packet/bgp: Getter functions for AS segment

This patch adds getter functions for the segment type and AS list of
each segment without using type assertion.

Signed-off-by: IWASE Yusuke <iwase.yusuke0@gmail.com>

8 files changed, 119 insertions, 91 deletions

diff --git a/gobgp/cmd/neighbor.go b/gobgp/cmd/neighbor.go
index 7414c17c..edcb11bf 100644
--- a/gobgp/cmd/neighbor.go
+++ b/gobgp/cmd/neighbor.go
@@ -565,8 +565,8 @@ func checkOriginAsWasNotShown(p *table.Path, shownAs map[uint32]struct{}) bool {
 	if len(asPath) == 0 {
 		return false
 	}
-	aslist := asPath[len(asPath)-1].(*bgp.As4PathParam).AS
-	origin := aslist[len(aslist)-1]
+	asList := asPath[len(asPath)-1].GetAS()
+	origin := asList[len(asList)-1]
 
 	if _, ok := shownAs[origin]; ok {
 		return false
@@ -585,8 +585,8 @@ func showValidationInfo(p *table.Path, shownAs map[uint32]struct{}) error {
 
 	status := p.Validation().Status
 	reason := p.Validation().Reason
-	aslist := asPath[len(asPath)-1].(*bgp.As4PathParam).AS
-	origin := aslist[len(aslist)-1]
+	asList := asPath[len(asPath)-1].GetAS()
+	origin := asList[len(asList)-1]
 
 	fmt.Printf("Target Prefix: %s, AS: %d\n", p.GetNlri().String(), origin)
 	fmt.Printf("  This route is %s", status)
diff --git a/packet/bgp/bgp.go b/packet/bgp/bgp.go
index 2fea8b44..ef2e3e20 100644
--- a/packet/bgp/bgp.go
+++ b/packet/bgp/bgp.go
@@ -5213,6 +5213,8 @@ var asPathParamFormatMap = map[uint8]*AsPathParamFormat{
 }
 
 type AsPathParamInterface interface {
+	GetType() uint8
+	GetAS() []uint32
 	Serialize() ([]byte, error)
 	DecodeFromBytes([]byte) error
 	Len() int
@@ -5227,6 +5229,18 @@ type AsPathParam struct {
 	AS   []uint16
 }
 
+func (a *AsPathParam) GetType() uint8 {
+	return a.Type
+}
+
+func (a *AsPathParam) GetAS() []uint32 {
+	nums := make([]uint32, 0, len(a.AS))
+	for _, as := range a.AS {
+		nums = append(nums, uint32(as))
+	}
+	return nums
+}
+
 func (a *AsPathParam) Serialize() ([]byte, error) {
 	buf := make([]byte, 2+len(a.AS)*2)
 	buf[0] = uint8(a.Type)
@@ -5314,6 +5328,14 @@ type As4PathParam struct {
 	AS   []uint32
 }
 
