diff options
Diffstat (limited to 'table/path.go')
| -rw-r--r-- | table/path.go | 101 |
1 files changed, 61 insertions, 40 deletions
diff --git a/table/path.go b/table/path.go index bd368ec6..302847f8 100644 --- a/table/path.go +++ b/table/path.go @@ -79,48 +79,10 @@ func (path *Path) UpdatePathAttrs(global *config.Global, peer *config.Neighbor) path.SetNexthop(peer.LocalAddress) // AS_PATH handling - // - // When a given BGP speaker advertises the route to an external - // peer, the advertising speaker updates the AS_PATH attribute - // as follows: - // 1) if the first path segment of the AS_PATH is of type - // AS_SEQUENCE, the local system prepends its own AS num as - // the last element of the sequence (put it in the left-most - // position with respect to the position of octets in the - // protocol message). If the act of prepending will cause an - // overflow in the AS_PATH segment (i.e., more than 255 - // ASes), it SHOULD prepend a new segment of type AS_SEQUENCE - // and prepend its own AS number to this new segment. - // - // 2) if the first path segment of the AS_PATH is of type AS_SET - // , the local system prepends a new path segment of type - // AS_SEQUENCE to the AS_PATH, including its own AS number in - // that segment. - // - // 3) if the AS_PATH is empty, the local system creates a path - // segment of type AS_SEQUENCE, places its own AS into that - // segment, and places that segment into the AS_PATH. - idx, originalAsPath := path.getPathAttr(bgp.BGP_ATTR_TYPE_AS_PATH) - if idx < 0 { - p := bgp.NewAs4PathParam(bgp.BGP_ASPATH_ATTR_TYPE_SEQ, []uint32{global.As}) - asPath := bgp.NewPathAttributeAsPath([]bgp.AsPathParamInterface{p}) - path.pathAttrs = append(path.pathAttrs, asPath) - } else { - asPath := cloneAsPath(originalAsPath.(*bgp.PathAttributeAsPath)) - path.pathAttrs[idx] = asPath - fst := asPath.Value[0].(*bgp.As4PathParam) - if len(asPath.Value) > 0 && fst.Type == bgp.BGP_ASPATH_ATTR_TYPE_SEQ && - fst.ASLen() < 255 { - fst.AS = append([]uint32{global.As}, fst.AS...) - fst.Num += 1 - } else { - p := bgp.NewAs4PathParam(bgp.BGP_ASPATH_ATTR_TYPE_SEQ, []uint32{global.As}) - asPath.Value = append([]bgp.AsPathParamInterface{p}, asPath.Value...) - } - } + path.PrependAsn(global.As, 1) // MED Handling - idx, _ = path.getPathAttr(bgp.BGP_ATTR_TYPE_MULTI_EXIT_DISC) + idx, _ := path.getPathAttr(bgp.BGP_ATTR_TYPE_MULTI_EXIT_DISC) if idx >= 0 { path.pathAttrs = append(path.pathAttrs[:idx], path.pathAttrs[idx+1:]...) } @@ -328,6 +290,65 @@ func (path *Path) getAsListofSpecificType(getAsSeq, getAsSet bool) []uint32 { return asList } +// PrependAsn prepends AS number. +// This function updates the AS_PATH attribute as follows. +// 1) if the first path segment of the AS_PATH is of type +// AS_SEQUENCE, the local system prepends the specified AS num as +// the last element of the sequence (put it in the left-most +// position with respect to the position of octets in the +// protocol message) the specified number of times. +// If the act of prepending will cause an overflow in the AS_PATH +// segment (i.e., more than 255 ASes), +// it SHOULD prepend a new segment of type AS_SEQUENCE +// and prepend its own AS number to this new segment. +// +// 2) if the first path segment of the AS_PATH is of other than type +// AS_SEQUENCE, the local system prepends a new path segment of type +// AS_SEQUENCE to the AS_PATH, including the specified AS number in +// that segment. +// +// 3) if the AS_PATH is empty, the local system creates a path +// segment of type AS_SEQUENCE, places the specified AS number +// into that segment, and places that segment into the AS_PATH. +func (path *Path) PrependAsn(asn uint32, repeat uint8) { + + idx, aspath := path.getPathAttr(bgp.BGP_ATTR_TYPE_AS_PATH) + + asns := make([]uint32, repeat) + for i, _ := range asns { + asns[i] = asn + } + + if idx < 0 { + p := bgp.NewAs4PathParam(bgp.BGP_ASPATH_ATTR_TYPE_SEQ, asns) + asPath := bgp.NewPathAttributeAsPath([]bgp.AsPathParamInterface{p}) + path.pathAttrs = append(path.pathAttrs, asPath) + } else { + aspathClone := cloneAsPath(aspath.(*bgp.PathAttributeAsPath)) + path.pathAttrs[idx] = aspathClone + fst := aspathClone.Value[0].(*bgp.As4PathParam) + + if fst.Type == bgp.BGP_ASPATH_ATTR_TYPE_SEQ && len(fst.AS) < 255 { + + // overflow case + if len(fst.AS)+int(repeat) > 255 { + rest := 255 - len(fst.AS) + fst.AS = append(asns[0:rest], fst.AS...) + fst.Num = 255 + + p := bgp.NewAs4PathParam(bgp.BGP_ASPATH_ATTR_TYPE_SEQ, asns[rest:]) + aspathClone.Value = append([]bgp.AsPathParamInterface{p}, aspathClone.Value...) + } else { + fst.AS = append(asns, fst.AS...) + fst.Num += repeat + } + } else { + p := bgp.NewAs4PathParam(bgp.BGP_ASPATH_ATTR_TYPE_SEQ, asns) + aspathClone.Value = append([]bgp.AsPathParamInterface{p}, aspathClone.Value...) + } + } +} + func (path *Path) GetCommunities() []uint32 { communityList := []uint32{} if _, attr := path.getPathAttr(bgp.BGP_ATTR_TYPE_COMMUNITIES); attr != nil { |