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# encoding: utf-8 |
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""" |
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mprnlri.py |
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Created by Thomas Mangin on 2009-11-05. |
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Copyright (c) 2009-2017 Exa Networks. All rights reserved. |
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License: 3-clause BSD. (See the COPYRIGHT file) |
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""" |
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from struct import unpack |
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from exabgp.protocol.ip import NoNextHop |
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from exabgp.protocol.family import AFI |
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from exabgp.protocol.family import SAFI |
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from exabgp.protocol.family import Family |
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from exabgp.bgp.message.direction import IN |
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# from exabgp.bgp.message.update.attribute.attribute import Attribute |
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from exabgp.bgp.message.update.attribute import Attribute |
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from exabgp.bgp.message.update.attribute import NextHop |
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from exabgp.bgp.message.update.nlri import NLRI |
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from exabgp.bgp.message.notification import Notify |
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from exabgp.bgp.message.open.capability import Negotiated |
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# ==================================================== MP Unreacheable NLRI (15) |
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# |
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@Attribute.register() |
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class MPRNLRI(Attribute, Family): |
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FLAG = Attribute.Flag.OPTIONAL |
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ID = Attribute.CODE.MP_REACH_NLRI |
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def __init__(self, afi, safi, nlris): |
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Family.__init__(self, afi, safi) |
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# all the routes must have the same next-hop |
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self.nlris = nlris |
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def __eq__(self, other): |
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return self.ID == other.ID and self.FLAG == other.FLAG and self.nlris == other.nlris |
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def __ne__(self, other): |
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return not self.__eq__(other) |
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def packed_attributes(self, negotiated, maximum=Negotiated.FREE_SIZE): |
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if not self.nlris: |
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return |
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# addpath = negotiated.addpath.send(self.afi,self.safi) |
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# nexthopself = negotiated.nexthopself(self.afi) |
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mpnlri = {} |
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for nlri in self.nlris: |
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if nlri.family() != self.family(): # nlri is not part of specified family |
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continue |
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if nlri.nexthop is NoNextHop: |
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# EOR and Flow may not have any next_hop |
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nexthop = b'' |
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else: |
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_, rd_size = Family.size.get(self.family(), (0, 0)) |
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nh_rd = bytes([0]) * rd_size if rd_size else b'' |
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try: |
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nexthop = nh_rd + nlri.nexthop.ton(negotiated, nlri.afi) |
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except TypeError: |
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# we could not match "next-hop self" with the BGP AFI of the BGP sesion |
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# attempting invalid IPv4 next-hop (0.0.0.0) to try to not kill the session |
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# and preserve some form of backward compatibility (for some vendors) |
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# the next-hop may have been IPv6 but not valided as the RFC says |
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# |
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# An UPDATE message that carries no NLRI, other than the one encoded in |
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# the MP_REACH_NLRI attribute, SHOULD NOT carry the NEXT_HOP attribute. |
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# If such a message contains the NEXT_HOP attribute, the BGP speaker |
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# that receives the message SHOULD ignore this attribute. |
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# |
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# Some vendors may have therefore not valided the next-hop |
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# and accepted invalid IPv6 next-hop in the past |
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nexthop = bytes([0]) * 4 |
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# mpunli[nexthop] = nlri |
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mpnlri.setdefault(nexthop, []).append(nlri.pack(negotiated)) |
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for nexthop, nlris in mpnlri.items(): |
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payload = self.afi.pack() + self.safi.pack() + bytes([len(nexthop)]) + nexthop + bytes([0]) |
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header_length = len(payload) |
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for nlri in nlris: |
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if self._len(payload + nlri) > maximum: |
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if len(payload) == header_length or len(payload) > maximum: |
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raise Notify(6, 0, 'attributes size is so large we can not even pack on MPRNLRI') |
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yield self._attribute(payload) |
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payload = self.afi.pack() + self.safi.pack() + bytes([len(nexthop)]) + nexthop + bytes([0]) + nlri |
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continue |
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payload = payload + nlri |
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if len(payload) == header_length or len(payload) > maximum: |
