Parsing issues with bgpdump (unknown attribute 0)

Hi Colin,

Thank you for your answer,

I was also suspecting file corruption, although I have to admit that I was hoping that it would not be it :)

I guess my next move is to understand why some of my files get corrupted.

Thank you agin for the help!

Cheers,
Alexis




> On 10 Oct 2015, at 04:22, Colin Petrie <cpetrie at ripe.net> wrote:
> 
> Hi Alexis,
> 
> I would suspect you have a corrupted dump file.
> 
> If I run 'bgpdump -v' over your provided dump file, I get the same
> output as you, but also on stderr:
> 
> [warn] ERROR attribute is truncated: expected=98 remaining=17
> [warn] ERROR attribute is truncated: expected=129 remaining=16
> [warn] ERROR attribute is truncated: expected=65535 remaining=29
> [warn] ERROR attribute is truncated: expected=65535 remaining=18
> [warn] ERROR attribute is truncated: expected=98 remaining=25
> [warn] ERROR attribute is truncated: expected=65535 remaining=11
> [warn] ERROR attribute is truncated: expected=65535 remaining=1
> [warn] ERROR attribute is truncated: expected=65535 remaining=1
> [warn] process_zebra_bgp_message: unsupported AFI 4096
> [warn] process_zebra_bgp_message: unsupported AFI 4096
> [warn] process_zebra_bgp_message: unsupported AFI 4096
> [warn] process_zebra_bgp_message: unsupported AFI 4096
> [warn] process_zebra_bgp_message: unsupported AFI 4096
> [warn] process_zebra_bgp_message: unsupported AFI 4096
> [error] bgpdump_read_next: incomplete dump record (0 bytes read,
> expecting -1)
> 
> So a length field somewhere is telling the parser to read an incorrect
> amount of data from the stream, which then throws off the field alignment.
> 
> You'd probably need to stare at your MRT file with a hex editor for a
> while if you want to find the problem :)
> 
> Of course, how bgpdump handles it (or doesn't!) might be better :) it
> could probably do a better job of trying to re-align on later messages.
> 
> Hope this helps,
> 
> Cheers,
> Colin
> 
> 
> On 09/10/15 19:35, Alexis Fasquel wrote:
>> Hello everyone,
>> 
>> I’ve been using BGPDump to collect BGP data across multiple BGP server.
>> Unfortunately, I’ve been having some issues parsing some MRT files.
>> 
>> So I have a file (provided in attachment) that has been created by a
>> Quagga instance (quagga-0.99.22.1-2013051601). All the beginning of the
>> file seems to be parsed correctly, but at some point, I get a message
>> with unknown attributes.  As you can see on the screenshot below, the
>> strange part about it is that the attribute type is supposedly 0 —which
>> is not a correct attribute type if I’m referring to the RFC. Different
>> versions of bgpdump have been tested, without any changes.
>> 
>> 
>> 
>> 
>> 
>> 
>> And the actual issues come up right after: every announcement after this
>> message seems to have something wrong (wrong prefix length/wrong AS path
>> values…):
>> 
>> 
>> 
>> 
>> 
>> Does anyone already encountered such troubles? Could it be a bug from
>> BGPDump somewhere?
>> 
>> Let me know if you have any idea or want some more detail about the issue.
> 
> --
> Colin Petrie
> Systems Engineer
> RIPE NCC

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