Give the ICMP Code its own type

This is  a preparatory commit for a larger commit working on
ICMP generation in error cases.
This is removal of technical debt and cleanup in the gvisor code
as part of gvisor issue 2211.

Updates #2211.

PiperOrigin-RevId: 326615389

12 files changed, 81 insertions, 40 deletions

diff --git a/pkg/tcpip/checker/checker.go b/pkg/tcpip/checker/checker.go
index 1e5f5abf2..b769094dc 100644
--- a/pkg/tcpip/checker/checker.go
+++ b/pkg/tcpip/checker/checker.go
@@ -699,7 +699,7 @@ func ICMPv4Type(want header.ICMPv4Type) TransportChecker {
 }
 
 // ICMPv4Code creates a checker that checks the ICMPv4 Code field.
-func ICMPv4Code(want byte) TransportChecker {
+func ICMPv4Code(want header.ICMPv4Code) TransportChecker {
 	return func(t *testing.T, h header.Transport) {
 		t.Helper()
 
@@ -757,7 +757,7 @@ func ICMPv6Type(want header.ICMPv6Type) TransportChecker {
 }
 
 // ICMPv6Code creates a checker that checks the ICMPv6 Code field.
-func ICMPv6Code(want byte) TransportChecker {
+func ICMPv6Code(want header.ICMPv6Code) TransportChecker {
 	return func(t *testing.T, h header.Transport) {
 		t.Helper()
 
diff --git a/pkg/tcpip/header/icmpv4.go b/pkg/tcpip/header/icmpv4.go
index 1a631b31a..be03fb086 100644
--- a/pkg/tcpip/header/icmpv4.go
+++ b/pkg/tcpip/header/icmpv4.go
@@ -54,6 +54,9 @@ const (
 // ICMPv4Type is the ICMP type field described in RFC 792.
 type ICMPv4Type byte
 
+// ICMPv4Code is the ICMP code field described in RFC 792.
+type ICMPv4Code byte
+
 // Typical values of ICMPv4Type defined in RFC 792.
 const (
 	ICMPv4EchoReply      ICMPv4Type = 0
@@ -69,12 +72,13 @@ const (
 	ICMPv4InfoReply      ICMPv4Type = 16
 )
 
-// Values for ICMP code as defined in RFC 792.
+// ICMP codes for ICMPv4 Destination Unreachable messages as defined in RFC 792.
 const (
-	ICMPv4TTLExceeded         = 0
-	ICMPv4HostUnreachable     = 1
-	ICMPv4PortUnreachable     = 3
-	ICMPv4FragmentationNeeded = 4
+	ICMPv4TTLExceeded         ICMPv4Code = 0
+	ICMPv4HostUnreachable     ICMPv4Code = 1
+	ICMPv4ProtoUnreachable    ICMPv4Code = 2
+	ICMPv4PortUnreachable     ICMPv4Code = 3
+	ICMPv4FragmentationNeeded ICMPv4Code = 4
 )
 
 // Type is the ICMP type field.
@@ -84,10 +88,10 @@ func (b ICMPv4) Type() ICMPv4Type { return ICMPv4Type(b[0]) }
 func (b ICMPv4) SetType(t ICMPv4Type) { b[0] = byte(t) }
 
 // Code is the ICMP code field. Its meaning depends on the value of Type.
-func (b ICMPv4) Code() byte { return b[1] }
+func (b ICMPv4) Code() ICMPv4Code { return ICMPv4Code(b[1]) }
 
 // SetCode sets the ICMP code field.
-func (b ICMPv4) SetCode(c byte) { b[1] = c }
+func (b ICMPv4) SetCode(c ICMPv4Code) { b[1] = byte(c) }
 
 // Checksum is the ICMP checksum field.
 func (b ICMPv4) Checksum() uint16 {
diff --git a/pkg/tcpip/header/icmpv6.go b/pkg/tcpip/header/icmpv6.go
index a13b4b809..20b01d8f4 100644
--- a/pkg/tcpip/header/icmpv6.go
+++ b/pkg/tcpip/header/icmpv6.go
@@ -92,7 +92,6 @@ const (
 // ICMPv6Type is the ICMP type field described in RFC 4443 and friends.
 type ICMPv6Type byte
 
