Filename: 272-valid-and-running-by-default.txt Title: Listed routers should be Valid, Running, and treated as such Created: 26 Aug 2016 Author: Nick Mathewson Status: Open

1. Introduction and proposal.

This proposal describes a change in how clients understand consensus flags, and how authorities vote on consensuses.

1.1. Authority-side changes

Back in proposal 138, we made it so that non-Running routers were not included in the consensus documents. We should do the same with the Valid flag. Specifically, after voting, if the authorities find that a router would not receive the Valid flag, they should not include it at all.

This will require the allocation of a new consensus method, since it is a change in how consensuses are made from votes.

In the most recent consensus, it will affect exactly 1 router.

1.2. Client-side changes

I propose that clients should consider every listed router to be listed as Running and Valid if any consensus method above or higher is in use.

2. Benefits

Removing the notion of listed but invalid routers will remove an opportunity for error, and let us remove some client side code.

More interestingly, the above changes would allow us to eventually stop including the Running and Valid flags, thereby providing an authority-side way to feature-gate clients off of the Tor network without a fast-zombie problem. (See proposal 266 for discussion.)

A. An additional possible change

Perhaps authorities might also treat BadExit like they treat the absence of Valid and Running: as sufficient reason to not include a router in the consensus. Right now, there are only 4 listed BadExit routers in the consensus, amounting to a small fraction of total bandwidth.

Making this change would allow us to remove the client-side badexit logic.

B. Does this solve the zombie problem?

I tested it a little, and it does seem to be a way to make even the most ancient consensus-understanding Tors stop fetching descriptors and using the network. More testing needed though.