commit 71dc93753bd6db9d4c9a2d3f1b4b8f7e3682221b Author: Nick Mathewson <nickm@torproject.org> Date: Thu Nov 30 07:55:06 2017 -0500 Add prop286: Controller APIs for hibernation access on mobile --- proposals/000-index.txt | 2 + proposals/286-hibernation-api.txt | 194 ++++++++++++++++++++++++++++++++++++++ 2 files changed, 196 insertions(+) diff --git a/proposals/000-index.txt b/proposals/000-index.txt index 3352d02..2bb7363 100644 --- a/proposals/000-index.txt +++ b/proposals/000-index.txt @@ -206,6 +206,7 @@ Proposals by number: 283 Move IPv6 ORPorts from microdescriptors to the microdesc consensus [OPEN] 284 Hidden Service v3 Control Port [OPEN] 285 Directory documents should be standardized as UTF-8 [OPEN] +286 Controller APIs for hibernation access on mobile [OPEN] Proposals by status: @@ -265,6 +266,7 @@ Proposals by status: 283 Move IPv6 ORPorts from microdescriptors to the microdesc consensus [for 0.3.3.x] 284 Hidden Service v3 Control Port 285 Directory documents should be standardized as UTF-8 + 286 Controller APIs for hibernation access on mobile ACCEPTED: 172 GETINFO controller option for circuit information 173 GETINFO Option Expansion diff --git a/proposals/286-hibernation-api.txt b/proposals/286-hibernation-api.txt new file mode 100644 index 0000000..25da5c2 --- /dev/null +++ b/proposals/286-hibernation-api.txt @@ -0,0 +1,194 @@ +Filename: 286-hibernation-api.txt +Title: Controller APIs for hibernation access on mobile +Author: Nick Mathewson +Created: 30-November-2017 +Status: Open + + +1. Introduction + + On mobile platforms, battery life is achieved by reducing + needless network access and CPU access. Tor currently provides + few ways for controllers and operating systems to tune its + behavior. + + This proposal describes controller APIs for better management of + Tor's hibernation mechanisms, and extensions to those mechanisms, + for better power management in mobile environments. + +1.1. Background: hibernation and idling in Tor today + + We have an existing "hibernation" mechanism that we use to + implement "bandwidth accounting" and "slow shutdown" mechanisms: + When a Tor instance is close to its bandwidth limit: it stops + accepting new connections or circuits, and only processes those + it has, until the bandwidth limit is reached. Once the bandwidth + limit is reached, Tor closes all connections and circuits, and + all non-controller listeners, until a new accounting limit + begins. + + Tor handles the INT signal on relays similarly: it stops + accepting new connections or circuits, and gives the existing + ones a short interval in which to shut down. Then Tor closes all + connections and exits the process entirely. + + Tor's "idle" mechanism is related to hibernation, though its + implementation is separate. When a Tor clients has passed a + certain amount of time without any user activity, it declares + itself "idle" and stops performing certain background tasks, such + as fetching directory information, or building circuits in + anticipation of future needs. (This is tied in the codebase to + the "predicted ports" mechanism, but it doesn't have to be.) + + +1.2. Background: power-management signals on mobile platforms + + (I'm not a mobile developer, so I'm about to wildly oversimplify. + Please let me know where I'm wrong.) + + Mobile platforms achieve long battery life by turning off the + parts they don't need. The most important parts to turn off are + the antenna(s) and the screen; the CPU can be run in a slower + mode. + + But it doesn't do much good turning things off when they're + unused, if some background app is going to make sure that they're + always in use! So mobile platforms use signals of various kinds + to tell applications "okay, shut up now". + + Some apps need to do online background activities periodically; + to help this out, mobile platforms give them a signal "Hey, now + is a good time if you want to do that" and "stop now!" + + +1.3. Mostly out-of-scope: limiting CPU wakeups when idle. + + The changes described here will be of limited use if we do not + also alter Tor so that, when it's idle, the CPU is pretty quiet. + That isn't the case right now: we have large numbers of callbacks + that happen periodically (every second, every