Draft: [NF] Support BFD

[rlaager]

This enables BFD in passive mode in the bird2 route server templates. Passive mode means that the route server will only speak BFD if the participant initiates it.

At this point, this is just an example. The following issues need to be resolved before this could be merged:

• Is BFD going to be enabled everywhere? If not, it needs an option. Is that option on or off by default? If on, should it be set to off for existing Routers on migration?
• Should the interval be customizable? Should the multiplier?

This builds on top of the commit from PR #852, which is also included here.

To do:

• Add a per-VLAN Interface (where "Route Server Client" is now) setting to enable BFD. Default to on.
• Add per-Router (or global in .env, but I like per-Router because, among other reasons, it allows someone to step into it one route server at a time) settings for whether BFD is enabled. Default to off.
• Add global in .env (or per-Router, but that seems unnecessary) settings for interval and multipler. Default the interval to 1s and the multiplier to 5, per Euro-IX recommendation.
• Write tests
• Write documentation

In addition to the above, I have reviewed the following:

• ensured all relevant template output is escaped to avoid XSS attached with <?= $t->ee( $data ) ?> or equivalent.
• ensured appropriate checks against user privilege / resources accessed
• API calls (particular for add/edit/delete/toggle) are not implemented with GET and use CSRF tokens to avoid CSRF attacks

[rlaager]

@barryo Can you make a call on this design? In other words, if I implemented the above (in a reasonable and correct way), would you merge this? If the answer to that is no, then we can stop here.

If the answer to it is yes, then I'll probably put in a small amount of work to determine how easy it would be to add those options, and then make a decision as to whether I want to attempt the whole thing.

[barryo]

Hey @rlaager - I have time set aside in Q4 for a pretty large refactoring of route server code and would like to put a pin in this until then if you don't mind. There's been a lot of discussion around this also at euro-ix which I need to catch up on. I just don't have the time until after august. There's a few building blocks on this including #173 #174 and #351 amongst others in ideas + openbgpd.