policy: modify path.GetAsSeqList() to insert 0 for non-seq-as-elems

GetAsSeqList() is used for AsPathSet matching and AsPathPrepend action.
Just eliminating non-seq-as-elems from what GetAsSeqList() returns cause
wrong results for these two match/action.

e.g path A's as-path: {100, 200} 300

currently, action 'as-path-prepend left-most repeat 2' will alter
as-path to 300 300 {100, 200} 300, which is not expected behavior.

To fix this, insert 0 for non-seq-as-elems.

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

3 files changed, 15 insertions, 6 deletions

diff --git a/table/path.go b/table/path.go
index bcf5b4ce..3cebdb96 100644
--- a/table/path.go
+++ b/table/path.go
@@ -393,6 +393,8 @@ func (path *Path) getAsListofSpecificType(getAsSeq, getAsSet bool) []uint32 {
 			}
 			if getAsSet && segment.Type == bgp.BGP_ASPATH_ATTR_TYPE_SET {
 				asList = append(asList, segment.AS...)
+			} else {
+				asList = append(asList, 0)
 			}
 		}
 	}
diff --git a/table/path_test.go b/table/path_test.go
index 1f2311f5..98e59092 100644
--- a/table/path_test.go
+++ b/table/path_test.go
@@ -146,7 +146,7 @@ func TestPathPrependAsnToExistingSeqAttr(t *testing.T) {
 	p := NewPath(peer[0], update.NLRI[0], false, update.PathAttributes, false, time.Now(), false)
 
 	p.PrependAsn(65000, 1)
-	assert.Equal([]uint32{65000, 65001, 65002, 65003, 65004, 65005}, p.GetAsSeqList())
+	assert.Equal([]uint32{65000, 65001, 65002, 65003, 65004, 65005, 0, 0, 0}, p.GetAsSeqList())
 	fmt.Printf("asns: %v", p.GetAsSeqList())
 }
 
@@ -197,7 +197,7 @@ func TestPathPrependAsnToNewAsPathSeq(t *testing.T) {
 
 	asn := uint32(65000)
 	p.PrependAsn(asn, 1)
-	assert.Equal([]uint32{asn}, p.GetAsSeqList())
+	assert.Equal([]uint32{asn, 0, 0, 0}, p.GetAsSeqList())
 	fmt.Printf("asns: %v", p.GetAsSeqList())
 }
 
@@ -227,7 +227,7 @@ func TestPathPrependAsnToEmptyAsPathAttr(t *testing.T) {
 
 	asn := uint32(65000)
 	p.PrependAsn(asn, 1)
-	assert.Equal([]uint32{asn}, p.GetAsSeqList())
+	assert.Equal([]uint32{asn, 0, 0, 0}, p.GetAsSeqList())
 	fmt.Printf("asns: %v", p.GetAsSeqList())
 }
 
@@ -266,7 +266,7 @@ func TestPathPrependAsnToFullPathAttr(t *testing.T) {
 		expected = append(expected, uint32(v))
 	}
 	p.PrependAsn(65000, 2)
-	assert.Equal(expected, p.GetAsSeqList())
+	assert.Equal(append(expected, []uint32{0, 0, 0}...), p.GetAsSeqList())
 	fmt.Printf("asns: %v", p.GetAsSeqList())
 }
 
diff --git a/table/policy.go b/table/policy.go
index 71793485..bc59799e 100644
--- a/table/policy.go
+++ b/table/policy.go
@@ -2021,16 +2021,23 @@ func (a *AsPathPrependAction) Apply(path *Path) *Path {
 			log.WithFields(log.Fields{
 				"Topic": "Policy",
 				"Type":  "AsPathPrepend Action",
-			}).Errorf("aspath length is zero.")
+			}).Warnf("aspath length is zero.")
 			return path
 		}
 		asn = aspath[0]
+		if asn == 0 {
+			log.WithFields(log.Fields{
+				"Topic": "Policy",
+				"Type":  "AsPathPrepend Action",
+			}).Warnf("left-most ASN is not seq")
+			return path
+		}
 		log.WithFields(log.Fields{
 			"Topic":  "Policy",
 			"Type":   "AsPathPrepend Action",
 			"LastAs": asn,
 			"Repeat": a.repeat,
-		}).Debug("use last AS.")
+		}).Debug("use left-most ASN")
 	} else {
 		asn = a.asn
 	}