutex
 	aRecords      map[string][]net.IP // domain -> list of IPv4 addresses
 	aaaaRecords   map[string][]net.IP // domain -> list of IPv6 addresses
 	aWildcards    map[string][]net.IP // wildcard pattern -> list of IPv4 addresses
 	aaaaWildcards map[string][]net.IP // wildcard pattern -> list of IPv6 addresses
+	ptrRecords    map[string]string   // IP address string -> domain name
 }
 
 // NewDNSRecordStore creates a new DNS record store
@@ -32,6 +35,7 @@ func NewDNSRecordStore() *DNSRecordStore {
 		aaaaRecords:   make(map[string][]net.IP),
 		aWildcards:    make(map[string][]net.IP),
 		aaaaWildcards: make(map[string][]net.IP),
+		ptrRecords:    make(map[string]string),
 	}
 }
 
@@ -39,6 +43,7 @@ func NewDNSRecordStore() *DNSRecordStore {
 // domain should be in FQDN format (e.g., "example.com.")
 // domain can contain wildcards: * (0+ chars) and ? (exactly 1 char)
 // ip should be a valid IPv4 or IPv6 address
+// Automatically adds a corresponding PTR record for non-wildcard domains
 func (s *DNSRecordStore) AddRecord(domain string, ip net.IP) error {
 	s.mu.Lock()
 	defer s.mu.Unlock()
@@ -60,6 +65,8 @@ func (s *DNSRecordStore) AddRecord(domain string, ip net.IP) error {
 			s.aWildcards[domain] = append(s.aWildcards[domain], ip)
 		} else {
 			s.aRecords[domain] = append(s.aRecords[domain], ip)
+			// Automatically add PTR record for non-wildcard domains
+			s.ptrRecords[ip.String()] = domain
 		}
 	} else if ip.To16() != nil {
 		// IPv6 address
@@ -67,6 +74,8 @@ func (s *DNSRecordStore) AddRecord(domain string, ip net.IP) error {
 			s.aaaaWildcards[domain] = append(s.aaaaWildcards[domain], ip)
 		} else {
 			s.aaaaRecords[domain] = append(s.aaaaRecords[domain], ip)
+			// Automatically add PTR record for non-wildcard domains
+			s.ptrRecords[ip.String()] = domain
 		}
 	} else {
 		return &net.ParseError{Type: "IP address", Text: ip.String()}
@@ -75,8 +84,30 @@ func (s *DNSRecordStore) AddRecord(domain string, ip net.IP) error {
 	return nil
 }
 
+// AddPTRRecord adds a PTR record mapping an IP address to a domain name
+// ip should be a valid IPv4 or IPv6 address
+// domain should be in FQDN format (e.g., "example.com.")
+func (s *DNSRecordStore) AddPTRRecord(ip net.IP, domain string) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	// Ensure domain ends with a dot (FQDN format)
+	if len(domain) == 0 || domain[len(domain)-1] != '.' {
+		domain = domain + "."
