Support Unknown Parameters in INIT Chunk

Start to implement section-3.2.1 and respect chunks with a action
of Skip. We don't properly report the values back yet.

Relates to #2618

chunk_init.go

@@ -38,6 +38,7 @@ var (
 	ErrInitInboundStreamRequestZero  = errors.New("INIT ACK inbound stream request must be > 0")
 	ErrInitOutboundStreamRequestZero = errors.New("INIT ACK outbound stream request must be > 0")
 	ErrInitAdvertisedReceiver1500    = errors.New("INIT ACK Advertised Receiver Window Credit (a_rwnd) must be >= 1500")
+	ErrInitUnknownParam              = errors.New("INIT with unknown param")
 )
 
 func (i *chunkInit) unmarshal(raw []byte) error {
@@ -89,8 +90,7 @@ func (i *chunkInit) check() (abort bool, err error) {
 	// to be 0, the receiver MUST treat it as an error and close the
 	// association by transmitting an ABORT.
 	if i.initiateTag == 0 {
-		abort = true
-		return abort, ErrChunkTypeInitInitateTagZero
+		return true, ErrChunkTypeInitInitateTagZero
 	}
 
 	// Defines the maximum number of streams the sender of this INIT
@@ -104,8 +104,7 @@ func (i *chunkInit) check() (abort bool, err error) {
 	// Note: A receiver of an INIT with the MIS value of 0 SHOULD abort
 	// the association.
 	if i.numInboundStreams == 0 {
-		abort = true
-		return abort, ErrInitInboundStreamRequestZero
+		return true, ErrInitInboundStreamRequestZero
 	}
 
 	// Defines the number of outbound streams the sender of this INIT
@@ -116,17 +115,22 @@ func (i *chunkInit) check() (abort bool, err error) {
 	// abort the association.
 
 	if i.numOutboundStreams == 0 {
-		abort = true
-		return abort, ErrInitOutboundStreamRequestZero
+		return true, ErrInitOutboundStreamRequestZero
 	}
 
 	// An SCTP receiver MUST be able to receive a minimum of 1500 bytes in
 	// one SCTP packet.  This means that an SCTP endpoint MUST NOT indicate
 	// less than 1500 bytes in its initial a_rwnd sent in the INIT or INIT
 	// ACK.
 	if i.advertisedReceiverWindowCredit < 1500 {
-		abort = true
-		return abort, ErrInitAdvertisedReceiver1500
+		return true, ErrInitAdvertisedReceiver1500
+	}
+
+	for _, p := range i.unrecognizedParams {
+		if p.unrecognizedAction == paramHeaderUnrecognizedActionStop ||
+			p.unrecognizedAction == paramHeaderUnrecognizedActionStopAndReport {
+			return true, ErrInitUnknownParam
+		}
 	}
 
 	return false, nil

chunk_init_common.go

@@ -49,6 +49,7 @@ type chunkInitCommon struct {
 	numInboundStreams              uint16
 	initialTSN                     uint32
 	params                         []param
+	unrecognizedParams             []paramHeader
 }
 
 const (
@@ -59,7 +60,6 @@ const (
 // Init chunk errors
 var (
 	ErrInitChunkParseParamTypeFailed = errors.New("failed to parse param type")
-	ErrInitChunkUnmarshalParam       = errors.New("failed unmarshalling param in Init Chunk")
 	ErrInitAckMarshalParam           = errors.New("unable to marshal parameter for INIT/INITACK")
 )
 
@@ -91,18 +91,21 @@ func (i *chunkInitCommon) unmarshal(raw []byte) error {
 	remaining := len(raw) - offset
 	for remaining > 0 {
 		if remaining > initOptionalVarHeaderLength {
-			pType, err := parseParamType(raw[offset:])
-			if err != nil {
+			var pHeader paramHeader
+			if err := pHeader.unmarshal(raw[offset:]); err != nil {
 				return fmt.Errorf("%w: %v", ErrInitChunkParseParamTypeFailed, err) //nolint:errorlint
 			}
-			p, err := buildParam(pType, raw[offset:])
+
+			p, err := buildParam(pHeader.typ, raw[offset:])
 			if err != nil {
-				return fmt.Errorf("%w: %v", ErrInitChunkUnmarshalParam, err) //nolint:errorlint
+				i.unrecognizedParams = append(i.unrecognizedParams, pHeader)
+			} else {
+				i.params = append(i.params, p)
 			}
-			i.params = append(i.params, p)
-			padding := getPadding(p.length())
-			offset += p.length() + padding
-			remaining -= p.length() + padding
+
+			padding := getPadding(pHeader.length())
+			offset += pHeader.length() + padding
+			remaining -= pHeader.length() + padding
 		} else {
 			break
 		}