-// Typical values of ICMPv6Type defined in RFC 4443.
 const (
 	ICMPv6DstUnreachable ICMPv6Type = 1
 	ICMPv6PacketTooBig   ICMPv6Type = 2
@@ -110,18 +109,38 @@ const (
 	ICMPv6RedirectMsg     ICMPv6Type = 137
 )
 
-// Values for ICMP destination unreachable code as defined in RFC 4443 section
-// 3.1.
+// ICMPv6Code is the ICMP code field described in RFC 4443.
+type ICMPv6Code byte
+
+// ICMP codes used with Destination Unreachable (Type 1). As per RFC 4443
+// section 3.1.
+const (
+	ICMPv6NetworkUnreachable ICMPv6Code = 0
+	ICMPv6Prohibited         ICMPv6Code = 1
+	ICMPv6BeyondScope        ICMPv6Code = 2
+	ICMPv6AddressUnreachable ICMPv6Code = 3
+	ICMPv6PortUnreachable    ICMPv6Code = 4
+	ICMPv6Policy             ICMPv6Code = 5
+	ICMPv6RejectRoute        ICMPv6Code = 6
+)
+
+// ICMP codes used with Time Exceeded (Type 3). As per RFC 4443 section 3.3.
 const (
-	ICMPv6NetworkUnreachable = 0
-	ICMPv6Prohibited         = 1
-	ICMPv6BeyondScope        = 2
-	ICMPv6AddressUnreachable = 3
-	ICMPv6PortUnreachable    = 4
-	ICMPv6Policy             = 5
-	ICMPv6RejectRoute        = 6
+	ICMPv6HopLimitExceeded  ICMPv6Code = 0
+	ICMPv6ReassemblyTimeout ICMPv6Code = 1
 )
 
+// ICMP codes used with Parameter Problem (Type 4). As per RFC 4443 section 3.4.
+const (
+	ICMPv6ErroneousHeader ICMPv6Code = 0
+	ICMPv6UnknownHeader   ICMPv6Code = 1
+	ICMPv6UnknownOption   ICMPv6Code = 2
+)
+
+// ICMPv6UnusedCode is the code value used with ICMPv6 messages which don't use
+// the code field. (Types not mentioned above.)
+const ICMPv6UnusedCode ICMPv6Code = 0
+
 // Type is the ICMP type field.
 func (b ICMPv6) Type() ICMPv6Type { return ICMPv6Type(b[0]) }
 
@@ -129,10 +148,10 @@ func (b ICMPv6) Type() ICMPv6Type { return ICMPv6Type(b[0]) }
 func (b ICMPv6) SetType(t ICMPv6Type) { b[0] = byte(t) }
 
 // Code is the ICMP code field. Its meaning depends on the value of Type.
-func (b ICMPv6) Code() byte { return b[1] }
+func (b ICMPv6) Code() ICMPv6Code { return ICMPv6Code(b[1]) }
 
 // SetCode sets the ICMP code field.
-func (b ICMPv6) SetCode(c byte) { b[1] = c }
+func (b ICMPv6) SetCode(c ICMPv6Code) { b[1] = byte(c) }
 