+	}
+
+	// Normalize domain to lowercase FQDN
+	domain = strings.ToLower(dns.Fqdn(domain))
+
+	// Store PTR record using IP string as key
+	s.ptrRecords[ip.String()] = domain
+
+	return nil
+}
+
 // RemoveRecord removes a specific DNS record mapping
 // If ip is nil, removes all records for the domain (including wildcards)
+// Automatically removes corresponding PTR records for non-wildcard domains
 func (s *DNSRecordStore) RemoveRecord(domain string, ip net.IP) {
 	s.mu.Lock()
 	defer s.mu.Unlock()
@@ -98,6 +129,23 @@ func (s *DNSRecordStore) RemoveRecord(domain string, ip net.IP) {
 			delete(s.aWildcards, domain)
 			delete(s.aaaaWildcards, domain)
 		} else {
+			// For non-wildcard domains, remove PTR records for all IPs
+			if ips, ok := s.aRecords[domain]; ok {
+				for _, ipAddr := range ips {
+					// Only remove PTR if it points to this domain
+					if ptrDomain, exists := s.ptrRecords[ipAddr.String()]; exists && ptrDomain == domain {
+						delete(s.ptrRecords, ipAddr.String())
+					}
+				}
+			}
+			if ips, ok := s.aaaaRecords[domain]; ok {
+				for _, ipAddr := range ips {
+					// Only remove PTR if it points to this domain
+					if ptrDomain, exists := s.ptrRecords[ipAddr.String()]; exists && ptrDomain == domain {
+						delete(s.ptrRecords, ipAddr.String())
+					}
+				}
+			}
 			delete(s.aRecords, domain)
 			delete(s.aaaaRecords, domain)
 		}
@@ -119,6 +167,10 @@ func (s *DNSRecordStore) RemoveRecord(domain string, ip net.IP) {
 				if len(s.aRecords[domain]) == 0 {
 					delete(s.aRecords, domain)
 				}
+				// Automatically remove PTR record if it points to this domain
+				if ptrDomain, exists := s.ptrRecords[ip.String()]; exists && ptrDomain == domain {
+					delete(s.ptrRecords, ip.String())
+				}
 			}
 		}
 	} else if ip.To16() != nil {
@@ -136,11 +188,23 @@ func (s *DNSRecordStore) RemoveRecord(domain string, ip net.IP) {
 				if len(s.aaaaRecords[domain]) == 0 {
 					delete(s.aaaaRecords, domain)
 				}
+				// Automatically remove PTR record if it points to this domain
+				if ptrDomain, exists := s.ptrRecords[ip.String()]; exists && ptrDomain == domain {
+					delete(s.ptrRecords, ip.String())
+				}
 			}
 		}
 	}
 }
 
+// RemovePTRRecord removes a PTR record for an IP address
+func (s *DNSRecordStore) RemovePTRRecord(ip net.IP) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	delete(s.ptrRecords, ip.String())
+}
+
 // GetRecords returns all IP addresses for a domain and record type
 // First checks for exact matches, then checks wildcard patterns
 func (s *DNSRecordStore) GetRecords(domain string, recordType RecordType) []net.IP {
@@ -198,6 +262,26 @@ func (s *DNSRecordStore) GetRecords(domain string, recordType RecordType) []net.
 	return records
 }
 
+// GetPTRRecord returns the domain name for a PTR record query
+// domain should be in reverse DNS format (e.g., "1.0.0.127.in-addr.arpa.")
+func (s *DNSRecordStore) GetPTRRecord(domain string) (string, bool) {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+
+	// Convert reverse DNS format to IP address
+	ip := reverseDNSToIP(domain)
+	if ip == nil {
+		return "", false
+	}
+
+	// Look up the PTR record
+	if ptrDomain, ok := s.ptrRecords[ip.String()]; ok {
+		return ptrDomain, true
+	}
+
+	return "", false
+}
+
 // HasRecord checks if a domain has any records of the specified type
 // Checks both exact matches and wildcard patterns
 func (s *DNSRecordStore) HasRecord(domain string, recordType RecordType) bool {
@@ -235,6 +319,21 @@ func (s *DNSRecordStore) HasRecord(domain string, recordType RecordType) bool {
 	return false
 }
 
+// HasPTRRecord checks if a PTR record exists for the given reverse DNS domain
+func (s *DNSRecordStore) HasPTRRecord(domain string) bool {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+
+	// Convert reverse DNS format to IP address
+	ip := reverseDNSToIP(domain)
+	if ip == nil {
+		return false
+	}
+
+	_, ok := s.ptrRecords[ip.String()]
+	return ok
+}
+
 // Clear removes all records from the store
 func (s *DNSRecordStore) Clear() {
 	s.mu.Lock()
@@ -244,6 +343,7 @@ func (s *DNSRecordStore) Clear() {
 	s.aaaaRecords = make(map[string][]net.IP)
 	s.aWildcards = make(map[string][]net.IP)
 	s.aaaaWildcards = make(map[string][]net.IP)
+	s.ptrRecords = make(map[string]string)
 }
 
 // removeIP is a helper function to remove a specific IP from a slice
@@ -323,3 +423,75 @@ func matchWildcardInternal(pattern, domain string, pi, di int) bool {
 
 	return matchWildcardInternal(pattern, domain, pi+1, di+1)
 }
+
+// reverseDNSToIP converts a reverse DNS query name to an IP address
+// Supports both IPv4 (in-addr.arpa) and IPv6 (ip6.arpa) formats
+func reverseDNSToIP(domain string) net.IP {
+	// Normalize to lowercase and ensure FQDN
+	domain = strings.ToLower(dns.Fqdn(domain))
+
+	// Check for IPv4 reverse DNS (in-addr.arpa)
+	if strings.HasSuffix(domain, ".in-addr.arpa.") {
+		// Remove the suffix
+		ipPart := strings.TrimSuffix(domain, ".in-addr.arpa.")