chunk_init_test.go

@@ -0,0 +1,35 @@
+// SPDX-FileCopyrightText: 2023 The Pion community <https://pion.ly>
+// SPDX-License-Identifier: MIT
+
+package sctp
+
+import (
+	"testing"
+)
+
+func TestChunkInit_UnrecognizedParameters(t *testing.T) {
+	initChunkHeader := []byte{
+		0x55, 0xb9, 0x64, 0xa5, 0x00, 0x02, 0x00, 0x00,
+		0x04, 0x00, 0x08, 0x00, 0xe8, 0x6d, 0x10, 0x30,
+	}
+
+	unrecognizedSkip := append([]byte{}, initChunkHeader...)
+	unrecognizedSkip = append(unrecognizedSkip, byte(paramHeaderUnrecognizedActionSkip), 0xFF, 0x00, 0x04, 0x00)
+
+	i := &chunkInitCommon{}
+	if err := i.unmarshal(unrecognizedSkip); err != nil {
+		t.Errorf("Unmarshal init Chunk failed: %v", err)
+	} else if len(i.unrecognizedParams) != 1 || i.unrecognizedParams[0].unrecognizedAction != paramHeaderUnrecognizedActionSkip {
+		t.Errorf("Unrecognized Param parsed incorrectly")
+	}
+
+	unrecognizedStop := append([]byte{}, initChunkHeader...)
+	unrecognizedStop = append(unrecognizedStop, byte(paramHeaderUnrecognizedActionStop), 0xFF, 0x00, 0x04, 0x00)
+
+	i = &chunkInitCommon{}
+	if err := i.unmarshal(unrecognizedStop); err != nil {
+		t.Errorf("Unmarshal init Chunk failed: %v", err)
+	} else if len(i.unrecognizedParams) != 1 || i.unrecognizedParams[0].unrecognizedAction != paramHeaderUnrecognizedActionStop {
+		t.Errorf("Unrecognized Param parsed incorrectly")
+	}
+}

param_ecn_capable_test.go

@@ -22,9 +22,10 @@ func TestParamECNCapabale_Success(t *testing.T) {
 			testParamECNCapabale(),
 			&paramECNCapable{
 				paramHeader: paramHeader{
-					typ: ecnCapable,
-					len: 4,
-					raw: []byte{},
+					typ:                ecnCapable,
+					unrecognizedAction: paramHeaderUnrecognizedActionSkip,
+					len:                4,
+					raw:                []byte{},
 				},
 			},
 		},

param_forward_tsn_supported_test.go

@@ -22,9 +22,10 @@ func TestParamForwardTSNSupported_Success(t *testing.T) {
 			testParamForwardTSNSupported(),
 			&paramForwardTSNSupported{
 				paramHeader: paramHeader{
-					typ: forwardTSNSupp,
-					len: 4,
-					raw: []byte{},
+					typ:                forwardTSNSupp,
+					len:                4,
+					unrecognizedAction: paramHeaderUnrecognizedActionSkipAndReport,
+					raw:                []byte{},
 				},
 			},
 		},

paramheader.go

@@ -10,13 +10,40 @@ import (
 	"fmt"
 )
 
+type paramHeaderUnrecognizedAction byte
+
 type paramHeader struct {
-	typ paramType
-	len int
-	raw []byte
+	typ                paramType
+	unrecognizedAction paramHeaderUnrecognizedAction
+	len                int
+	raw                []byte
 }
 
+/*
+	 The Parameter Types are encoded such that the highest-order 2 bits specify
+	 the action that is taken if the processing endpoint does not recognize the
+	 Parameter Type.
+
+	 00 - Stop processing this parameter and do not process any further parameters within this chunk.
+
+	 01 - Stop processing this parameter, do not process any further parameters within this chunk, and
+		  report the unrecognized parameter, as described in Section 3.2.2.
+
+	 10 - Skip this parameter and continue processing.
+
+	 11 - Skip this parameter and continue processing, but report the unrecognized
+		  parameter, as described in Section 3.2.2.
+
+	 https://www.rfc-editor.org/rfc/rfc9260.html#section-3.2.1
+*/
+
 const (
+	paramHeaderUnrecognizedActionMask                                        = 0b11000000
+	paramHeaderUnrecognizedActionStop          paramHeaderUnrecognizedAction = 0b00000000
+	paramHeaderUnrecognizedActionStopAndReport paramHeaderUnrecognizedAction = 0b01000000
+	paramHeaderUnrecognizedActionSkip          paramHeaderUnrecognizedAction = 0b10000000
+	paramHeaderUnrecognizedActionSkipAndReport paramHeaderUnrecognizedAction = 0b11000000
+
 	paramHeaderLength = 4
 )
 
@@ -57,6 +84,7 @@ func (p *paramHeader) unmarshal(raw []byte) error {
 		return fmt.Errorf("%w: %v", ErrParamHeaderParseFailed, err) //nolint:errorlint
 	}
 	p.typ = typ
+	p.unrecognizedAction = paramHeaderUnrecognizedAction(raw[0] & paramHeaderUnrecognizedActionMask)
 	p.raw = raw[paramHeaderLength:paramLengthPlusHeader]
 	p.len = int(paramLengthPlusHeader)