+func (a *As4PathParam) GetType() uint8 {
+	return a.Type
+}
+
+func (a *As4PathParam) GetAS() []uint32 {
+	return a.AS
+}
+
 func (a *As4PathParam) Serialize() ([]byte, error) {
 	buf := make([]byte, 2+len(a.AS)*4)
 	buf[0] = a.Type
diff --git a/packet/bgp/validate.go b/packet/bgp/validate.go
index ecc67067..1b8f27c9 100644
--- a/packet/bgp/validate.go
+++ b/packet/bgp/validate.go
@@ -173,23 +173,16 @@ func ValidateAttribute(a PathAttributeInterface, rfs map[RouteFamily]BGPAddPathM
 			}
 		}
 	case *PathAttributeAsPath:
-		getSegType := func(p AsPathParamInterface) uint8 {
-			asParam, y := p.(*As4PathParam)
-			if y {
-				return asParam.Type
-			} else {
-				return p.(*AsPathParam).Type
-			}
-		}
 		if isEBGP {
 			if isConfed {
-				if segType := getSegType(p.Value[0]); segType != BGP_ASPATH_ATTR_TYPE_CONFED_SEQ {
+				if segType := p.Value[0].GetType(); segType != BGP_ASPATH_ATTR_TYPE_CONFED_SEQ {
 					return false, NewMessageError(eCode, eSubCodeMalformedAspath, nil, fmt.Sprintf("segment type is not confederation seq (%d)", segType))
 				}
 			} else {
-				for _, paramIf := range p.Value {
-					segType := getSegType(paramIf)
-					if segType == BGP_ASPATH_ATTR_TYPE_CONFED_SET || segType == BGP_ASPATH_ATTR_TYPE_CONFED_SEQ {
+				for _, param := range p.Value {
+					segType := param.GetType()
+					switch segType {
+					case BGP_ASPATH_ATTR_TYPE_CONFED_SET, BGP_ASPATH_ATTR_TYPE_CONFED_SEQ:
 						err := NewMessageErrorWithErrorHandling(
 							eCode, eSubCodeMalformedAspath, nil, getErrorHandlingFromPathAttribute(p.GetType()), nil, fmt.Sprintf("segment type confederation(%d) found", segType))
 						if err.(*MessageError).Stronger(strongestError) {
diff --git a/server/fsm.go b/server/fsm.go
index 2c2128cb..c121c85f 100644
--- a/server/fsm.go
+++ b/server/fsm.go
@@ -677,10 +677,10 @@ func getPathAttrFromBGPUpdate(m *bgp.BGPUpdate, typ bgp.BGPAttrType) bgp.PathAtt
 	return nil
 }
 
-func hasOwnASLoop(ownAS uint32, limit int, aspath *bgp.PathAttributeAsPath) bool {
+func hasOwnASLoop(ownAS uint32, limit int, asPath *bgp.PathAttributeAsPath) bool {
 	cnt := 0
-	for _, i := range aspath.Value {
-		for _, as := range i.(*bgp.As4PathParam).AS {
+	for _, param := range asPath.Value {
+		for _, as := range param.GetAS() {
 			if as == ownAS {
 				cnt++
 				if cnt > limit {
diff --git a/server/rpki.go b/server/rpki.go
index 8f286930..75f25409 100644
--- a/server/rpki.go
+++ b/server/rpki.go
@@ -511,13 +511,14 @@ func ValidatePath(ownAs uint32, tree *radix.Tree, cidr string, asPath *bgp.PathA
 	if asPath == nil || len(asPath.Value) == 0 {
 		as = ownAs
 	} else {
-		asParam := asPath.Value[len(asPath.Value)-1].(*bgp.As4PathParam)
-		switch asParam.Type {
+		param := asPath.Value[len(asPath.Value)-1]
+		switch param.GetType() {
 		case bgp.BGP_ASPATH_ATTR_TYPE_SEQ:
-			if len(asParam.AS) == 0 {
+			asList := param.GetAS()
+			if len(asList) == 0 {
 				as = ownAs
 			} else {
-				as = asParam.AS[len(asParam.AS)-1]
+				as = asList[len(asList)-1]
 			}
 		case bgp.BGP_ASPATH_ATTR_TYPE_CONFED_SET, bgp.BGP_ASPATH_ATTR_TYPE_CONFED_SEQ:
 			as = ownAs
diff --git a/table/destination.go b/table/destination.go
index f9ed3509..fd32371d 100644
--- a/table/destination.go
+++ b/table/destination.go
@@ -861,17 +861,18 @@ func compareByMED(path1, path2 *Path) *Path {
 