+		// Split by dots and reverse
+		parts := strings.Split(ipPart, ".")
+		if len(parts) != 4 {
+			return nil
+		}
+		// Reverse the octets
+		reversed := make([]string, 4)
+		for i := 0; i < 4; i++ {
+			reversed[i] = parts[3-i]
+		}
+		// Parse as IP
+		return net.ParseIP(strings.Join(reversed, "."))
+	}
+
+	// Check for IPv6 reverse DNS (ip6.arpa)
+	if strings.HasSuffix(domain, ".ip6.arpa.") {
+		// Remove the suffix
+		ipPart := strings.TrimSuffix(domain, ".ip6.arpa.")
+		// Split by dots and reverse
+		parts := strings.Split(ipPart, ".")
+		if len(parts) != 32 {
+			return nil
+		}
+		// Reverse the nibbles and group into 16-bit hex values
+		reversed := make([]string, 32)
+		for i := 0; i < 32; i++ {
+			reversed[i] = parts[31-i]
+		}
+		// Join into IPv6 format (groups of 4 nibbles separated by colons)
+		var ipv6Parts []string
+		for i := 0; i < 32; i += 4 {
+			ipv6Parts = append(ipv6Parts, reversed[i]+reversed[i+1]+reversed[i+2]+reversed[i+3])
+		}
+		// Parse as IP
+		return net.ParseIP(strings.Join(ipv6Parts, ":"))
+	}
+
+	return nil
+}
+
+// IPToReverseDNS converts an IP address to reverse DNS format
+// Returns the domain name for PTR queries (e.g., "1.0.0.127.in-addr.arpa.")
+func IPToReverseDNS(ip net.IP) string {
+	if ip4 := ip.To4(); ip4 != nil {
+		// IPv4: reverse octets and append .in-addr.arpa.
+		return dns.Fqdn(fmt.Sprintf("%d.%d.%d.%d.in-addr.arpa",
+			ip4[3], ip4[2], ip4[1], ip4[0]))
+	}
+
+	if ip6 := ip.To16(); ip6 != nil && ip.To4() == nil {
+		// IPv6: expand to 32 nibbles, reverse, and append .ip6.arpa.
+		var nibbles []string
+		for i := 15; i >= 0; i-- {
+			nibbles = append(nibbles, fmt.Sprintf("%x", ip6[i]&0x0f))
+			nibbles = append(nibbles, fmt.Sprintf("%x", ip6[i]>>4))
+		}
+		return dns.Fqdn(strings.Join(nibbles, ".") + ".ip6.arpa")
+	}
+
+	return ""
+}

dns/dns_records_test.go

@@ -413,3 +413,452 @@ func TestDNSRecordStoreCaseInsensitive(t *testing.T) {
 		t.Error("Expected HasRecord to return true for mixed case wildcard match")
 	}
 }
+
+func TestPTRRecordIPv4(t *testing.T) {
+	store := NewDNSRecordStore()
+
+	// Add PTR record for IPv4
+	ip := net.ParseIP("192.168.1.1")
+	domain := "host.example.com."
