add support for parsing IPv4-mapped IPv6 addresses

Fixes #94

Author: drakkan

go.mod

@@ -1,3 +1,3 @@
 module github.com/pires/go-proxyproto
 
-go 1.13
+go 1.18

header_test.go

@@ -15,6 +15,7 @@ import (
 const (
 	NO_PROTOCOL   = "There is no spoon"
 	IP4_ADDR      = "127.0.0.1"
+	IP4IN6_ADDR   = "::ffff:127.0.0.1"
 	IP6_ADDR      = "::1"
 	IP6_LONG_ADDR = "1234:5678:9abc:def0:cafe:babe:dead:2bad"
 	PORT          = 65533

v1.go

@@ -5,6 +5,7 @@ import (
 	"bytes"
 	"fmt"
 	"net"
+	"net/netip"
 	"strconv"
 	"strings"
 )
@@ -221,11 +222,22 @@ func parseV1PortNumber(portStr string) (int, error) {
 	return port, nil
 }
 
-func parseV1IPAddress(protocol AddressFamilyAndProtocol, addrStr string) (addr net.IP, err error) {
-	addr = net.ParseIP(addrStr)
-	tryV4 := addr.To4()
-	if (protocol == TCPv4 && tryV4 == nil) || (protocol == TCPv6 && tryV4 != nil) {
-		err = ErrInvalidAddress
+func parseV1IPAddress(protocol AddressFamilyAndProtocol, addrStr string) (net.IP, error) {
+	addr, err := netip.ParseAddr(addrStr)
+	if err != nil {
+		return nil, ErrInvalidAddress
 	}
-	return
+
+	switch protocol {
+	case TCPv4:
+		if addr.Is4() {
+			return net.IP(addr.AsSlice()), nil
+		}
+	case TCPv6:
+		if addr.Is6() || addr.Is4In6() {
+			return net.IP(addr.AsSlice()), nil
+		}
+	}
+
+	return nil, ErrInvalidAddress
 }

v1_test.go

@@ -13,12 +13,14 @@ import (
 
 var (
 	IPv4AddressesAndPorts        = strings.Join([]string{IP4_ADDR, IP4_ADDR, strconv.Itoa(PORT), strconv.Itoa(PORT)}, separator)
+	IPv4In6AddressesAndPorts     = strings.Join([]string{IP4IN6_ADDR, IP4IN6_ADDR, strconv.Itoa(PORT), strconv.Itoa(PORT)}, separator)
 	IPv4AddressesAndInvalidPorts = strings.Join([]string{IP4_ADDR, IP4_ADDR, strconv.Itoa(INVALID_PORT), strconv.Itoa(INVALID_PORT)}, separator)
 	IPv6AddressesAndPorts        = strings.Join([]string{IP6_ADDR, IP6_ADDR, strconv.Itoa(PORT), strconv.Itoa(PORT)}, separator)
 	IPv6LongAddressesAndPorts    = strings.Join([]string{IP6_LONG_ADDR, IP6_LONG_ADDR, strconv.Itoa(PORT), strconv.Itoa(PORT)}, separator)
 
-	fixtureTCP4V1 = "PROXY TCP4 " + IPv4AddressesAndPorts + crlf + "GET /"
-	fixtureTCP6V1 = "PROXY TCP6 " + IPv6AddressesAndPorts + crlf + "GET /"
+	fixtureTCP4V1    = "PROXY TCP4 " + IPv4AddressesAndPorts + crlf + "GET /"
+	fixtureTCP6V1    = "PROXY TCP6 " + IPv6AddressesAndPorts + crlf + "GET /"
+	fixtureTCP4IN6V1 = "PROXY TCP6 " + IPv4In6AddressesAndPorts + crlf + "GET /"
 
 	fixtureTCP6V1Overflow = "PROXY TCP6 " + IPv6LongAddressesAndPorts
 
@@ -66,6 +68,11 @@ var invalidParseV1Tests = []struct {
 		reader:        newBufioReader([]byte("PROXY TCP4 " + IPv4AddressesAndPorts)),
 		expectedError: ErrCantReadVersion1Header,
 	},
+	{
+		desc:          "invalid IP address",
+		reader:        newBufioReader([]byte("PROXY TCP4 invalid invalid 65533 65533" + crlf)),
+		expectedError: ErrInvalidAddress,
+	},
 	{
 		desc:          "TCP6 with IPv4 addresses",
 		reader:        newBufioReader([]byte("PROXY TCP6 " + IPv4AddressesAndPorts + crlf)),
@@ -76,6 +83,11 @@ var invalidParseV1Tests = []struct {
 		reader:        newBufioReader([]byte("PROXY TCP4 " + IPv6AddressesAndPorts + crlf)),
 		expectedError: ErrInvalidAddress,
 	},
+	{
+		desc:          "TCP4 with IPv4 mapped addresses",
+		reader:        newBufioReader([]byte("PROXY TCP4 " + IPv4In6AddressesAndPorts + crlf)),
+		expectedError: ErrInvalidAddress,
+	},
 	{
 		desc:          "TCP4 with invalid port",
 		reader:        newBufioReader([]byte("PROXY TCP4 " + IPv4AddressesAndInvalidPorts + crlf)),
@@ -102,6 +114,7 @@ var validParseAndWriteV1Tests = []struct {
 	desc           string
 	reader         *bufio.Reader
 	expectedHeader *Header
+	skipWrite      bool
 }{
 	{
 		desc:   "TCP4",
@@ -125,6 +138,21 @@ var validParseAndWriteV1Tests = []struct {
 			DestinationAddr:   v6addr,
 		},
 	},
+	{
+		desc:   "TCP4IN6",
+		reader: bufio.NewReader(strings.NewReader(fixtureTCP4IN6V1)),
+		expectedHeader: &Header{
+			Version:           1,
+			Command:           PROXY,
+			TransportProtocol: TCPv6,
+			SourceAddr:        v4addr,
+			DestinationAddr:   v4addr,
+		},
+		// we skip write test because net.ParseIP converts ::ffff:127.0.0.1 to v4
+		// instead of preserving the v4 in v6 form, so, after serializing the header,
+		// we end up with v6 protocol and a v4 IP which is invalid
+		skipWrite: true,
+	},
 	{
 		desc:   "unknown",
 		reader: bufio.NewReader(strings.NewReader(fixtureUnknown)),
@@ -165,6 +193,9 @@ func TestParseV1Valid(t *testing.T) {
 
 func TestWriteV1Valid(t *testing.T) {
 	for _, tt := range validParseAndWriteV1Tests {
+		if tt.skipWrite {
+			continue
+		}
 		t.Run(tt.desc, func(t *testing.T) {
 			var b bytes.Buffer
 			w := bufio.NewWriter(&b)