 // Checksum is the ICMP checksum field.
 func (b ICMPv6) Checksum() uint16 {
diff --git a/pkg/tcpip/network/ip_test.go b/pkg/tcpip/network/ip_test.go
index e6768258a..491d936a1 100644
--- a/pkg/tcpip/network/ip_test.go
+++ b/pkg/tcpip/network/ip_test.go
@@ -321,7 +321,7 @@ func TestIPv4ReceiveControl(t *testing.T) {
 		name           string
 		expectedCount  int
 		fragmentOffset uint16
-		code           uint8
+		code           header.ICMPv4Code
 		expectedTyp    stack.ControlType
 		expectedExtra  uint32
 		trunc          int
@@ -579,7 +579,7 @@ func TestIPv6ReceiveControl(t *testing.T) {
 		expectedCount  int
 		fragmentOffset *uint16
 		typ            header.ICMPv6Type
-		code           uint8
+		code           header.ICMPv6Code
 		expectedTyp    stack.ControlType
 		expectedExtra  uint32
 		trunc          int
diff --git a/pkg/tcpip/network/ipv6/ndp_test.go b/pkg/tcpip/network/ipv6/ndp_test.go
index fe159b24f..2efa82e60 100644
--- a/pkg/tcpip/network/ipv6/ndp_test.go
+++ b/pkg/tcpip/network/ipv6/ndp_test.go
@@ -637,7 +637,7 @@ func TestNDPValidation(t *testing.T) {
 		name           string
 		atomicFragment bool
 		hopLimit       uint8
-		code           uint8
+		code           header.ICMPv6Code
 		valid          bool
 	}{
 		{
@@ -730,7 +730,7 @@ func TestRouterAdvertValidation(t *testing.T) {
 		name            string
 		src             tcpip.Address
 		hopLimit        uint8
-		code            uint8
+		code            header.ICMPv6Code
 		ndpPayload      []byte
 		expectedSuccess bool
 	}{
diff --git a/pkg/tcpip/transport/tcp/testing/context/context.go b/pkg/tcpip/transport/tcp/testing/context/context.go
index 927bc71e0..b6031354e 100644
--- a/pkg/tcpip/transport/tcp/testing/context/context.go
+++ b/pkg/tcpip/transport/tcp/testing/context/context.go
@@ -292,7 +292,7 @@ func (c *Context) GetPacketNonBlocking() []byte {
 }
 
 // SendICMPPacket builds and sends an ICMPv4 packet via the link layer endpoint.
-func (c *Context) SendICMPPacket(typ header.ICMPv4Type, code uint8, p1, p2 []byte, maxTotalSize int) {
+func (c *Context) SendICMPPacket(typ header.ICMPv4Type, code header.ICMPv4Code, p1, p2 []byte, maxTotalSize int) {
 	// Allocate a buffer data and headers.
 	buf := buffer.NewView(header.IPv4MinimumSize + header.ICMPv4PayloadOffset + len(p2))
 	if len(buf) > maxTotalSize {
diff --git a/test/packetimpact/testbench/layers.go b/test/packetimpact/testbench/layers.go
index 24aa46cce..a35562ca8 100644
--- a/test/packetimpact/testbench/layers.go
+++ b/test/packetimpact/testbench/layers.go
@@ -775,7 +775,7 @@ func (l *IPv6FragmentExtHdr) String() string {
 type ICMPv6 struct {
 	LayerBase
 	Type     *header.ICMPv6Type
-	Code     *byte
+	Code     *header.ICMPv6Code
 	Checksum *uint16
 	Payload  []byte
 }
@@ -823,6 +823,12 @@ func ICMPv6Type(v header.ICMPv6Type) *header.ICMPv6Type {
 	return &v
 }
 
+// ICMPv6Code is a helper routine that allocates a new ICMPv6Type value to store
+// v and returns a pointer to it.
+func ICMPv6Code(v header.ICMPv6Code) *header.ICMPv6Code {
+	return &v
+}
+
 // Byte is a helper routine that allocates a new byte value to store
 // v and returns a pointer to it.
 func Byte(v byte) *byte {
@@ -834,7 +840,7 @@ func parseICMPv6(b []byte) (Layer, layerParser) {
 	h := header.ICMPv6(b)
 	icmpv6 := ICMPv6{
 		Type:     ICMPv6Type(h.Type()),
-		Code:     Byte(h.Code()),
+		Code:     ICMPv6Code(h.Code()),
 		Checksum: Uint16(h.Checksum()),
 		Payload:  h.NDPPayload(),
 	}
@@ -861,11 +867,17 @@ func ICMPv4Type(t header.ICMPv4Type) *header.ICMPv4Type {
 	return &t
 }
 