+	err := store.AddPTRRecord(ip, domain)
+	if err != nil {
+		t.Fatalf("Failed to add PTR record: %v", err)
+	}
+
+	// Test reverse DNS lookup
+	reverseDomain := "1.1.168.192.in-addr.arpa."
+	result, ok := store.GetPTRRecord(reverseDomain)
+	if !ok {
+		t.Error("Expected PTR record to be found")
+	}
+	if result != domain {
+		t.Errorf("Expected domain %q, got %q", domain, result)
+	}
+
+	// Test HasPTRRecord
+	if !store.HasPTRRecord(reverseDomain) {
+		t.Error("Expected HasPTRRecord to return true")
+	}
+
+	// Test non-existent PTR record
+	_, ok = store.GetPTRRecord("2.1.168.192.in-addr.arpa.")
+	if ok {
+		t.Error("Expected PTR record not to be found for different IP")
+	}
+}
+
+func TestPTRRecordIPv6(t *testing.T) {
+	store := NewDNSRecordStore()
+
+	// Add PTR record for IPv6
+	ip := net.ParseIP("2001:db8::1")
+	domain := "ipv6host.example.com."
+	err := store.AddPTRRecord(ip, domain)
+	if err != nil {
+		t.Fatalf("Failed to add PTR record: %v", err)
+	}
+
+	// Test reverse DNS lookup
+	// 2001:db8::1 = 2001:0db8:0000:0000:0000:0000:0000:0001
+	// Reverse: 1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa.
+	reverseDomain := "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa."
+	result, ok := store.GetPTRRecord(reverseDomain)
+	if !ok {
+		t.Error("Expected IPv6 PTR record to be found")
+	}
+	if result != domain {
+		t.Errorf("Expected domain %q, got %q", domain, result)
+	}
+
+	// Test HasPTRRecord
+	if !store.HasPTRRecord(reverseDomain) {
+		t.Error("Expected HasPTRRecord to return true for IPv6")
+	}
+}
+
+func TestRemovePTRRecord(t *testing.T) {
+	store := NewDNSRecordStore()
+
+	// Add PTR record
+	ip := net.ParseIP("10.0.0.1")
+	domain := "test.example.com."
+	err := store.AddPTRRecord(ip, domain)
+	if err != nil {
+		t.Fatalf("Failed to add PTR record: %v", err)
+	}
+
+	// Verify it exists
+	reverseDomain := "1.0.0.10.in-addr.arpa."
+	_, ok := store.GetPTRRecord(reverseDomain)
+	if !ok {
+		t.Error("Expected PTR record to exist before removal")
+	}
+
+	// Remove PTR record
+	store.RemovePTRRecord(ip)
+
+	// Verify it's gone
+	_, ok = store.GetPTRRecord(reverseDomain)
+	if ok {
+		t.Error("Expected PTR record to be removed")
+	}
+
+	// Test HasPTRRecord after removal
+	if store.HasPTRRecord(reverseDomain) {
+		t.Error("Expected HasPTRRecord to return false after removal")
+	}
+}
+
+func TestIPToReverseDNS(t *testing.T) {
+	tests := []struct {
+		name     string
+		ip       string
+		expected string
+	}{
+		{
+			name:     "IPv4 simple",
+			ip:       "192.168.1.1",
+			expected: "1.1.168.192.in-addr.arpa.",
+		},
+		{
+			name:     "IPv4 localhost",
+			ip:       "127.0.0.1",
+			expected: "1.0.0.127.in-addr.arpa.",
+		},
+		{
+			name:     "IPv4 with zeros",
+			ip:       "10.0.0.1",
+			expected: "1.0.0.10.in-addr.arpa.",
+		},
+		{
+			name:     "IPv6 simple",
+			ip:       "2001:db8::1",