minute, etc) + whether they need to or not. We're hoping to limit those, but + that's not what this proposal is about. + + +2. Improvements to the hibernation model + + To present a consistent interface that applications and + controllers can use to manage power consumption, we make these + enhancements to our hibernation model. + + First, we add three new hibernation states: "IDLE", + "IDLE_UPDATING", "SLEEP", and "SLEEP_UPDATING". + + "IDLE" is like the current "idle" or "no predicted ports" state: + Tor doesn't launch circuits or start any directory activity, but + its listeners are still open. Tor clients can enter the IDLE + state on their own when they are LIVE, but haven't gotten any + client activity for a while. Existing connections and circuits + are not closed. If the Tor instance receives any new connections, + it becomes LIVE. + + "IDLE_UPDATING" is like IDLE, except that Tor should check for + directory updates as appropriate. If there are any, it should + fetch directory information, and then become IDLE again. + + "SLEEPING" is like the current "dormant state we use for + bandwidth exhaustion, but it is controller-initiated: it begins + when Tor is told to enter it, and ends when Tor is told to leave + it. Existing connections and circuits are closed; listeners are + closed too. + + "SLEEP_UPDATING" is like SLEEP, except that Tor should check for + directory updates as appropriate. If there are any, it should + fetch directory information, and then SLEEP again. + + +2.1. Relay operation + + Relays and bridges should not automatically become IDLE on their + own. + + +2.2. Onion service operation + + When a Tor instance that is running an onion service is IDLE, it + does the minimum to try to remain responsive on the onion + service: It keeps its introduction points open if it can. Once a + day, it fetches new directory information and opens new + introduction points. + + +3. Controller hibernation API + +3.1. Examining the current hibernation state + + We define a new "GETINFO status/hibernation" to inspect the + current hibernation state. Possible values are: + - "live" + - "idle:control" + - "idle:no-activity" + - "sleep:control" + - "sleep:accounting" + - "idle-update:control" + - "sleep-update:control" + - "shutdown:exiting" + - "shutdown:accounting" + - "shutdown:control" + + The first part of each value indicates Tor's current state: + "live" -- completely awake + "idle" -- waiting to see if anything happens + "idle-update" -- waiting to see if anything happens; probing + for directory information + "sleep" -- completely unresponsive + "shutdown" -- unresponsive to new requests; still processing + existing requests. + + The second part of each value indicates the reason that Tor + entered this state: + "control" -- a controller told us to do this. + "no-activity" -- Tor became idle on its own due to not + noticing any requests. + "accounting" -- the bandwidth system told us to enter this + state. + "exiting" -- Tor is in this state because it's getting ready + to exit. + + We add a STATUS_GENERAL hibernation event as follows: + + HIBERNATION + "STATUS=" (one of the status pairs above.) + + Indicates that Tor's hibernation status has changed. + + Note: Controllers MUST accept status values here that they don't + recognize. + + The "GETINFO accounting/hibernating" value and the "STATUS_SERVER + HIBERANATION_STATUS" event keep their old meaning. + +3.2. Changing the hibernation state + + We add the following new possible values to the SIGNAL controller + command: + "SLEEP" -- enter the sleep state, after an appropriate + shutdown interval. + + "IDLE" -- enter the idle state + + "SLEEPWALK" -- If in sleep or idle, start probing for + directory information in the sleep-update or idle-update + state respectively. Remain in that state until we've + probed for directory information, or until we're told to + IDLE or SLEEP again, or (if we're idle) until we get client + activity. Has no effect if not in sleep or idle. + + "WAKEUP" -- If in sleep, sleep-update, idle, idle-update, or + shutdown:sleep state, enter the live state. Has no effect + in any other state. + +3.3. New configuration parameters + + StartIdle -- Boolean. If set to 1, Tor begins in IDLE mode. + +