 	isSameAS := func() bool {
 		firstAS := func(path *Path) uint32 {
-			if aspath := path.GetAsPath(); aspath != nil {
-				asPathParam := aspath.Value
-				for i := 0; i < len(asPathParam); i++ {
-					asPath := asPathParam[i].(*bgp.As4PathParam)
-					if asPath.Num == 0 {
+			if asPath := path.GetAsPath(); asPath != nil {
+				for _, v := range asPath.Value {
+					segType := v.GetType()
+					asList := v.GetAS()
+					if len(asList) == 0 {
 						continue
 					}
-					if asPath.Type == bgp.BGP_ASPATH_ATTR_TYPE_CONFED_SET || asPath.Type == bgp.BGP_ASPATH_ATTR_TYPE_CONFED_SEQ {
+					switch segType {
+					case bgp.BGP_ASPATH_ATTR_TYPE_CONFED_SET, bgp.BGP_ASPATH_ATTR_TYPE_CONFED_SEQ:
 						continue
 					}
-					return asPath.AS[0]
+					return asList[0]
 				}
 			}
 			return 0
diff --git a/table/message.go b/table/message.go
index 0909d08f..a7195ac6 100644
--- a/table/message.go
+++ b/table/message.go
@@ -45,9 +45,10 @@ func UpdatePathAttrs2ByteAs(msg *bgp.BGPUpdate) error {
 	as2Params := make([]bgp.AsPathParamInterface, 0, len(asAttr.Value))
 	mkAs4 := false
 	for _, param := range asAttr.Value {
-		as4Param := param.(*bgp.As4PathParam)
-		as2Path := make([]uint16, 0, len(as4Param.AS))
-		for _, as := range as4Param.AS {
+		segType := param.GetType()
+		asList := param.GetAS()
+		as2Path := make([]uint16, 0, len(asList))
+		for _, as := range asList {
 			if as > (1<<16)-1 {
 				mkAs4 = true
 				as2Path = append(as2Path, bgp.AS_TRANS)
@@ -55,15 +56,20 @@ func UpdatePathAttrs2ByteAs(msg *bgp.BGPUpdate) error {
 				as2Path = append(as2Path, uint16(as))
 			}
 		}
-		as2Params = append(as2Params, bgp.NewAsPathParam(as4Param.Type, as2Path))
+		as2Params = append(as2Params, bgp.NewAsPathParam(segType, as2Path))
 
 		// RFC 6793 4.2.2 Generating Updates
 		//
 		// Whenever the AS path information contains the AS_CONFED_SEQUENCE or
 		// AS_CONFED_SET path segment, the NEW BGP speaker MUST exclude such
 		// path segments from the AS4_PATH attribute being constructed.
-		if as4Param.Type != bgp.BGP_ASPATH_ATTR_TYPE_CONFED_SEQ && as4Param.Type != bgp.BGP_ASPATH_ATTR_TYPE_CONFED_SET {
-			as4Params = append(as4Params, as4Param)
+		switch segType {
+		case bgp.BGP_ASPATH_ATTR_TYPE_CONFED_SEQ, bgp.BGP_ASPATH_ATTR_TYPE_CONFED_SET:
+			// pass
+		default:
+			if as4param, ok := param.(*bgp.As4PathParam); ok {
+				as4Params = append(as4Params, as4param)
+			}
 		}
 	}
 	msg.PathAttributes[idx] = bgp.NewPathAttributeAsPath(as2Params)
@@ -111,21 +117,20 @@ func UpdatePathAttrs4ByteAs(msg *bgp.BGPUpdate) error {
 
 	asLen := 0
 	asConfedLen := 0
-	asParams := make([]*bgp.As4PathParam, 0, len(asAttr.Value))
+	asParams := make([]bgp.AsPathParamInterface, 0, len(asAttr.Value))
 	for _, param := range asAttr.Value {
 		asLen += param.ASLen()
-		p := param.(*bgp.As4PathParam)
-		switch p.Type {
+		switch param.GetType() {
 		case bgp.BGP_ASPATH_ATTR_TYPE_CONFED_SET:
-			asConfedLen += 1
+			asConfedLen++
 		case bgp.BGP_ASPATH_ATTR_TYPE_CONFED_SEQ:
-			asConfedLen += len(p.AS)
+			asConfedLen += len(param.GetAS())
 		}
-		asParams = append(asParams, p)
+		asParams = append(asParams, param)
 	}
 