+			expected: "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa.",
+		},
+		{
+			name:     "IPv6 localhost",
+			ip:       "::1",
+			expected: "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa.",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			ip := net.ParseIP(tt.ip)
+			if ip == nil {
+				t.Fatalf("Failed to parse IP: %s", tt.ip)
+			}
+			result := IPToReverseDNS(ip)
+			if result != tt.expected {
+				t.Errorf("IPToReverseDNS(%s) = %q, want %q", tt.ip, result, tt.expected)
+			}
+		})
+	}
+}
+
+func TestReverseDNSToIP(t *testing.T) {
+	tests := []struct {
+		name        string
+		reverseDNS  string
+		expectedIP  string
+		shouldMatch bool
+	}{
+		{
+			name:        "IPv4 simple",
+			reverseDNS:  "1.1.168.192.in-addr.arpa.",
+			expectedIP:  "192.168.1.1",
+			shouldMatch: true,
+		},
+		{
+			name:        "IPv4 localhost",
+			reverseDNS:  "1.0.0.127.in-addr.arpa.",
+			expectedIP:  "127.0.0.1",
+			shouldMatch: true,
+		},
+		{
+			name:        "IPv6 simple",
+			reverseDNS:  "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa.",
+			expectedIP:  "2001:db8::1",
+			shouldMatch: true,
+		},
+		{
+			name:        "Invalid IPv4 format",
+			reverseDNS:  "1.1.168.in-addr.arpa.",
+			expectedIP:  "",
+			shouldMatch: false,
+		},
+		{
+			name:        "Invalid IPv6 format",
+			reverseDNS:  "1.0.0.0.ip6.arpa.",
+			expectedIP:  "",
+			shouldMatch: false,
+		},
+		{
+			name:        "Not a reverse DNS domain",
+			reverseDNS:  "example.com.",
+			expectedIP:  "",
+			shouldMatch: false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := reverseDNSToIP(tt.reverseDNS)
+			if tt.shouldMatch {
+				if result == nil {
+					t.Errorf("reverseDNSToIP(%q) returned nil, expected IP", tt.reverseDNS)
+					return
+				}
+				expectedIP := net.ParseIP(tt.expectedIP)
+				if !result.Equal(expectedIP) {
+					t.Errorf("reverseDNSToIP(%q) = %v, want %v", tt.reverseDNS, result, expectedIP)
+				}
+			} else {
+				if result != nil {
+					t.Errorf("reverseDNSToIP(%q) = %v, expected nil", tt.reverseDNS, result)
+				}
+			}
+		})
+	}
+}
+
+func TestPTRRecordCaseInsensitive(t *testing.T) {
+	store := NewDNSRecordStore()
+
+	// Add PTR record with mixed case domain
+	ip := net.ParseIP("192.168.1.1")
+	domain := "MyHost.Example.Com"
+	err := store.AddPTRRecord(ip, domain)
+	if err != nil {
+		t.Fatalf("Failed to add PTR record: %v", err)
+	}
+
+	// Test lookup with different cases in reverse DNS format
+	reverseDomain := "1.1.168.192.in-addr.arpa."
+	result, ok := store.GetPTRRecord(reverseDomain)
+	if !ok {
+		t.Error("Expected PTR record to be found")
+	}
+	// Domain should be normalized to lowercase
+	if result != "myhost.example.com." {
+		t.Errorf("Expected normalized domain %q, got %q", "myhost.example.com.", result)
+	}
+
+	// Test with uppercase reverse DNS
+	reverseDomainUpper := "1.1.168.192.IN-ADDR.ARPA."