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raise Notify(6, 0, 'attributes size is so large we can not even pack on MPRNLRI') |
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yield self._attribute(payload) |
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def pack(self, negotiated): |
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return b''.join(self.packed_attributes(negotiated)) |
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def __len__(self): |
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raise RuntimeError('we can not give you the size of an MPRNLRI - was it with our witout addpath ?') |
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# return len(self.pack(False)) |
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def __repr__(self): |
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return "MP_REACH_NLRI for %s %s with %d NLRI(s)" % (self.afi, self.safi, len(self.nlris)) |
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@classmethod |
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def unpack(cls, data, negotiated): |
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nlris = [] |
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# -- Reading AFI/SAFI |
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_afi, _safi = unpack('!HB', data[:3]) |
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afi, safi = AFI.create(_afi), SAFI.create(_safi) |
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offset = 3 |
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nh_afi = afi |
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# we do not want to accept unknown families |
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if negotiated and (afi, safi) not in negotiated.families: |
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raise Notify(3, 0, 'presented a non-negotiated family %s/%s' % (afi, safi)) |
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# -- Reading length of next-hop |
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len_nh = data[offset] |
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offset += 1 |
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if (afi, safi) not in Family.size: |
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raise Notify(3, 0, 'unsupported %s %s' % (afi, safi)) |
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length, rd = Family.size[(afi, safi)] |
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# Is the peer going to send us some Path Information with the route (AddPath) |
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# It need to be done before adapting the family for another possible next-hop |
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addpath = negotiated.addpath.receive(afi, safi) |
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if negotiated.nexthop: |
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if len_nh in (16, 32, 24): |
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nh_afi = AFI.ipv6 |
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elif len_nh in (4, 12): |
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nh_afi = AFI.ipv4 |
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else: |
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raise Notify(3, 0, 'unsupported family %s %s with extended next-hop capability enabled' % (afi, safi)) |
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length, _ = Family.size[(nh_afi, safi)] |
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if len_nh not in length: |
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raise Notify( |
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3, |
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0, |
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'invalid %s %s next-hop length %d expected %s' |
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% (afi, safi, len_nh, ' or '.join(str(_) for _ in length)), |
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) |
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size = len_nh - rd |
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# XXX: FIXME: GET IT FROM CACHE HERE ? |
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nhs = data[offset + rd : offset + rd + size] |
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nexthops = [nhs[pos : pos + 16] for pos in range(0, len(nhs), 16)] |
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# chech the RD is well zero |
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if rd and sum([int(_) for _ in data[offset:8]]) != 0: |
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raise Notify(3, 0, "MP_REACH_NLRI next-hop's route-distinguisher must be zero") |
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offset += len_nh |
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# Skip a reserved bit as somone had to bug us ! |
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reserved = data[offset] |
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offset += 1 |
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if reserved != 0: |
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raise Notify(3, 0, 'the reserved bit of MP_REACH_NLRI is not zero') |
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# Reading the NLRIs |
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data = data[offset:] |
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if not data: |
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raise Notify(3, 0, 'No data to decode in an MPREACHNLRI but it is not an EOR %d/%d' % (afi, safi)) |
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while data: |
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if nexthops: |
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for nexthop in nexthops: |
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nlri, left = NLRI.unpack_nlri(afi, safi, data, IN.ANNOUNCED, addpath) |
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# allow unpack_nlri to return none for "treat as withdraw" controlled by NLRI.unpack_nlri |
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if nlri: |
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nlri.nexthop = NextHop.unpack(nexthop) |
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nlris.append(nlri) |
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else: |
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nlri, left = NLRI.unpack_nlri(afi, safi, data, IN.ANNOUNCED, addpath) |
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# allow unpack_nlri to return none for "treat as withdraw" controlled by NLRI.unpack_nlri |
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if nlri: |
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nlris.append(nlri) |
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if left == data: |
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raise RuntimeError("sub-calls should consume data") |
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data = left |
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return cls(afi, safi, nlris) |
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EMPTY_MPRNLRI = MPRNLRI(AFI.undefined, SAFI.undefined, []) |
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Exa-Networks /
exabgp
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