Comment by ExoticPearTree | Hacker News Reader

Comment by ExoticPearTree | Hacker News Reader

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Funny enough, I actually have a few routers with a DFZ, so I have an idea or two about how BGP works.

My point is that:

- if you drop a connection, especially one through which you announce the full routing table, it is going to create a lot of churn to your downstreams. Depending on the kind of routers they use, it can create some network instability for quite a while. And if you drop it again when you receive that malformed route, the instability continues

- removing only the malformed attribute maybe changes the way you treat traffic but you still route it. OK, you send it to maybe another interface, but no biggie

- if you’re using a DFZ setup, dropping that single route could blackhole traffic to that destination if you’re the only upstream to another router

> Funny enough, I actually have a few routers with a DFZ, so I have an idea or two about how BGP works.

And I'm TSC emeritus and >10 year maintainer on FRRouting, and active at IETF. Yet I hugely respect the other people there, all of whom have areas of expertise where they far outrank my own.

Nice! (no sarcasm)

I have very strong opinions about some subjects, one of them being BGP.

I believe sessions should not be tear down just because you receive malformed data. You should be able to remove just the corrupt data. Or treat as a withdraw message like one of the RFC recommends.

I for one one would like knobs to match on any attribute and value and remove/rewrite them at will. Imagine something akin to a very smart HTTP proxy.

Blackholes are acceptable when it comes to broken attributes. Blackholes spreading is not.

If you just drop malfromed attributes, there is no blackhole spreading.

If the attribute says "encapsulate this", dropping just the attribute will create a blackhole as you will attract traffic that should be encapsulated and packets following this route will be dropped it if not.

I guess you're referring to RFC9012.

Yes, but then again since you have logs of why it was dropped (like I suggested in my first post, to log everything dropped), you can easily troubleshoot the problem. A much better outcome than flapping a BGP session for no good reason and creating route churn and network instability.

Or just drop the announced route (not the session) with the attribute you can't work with

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