+// ICMPv4Code is a helper routine that allocates a new header.ICMPv4Code value
+// to store t and returns a pointer to it.
+func ICMPv4Code(t header.ICMPv4Code) *header.ICMPv4Code {
+	return &t
+}
+
 // ICMPv4 can construct and match an ICMPv4 encapsulation.
 type ICMPv4 struct {
 	LayerBase
 	Type     *header.ICMPv4Type
-	Code     *uint8
+	Code     *header.ICMPv4Code
 	Checksum *uint16
 }
 
@@ -881,7 +893,7 @@ func (l *ICMPv4) ToBytes() ([]byte, error) {
 		h.SetType(*l.Type)
 	}
 	if l.Code != nil {
-		h.SetCode(byte(*l.Code))
+		h.SetCode(*l.Code)
 	}
 	if l.Checksum != nil {
 		h.SetChecksum(*l.Checksum)
@@ -901,7 +913,7 @@ func parseICMPv4(b []byte) (Layer, layerParser) {
 	h := header.ICMPv4(b)
 	icmpv4 := ICMPv4{
 		Type:     ICMPv4Type(h.Type()),
-		Code:     Uint8(h.Code()),
+		Code:     ICMPv4Code(h.Code()),
 		Checksum: Uint16(h.Checksum()),
 	}
 	return &icmpv4, parsePayload
diff --git a/test/packetimpact/testbench/layers_test.go b/test/packetimpact/testbench/layers_test.go
index a2a763034..eca0780b5 100644
--- a/test/packetimpact/testbench/layers_test.go
+++ b/test/packetimpact/testbench/layers_test.go
@@ -594,7 +594,7 @@ func TestIPv6ExtHdrOptions(t *testing.T) {
 				},
 				&ICMPv6{
 					Type:     ICMPv6Type(header.ICMPv6ParamProblem),
-					Code:     Byte(0),
+					Code:     ICMPv6Code(header.ICMPv6ErroneousHeader),
 					Checksum: Uint16(0x5f98),
 					Payload:  []byte{0x00, 0x00, 0x00, 0x06},
 				},
diff --git a/test/packetimpact/tests/ipv6_fragment_reassembly_test.go b/test/packetimpact/tests/ipv6_fragment_reassembly_test.go
index b5f94ad4b..a24c85566 100644
--- a/test/packetimpact/tests/ipv6_fragment_reassembly_test.go
+++ b/test/packetimpact/tests/ipv6_fragment_reassembly_test.go
@@ -67,7 +67,7 @@ func TestIPv6FragmentReassembly(t *testing.T) {
 	rIP := tcpip.Address(net.ParseIP(testbench.RemoteIPv6).To16())
 	icmpv6 := testbench.ICMPv6{
 		Type:    testbench.ICMPv6Type(header.ICMPv6EchoRequest),
-		Code:    testbench.Byte(0),
+		Code:    testbench.ICMPv6Code(header.ICMPv6UnusedCode),
 		Payload: icmpv6EchoPayload,
 	}
 	icmpv6Bytes, err := icmpv6.ToBytes()
@@ -89,7 +89,7 @@ func TestIPv6FragmentReassembly(t *testing.T) {
 		},
 		&testbench.ICMPv6{
 			Type:     testbench.ICMPv6Type(header.ICMPv6EchoRequest),
-			Code:     testbench.Byte(0),
+			Code:     testbench.ICMPv6Code(header.ICMPv6UnusedCode),
 			Payload:  icmpv6EchoPayload,
 			Checksum: &cksum,
 		})
@@ -116,7 +116,7 @@ func TestIPv6FragmentReassembly(t *testing.T) {
 		},
 		&testbench.ICMPv6{
 			Type: testbench.ICMPv6Type(header.ICMPv6EchoReply),
-			Code: testbench.Byte(0),
+			Code: testbench.ICMPv6Code(header.ICMPv6UnusedCode),
 		},
 	}, time.Second)
 	if err != nil {
diff --git a/test/packetimpact/tests/ipv6_unknown_options_action_test.go b/test/packetimpact/tests/ipv6_unknown_options_action_test.go
index d7d63cbd2..e79d74476 100644
--- a/test/packetimpact/tests/ipv6_unknown_options_action_test.go
+++ b/test/packetimpact/tests/ipv6_unknown_options_action_test.go
@@ -172,7 +172,7 @@ func TestIPv6UnknownOptionAction(t *testing.T) {
 				&testbench.IPv6{},
 				&testbench.ICMPv6{
 					Type:    testbench.ICMPv6Type(header.ICMPv6ParamProblem),
-					Code:    testbench.Byte(2),
+					Code:    testbench.ICMPv6Code(header.ICMPv6UnknownOption),
 					Payload: icmpv6Payload,
 				},
 			}, time.Second)
diff --git a/test/packetimpact/tests/tcp_network_unreachable_test.go b/test/packetimpact/tests/tcp_network_unreachable_test.go
index 900352fa1..2f57dff19 100644
--- a/test/packetimpact/tests/tcp_network_unreachable_test.go
+++ b/test/packetimpact/tests/tcp_network_unreachable_test.go
@@ -72,7 +72,9 @@ func TestTCPSynSentUnreachable(t *testing.T) {
 	if !ok {
 		t.Fatalf("expected %s to be TCP", tcpLayers[tcpLayer])
 	}
-	var icmpv4 testbench.ICMPv4 = testbench.ICMPv4{Type: testbench.ICMPv4Type(header.ICMPv4DstUnreachable), Code: testbench.Uint8(header.ICMPv4HostUnreachable)}
+	var icmpv4 testbench.ICMPv4 = testbench.ICMPv4{
+		Type: testbench.ICMPv4Type(header.ICMPv4DstUnreachable),
+		Code: testbench.ICMPv4Code(header.ICMPv4HostUnreachable)}
 	layers = append(layers, &icmpv4, ip, tcp)
 	rawConn.SendFrameStateless(t, layers)
 
