This commit fixes a parsing error when a BGP update contains a "withdraw label" equal to 0x000000 instead of 0x8000000 as stated in RFC 3107. This commits treats both labels as "withdraw label"
cr https://code.amazon.com/reviews/CR-4121738 Signed-off-by: Benjamin Villain <villa...@amazon.com> --- ryu/lib/packet/bgp.py | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) diff --git a/ryu/lib/packet/bgp.py b/ryu/lib/packet/bgp.py index 9e501515..89ed191e 100644 --- a/ryu/lib/packet/bgp.py +++ b/ryu/lib/packet/bgp.py @@ -782,7 +782,16 @@ class _LabelledAddrPrefix(_AddrPrefix): # Routes field should be set to 0x800000. (Of course, terminating the # BGP session also withdraws all the previously advertised routes.) # - _WITHDRAW_LABEL = 0x800000 + # RFC8227 + # 2.4 How to Explicitly Withdraw the Binding of a Label to a Prefix + # [RFC3107] also made it possible to withdraw a binding without specifying + # the label explicitly, by setting the Compatibility field to 0x800000. + # However, some implementations set it to 0x000000. In order to ensure + # backwards compatibility, it is RECOMMENDED by this document that the + # Compatibility field be set to 0x800000, but it is REQUIRED that it be + # ignored upon reception. + # + _WITHDRAW_LABELS = [0x800000, 0x000000] def __init__(self, length, addr, labels=None, **kwargs): labels = labels if labels else [] @@ -823,7 +832,7 @@ class _LabelledAddrPrefix(_AddrPrefix): labels = addr[0] rest = addr[1:] labels = [x << 4 for x in labels] - if labels and labels[-1] != cls._WITHDRAW_LABEL: + if labels and labels[-1] not in cls._WITHDRAW_LABELS: labels[-1] |= 1 # bottom of stack bin_labels = list(cls._label_to_bin(l) for l in labels) return bytes(reduce(lambda x, y: x + y, bin_labels, @@ -837,7 +846,7 @@ class _LabelledAddrPrefix(_AddrPrefix): while True: (label, bin_) = cls._label_from_bin(bin_) labels.append(label) - if label & 1 or label == cls._WITHDRAW_LABEL: + if label & 1 or label in cls._WITHDRAW_LABELS: break assert length > struct.calcsize(cls._LABEL_PACK_STR) * len(labels) except struct.error: @@ -857,7 +866,7 @@ class _LabelledAddrPrefix(_AddrPrefix): while True: (label, rest) = cls._label_from_bin(rest) labels.append(label >> 4) - if label & 1 or label == cls._WITHDRAW_LABEL: + if label & 1 or label in cls._WITHDRAW_LABELS: break return (labels,) + cls._prefix_from_bin(rest) -- 2.17.1 _______________________________________________ Ryu-devel mailing list Ryu-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/ryu-devel