+	result, ok = store.GetPTRRecord(reverseDomainUpper)
+	if !ok {
+		t.Error("Expected PTR record to be found with uppercase reverse DNS")
+	}
+	if result != "myhost.example.com." {
+		t.Errorf("Expected normalized domain %q, got %q", "myhost.example.com.", result)
+	}
+}
+
+func TestClearPTRRecords(t *testing.T) {
+	store := NewDNSRecordStore()
+
+	// Add some PTR records
+	ip1 := net.ParseIP("192.168.1.1")
+	ip2 := net.ParseIP("192.168.1.2")
+	store.AddPTRRecord(ip1, "host1.example.com.")
+	store.AddPTRRecord(ip2, "host2.example.com.")
+
+	// Add some A records too
+	store.AddRecord("test.example.com.", net.ParseIP("10.0.0.1"))
+
+	// Verify PTR records exist
+	if !store.HasPTRRecord("1.1.168.192.in-addr.arpa.") {
+		t.Error("Expected PTR record to exist before clear")
+	}
+
+	// Clear all records
+	store.Clear()
+
+	// Verify PTR records are gone
+	if store.HasPTRRecord("1.1.168.192.in-addr.arpa.") {
+		t.Error("Expected PTR record to be cleared")
+	}
+	if store.HasPTRRecord("2.1.168.192.in-addr.arpa.") {
+		t.Error("Expected PTR record to be cleared")
+	}
+
+	// Verify A records are also gone
+	if store.HasRecord("test.example.com.", RecordTypeA) {
+		t.Error("Expected A record to be cleared")
+	}
+}
+
+func TestAutomaticPTRRecordOnAdd(t *testing.T) {
+	store := NewDNSRecordStore()
+
+	// Add an A record - should automatically add PTR record
+	domain := "host.example.com."
+	ip := net.ParseIP("192.168.1.100")
+	err := store.AddRecord(domain, ip)
+	if err != nil {
+		t.Fatalf("Failed to add A record: %v", err)
+	}
+
+	// Verify PTR record was automatically created
+	reverseDomain := "100.1.168.192.in-addr.arpa."
+	result, ok := store.GetPTRRecord(reverseDomain)
+	if !ok {
+		t.Error("Expected PTR record to be automatically created")
+	}
+	if result != domain {
+		t.Errorf("Expected PTR to point to %q, got %q", domain, result)
+	}
+
+	// Add AAAA record - should also automatically add PTR record
+	domain6 := "ipv6host.example.com."
+	ip6 := net.ParseIP("2001:db8::1")
+	err = store.AddRecord(domain6, ip6)
+	if err != nil {
+		t.Fatalf("Failed to add AAAA record: %v", err)
+	}
+
+	// Verify IPv6 PTR record was automatically created
+	reverseDomain6 := "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa."
+	result6, ok := store.GetPTRRecord(reverseDomain6)
+	if !ok {
+		t.Error("Expected IPv6 PTR record to be automatically created")
+	}
+	if result6 != domain6 {
+		t.Errorf("Expected PTR to point to %q, got %q", domain6, result6)
+	}
+}
+
+func TestAutomaticPTRRecordOnRemove(t *testing.T) {
+	store := NewDNSRecordStore()
+
+	// Add an A record (with automatic PTR)
+	domain := "host.example.com."
+	ip := net.ParseIP("192.168.1.100")
+	store.AddRecord(domain, ip)
+
+	// Verify PTR exists
+	reverseDomain := "100.1.168.192.in-addr.arpa."
+	if !store.HasPTRRecord(reverseDomain) {
+		t.Error("Expected PTR record to exist after adding A record")
+	}
+
+	// Remove the A record
+	store.RemoveRecord(domain, ip)
+
+	// Verify PTR was automatically removed
+	if store.HasPTRRecord(reverseDomain) {
+		t.Error("Expected PTR record to be automatically removed")
+	}
+
+	// Verify A record is also gone
+	ips := store.GetRecords(domain, RecordTypeA)
+	if len(ips) != 0 {
+		t.Errorf("Expected A record to be removed, got %d records", len(ips))
+	}
+}
+
+func TestAutomaticPTRRecordOnRemoveAll(t *testing.T) {
+	store := NewDNSRecordStore()
+
+	// Add multiple IPs for the same domain
+	domain := "host.example.com."