@@ -126,7 +128,7 @@ func TestTCPSynSentUnreachable6(t *testing.T) {
 	}
 	var icmpv6 testbench.ICMPv6 = testbench.ICMPv6{
 		Type: testbench.ICMPv6Type(header.ICMPv6DstUnreachable),
-		Code: testbench.Uint8(header.ICMPv6NetworkUnreachable),
+		Code: testbench.ICMPv6Code(header.ICMPv6NetworkUnreachable),
 		// Per RFC 4443 3.1, the payload contains 4 zeroed bytes.
 		Payload: []byte{0, 0, 0, 0},
 	}
diff --git a/test/packetimpact/tests/udp_icmp_error_propagation_test.go b/test/packetimpact/tests/udp_icmp_error_propagation_test.go
index b47ddb6c3..df35d16c8 100644
--- a/test/packetimpact/tests/udp_icmp_error_propagation_test.go
+++ b/test/packetimpact/tests/udp_icmp_error_propagation_test.go
@@ -62,9 +62,13 @@ func (e icmpError) String() string {
 func (e icmpError) ToICMPv4() *testbench.ICMPv4 {
 	switch e {
 	case portUnreachable:
-		return &testbench.ICMPv4{Type: testbench.ICMPv4Type(header.ICMPv4DstUnreachable), Code: testbench.Uint8(header.ICMPv4PortUnreachable)}
+		return &testbench.ICMPv4{
+			Type: testbench.ICMPv4Type(header.ICMPv4DstUnreachable),
+			Code: testbench.ICMPv4Code(header.ICMPv4PortUnreachable)}
 	case timeToLiveExceeded:
-		return &testbench.ICMPv4{Type: testbench.ICMPv4Type(header.ICMPv4TimeExceeded), Code: testbench.Uint8(header.ICMPv4TTLExceeded)}
+		return &testbench.ICMPv4{
+			Type: testbench.ICMPv4Type(header.ICMPv4TimeExceeded),
+			Code: testbench.ICMPv4Code(header.ICMPv4TTLExceeded)}
 	}
 	return nil
 }