 	as4Len := 0
-	as4Params := make([]*bgp.As4PathParam, 0, len(as4Attr.Value))
+	as4Params := make([]bgp.AsPathParamInterface, 0, len(as4Attr.Value))
 	if as4Attr != nil {
 		for _, p := range as4Attr.Value {
 			// RFC 6793 6. Error Handling
@@ -162,14 +167,14 @@ func UpdatePathAttrs4ByteAs(msg *bgp.BGPUpdate) error {
 
 	keepNum := asLen + asConfedLen - as4Len
 
-	newParams := make([]*bgp.As4PathParam, 0, len(asAttr.Value))
+	newParams := make([]bgp.AsPathParamInterface, 0, len(asAttr.Value))
 	for _, param := range asParams {
 		if keepNum-param.ASLen() >= 0 {
 			newParams = append(newParams, param)
 			keepNum -= param.ASLen()
 		} else {
 			// only SEQ param reaches here
-			newParams = append(newParams, bgp.NewAs4PathParam(param.Type, param.AS[:keepNum]))
+			newParams = append(newParams, bgp.NewAs4PathParam(param.GetType(), param.GetAS()[:keepNum]))
 			keepNum = 0
 		}
 
@@ -180,12 +185,15 @@ func UpdatePathAttrs4ByteAs(msg *bgp.BGPUpdate) error {
 
 	for _, param := range as4Params {
 		lastParam := newParams[len(newParams)-1]
-		if param.Type == lastParam.Type && param.Type == bgp.BGP_ASPATH_ATTR_TYPE_SEQ {
-			if len(lastParam.AS)+len(param.AS) > 255 {
-				newParams[len(newParams)-1] = bgp.NewAs4PathParam(param.Type, append(lastParam.AS, param.AS[:255-len(lastParam.AS)]...))
-				newParams = append(newParams, bgp.NewAs4PathParam(param.Type, param.AS[255-len(lastParam.AS):]))
+		lastParamAS := lastParam.GetAS()
+		paramType := param.GetType()
+		paramAS := param.GetAS()
+		if paramType == lastParam.GetType() && paramType == bgp.BGP_ASPATH_ATTR_TYPE_SEQ {
+			if len(lastParamAS)+len(paramAS) > 255 {
+				newParams[len(newParams)-1] = bgp.NewAs4PathParam(paramType, append(lastParamAS, paramAS[:255-len(lastParamAS)]...))
+				newParams = append(newParams, bgp.NewAs4PathParam(paramType, paramAS[255-len(lastParamAS):]))
 			} else {
-				newParams[len(newParams)-1] = bgp.NewAs4PathParam(param.Type, append(lastParam.AS, param.AS...))
+				newParams[len(newParams)-1] = bgp.NewAs4PathParam(paramType, append(lastParamAS, paramAS...))
 			}
 		} else {
 			newParams = append(newParams, param)
diff --git a/table/path.go b/table/path.go
index a04e0d66..de60e615 100644
--- a/table/path.go
+++ b/table/path.go
@@ -196,10 +196,10 @@ func (path *Path) IsEOR() bool {
 func cloneAsPath(asAttr *bgp.PathAttributeAsPath) *bgp.PathAttributeAsPath {
 	newASparams := make([]bgp.AsPathParamInterface, len(asAttr.Value))
 	for i, param := range asAttr.Value {
-		asParam := param.(*bgp.As4PathParam)
-		as := make([]uint32, len(asParam.AS))
-		copy(as, asParam.AS)
-		newASparams[i] = bgp.NewAs4PathParam(asParam.Type, as)
+		asList := param.GetAS()
+		as := make([]uint32, len(asList))
+		copy(as, asList)
+		newASparams[i] = bgp.NewAs4PathParam(param.GetType(), as)
 	}
 	return bgp.NewPathAttributeAsPath(newASparams)
 }
@@ -439,11 +439,11 @@ func (path *Path) GetSourceAs() uint32 {
 		if len(asPathParam) == 0 {
 			return 0
 		}
-		asPath := asPathParam[len(asPathParam)-1].(*bgp.As4PathParam)
-		if asPath.Num == 0 {
+		asList := asPathParam[len(asPathParam)-1].GetAS()
+		if len(asList) == 0 {
 			return 0
 		}
-		return asPath.AS[asPath.Num-1]
+		return asList[len(asList)-1]
 	}
 	return 0
 }
@@ -631,14 +631,15 @@ func (path *Path) GetAsPathLen() int {
 func (path *Path) GetAsString() string {
 	s := bytes.NewBuffer(make([]byte, 0, 64))
 	if aspath := path.GetAsPath(); aspath != nil {
-		for i, paramIf := range aspath.Value {
-			segment := paramIf.(*bgp.As4PathParam)
+		for i, param := range aspath.Value {
+			segType := param.GetType()
+			asList := param.GetAS()
 			if i != 0 {
 				s.WriteString(" ")
 			}
 
