Exact Definition of numbers-match bitmask-match and fragmentation-type

[Matt Corallo]

Replies to both responses.

On 4/5/21 05:04, Maria Matejka wrote:
> Hello!
> 
> On 4/4/21 6:18 PM, Matt Corallo wrote:
>> For context, I'm currently writing a birdc-flowspec -> XDP parser/transpiler, so exact formal grammar and behavior is 
>> important :). You can find it at https://github.com/TheBlueMatt/flowspec-xdp.
> 
> Would you benefit from having Python API in BIRD, getting the flowspec rules as proper objects?

Hmm, probably, I guess? Its not really that hard to parse the birdc output as long as I figure out the exact semantics 
to convert a X-match string into an AST. Putting in the work to write a whole Python API sounds like more work than its 
worth, but, hey, if you build it, I'll use it :)

>> It currently only supports drop/pass, however, and doesn't parse the action communities as it doesn't appear BIRD 
>> supports them? The RFC indicates extended community types in the 0x800X range, but BIRD appears to only support rt/ro. 
>> I may be missing something entirely obvious here, though.
> 
> I remember coding something around that, anyway I don't remember whether we actually merged it. Will look for that.

See below from Tim - (generic, X, Y). I do not believe this is documented anywhere.

On 4/5/21 03:49, Tim Weippert wrote:
 > You can add the exetended communities via generic extended communitiy in
 > bird:
 >
 > bgp_ext_community.add( (generic, 0x80060000, 0x00000000 ) );
 >
 > the output in birdc will look like:
 >
 > flow4 { dst 203.0.113.53/32; src 198.51.100.10/32; }  [S_FLOWSPEC_v4 07:48:34.659] * (200)
 >          Type: static univ
 >          BGP.ext_community: (generic, 0x80060000, 0x0)
 >

Thanks! Will update to at least do rate limiting by maps this week/weekend.

Matt