+	ip1 := net.ParseIP("192.168.1.100")
+	ip2 := net.ParseIP("192.168.1.101")
+	store.AddRecord(domain, ip1)
+	store.AddRecord(domain, ip2)
+
+	// Verify both PTR records exist
+	reverseDomain1 := "100.1.168.192.in-addr.arpa."
+	reverseDomain2 := "101.1.168.192.in-addr.arpa."
+	if !store.HasPTRRecord(reverseDomain1) {
+		t.Error("Expected first PTR record to exist")
+	}
+	if !store.HasPTRRecord(reverseDomain2) {
+		t.Error("Expected second PTR record to exist")
+	}
+
+	// Remove all records for the domain
+	store.RemoveRecord(domain, nil)
+
+	// Verify both PTR records were removed
+	if store.HasPTRRecord(reverseDomain1) {
+		t.Error("Expected first PTR record to be removed")
+	}
+	if store.HasPTRRecord(reverseDomain2) {
+		t.Error("Expected second PTR record to be removed")
+	}
+}
+
+func TestNoPTRForWildcardRecords(t *testing.T) {
+	store := NewDNSRecordStore()
+
+	// Add wildcard record - should NOT create PTR record
+	domain := "*.example.com."
+	ip := net.ParseIP("192.168.1.100")
+	err := store.AddRecord(domain, ip)
+	if err != nil {
+		t.Fatalf("Failed to add wildcard record: %v", err)
+	}
+
+	// Verify no PTR record was created
+	reverseDomain := "100.1.168.192.in-addr.arpa."
+	_, ok := store.GetPTRRecord(reverseDomain)
+	if ok {
+		t.Error("Expected no PTR record for wildcard domain")
+	}
+
+	// Verify wildcard A record exists
+	if !store.HasRecord("host.example.com.", RecordTypeA) {
+		t.Error("Expected wildcard A record to exist")
+	}
+}
+
+func TestPTRRecordOverwrite(t *testing.T) {
+	store := NewDNSRecordStore()
+
+	// Add first domain with IP
+	domain1 := "host1.example.com."
+	ip := net.ParseIP("192.168.1.100")
+	store.AddRecord(domain1, ip)
+
+	// Verify PTR points to first domain
+	reverseDomain := "100.1.168.192.in-addr.arpa."
+	result, ok := store.GetPTRRecord(reverseDomain)
+	if !ok {
+		t.Fatal("Expected PTR record to exist")
+	}
+	if result != domain1 {
+		t.Errorf("Expected PTR to point to %q, got %q", domain1, result)
+	}
+
+	// Add second domain with same IP - should overwrite PTR
+	domain2 := "host2.example.com."
+	store.AddRecord(domain2, ip)
+
+	// Verify PTR now points to second domain (last one added)
+	result, ok = store.GetPTRRecord(reverseDomain)
+	if !ok {
+		t.Fatal("Expected PTR record to still exist")
+	}
+	if result != domain2 {
+		t.Errorf("Expected PTR to point to %q (overwritten), got %q", domain2, result)
+	}
+
+	// Remove first domain - PTR should remain pointing to second domain
+	store.RemoveRecord(domain1, ip)
+	result, ok = store.GetPTRRecord(reverseDomain)
+	if !ok {
+		t.Error("Expected PTR record to still exist after removing first domain")
+	}
+	if result != domain2 {
+		t.Errorf("Expected PTR to still point to %q, got %q", domain2, result)
+	}
+
+	// Remove second domain - PTR should now be gone
+	store.RemoveRecord(domain2, ip)
+	_, ok = store.GetPTRRecord(reverseDomain)
+	if ok {
+		t.Error("Expected PTR record to be removed after removing second domain")
+	}
+}