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# encoding: utf-8 |
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""" |
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sradj.py |
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Created by Evelio Vila |
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Copyright (c) 2014-2017 Exa Networks. All rights reserved. |
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""" |
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import json |
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from struct import unpack |
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from exabgp.vendoring import six |
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from exabgp.util import hexstring |
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from exabgp.vendoring.bitstring import BitArray |
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from exabgp.bgp.message.update.attribute.bgpls.linkstate import LINKSTATE, LsGenericFlags |
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# draft-gredler-idr-bgp-ls-segment-routing-ext-03 |
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# 0 1 2 3 |
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# 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 |
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# +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
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# | Type | Length | |
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# +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
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# | Flags | Weight | Reserved | |
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# +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
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# | SID/Label/Index (variable) | |
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# +---------------------------------------------------------------+ |
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# |
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View Code Duplication |
@LINKSTATE.register() |
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class SrAdjacency(object): |
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TLV = 1099 |
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_sr_adj_sids = [] |
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def __init__ (self): |
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self.sr_adj_sids = SrAdjacency._sr_adj_sids.copy() |
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def __repr__ (self): |
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return "sr-adj-sids: {}".format(self.sr_adj_sids) |
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@classmethod |
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def unpack (cls,data,length): |
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# We only support IS-IS flags for now. |
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flags = LsGenericFlags.unpack(data[0:1],LsGenericFlags.ISIS_SR_ADJ_FLAGS).flags |
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# Parse adj weight |
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weight = six.indexbytes(data,1) |
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# Move pointer 4 bytes: Flags(1) + Weight(1) + Reserved(2) |
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data = data[4:] |
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# SID/Index/Label: according to the V and L flags, it contains |
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# either: |
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# * A 3 octet local label where the 20 rightmost bits are used for |
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# encoding the label value. In this case the V and L flags MUST |
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# be set. |
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# |
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# * A 4 octet index defining the offset in the SID/Label space |
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# advertised by this router using the encodings defined in |
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# Section 3.1. In this case V and L flags MUST be unset. |
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raw = [] |
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while data: |
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# Range Size: 3 octet value indicating the number of labels in |
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# the range. |
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if int(flags['V']) and int(flags['L']): |
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b = BitArray(bytes=data[:3]) |
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sid = b.unpack('uintbe:24')[0] |
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data = data[3:] |
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elif (not flags['V']) and (not flags['L']): |
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sid = unpack('!I',data[:4])[0] |
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data = data[4:] |
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else: |
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raw.append(hexstring(data)) |
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break |
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cls._sr_adj_sids.append({'flags': flags, 'weight': weight, 'sid': sid, 'undecoded': raw}) |
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return cls() |
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def json (self,compact=None): |
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return '"sr-adj-sids": {}'.format(json.dumps(self.sr_adj_sids)) |
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@classmethod |
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def reset(cls): |
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cls._sr_adj_sids = [] |
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Exa-Networks /
exabgp
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