 			sep := " "
-			switch segment.Type {
+			switch segType {
 			case bgp.BGP_ASPATH_ATTR_TYPE_CONFED_SEQ:
 				s.WriteString("(")
 			case bgp.BGP_ASPATH_ATTR_TYPE_CONFED_SET:
@@ -648,13 +649,13 @@ func (path *Path) GetAsString() string {
 				s.WriteString("{")
 				sep = ","
 			}
-			for j, as := range segment.AS {
+			for j, as := range asList {
 				s.WriteString(fmt.Sprintf("%d", as))
-				if j != len(segment.AS)-1 {
+				if j != len(asList)-1 {
 					s.WriteString(sep)
 				}
 			}
-			switch segment.Type {
+			switch segType {
 			case bgp.BGP_ASPATH_ATTR_TYPE_CONFED_SEQ:
 				s.WriteString(")")
 			case bgp.BGP_ASPATH_ATTR_TYPE_CONFED_SET:
@@ -668,26 +669,26 @@ func (path *Path) GetAsString() string {
 }
 
 func (path *Path) GetAsList() []uint32 {
-	return path.getAsListofSpecificType(true, true)
+	return path.getAsListOfSpecificType(true, true)
 
 }
 
 func (path *Path) GetAsSeqList() []uint32 {
-	return path.getAsListofSpecificType(true, false)
+	return path.getAsListOfSpecificType(true, false)
 
 }
 
-func (path *Path) getAsListofSpecificType(getAsSeq, getAsSet bool) []uint32 {
+func (path *Path) getAsListOfSpecificType(getAsSeq, getAsSet bool) []uint32 {
 	asList := []uint32{}
 	if aspath := path.GetAsPath(); aspath != nil {
-		for _, paramIf := range aspath.Value {
-			segment := paramIf.(*bgp.As4PathParam)
-			if getAsSeq && segment.Type == bgp.BGP_ASPATH_ATTR_TYPE_SEQ {
-				asList = append(asList, segment.AS...)
+		for _, param := range aspath.Value {
+			segType := param.GetType()
+			if getAsSeq && segType == bgp.BGP_ASPATH_ATTR_TYPE_SEQ {
+				asList = append(asList, param.GetAS()...)
 				continue
 			}
-			if getAsSet && segment.Type == bgp.BGP_ASPATH_ATTR_TYPE_SET {
-				asList = append(asList, segment.AS...)
+			if getAsSet && segType == bgp.BGP_ASPATH_ATTR_TYPE_SET {
+				asList = append(asList, param.GetAS()...)
 			} else {
 				asList = append(asList, 0)
 			}
@@ -757,7 +758,7 @@ func (path *Path) PrependAsn(asn uint32, repeat uint8, confed bool) {
 	original := path.GetAsPath()
 
 	asns := make([]uint32, repeat)
-	for i, _ := range asns {
+	for i := range asns {
 		asns[i] = asn
 	}
 
