*: support remove private as

cli

```
$ gobgp n add <neighbor-addr> as <asn> remove-private-as (all|replace)
```

config

```
neighbor:
  config:
    peer-as: <asn>
    neighbor-address: <neighbor-addr>
    remove-private-as: all
```

Signed-off-by: Wataru Ishida <ishida.wataru@lab.ntt.co.jp>

2 files changed, 58 insertions, 0 deletions

diff --git a/table/path.go b/table/path.go
index ef63d720..3b0fc40d 100644
--- a/table/path.go
+++ b/table/path.go
@@ -188,6 +188,9 @@ func UpdatePathAttrs(global *config.Global, peer *config.Neighbor, info *PeerInf
 			path.SetNexthop(localAddress)
 		}
 
+		// remove-private-as handling
+		path.RemovePrivateAS(peer.Config.LocalAs, peer.State.RemovePrivateAs)
+
 		// AS_PATH handling
 		path.PrependAsn(peer.Config.LocalAs, 1)
 
@@ -677,6 +680,39 @@ func (path *Path) PrependAsn(asn uint32, repeat uint8) {
 	path.setPathAttr(asPath)
 }
 
+func isPrivateAS(as uint32) bool {
+	return (64512 <= as && as <= 65534) || (4200000000 <= as && as <= 4294967294)
+}
+
+func (path *Path) RemovePrivateAS(localAS uint32, option config.RemovePrivateAsOption) {
+	original := path.GetAsPath()
+	if original == nil {
+		return
+	}
+	switch option {
+	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 {
+				if isPrivateAS(as) {
+					if option == config.REMOVE_PRIVATE_AS_OPTION_REPLACE {
+						newASParam = append(newASParam, localAS)
+					}
+				} else {
+					newASParam = append(newASParam, as)
+				}
+			}
+			if len(newASParam) > 0 {
+				newASParams = append(newASParams, bgp.NewAs4PathParam(asParam.Type, newASParam))
+			}
+		}
+		path.setPathAttr(bgp.NewPathAttributeAsPath(newASParams))
+	}
+	return
+}
+
 func (path *Path) GetCommunities() []uint32 {
 	communityList := []uint32{}
 	if attr := path.getPathAttr(bgp.BGP_ATTR_TYPE_COMMUNITIES); attr != nil {
diff --git a/table/path_test.go b/table/path_test.go
index 6e7a3534..29a296ac 100644
--- a/table/path_test.go
+++ b/table/path_test.go
@@ -6,6 +6,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/osrg/gobgp/config"
 	"github.com/osrg/gobgp/packet/bgp"
 	"github.com/stretchr/testify/assert"
 )
@@ -331,3 +332,24 @@ func updateMsgP3() *bgp.BGPMessage {
 	withdrawnRoutes := []*bgp.IPAddrPrefix{w1}
 	return bgp.NewBGPUpdateMessage(withdrawnRoutes, pathAttributes, nlri)
 }
+
+func TestRemovePrivateAS(t *testing.T) {
+	aspathParam := []bgp.AsPathParamInterface{bgp.NewAs4PathParam(2, []uint32{64512, 64513, 1, 2})}
+	aspath := bgp.NewPathAttributeAsPath(aspathParam)
+	nlri := bgp.NewIPAddrPrefix(24, "30.30.30.0")
+	path := NewPath(nil, nlri, false, []bgp.PathAttributeInterface{aspath}, time.Now(), false)
+	path.RemovePrivateAS(10, config.REMOVE_PRIVATE_AS_OPTION_ALL)
+	list := path.GetAsList()
+	assert.Equal(t, len(list), 2)
+	assert.Equal(t, list[0], uint32(1))
+	assert.Equal(t, list[1], uint32(2))
+
+	path = NewPath(nil, nlri, false, []bgp.PathAttributeInterface{aspath}, time.Now(), false)
+	path.RemovePrivateAS(10, config.REMOVE_PRIVATE_AS_OPTION_REPLACE)
+	list = path.GetAsList()
+	assert.Equal(t, len(list), 4)
+	assert.Equal(t, list[0], uint32(10))
+	assert.Equal(t, list[1], uint32(10))
+	assert.Equal(t, list[2], uint32(1))
+	assert.Equal(t, list[3], uint32(2))
+}