@@ -769,13 +770,14 @@ func (path *Path) PrependAsn(asn uint32, repeat uint8, confed bool) {
 	}
 
 	if len(asPath.Value) > 0 {
-		fst := asPath.Value[0].(*bgp.As4PathParam)
-		if fst.Type == segType {
-			if len(fst.AS)+int(repeat) > 255 {
-				repeat = uint8(255 - len(fst.AS))
+		param := asPath.Value[0]
+		asList := param.GetAS()
+		if param.GetType() == segType {
+			if int(repeat)+len(asList) > 255 {
+				repeat = uint8(255 - len(asList))
 			}
-			fst.AS = append(asns[:int(repeat)], fst.AS...)
-			fst.Num += repeat
+			newAsList := append(asns[:int(repeat)], asList...)
+			asPath.Value[0] = bgp.NewAs4PathParam(segType, newAsList)
 			asns = asns[int(repeat):]
 		}
 	}
@@ -800,9 +802,9 @@ func (path *Path) RemovePrivateAS(localAS uint32, option config.RemovePrivateAsO
 	case config.REMOVE_PRIVATE_AS_OPTION_ALL, config.REMOVE_PRIVATE_AS_OPTION_REPLACE:
 		newASParams := make([]bgp.AsPathParamInterface, 0, len(original.Value))
 		for _, param := range original.Value {
-			asParam := param.(*bgp.As4PathParam)
-			newASParam := make([]uint32, 0, len(asParam.AS))
-			for _, as := range asParam.AS {
+			asList := param.GetAS()
+			newASParam := make([]uint32, 0, len(asList))
+			for _, as := range asList {
 				if isPrivateAS(as) {
 					if option == config.REMOVE_PRIVATE_AS_OPTION_REPLACE {
 						newASParam = append(newASParam, localAS)
@@ -812,7 +814,7 @@ func (path *Path) RemovePrivateAS(localAS uint32, option config.RemovePrivateAsO
 				}
 			}
 			if len(newASParam) > 0 {
-				newASParams = append(newASParams, bgp.NewAs4PathParam(asParam.Type, newASParam))
+				newASParams = append(newASParams, bgp.NewAs4PathParam(param.GetType(), newASParam))
 			}
 		}
 		path.setPathAttr(bgp.NewPathAttributeAsPath(newASParams))
@@ -826,10 +828,10 @@ func (path *Path) removeConfedAs() {
 		return
 	}
 	newAsParams := make([]bgp.AsPathParamInterface, 0, len(original.Value))
-	for _, v := range original.Value {
-		p := v.(*bgp.As4PathParam)
-		if p.Type == bgp.BGP_ASPATH_ATTR_TYPE_SEQ || p.Type == bgp.BGP_ASPATH_ATTR_TYPE_SET {
-			newAsParams = append(newAsParams, p)
+	for _, param := range original.Value {
+		switch param.GetType() {
+		case bgp.BGP_ASPATH_ATTR_TYPE_SEQ, bgp.BGP_ASPATH_ATTR_TYPE_SET:
+			newAsParams = append(newAsParams, param)
 		}
 	}
 	path.setPathAttr(bgp.NewPathAttributeAsPath(newAsParams))
@@ -843,16 +845,17 @@ func (path *Path) ReplaceAS(localAS, peerAS uint32) *Path {
 	newASParams := make([]bgp.AsPathParamInterface, 0, len(original.Value))
 	changed := false
 	for _, param := range original.Value {
-		asParam := param.(*bgp.As4PathParam)
-		newASParam := make([]uint32, 0, len(asParam.AS))
-		for _, as := range asParam.AS {
+		segType := param.GetType()
+		asList := param.GetAS()
+		newASParam := make([]uint32, 0, len(asList))
+		for _, as := range asList {
 			if as == peerAS {
 				as = localAS
 				changed = true
 			}
 			newASParam = append(newASParam, as)
 		}
-		newASParams = append(newASParams, bgp.NewAs4PathParam(asParam.Type, newASParam))
+		newASParams = append(newASParams, bgp.NewAs4PathParam(segType, newASParam))
 	}
 	if changed {
 		path = path.Clone(path.IsWithdraw)